We investigate the impact of sediment layers on ground motion characteristics during subshear and supershear rupture growth. Our findings suggest that sediment layers may lead to local supershear propagation, affecting ground motion, especially in the fault parallel (FP) direction. In contrast to homogeneous material models, we find that in the presence of sediment layers, a larger fault normal (FN) compared to fault parallel (FP) particle velocity jump, reflects shear propagation at depth but does not rule out shallow supershear propagation. Conversely, a large fault parallel (FP) compared to fault normal (FN) particle velocity jump indicates supershear propagation at depth. In the presence of a shallow layer, we also uncover a non-monotonic behavior in the sediment's influence on supershear transition and ground motion characteristics. During supershear propagation at depth we observe that sediment layers contribute to enhancing FP velocity pulses while minimally affecting the FN component. Furthermore, in the limit of global supershear propagation we identify local supersonic propagation within the sediment layers that significantly alters the velocity field around the rupture tip as observed on the free surface, creating both dilatational and shear Mach cones. In all our models with sediments we also find a significant enhancement in the fault vertical component of ground velocity. This could have particular implications for hazard assessments, such as in applications related to linear infrastructure, or a higher propensity to tsunami wave generation. Our research unravels the importance of considering heterogeneous subsurface material distribution in our physical models as they can have drastic implications on earthquake source physics.
", "doi": "10.1093/gji/ggae422", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2025-02", "series_number": "2", "volume": "240", "issue": "2", "pages": "967-987" }, { "id": "authors:wfcp2-7wc22", "collection": "authors", "collection_id": "wfcp2-7wc22", "cite_using_url": "https://authors.library.caltech.edu/records/wfcp2-7wc22", "type": "article", "title": "Dispersion and attenuation relations in flexoelectricity", "author": [ { "family_name": "Giannakopoulos", "given_name": "Antonios E.", "orcid": "0000-0002-0581-6258", "clpid": "Giannakopoulos-Antonios-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "clpid": "Rosakis-A-J" } ], "abstract": "The dispersion relations in flexoelectricity are examined for plane time-harmonic waves that propagate in the flexoelectric materials. In contrast to classic elastodynamics, dispersion is observed in the displacement field due to two micro-structural and two micro-inertial lengths that emerge from the electromechanical coupling. In the absence of such coupling, we return to the classic elastodynamic results. The problem dissociates in longitudinal and transverse waves, as is the case in classic elastodynamics. The group velocity of the mechanical field is also the velocity of the energy transfer across the planes of the waves. An optical branch of the dispersion relation appears due to the polarization field that follows the mechanical field. The longitudinal and transverse velocities of the plane waves was found to depend on the corresponding microstructural lengths and are less than or equal to the classic plane wave velocities because the micro-inertial lengths are greater than or equal to the micro-structural length. The opposite effect is expected when we encounter flexoelectric metamaterials in which case the micro-inertial lengths are less than the micro-structural length.
\nThis paper discusses the results of 1\u223625 scale shake table tests evaluating the seismic response of multiblock tower structures (MTSs) conceived as energy storage systems. The tests described here are a part of a comprehensive research campaign involving smaller physical models, computational model validation, and the theoretical background required to compare results across scales. The 6.46-m-high MTSs consisted of over 7,000 concrete blocks stacked vertically without any bonding agent, interacting only by friction and rocking. Three MTSs were tested under two different ground motions. Dynamic digital image correlation (DIC) and low-cost micro electrical mechanical system (MEMS) accelerometers were used for dynamic response measurements. Towers 1 and 3, subjected to repeated strong-intensity earthquake ground motions, collapsed during the third repetition due to the accumulation of residual displacements. Tower 2 was subjected to a single near-fault ground motion representing an extreme event and collapsed during the test. Different collapse mechanisms were identified in the test program. Data collected from individual blocks showed in-plane and out-of-phase block rotation and sliding, which contributed to the system’s energy dissipation during the tests.
", "doi": "10.1061/jsendh.steng-13144", "issn": "0733-9445", "publisher": "American Society for Civil Engineering", "publication": "Journal of Structural Engineering", "publication_date": "2024-05", "series_number": "5", "volume": "150", "issue": "5", "pages": "JSENDH.STENG-13144" }, { "id": "authors:p2hzh-mv009", "collection": "authors", "collection_id": "p2hzh-mv009", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230509-291707400.3", "type": "article", "title": "Predicting the seismic behavior of multiblock tower structures using the level set discrete element method", "author": [ { "family_name": "Harmon", "given_name": "John M.", "clpid": "Harmon-John-M" }, { "family_name": "Gabuchian", "given_name": "Vahe", "clpid": "Gabuchian-Vahe" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Conte", "given_name": "Joel P.", "orcid": "0000-0003-2068-7965", "clpid": "Conte-Joel-P" }, { "family_name": "Restrepo", "given_name": "Jos\u00e9 I.", "clpid": "Restrepo-Jos\u00e9-I" }, { "family_name": "Rodriguez", "given_name": "Andr\u00e9s", "clpid": "Rodriguez-Andr\u00e9s" }, { "family_name": "Nema", "given_name": "Arpit", "clpid": "Nema-Arpit" }, { "family_name": "Pedretti", "given_name": "Andrea R.", "clpid": "Pedretti-Andrea-R" }, { "family_name": "Andrade", "given_name": "Jos\u00e9 E.", "orcid": "0000-0003-3741-0364", "clpid": "Andrade-J-E" } ], "abstract": "In this paper a modeling method is validated at multiple scales for the seismic performance of multiblock tower structure (MTS). MTS are a proposed concept for large-capacity gravitational energy storage that will enable renewable energy sources. The structure modeled is a tower of 7144 nominally identical blocks arranged in a 38-layered annular pattern with no adhesive mechanisms between the blocks or the blocks and the foundation. The level set discrete element method is used to model the dynamics of the tower structure experiencing a ground motion. Experimental determination of each model parameter is shown from the use of individual blocks before construction. Close comparisons to experimental results are shown for the dynamic motion of the tower over a full ground motion time history for multiple scales, materials and ground motions. When the tower was brought to failure, the two ground motions used produced distinct failure modes of the tower showing both a peeling and buckling behavior. Both the effect of the friction coefficient and unequal block heights are investigated. Friction coefficient has a noticeable effect on the amplitude of motion of the tower while the unevenness of the block heights affects mostly the structural speed.", "doi": "10.1002/eqe.3883", "issn": "0098-8847", "publisher": "Wiley", "publication": "Earthquake Engineering and Structural Dynamics", "publication_date": "2023-05-13" }, { "id": "authors:bh7ea-yp672", "collection": "authors", "collection_id": "bh7ea-yp672", "cite_using_url": "https://authors.library.caltech.edu/records/bh7ea-yp672", "type": "article", "title": "Uncertainty Analysis of Dynamic Rupture Measurements Obtained Through Ultrahigh-Speed Digital Image Correlation", "author": [ { "family_name": "Lattanzi", "given_name": "A.", "orcid": "0000-0001-7540-3136", "clpid": "Lattanzi-Attilio" }, { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Rossi", "given_name": "M.", "clpid": "Rossi-M" }, { "family_name": "Donzelli", "given_name": "A.", "clpid": "Donzelli-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Background: The full-field behavior of dynamic shear cracks, with their highly transient features, has recently been quantified by employing Digital Image Correlation (DIC) coupled with ultrahigh-speed photography (at 1-2 million frames/sec). The use of ultrahigh-speed DIC has enabled the observation of complex structures associated with the evolution of the dynamic shear fractures under controlled laboratory conditions, providing a detailed description of their distinctive full-field kinematic features. This has allowed to identify, for instance, the spatiotemporal characteristics of sub-Rayleigh and intersonic shear ruptures, and to measure the evolution of dynamic friction during rupture propagation of frictional shear ruptures. \n\nObjective: Capturing such highly transient phenomena represents a challenging metrological process influenced by both ultra-fast imaging procedures and DIC analysis parameters. However, the effect of these parameters on the quantification of the rupture features has not been assessed yet. Here, a simulated experiment framework is presented and employed to evaluate the uncertainties associated with ultrahigh-speed DIC measurements. \n\nMethods: Finite element simulations replicate laboratory experiments of dynamic ruptures spontaneously propagating along frictional interfaces. Experimental images of the specimen acquired with an ultrahigh-speed camera are numerically deformed by the displacement fields obtained from the numerical simulations and are analyzed using the same DIC analysis procedure as in the laboratory experiments. \n\nResults: The displacement, particle velocity, and strain fields obtained from the DIC analysis are compared with the ground-truth fields of the numerical simulations, correlating the measurement resolution with the physical length scale of the propagating Mode II rupture. In addition, the full-field data are employed to estimate the capability of the ultrahigh-speed DIC setup to infer the dynamic friction evolution. \n\nConclusions: This methodology allows us to quantify the accuracy of the ultrahigh-speed DIC measurements in resolving the complex spatiotemporal structures of dynamic shear ruptures, focusing on the impact of the key correlation parameters.", "doi": "10.1007/s11340-022-00932-9", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2023-03", "series_number": "3", "volume": "63", "issue": "3", "pages": "529-563" }, { "id": "authors:bb5m8-dbf50", "collection": "authors", "collection_id": "bb5m8-dbf50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221205-666301600.10", "type": "article", "title": "A Framework to Assess the Seismic Performance of Multiblock Tower Structures as Gravity Energy Storage Systems", "author": [ { "family_name": "Andrade", "given_name": "Jos\u00e9 E.", "orcid": "0000-0003-3741-0364", "clpid": "Andrade-J-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Conte", "given_name": "Joel P.", "orcid": "0000-0003-2068-7965", "clpid": "Conte-Joel-P" }, { "family_name": "Restrepo", "given_name": "Jos\u00e9 I.", "clpid": "Restrepo-Jos\u00e9-I" }, { "family_name": "Gabuchian", "given_name": "Vahe", "clpid": "Gabuchian-Vahe" }, { "family_name": "Harmon", "given_name": "John M.", "clpid": "Harmon-John-M" }, { "family_name": "Rodriguez", "given_name": "Andr\u00e9s", "clpid": "Rodriguez-Andr\u00e9s" }, { "family_name": "Nema", "given_name": "Arpit", "clpid": "Nema-Arpit" }, { "family_name": "Pedretti", "given_name": "Andrea R.", "clpid": "Pedretti-Andrea-R" } ], "abstract": "This paper proposes a framework for seismic performance assessment of mutiblock tower structures designed to store renewable energy. To perform our assessment, we deployed, in tandem, physical and numerical models that were developed using appropriate scaling for Newtonian systems that interact via frictional contact. The approach is novel, breaking away from continuum structures for which Cauchy scaling and continuum mechanics are used to model systems. We show that our discontinuous approach is predictive and consistent. We demonstrate predictiveness by showing that the numerical models can reproduce with high fidelity the physical models deployed across two different scales. Consistency is demonstrated by showing that our models can be seamlessly compared across scales and without regard for whether the model is physical or numerical. The integrated theoretical-numerical-experimental approach provides a robust framework to study multiblock tower structures, and the results of our seismic performance assessments are promising. These findings may open the door for new analysis tools in structural mechanics, particularly those applied to gravity energy storage systems.", "doi": "10.1061/(asce)em.1943-7889.0002159", "issn": "0733-9399", "publisher": "American Society of Civil Engineers", "publication": "Journal of Engineering Mechanics", "publication_date": "2023-01", "series_number": "1", "volume": "149", "issue": "1", "pages": "Art. No. 2159" }, { "id": "authors:7wsht-vpr07", "collection": "authors", "collection_id": "7wsht-vpr07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220928-285212100.5", "type": "article", "title": "Dynamic magneto-flexoelectricity and seismo-electromagnetic phenomena: Connecting mechanical response to electromagnetic signatures", "author": [ { "family_name": "Giannakopoulos", "given_name": "Antonios E.", "clpid": "Giannakopoulos-Antonios-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The electromagnetic aspects of the fully dynamic flexoelectric problem are examined for dielectric solids by introducing a new theoretical framework which incorporates both gradients of electric polarization and flexoelectricity due to strain gradients and also includes a weak coupling with the magnetic field. This formulation predicts the existence of linear relations between the electric field and the dilatational components of the particle accelerations. It also shows that the magnetic flux and the magnetic field are proportional to the shear components of the particle velocities. Our continuum theory, although based on very different assumptions, seems to be analogous to the electrokinetic theory of Pride which has been used to assess seismo-magnetic phenomena and measurements in earthquake events.", "doi": "10.1016/j.jmps.2022.105058", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2022-11", "volume": "168", "pages": "Art. No. 105058" }, { "id": "authors:ac5dy-bex62", "collection": "authors", "collection_id": "ac5dy-bex62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220715-744200000", "type": "article", "title": "Supershear shock front contribution to the tsunami from the 2018 M_w 7.5 Palu, Indonesia earthquake", "author": [ { "family_name": "Amlani", "given_name": "Faisal", "orcid": "0000-0003-4022-8088", "clpid": "Amlani-Faisal" }, { "family_name": "Bhat", "given_name": "Harsha S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-S" }, { "family_name": "Simons", "given_name": "Wim J. F.", "clpid": "Sions-Wim-J-F" }, { "family_name": "Schubnel", "given_name": "Alexandre", "clpid": "Schubnel-Alexandre" }, { "family_name": "Vigny", "given_name": "Christophe", "clpid": "Vigny-Christophe" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Efendi", "given_name": "Joni", "clpid": "Efendi-Joni" }, { "family_name": "Elbanna", "given_name": "Ahmed E.", "clpid": "Elbanna-Ahmed-E" }, { "family_name": "Dubernet", "given_name": "Pierpaolo", "clpid": "Dubernet-Pierpaolo" }, { "family_name": "Abidin", "given_name": "Hasanuddin Z.", "clpid": "Abidin-Hasanuddin-Z" } ], "abstract": "Hazardous tsunamis are known to be generated predominantly at subduction zones. However, the 2018 M_w 7.5 Palu (Indonesia) earthquake on a strike-slip fault generated a tsunami that devastated the city of Palu. The mechanism by which this tsunami originated from such an earthquake is being debated. Here we present near-field ground motion (GPS) data confirming that the earthquake attained supershear speed, i.e. a rupture speed greater than the shear wave speed of the host medium. We subsequently study the effect of this supershear rupture on tsunami generation by coupling the ground motion to a 1-D non-linear shallow-water wave model accounting for both time-dependent bathymetric displacement and velocity. With the local bathymetric profile of Palu bay around a tidal station, our simulations reproduce the tsunami arrival and motions observed by CCTV cameras. We conclude that Mach (shock) fronts, generated by the supershear speed, interacted with the bathymetry and contributed to the tsunami.", "doi": "10.1093/gji/ggac162", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2022-09", "series_number": "3", "volume": "230", "issue": "3", "pages": "2089-2097" }, { "id": "authors:6gcmj-reb48", "collection": "authors", "collection_id": "6gcmj-reb48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220602-794026200", "type": "article", "title": "Intermittent lab earthquakes in dynamically weakening fault gouge", "author": [ { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Large and destructive earthquakes on mature faults in Earth's crust occur as slip in a layer of a fine granular material\u2014fault gouge\u2014produced by comminution during sliding. A range of insights into the frictional resistance of faults\u2014one of the main factors controlling earthquake nucleation, dynamic propagation and arrest, and hence the destructive ground shaking of earthquakes\u2014has been obtained in experiments with spatially uniform slip imposed in small samples. However, how various features of gouge friction combine to determine spontaneous progression of earthquakes is difficult to study in the lab owing to substantial challenges with sample sizes and adequate imaging. Here, using lab experiments, we show that spontaneously propagating dynamic ruptures navigate a fault region with fine rock gouge through complex, intermittent slip processes with dramatic friction evolution. These include repeated arrest of rupture propagation caused by friction strengthening at lower slip rates and dynamic earthquake re-nucleation enabled by pronounced rapid friction weakening at higher slip rates consistent with flash heating. The spontaneous repeated weakening and strengthening of friction in fine rock gouge highlights the fundamental dependence of friction on slip rate and associated processes, such as shear heating, localization and delocalization of shear, and dilation and compaction of the shear layer. Our findings expand experimental support of the concept that co-seismic weakening may enable earthquake rupture to break through stable fault regions, with substantial implications for seismic hazard.", "doi": "10.1038/s41586-022-04749-3", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2022-06-30", "volume": "606", "pages": "922-929" }, { "id": "authors:z2msj-wj442", "collection": "authors", "collection_id": "z2msj-wj442", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220317-377260000", "type": "article", "title": "Dynamics and Near-Field Surface Motions of Transitioned Supershear Laboratory Earthquakes in Thrust Faults", "author": [ { "family_name": "Tal", "given_name": "Yuval", "orcid": "0000-0001-7308-9294", "clpid": "Tal-Yuval" }, { "family_name": "Rubino", "given_name": "Vito", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "We study how the asymmetric geometry of thrust faults affects the dynamics of supershear ruptures and their associated trailing Rayleigh ruptures as they interact with the free surface, and investigate the resulting near-field ground motions. Earthquakes are mimicked by propagating laboratory ruptures along a frictional interface with a 61\u00b0 dip angle. Using an experimental technique that combines ultrahigh-speed photography with digital image correlation, we produce sequences of full-field evolving measurements of particle displacements and velocities. Our full-field measurement capability allows us to confirm and quantify the asymmetry between the experimental motions of the hanging and footwalls, with larger velocity magnitudes occurring at the hanging wall. Interestingly, because the motion of the hanging wall is generally near-vertical, while that of the footwall is at dip direction shallower than the dip angle of the fault, the horizontal surface velocity components are found to be larger at the footwall than at the hanging wall. The attenuation in surface velocity with distance from the fault trace is generally larger at the hanging wall than at the footwall and it is more pronounced in the vertical component than in the horizontal one. Measurements of the rotations in surface motions confirm experimentally that the interaction of the rupture with the free surface can be interpreted through a torqueing mechanism that leads to reduction in normal stress near the free surface for thrust earthquakes. Nondimensional analysis shows that the experimental measurements are consistent with larger-scale numerical simulations as well as field observations from thrust earthquakes.", "doi": "10.1029/2021jb023733", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2022-03", "series_number": "3", "volume": "127", "issue": "3", "pages": "Art. No. e2021JB023733" }, { "id": "authors:9a0bn-r5r72", "collection": "authors", "collection_id": "9a0bn-r5r72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211123-233319584", "type": "article", "title": "Three-dimensional stress state during dynamic shear rupture propagation along frictional interfaces in elastic plates", "author": [ { "family_name": "Rezakhani", "given_name": "R.", "orcid": "0000-0002-7439-9080", "clpid": "Rezakhani-Roozbeh" }, { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Molinari", "given_name": "J.-F.", "clpid": "Molinari-Jean-Fran\u00e7ois" }, { "family_name": "Rosakis", "given_name": "A.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The state of stress in plates, where one geometric dimensions is much smaller than the others, is often assumed to be of plane stress. This assumption is justified by the fact that the out-of-plane stress components are zero on the free-surfaces of a plate to satisfy the boundary conditions, and have little chance to develop in the bulk, due to the small thickness of the plate. At the same time, it is known that the static stress field associated with cracks approximates plane-strain conditions in the near-crack tip. However, it is not clear how the pre-existing plane-stress field of a plate is modified by a propagating dynamic shear rupture. Here we study the particle velocities and stress fields of dynamic shear ruptures in mode II propagating along the predefined frictional interface of two plates of an elastic material, loaded in compression and shear, using three-dimensional finite element modeling. The numerical simulations show the rapid development of out-of-plane stresses in the interior of the specimen, between the free surfaces. The out-of-plane normal stress is characterized by an anti-symmetric pattern with lobes of alternating polarity, in planes parallel to the free-surfaces. On the interface plane, the out-of-plane stress has a complex pattern exhibiting an initial sudden variation over the plane-stress conditions followed by crisscrossing features, behind the rupture tip. This study shows how plane-stress conditions, defining the state of stress before rupture arrival, are suddenly altered during dynamic rupture propagation. The out-of-plane stress rapidly deviates from the free-surface condition and a state of equivalent plane-strain in the stress-changes field is attained at the rupture tip, while behind the rupture tip a fully three-dimensional stress state is established. The three-dimensional finite element simulations presented here help interpret and explain previous experiments of dynamic shear ruptures by showing the complex particle velocity and stress fields in the interior of the specimen and along the interface plane, which are currently not accessible to full-field experimental measurements.", "doi": "10.1016/j.mechmat.2021.104098", "issn": "0167-6636", "publisher": "Elsevier", "publication": "Mechanics of Materials", "publication_date": "2022-01", "volume": "164", "pages": "Art. No. 104098" }, { "id": "authors:dv27e-2sy47", "collection": "authors", "collection_id": "dv27e-2sy47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211217-790936300", "type": "article", "title": "Dynamic rupture initiation and propagation in a fluid-injection laboratory setup with diagnostics across multiple temporal scales", "author": [ { "family_name": "Gori", "given_name": "Marcello", "orcid": "0000-0002-7380-3723", "clpid": "Gori-Marcello" }, { "family_name": "Rubino", "given_name": "Vito", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Fluids are known to trigger a broad range of slip events, from slow, creeping transients to dynamic earthquake ruptures. Yet, the detailed mechanics underlying these processes and the conditions leading to different rupture behaviors are not well understood. Here, we use a laboratory earthquake setup, capable of injecting pressurized fluids, to compare the rupture behavior for different rates of fluid injection, slow (megapascals per hour) versus fast (megapascals per second). We find that for the fast injection rates, dynamic ruptures are triggered at lower pressure levels and over spatial scales much smaller than the quasistatic theoretical estimates of nucleation sizes, suggesting that such fast injection rates constitute dynamic loading. In contrast, the relatively slow injection rates result in gradual nucleation processes, with the fluid spreading along the interface and causing stress changes consistent with gradually accelerating slow slip. The resulting dynamic ruptures propagating over wetted interfaces exhibit dynamic stress drops almost twice as large as those over the dry interfaces. These results suggest the need to take into account the rate of the pore-pressure increase when considering nucleation processes and motivate further investigation on how friction properties depend on the presence of fluids.", "doi": "10.1073/pnas.2023433118", "pmcid": "PMC8713790", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2021-12-21", "series_number": "51", "volume": "118", "issue": "51", "pages": "Art. No. e2023433118" }, { "id": "authors:egw53-paw40", "collection": "authors", "collection_id": "egw53-paw40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211222-35979500", "type": "article", "title": "Signature of transition to supershear rupture speed in the coseismic off-fault damage zone", "author": [ { "family_name": "Jara", "given_name": "Jorge", "orcid": "0000-0003-3176-0689", "clpid": "Jara-Jorge" }, { "family_name": "Bruhat", "given_name": "Lucile", "orcid": "0000-0002-3916-4147", "clpid": "Bruhat-Lucile" }, { "family_name": "Thomas", "given_name": "Marion Y.", "orcid": "0000-0002-4335-8841", "clpid": "Thomas-Marion-Y" }, { "family_name": "Antoine", "given_name": "Sol\u00e8ne L.", "orcid": "0000-0002-5663-7292", "clpid": "Antoine-Sol\u00e8ne-L" }, { "family_name": "Okubo", "given_name": "Kurama", "orcid": "0000-0001-6453-8238", "clpid": "Okubo-Kurama" }, { "family_name": "Rougier", "given_name": "Esteban", "orcid": "0000-0002-4624-2844", "clpid": "Rougier-Esteban" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Sammis", "given_name": "Charles G.", "orcid": "0000-0001-6377-3746", "clpid": "Sammis-Charles-G" }, { "family_name": "Klinger", "given_name": "Yann", "orcid": "0000-0003-2119-6391", "clpid": "Klinger-Yann" }, { "family_name": "Jolivet", "given_name": "Romain", "orcid": "0000-0002-9896-3651", "clpid": "Jolivet-Romain" }, { "family_name": "Bhat", "given_name": "Harsha S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-S" } ], "abstract": "Most earthquake ruptures propagate at speeds below the shear wave velocity within the crust, but in some rare cases, ruptures reach supershear speeds. The physics underlying the transition of natural subshear earthquakes to supershear ones is currently not fully understood. Most observational studies of supershear earthquakes have focused on determining which fault segments sustain fully grown supershear ruptures. Experimentally cross-validated numerical models have identified some of the key ingredients required to trigger a transition to supershear speed. However, the conditions for such a transition in nature are still unclear, including the precise location of this transition. In this work, we provide theoretical and numerical insights to identify the precise location of such a transition in nature. We use fracture mechanics arguments with multiple numerical models to identify the signature of supershear transition in coseismic off-fault damage. We then cross-validate this signature with high-resolution observations of fault zone width and early aftershock distributions. We confirm that the location of the transition from subshear to supershear speed is characterized by a decrease in the width of the coseismic off-fault damage zone. We thus help refine the precise location of such a transition for natural supershear earthquakes.", "doi": "10.1098/rspa.2021.0364", "pmcid": "PMC8595990", "issn": "1364-5021", "publisher": "Royal Society of London", "publication": "Proceedings of the Royal Society A: Mathematical, physical, and engineering sciences", "publication_date": "2021-11", "series_number": "2255", "volume": "477", "issue": "2255", "pages": "Art. No. 20210364" }, { "id": "authors:fpwm2-c9z86", "collection": "authors", "collection_id": "fpwm2-c9z86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211006-161417119", "type": "article", "title": "Evolution of dynamic shear strength of frictional interfaces during rapid normal stress variations", "author": [ { "family_name": "Rubino", "given_name": "Vito", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Tal", "given_name": "Yuval", "orcid": "0000-0001-7308-9294", "clpid": "Tal-Yuval" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Pressure shear plate impact tests have revealed that when normal stress changes rapidly enough, the frictional shear resistance is no longer proportional to the normal stress but rather evolves with slip gradually. Motivated by these findings, we focus on characterizing the dynamic shear strength of frictional interfaces subject to rapid variations in normal stress. To study this problem, we use laboratory experiments featuring dynamic shear cracks interacting with a free surface and resulting in pronounced and rapid normal stress variations. As dynamic cracks tend to propagate close to the wave speeds of the material, capturing their behavior poses the metrological challenge of resolving displacements on the order of microns over timescales microseconds. Here we present our novel approach to quantify the full-field behavior of dynamic shear ruptures and the evolution of friction during sudden variations in normal stress, based on ultrahighspeed photography (at 1-2 million frames/sec) combined with digital image correlation. Our measurements allow us to capture the evolution of dynamic shear cracks during these short transients and enable us to decode the nature of dynamic friction.", "doi": "10.1051/epjconf/202125001016", "issn": "2100-014X", "publisher": "EDP Sciences", "publication": "EPJ Web of Conferences", "publication_date": "2021-09-08", "volume": "250", "pages": "Art. No. 01016" }, { "id": "authors:q7dmg-rs666", "collection": "authors", "collection_id": "q7dmg-rs666", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210929-175142710", "type": "article", "title": "Implications of Buckingham's Pi Theorem to the Study of Similitude in Discrete Structures: Introduction of the R_F^N, \u03bc^N, and S^N Dimensionless Numbers and the Concept of Structural Speed", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Andrade", "given_name": "Jos\u00e9 E.", "orcid": "0000-0003-3741-0364", "clpid": "Andrade-J-E" }, { "family_name": "Gabuchian", "given_name": "Vahe", "clpid": "Gabuchian-Vahe" }, { "family_name": "Harmon", "given_name": "John M.", "clpid": "Harmon-John-M" }, { "family_name": "Conte", "given_name": "Joel P.", "orcid": "0000-0003-2068-7965", "clpid": "Conte-Joel-P" }, { "family_name": "Restrepo", "given_name": "Jos\u00e9 I.", "clpid": "Restrepo-Jos\u00e9-I" }, { "family_name": "Rodriguez", "given_name": "Andr\u00e9s", "clpid": "Rodriguez-Andr\u00e9s" }, { "family_name": "Nema", "given_name": "Arpit", "clpid": "Nema-Arpit" }, { "family_name": "Pedretti", "given_name": "Andrea R.", "clpid": "Pedretti-Andrea-R" } ], "abstract": "Motivated by the need to evaluate the seismic response of large-capacity gravity energy storage systems (potential energy batteries) such as the proposed frictional Multiblock Tower Structures (MTS) recently discussed by Andrade et al. (2021, \"Seismic Performance Assessment of Multiblock Tower Structures As Gravity Energy Storage Systems,\" ASME J. Appl. Mech., Submitted), we apply Buckingham's Pi theorem (Buckingham, E., 1914, \"On Physically Similar Systems; Illustrations of the Use of Dimensional Equations,\" Phys. Rev., 4, pp. 345\u2013376) to identify the most general forms of dimensionless numbers and dynamic similitude laws appropriate for scaling discontinuous multiblock structural systems involving general restoring forces resisting inertial loading. We begin by introducing the dimensionless \"mu-number\" (\u03bc^N) appropriate for both gravitational and frictional restoring forces and then generalize by introducing the \"arbitrary restoring force number\" (\u2060R^N_F\u2060). R^N_F is subsequently employed to study similitude in various types of discontinuous or discrete systems featuring frictional, gravitational, cohesive, elastic, and mixed restoring forces acting at the block interfaces. In the process, we explore the additional consequences of inter and intra-block elasticity on scaling. We also formulate a model describing the mechanism of structural signal transmission for the case of rigid MTS featuring inter-block restoring forces composed of elastic springs and interfacial friction, introducing the concept of \"structural speed.\" Finally, we validate our results by demonstrating that dynamic time-histories of field quantities and structural speeds between MTS models at various scales are governed by our proposed similitude laws, thus demonstrating the consistency of our approach.", "doi": "10.1115/1.4051338", "issn": "0021-8936", "publisher": "American Society of Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2021-09", "series_number": "9", "volume": "88", "issue": "9", "pages": "Art. No. 091008" }, { "id": "authors:6jgym-qnw17", "collection": "authors", "collection_id": "6jgym-qnw17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210422-124549446", "type": "article", "title": "Laboratory earthquakes along faults with a low velocity zone: Directionality and pulse-like ruptures", "author": [ { "family_name": "Xia", "given_name": "Kaiwen", "clpid": "Xia-Kaiwen" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Low velocity zone (LVZ) is a common structural feature in geological faults. To examine the effect of LVZ on faulting, a laboratory fault model considering the LVZ is constructed and loaded to different levels. Subsequently ruptures are triggered on one of its contact boundaries with the host rock. The bilateral rupture propagation along this laboratory fault that separates different materials shows distinct directionality in both rupture speeds and rupture modes. The rupture in the positive direction with respect to the fault is always crack-like growing at the Generalized Rayleigh (GR) wave speed. However, in the negative direction both stable and unstable slip pulses are observed. Higher load and thinner LVZ facilitate the unstable slip pulses. The trailing tip for both types of pulses propagates at the GR wave speed, the leading tip of the stable pulse propagates with the GR wave speed while that of the unstable pulse features a supershear speed.", "doi": "10.1016/j.eml.2021.101321", "issn": "2352-4316", "publisher": "Elsevier", "publication": "Extreme Mechanics Letters", "publication_date": "2021-07", "volume": "46", "pages": "Art. No. 101321" }, { "id": "authors:2zkvm-qy994", "collection": "authors", "collection_id": "2zkvm-qy994", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210503-164752484", "type": "article", "title": "Anatomy of strike-slip fault tsunami genesis", "author": [ { "family_name": "Elbanna", "given_name": "Ahmed", "orcid": "0000-0003-4079-2607", "clpid": "Elbanna-Ahmed" }, { "family_name": "Abdelmeguid", "given_name": "Mohamed", "orcid": "0000-0002-3985-1721", "clpid": "Abdelmeguid-Mohamed" }, { "family_name": "Ma", "given_name": "Xiao", "orcid": "0000-0002-2125-0880", "clpid": "Ma-Xiao" }, { "family_name": "Amlani", "given_name": "Faisal", "orcid": "0000-0003-4022-8088", "clpid": "Amlani-Faisal" }, { "family_name": "Bhat", "given_name": "Harsha S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-S" }, { "family_name": "Synolakis", "given_name": "Costas", "orcid": "0000-0003-0140-5379", "clpid": "Synolakis-Costas-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Tsunami generation from earthquake-induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been considered insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the generation of large tsunamis (>1 m), under rather generic conditions. To this end, we developed a computational framework that integrates models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time-dependent vertical and horizontal ground motions from spontaneous dynamic rupture models are used to drive boundary motions in the tsunami model. Our results suggest that supershear ruptures propagating along strike-slip faults, traversing narrow and shallow bays, are prime candidates for tsunami generation. We show that dynamic focusing and the large horizontal displacements, characteristic of strike-slip earthquakes on long faults, are critical drivers for the tsunami hazard. These findings point to intrinsic mechanisms for sizable tsunami generation by strike-slip faulting, which do not require complex seismic sources, landslides, or complicated bathymetry. Furthermore, our model identifies three distinct phases in the tsunamic motion, an instantaneous dynamic phase, a lagging coseismic phase, and a postseismic phase, each of which may affect coastal areas differently. We conclude that near-source tsunami hazards and risk from strike-slip faulting need to be re-evaluated.", "doi": "10.1073/pnas.2025632118", "pmcid": "PMC8126766", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2021-05-11", "series_number": "19", "volume": "118", "issue": "19", "pages": "Art. No. e2025632118" }, { "id": "authors:3zw5c-60v02", "collection": "authors", "collection_id": "3zw5c-60v02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200818-083332830", "type": "article", "title": "Illuminating the physics of dynamic friction through laboratory earthquakes on thrust faults", "author": [ { "family_name": "Tal", "given_name": "Yuval", "orcid": "0000-0001-7308-9294", "clpid": "Tal-Yuval" }, { "family_name": "Rubino", "given_name": "Vito", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Large, destructive earthquakes often propagate along thrust faults including megathrusts. The asymmetric interaction of thrust earthquake ruptures with the free surface leads to sudden variations in fault-normal stress, which affect fault friction. Here, we present full-field experimental measurements of displacements, particle velocities, and stresses that characterize the rupture interaction with the free surface, including the large normal stress reductions. We take advantage of these measurements to investigate the dependence of dynamic friction on transient changes in normal stress, demonstrate that the shear frictional resistance exhibits a significant lag in response to such normal stress variations, and identify a predictive frictional formulation that captures this effect. Properly accounting for this delay is important for simulations of fault slip, ground motion, and associated tsunami excitation.", "doi": "10.1073/pnas.2004590117", "pmcid": "PMC7474586", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2020-09-01", "series_number": "35", "volume": "117", "issue": "35", "pages": "21095-21100" }, { "id": "authors:98wvm-6e862", "collection": "authors", "collection_id": "98wvm-6e862", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210218-162638462", "type": "article", "title": "Dynamics of Flexoelectric Materials: Subsonic, Intersonic, and Supersonic Ruptures and Mach Cone Formation", "author": [ { "family_name": "Giannakopoulos", "given_name": "Antonios E.", "clpid": "Giannakopoulos-Antonios-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Motivated by recent, unexpected, experimental observations of \"intersonic\" rupture growth in which both shear and dilatational Mach fronts were observed at the tips of dynamic frictional ruptures propagating at rupture speeds below the dilatational wave speed of the surrounding solid, and we formulate the general dynamic flexoelectric problem and we investigate its plane strain/plane polarization specialization. The coupling of the mechanical problem is analogous to a problem of Toupin\u2013Mindlin gradient elasticity, where two micromechanical characteristic lengths and two microinertial lengths emerge as a combination of the mechanical, dielectric, and flexoelectric constants. The solution of the rupture growth problem allows us to provide an explanation of the experimental results. This becomes possible since flexoelectricity predicts a new aspect that was not observed in the classical analysis: subsonic super shear and supersonic crack tip (or rupture) motions are not related exclusively with the problem being elliptic or hyperbolic, respectively. This is due to the influence of the microinertial lengths, which, in addition to the ratios of the rupture to the wave speeds, also affect the slopes of the Mach cones. Moreover, we are able to explain the experimental paradox of the observation of double Mach cone pairs at the tips of supershear, but subsonic, frictional, ruptures in poly-methyl-methacrtylate (PMMA) by demonstrating that both dilatational and shear Mach cones could appear in flexoelectric solids at rupture speeds below the material dilatation wave speed, something that is impossible from the classical elasticity analysis and is due to the dispersive nature of the present problem. Our analysis is of relevance to the dynamic deformation and fracture of both synthetic and naturally occurring flexoelectric materials and systems, with implications to both engineering and earthquake source mechanics.", "doi": "10.1115/1.4046634", "issn": "0021-8936", "publisher": "American Society of Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2020-06", "series_number": "6", "volume": "87", "issue": "6", "pages": "Art. No. 061004" }, { "id": "authors:gha4w-hxy53", "collection": "authors", "collection_id": "gha4w-hxy53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200113-161350780", "type": "article", "title": "Recent Milestones in Unraveling the Full-Field Structure of Dynamic Shear Cracks and Fault Ruptures in Real-Time: From Photoelasticity to Ultrahigh-Speed Digital Image Correlation", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "The last few decades have seen great achievements in dynamic fracture mechanics. Yet, it was not possible to experimentally quantify the full-field behavior of dynamic fractures, until very recently. Here, we review our recent work on the full-field quantification of the temporal evolution of dynamic shear ruptures. Our newly developed approach based on digital image correlation combined with ultrahigh-speed photography has revolutionized the capabilities of measuring highly transient phenomena and enabled addressing key ques- tions of rupture dynamics. Recent milestones include the visualization of the complete displacement, particle velocity, strain, stress and strain rate fields near growing ruptures, capturing the evolution of dynamic friction during individual rupture growth, and the detailed study of rupture speed limits. For example, dynamic friction has been the big- gest unknown controlling how frictional ruptures develop but it has been impossible, until now, to measure dynamic friction during spontaneous rupture propagation and to understand its dependence on other quantities. Our recent measurements allow, by simul- taneously tracking tractions and sliding speeds on the rupturing interface, to disentangle its complex dependence on the slip, slip velocity, and on their history. In another application, we have uncovered new phenomena that could not be detected with previous methods, such as the formation of pressure shock fronts associated with \"supersonic\" propagation of shear ruptures in viscoelastic materials where the wave speeds are shown to depend strongly on the strain rate.", "doi": "10.1115/1.4045715", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2020-03", "series_number": "3", "volume": "87", "issue": "3", "pages": "Art. No. 030801" }, { "id": "authors:kz506-yqx70", "collection": "authors", "collection_id": "kz506-yqx70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200204-112042828", "type": "article", "title": "Spatiotemporal Properties of Sub\u2010Rayleigh and Supershear Ruptures Inferred From Full\u2010Field Dynamic Imaging of Laboratory Experiments", "author": [ { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Many earthquakes propagate at sub\u2010Rayleigh speeds. Earthquakes propagating at supershear speeds, though less common, are by far more destructive. Hence, it is important to quantify the motion characteristics associated with both types of earthquake ruptures. Here we report on the spatiotemporal properties of dynamic ruptures measured in our laboratory experiments using the dynamic digital image correlation technique. Earthquakes are mimicked by the frictional rupture propagating along the interface of two Homalite plates. Digital images of the propagating ruptures are captured by an ultrahigh\u2010speed camera and processed with digital image correlation in order to produce sequences of evolving displacement and velocity maps. Our measurements reveal the full\u2010field structure of the velocity components, bridge the gap between previous spatially sparse velocimeter measurements available only at two to three locations, and enable us to quantify the attenuation patterns away from the interface.", "doi": "10.1029/2019JB018922", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research: Solid Earth", "publication_date": "2020-02", "series_number": "2", "volume": "125", "issue": "2", "pages": "Art. No. e2019JB018922" }, { "id": "authors:0jpg6-f8r64", "collection": "authors", "collection_id": "0jpg6-f8r64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191220-103522644", "type": "article", "title": "Report on 'Representing Mega Earthquakes in the Laboratory: The Discovery of Super-shear, or Intersonic, Earthquake Ruptures'", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Krishnamurthy", "given_name": "P.", "clpid": "Krishnamurthy-P" }, { "family_name": "Simha", "given_name": "K. R. Y.", "clpid": "Simha-K-R-Y" } ], "abstract": "Earthquakes are one of the most challenging natural hazards that\ndefy prediction with any reasonable warning time that may be possible in the case of hurricanes, cyclones or tsunamis. Studying earthquakes both in the field and laboratories, presents a host of challenges to the seismologist; and, the most obvious ones being the inability to trigger an earthquake in the laboratory and simulate the behaviour of slip along the fault zone at depths. In an enthralling lecture, Prof. Rosakis illuminated the concept of Laboratory Earthquakes as well as the experimental discovery of super-shear earthquake ruptures, whose speeds exceed the shear wave speed of crustal rocks.", "doi": "10.1007/s12594-019-1334-2", "issn": "0016-7622", "publisher": "Geological Society of India", "publication": "Journal of the Geological Society of India", "publication_date": "2019-10", "series_number": "4", "volume": "94", "issue": "4", "pages": "441-441" }, { "id": "authors:gq28f-7cb06", "collection": "authors", "collection_id": "gq28f-7cb06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190905-102805142", "type": "article", "title": "Full-field Ultrahigh-speed Quantification of Dynamic Shear Ruptures Using Digital Image Correlation", "author": [ { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Producing dynamic ruptures in the laboratory allows us to study fundamental characteristics of interface dynamics. Our laboratory earthquake experimental setup has been successfully used to reproduce a number of dynamic rupture phenomena, including supershear transition, bimaterial effect, and pulse-like rupture propagation. However, previous diagnostics, based on photoelasticity and laser velocimeters, were not able to quantify the full-field behavior of dynamic ruptures and, as a consequence, many key rupture features remained obscure. Here we report on our dynamic full-field measurements of displacement, velocities, strains and strain rates associated with the spontaneous propagation of shear ruptures in the laboratory earthquake setup. These measurements are obtained by combining ultrahigh-speed photography with the digital image correlation (DIC) method, enhanced to capture displacement discontinuities. Images of dynamic shear ruptures are taken at 1-2 million frames/s over several sizes of the field of view and analyzed with DIC to produce a sequence of evolving full-field maps. The imaging area size is selected to either capture the rupture features in the far field or to focus on near-field structures, at an enhanced spatial resolution. Simultaneous velocimeter measurements on selected experiments verify the accuracy of the DIC measurements. Owing to the increased ability of our measurements to resolve the characteristic field structures of shear ruptures, we have recently been able to observe rupture dynamics at an unprecedented level of detail, including the formation of pressure and shear shock fronts in viscoelastic materials and the evolution of dynamic friction.", "doi": "10.1007/s11340-019-00501-7", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2019-06", "series_number": "5", "volume": "59", "issue": "5", "pages": "551-582" }, { "id": "authors:xd4kt-9qm38", "collection": "authors", "collection_id": "xd4kt-9qm38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190418-111823081", "type": "article", "title": "Enhanced Digital Image Correlation Analysis of Ruptures with Enforced Traction Continuity Conditions Across Interfaces", "author": [ { "family_name": "Tal", "given_name": "Yuval", "orcid": "0000-0001-7308-9294", "clpid": "Tal-Yuval" }, { "family_name": "Rubino", "given_name": "Vito", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Accurate measurements of displacements around opening or interfacial shear cracks (shear ruptures) are challenging when digital image correlation (DIC) is used to quantify strain and stress fields around such cracks. This study presents an algorithm to locally adjust the displacements computed by DIC near frictional interfaces of shear ruptures, in order for the local stress fields to satisfy the continuity of tractions across the interface. In the algorithm, the stresses near the interface are extrapolated by local polynomials that are constructed using a constrained inversion. This inversion is such that the traction continuity (TC) conditions are satisfied at the interface while simultaneously matching the displacements produced by the DIC solution at the pixels closest to the center of the subset, where the DIC fields are more accurate. We apply the algorithm to displacement fields of experimental shear ruptures obtained using a local DIC approach and show that the algorithm produces the desired continuous traction field across the interface. The experimental data are also used to examine the sensitivity of the algorithm against different geometrical parameters related to construction of the polynomials in order to avoid artifacts in the stress field.", "doi": "10.3390/app9081625", "issn": "2076-3417", "publisher": "MDPI", "publication": "Applied Sciences", "publication_date": "2019-04-02", "series_number": "8", "volume": "9", "issue": "8", "pages": "Art. No. 1625" }, { "id": "authors:gzsmv-ef335", "collection": "authors", "collection_id": "gzsmv-ef335", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190523-154725919", "type": "article", "title": "2018 Timoshenko Medal Acceptance Lecture: Academic Family", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Dedicated to my immediate academic family, my wonderful graduate students and postdocs and Stefan Timoshenko's academic great, great, great, great, great, great grandchildren. \n\nDear friends, \n\nI was brought up in Greece to believe in the power of families. As a result families are very important to me and so are all of you, whom I consider to be my extended academic family. This is exactly the reason for which I feel so excited and honored to receive the Timoshenko Medal in front of you tonight since I truly consider all of you, working in the general area of mechanics at all length and time scales, as my cherished academic brothers and sisters, parents and grandparents.\n\nSo please allow me to make \"Academic Family\" my theme for tonight, because I truly feel that in addition to inspiration and creativity, collegiality and mentoring are the two most important corner stones of our profession.", "doi": "10.1115/1.4042130", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2019-02", "series_number": "2", "volume": "86", "issue": "2", "pages": "Art. No. 020301" }, { "id": "authors:4nhek-3gd70", "collection": "authors", "collection_id": "4nhek-3gd70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190117-081917303", "type": "article", "title": "Neutron imaging: a new possibility for laboratory observation of hydraulic fractures in shale?", "author": [ { "family_name": "Roshankhah", "given_name": "S.", "orcid": "0000-0002-1160-7882", "clpid": "Roshankhah-S" }, { "family_name": "Marshall", "given_name": "J. P.", "orcid": "0000-0001-6208-1801", "clpid": "Marshall-J-P" }, { "family_name": "Tengattini", "given_name": "A.", "clpid": "Tengattini-A" }, { "family_name": "Ando", "given_name": "E.", "clpid": "Ando-E" }, { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Viggiani", "given_name": "G.", "clpid": "Viggiani-G" }, { "family_name": "Andrade", "given_name": "J. E.", "clpid": "Andrade-J-E" } ], "abstract": "Hydraulic fracturing, the creation of fractures by high-pressure fluid injection into a solid medium, is of interest to enhance the permeability of rocks. This complex three-dimensional hydro-mechanical process, however, has only been studied in the laboratory by boundary measurements or acoustic techniques with low spatio-temporal resolutions until now. In this paper, direct, high spatial resolution, and near real-time visualisation results of hydraulic fracture generation and propagation in prismatic specimens of Marcellus shale rock under in situ conditions (70\u2009MPa, plane strain) are presented. Poly-methyl methacrylate specimens are also tested under the same conditions to highlight the importance of rocks' internal structure on the response of the tested rock. The results reveal a complex interaction among the injected fluid, the pre-existing natural fractures in shale structure, and the hydraulically induced fracture highlighting the governing role of rock fabric even under high stresses. These measurements are possible due to the unique sensitivity of neutrons to water. Besides the intrinsic interest of the results presented, this exploratory investigation highlights the potential of neutron imaging in elucidating the evolution of fluid flow and fluid-driven fractures, as X-rays have done for the evolution of solid structure only. Further, understanding of the mechanics of fracking will lead to development of more accurate hydro-mechanical constitutive models thus enabling the design of field operations with higher efficiencies.", "doi": "10.1680/jgele.18.00129", "issn": "2045-2543", "publisher": "ICE Publishing", "publication": "G\u00e9otechnique Letters", "publication_date": "2018-12", "series_number": "4", "volume": "8", "issue": "4", "pages": "316-323" }, { "id": "authors:59j5y-3d634", "collection": "authors", "collection_id": "59j5y-3d634", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181113-112608952", "type": "article", "title": "Pressure shock fronts formed by ultra-fast shear cracks in viscoelastic materials", "author": [ { "family_name": "Gori", "given_name": "M.", "orcid": "0000-0002-7380-3723", "clpid": "Gori-Marcello" }, { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Spontaneously propagating cracks in solids emit both pressure and shear waves. When a shear crack propagates faster than the shear wave speed of the material, the coalescence of the shear wavelets emitted by the near-crack-tip region forms a shock front that significantly concentrates particle motion. Such a shock front should not be possible for pressure waves, because cracks should not be able to exceed the pressure wave speed in isotropic linear-elastic solids. In this study, we present full-field experimental measurements of dynamic shear cracks in viscoelastic polymers that result in the formation of a pressure shock front, in addition to the shear one. The apparent violation of classic theories is explained by the strain-rate-dependent material behavior of polymers, where the crack speed remains below the highest pressure wave speed prevailing locally around the crack tip. These findings have important implications for the physics and dynamics of shear cracks such as earthquakes.", "doi": "10.1038/s41467-018-07139-4", "pmcid": "PMC6232150", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2018-11-12", "volume": "9", "pages": "Art. No. 4754" }, { "id": "authors:y52z8-p2409", "collection": "authors", "collection_id": "y52z8-p2409", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170629-084215836", "type": "article", "title": "Understanding dynamic friction through spontaneously evolving laboratory earthquakes", "author": [ { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-Vito" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Friction plays a key role in how ruptures unzip faults in the Earth's crust and release waves that cause destructive shaking. Yet dynamic friction evolution is one of the biggest uncertainties in earthquake science. Here we report on novel measurements of evolving local friction during spontaneously developing mini-earthquakes in the laboratory, enabled by our ultrahigh speed full-field imaging technique. The technique captures the evolution of displacements, velocities and stresses of dynamic ruptures, whose rupture speed range from sub-Rayleigh to supershear. The observed friction has complex evolution, featuring initial velocity strengthening followed by substantial velocity weakening. Our measurements are consistent with rate-and-state friction formulations supplemented with flash heating but not with widely used slip-weakening friction laws. This study develops a new approach for measuring local evolution of dynamic friction and has important implications for understanding earthquake hazard since laws governing frictional resistance of faults are vital ingredients in physically-based predictive models of the earthquake source.", "doi": "10.1038/ncomms15991", "pmcid": "PMC5493769", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2017-06-28", "volume": "8", "pages": "Art. No. 15991" }, { "id": "authors:ctw5v-4sa64", "collection": "authors", "collection_id": "ctw5v-4sa64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170303-135644069", "type": "article", "title": "Experimental evidence that thrust earthquake ruptures might open faults", "author": [ { "family_name": "Gabuchian", "given_name": "Vahe", "clpid": "Gabuchian-V" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Bhat", "given_name": "Harsha S.", "clpid": "Bhat-H-S" }, { "family_name": "Madariaga", "given_name": "Ra\u00fal", "orcid": "0000-0003-2524-9489", "clpid": "Madariaga-R" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "abstract": "Many of Earth's great earthquakes occur on thrust faults. These earthquakes predominantly occur within subduction zones, such as the 2011 moment magnitude 9.0 eathquake in Tohoku-Oki, Japan, or along large collision zones, such as the 1999 moment magnitude 7.7 earthquake in Chi-Chi, Taiwan. Notably, these two earthquakes had a maximum slip that was very close to the surface. This contributed to the destructive tsunami that occurred during the Tohoku-Oki event and to the large amount of structural damage caused by the Chi-Chi event. The mechanism that results in such large slip near the surface is poorly understood as shallow parts of thrust faults are considered to be frictionally stable. Here we use earthquake rupture experiments to reveal the existence of a torquing mechanism of thrust fault ruptures near the free surface that causes them to unclamp and slip large distances. Complementary numerical modelling of the experiments confirms that the hanging-wall wedge undergoes pronounced rotation in one direction as the earthquake rupture approaches the free surface, and this torque is released as soon as the rupture breaks the free surface, resulting in the unclamping and violent 'flapping' of the hanging-wall wedge. Our results imply that the shallow extent of the seismogenic zone of a subducting interface is not fixed and can extend up to the trench during great earthquakes through a torquing mechanism.", "doi": "10.1038/nature22045", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2017-05-18", "series_number": "7654", "volume": "545", "issue": "7654", "pages": "336-339" }, { "id": "authors:kvn0y-wzb13", "collection": "authors", "collection_id": "kvn0y-wzb13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160909-080901162", "type": "article", "title": "Spatiotemporal properties of Sub-Rayleigh and supershear rupture velocity fields: Theory and experiments", "author": [ { "family_name": "Mello", "given_name": "Michael", "orcid": "0000-0003-2129-9235", "clpid": "Mello-M" }, { "family_name": "Bhat", "given_name": "Harsha S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-S" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Fundamental spatiotemporal field properties and particle velocity waveform signatures of sub-Rayleigh and supershear ruptures were experimentally investigated through a series of laboratory earthquake experiments. We appeal to dynamic rupture theory to extract and highlight previously unnoticed aspects and results, which are of direct relevance to our new experiments. Kinematic relationships derived from both singular and non-singular solutions are applied to analyze and interpret various features observed in these experiments.\n\nA strong correspondence is demonstrated between particle velocity records obtained in lab experiments and synthetic particle velocity waveform profiles derived from theory. Predicted temporal profiles, sense of particle motion, and amplitude decay properties of sub-Rayleigh and supershear particle velocity waveforms are experimentally verified. In a particular set of supershear rupture experiments, the fault-normal (FN) and fault-parallel (FP) velocity waveforms were simultaneously recorded at fixed, off-fault field points as a shear Mach front swept these locations. Particle velocity records collected over a broad range of stable supershear rupture speeds validate the predicted scaling relationship \u03b4u_1s/\u03b4u_2s = \u221aV_r^2/C_s^2\u22121=\u03b2_s, between the FP (\u03b4u_1^\u1e61) and the FN (\u03b4u_2^\u1e61) velocity jumps propagated by a shear Mach front. Additional experimental findings include detailed rupture speed measurements of sub-Rayleigh and supershear ruptures and the observation of a supershear daughter crack with vanishing shear Mach front.\n\nPreviously unappreciated scaling relations between particle velocity field components, attributed to dilatational and shear waves, are also developed and experimentally verified. In particular, the FP velocity jump \u03b4u_1^\u1e61(x_1,x_2) propagated by the shear Mach front, and the sliding speed \u03b4u_1(x_1,0^+), measured at a field point positioned extremely close to the frictional fault plane, are shown to obey a speed-dependent scaling relationship given by \u03b4u_1^s/\u03b4u_1^+ = 1 \u2212 2^(Cs2)/_(Vr2), which was gleaned from a non-singular, steady state velocity field solution.", "doi": "10.1016/j.jmps.2016.02.031", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2016-08", "volume": "93", "pages": "153-181" }, { "id": "authors:fcdba-ht686", "collection": "authors", "collection_id": "fcdba-ht686", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150402-135439354", "type": "article", "title": "Static Laboratory Earthquake Measurements with the Digital Image Correlation Method", "author": [ { "family_name": "Rubino", "given_name": "V.", "orcid": "0000-0002-4023-8668", "clpid": "Rubino-V" }, { "family_name": "Lapusta", "given_name": "N.", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Leprince", "given_name": "S.", "orcid": "0000-0003-4555-8975", "clpid": "Leprince-S" }, { "family_name": "Avouac", "given_name": "J. P.", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" } ], "abstract": "Mapping full-field displacement and strain changes on the Earth's surface following an earthquake is of paramount importance to enhance our understanding of earthquake mechanics. Currently, aerial and satellite images taken pre- and post-earthquake can be processed with sub-pixel correlation algorithms to infer the co-seismic ground deformations (e.g., [1, 2]). However, the interpretation of this data is not straightforward due to the inherent complexity of natural faults and deformation fields. To gain understanding into rupture mechanics and to help interpret complex rupture features occurring in nature, we develop a laboratory earthquake setup capable of reproducing displacement and strain maps similar to those obtained in the field, while maintaining enough simplicity so that clear conclusions can be drawn. Earthquakes are mimicked in the laboratory by dynamic rupture propagating along an inclined frictional interface formed by two Homalite plates under compression (e.g., [3]). In our study, the interface is partially glued, in order to confine the rupture before it reaches the ends of the specimen. The specimens are painted with a speckle pattern to provide the surface with characteristic features for image matching. Images of the specimens are taken before and after dynamic rupture with a 4 Megapixels resolution CCD camera. The digital images are analyzed with two software packages for sub-pixel correlation: VIC-2D (Correlated Solutions Inc.) and COSI-Corr. Both VIC-2D and COSI-Corr are able to characterize the full-field static displacement of the experimentally produced dynamic shear ruptures. The correlation analysis performed with either software clearly shows (i) the relative displacement (slip) along the frictional interface, (ii) the rupture arrest on the glued boundaries, and (iii) the presence of wing cracks. The obtained displacement measurements are converted to strains, using non-local de-noising techniques; stresses are obtained by introducing Homalite's constitutive properties. This study is a first step towards using the digital image correlation method in combination with high-speed photography to capture the highly transient phenomena involved in dynamic rupture.", "doi": "10.1007/s11340-014-9893-z", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2015-01", "series_number": "1", "volume": "55", "issue": "1", "pages": "77-94" }, { "id": "authors:8sfcn-79y08", "collection": "authors", "collection_id": "8sfcn-79y08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150320-155256012", "type": "article", "title": "Pressure-Dependent, Infrared-Emitting Phenomenon in Hypervelocity Impact", "author": [ { "family_name": "Mihaly", "given_name": "Jonathan M.", "clpid": "Mihaly-J-M" }, { "family_name": "Tandy", "given_name": "Jonathan D.", "clpid": "Tandy-J-D" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Adams", "given_name": "M. A.", "clpid": "Adams-M-A" }, { "family_name": "Pullin", "given_name": "D.", "orcid": "0009-0007-5991-2863", "clpid": "Pullin-D-I" } ], "abstract": "A series of hypervelocity impact experiments were conducted with variable target chamber atmospheric pressure ranging from 0.9 to 21.5\u2009Torr. Using a two-stage light-gas gun, 5.7\u2009mg nylon 6/6 right-cylinders were accelerated to speeds ranging between 6.0 and 6.3\u2009km/s to impact 1.5\u2009mm thick 6061-T6 aluminum plates. Full-field images of near-IR emission (0.9 to 1.7\u2009\u03bcm) were measured using a high-speed spectrograph system with image exposure times of 1\u2009\u03bcs. The radial expansion of an IR-emitting impact-generated phenomenon was observed to be dependent upon the ambient target chamber atmospheric pressures. Higher chamber pressures demonstrated lower radial expansions of the subsequently measured IR-emitting region uprange of the target. Dimensional analysis, originally presented by Taylor to describe the expansion of a hemispherical blast wave, is applied to describe the observed pressure-dependence of the IR-emitting cloud expansion. Experimental results are used to empirically determine two dimensionless constants for the analysis. The maximum radial expansion of the observed IR-emitting cloud is described by the Taylor blast-wave theory, with experimental results demonstrating the characteristic nonlinear dependence on atmospheric pressure. Furthermore, the edges of the measured IR-emitting clouds are observed to expand at extreme speeds ranging from approximately 13 to 39\u2009km/s. In each experiment, impact ejecta and debris are simultaneously observed in the visible range using an ultrahigh-speed laser shadowgraph system. For the considered experiments, ejecta and debris speeds are measured between 0.6 and 5.1\u2009km/s. Such a disparity in observed phenomena velocities suggests the IR-emitting cloud is a distinctly different phenomenon to both the uprange ejecta and downrange debris generated during a hypervelocity impact.", "doi": "10.1115/1.4028856", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2015-01", "series_number": "1", "volume": "82", "issue": "1", "pages": "Art. No. 011004" }, { "id": "authors:4nyap-rys62", "collection": "authors", "collection_id": "4nyap-rys62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140911-100018539", "type": "article", "title": "Examining the temporal evolution of hypervelocity impact phenomena via high-speed imaging and ultraviolet-visible emission spectroscopy", "author": [ { "family_name": "Tandy", "given_name": "J. D.", "clpid": "Tandy-J-D" }, { "family_name": "Mihaly", "given_name": "J. M.", "clpid": "Mihaly-J-M" }, { "family_name": "Adams", "given_name": "M. A.", "clpid": "Adams-M-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The temporal evolution of a previously observed hypervelocity impact-induced vapor cloud [Mihaly et al., Int. J. Impact Eng. 62, 13 (2013)] was measured by simultaneously recording several full-field, near-IR images of the resulting emission using an OMA-V high-speed camera. A two-stage light-gas gun was used to accelerate 5\u2009mg Nylon 6/6 right-cylinders to speeds between 5\u2009km/s and 7\u2009km/s to impact 1.5\u2009mm thick 6061-T6 aluminum target plates. Complementary laser-side-lighting [Mihaly et al ., Int. J. Impact Eng. 62, 13 (2013); Proc. Eng. 58, 363 (2013)] and front-of-target (without laser illumination) images were also captured using a Cordin ultra-high-speed camera. The rapid expansion of the vapor cloud was observed to contain a bright, emitting exterior, and a darker, optically thick interior. The shape of this phenomenon was also observed to vary considerably between experiments due to extremely high-rate (>250\u2009000\u2009rpm) of tumbling of the cylindrical projectiles. Additionally, UV-vis emission spectra were simultaneously recorded to investigate the temporal evolution of the atomic and molecular composition of the up-range, impact-induced vapor plume. A PI-MAX3 high-speed camera coupled to an Acton spectrograph was utilized to capture the UV-vis spectra, which shows an overall peak in emission intensity between approximately 6\u201310\u2009\u03bcs after impact trigger, corresponding to an increased quantity of emitting vapor/plasma passing through the spectrometer slit during this time period. The relative intensity of the numerous spectral bands was also observed to vary according to the exposure delay of the camera, indicating that the different atomic/molecular species exhibit a varied temporal evolution during the vapor cloud expansion. Higher resolution spectra yielded additional emission lines/bands that provide further evidence of interaction between fragmented projectile material and the 1\u2009mmHg atmosphere inside the target chamber. A comparison of the data to down-range emission spectra also revealed differences in the relative intensities of the atomic/molecular composition of the observed vapor clouds.", "doi": "10.1063/1.4890230", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "2014-07-21", "series_number": "3", "volume": "116", "issue": "3", "pages": "Art. No. 034901" }, { "id": "authors:f6n6q-38m42", "collection": "authors", "collection_id": "f6n6q-38m42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140313-082925394", "type": "article", "title": "Reproducing the supershear portion of the 2002 Denali earthquake rupture in laboratory", "author": [ { "family_name": "Mello", "given_name": "M.", "orcid": "0000-0003-2129-9235", "clpid": "Mello-M" }, { "family_name": "Bhat", "given_name": "H. S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-S" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kanamori", "given_name": "H.", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "abstract": "A notable feature of the 2002 View the M_w 7.9 Denali, Alaska, earthquake was that a unique set of near-field seismic ground motion records, at Pump Station 10 (PS10), captured the passage of a supershear rupture followed by what was surmised to be a secondary slip pulse, 'Trailing Rayleigh Pulse' (Dunham and Archuleta, 2004 and Mello et al., 2010). Motivated by the unique features contained in these near-field ground motion records, which were obtained only 3 km away from the fault, a series of scaled laboratory earthquake experiments was conducted in an attempt to replicate the dominant features of the PS10 ground motion signatures. Particle velocity records bearing a striking similarity to the Denali ground motion records are presented and discussed. The success of the comparison opens up the possibility of routinely generating near source ground motion records in a scaled and controlled laboratory setting that could be of great societal interest towards assessing seismic hazard from large and potentially devastating earthquakes.", "doi": "10.1016/j.epsl.2013.11.030", "issn": "0012-821X", "publisher": "Elsevier", "publication": "Earth and Planetary Science Letters", "publication_date": "2014-02-01", "volume": "387", "pages": "89-96" }, { "id": "authors:nnzw3-15242", "collection": "authors", "collection_id": "nnzw3-15242", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140613-101245398", "type": "article", "title": "Experimental investigation of strong ground motion due to thrust fault earthquakes", "author": [ { "family_name": "Gabuchian", "given_name": "Vahe", "clpid": "Gabuchian-V" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Oglesby", "given_name": "David D.", "clpid": "Oglesby-D-D" } ], "abstract": "Thrust fault earthquakes are studied in a laboratory earthquake setup previously used to investigate analog strike-slip seismic events. Dynamic mode II ruptures are generated along preexisting faults in an analog material, Homalite H-100, and their interaction with the free surface is studied for both sub-Rayleigh and supershear rupture speeds. High-speed digital photography and laser velocimeter diagnostics are used synergistically to identify and study the ground velocity signatures caused by the various features of the generated ruptures. The obtained surface-normal motions of both sub-Rayleigh and supershear ruptures show substantial asymmetry between the hanging and footwall, with the hanging wall experiencing much larger velocity amplitudes. The main features of the surface velocity traces at various stations can be explained by the calculated arrivals of various waves and fronts\u2014Mach cones, Pand S waves, and sub-Rayleigh features. In both the sub-Rayleigh and supershear cases, the arrival of the rupture tip generates a prominent Rayleigh wave traveling along the simulated Earth's surface. Supershear events feature larger amplitudes of ground shaking profiles. All signatures in the surface motion records attenuate and broaden with increasing distance from the fault trace. The signatures corresponding to the arrival of the Mach fronts attenuate with distance at a slower rate than those from sub-Rayleigh ruptures. The arrival of the updip supershear rupture at the free surface creates a downdip propagating slip feature with its own Mach cone. These additional Mach fronts further amplify ground shaking on the hanging and footwalls.", "doi": "10.1002/2013JB010409", "issn": "2169-9313", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research. Solid Earth", "publication_date": "2014-02", "series_number": "2", "volume": "119", "issue": "2", "pages": "1316-1336" }, { "id": "authors:ah1ax-8d891", "collection": "authors", "collection_id": "ah1ax-8d891", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131024-152446516", "type": "article", "title": "In situ diagnostics for a small-bore hypervelocity impact facility", "author": [ { "family_name": "Mihaly", "given_name": "J. M.", "clpid": "Mihaly-J-M" }, { "family_name": "Tandy", "given_name": "J. D.", "clpid": "Tandy-J-D" }, { "family_name": "Adams", "given_name": "M. A.", "clpid": "Adams-M-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "New in situ diagnostic capabilities and improvements made to the previously reported 1.8 mm bore, two-stage light-gas gun facility located at the California Institute of Technology are described. The Small Particle Hypervelocity Impact Range (SPHIR) facility is capable of routinely producing launch speeds of 5\u20137 km/s for launch package masses < 6 mg, with maximum speeds exceeding 10 km/s. The facility features a comprehensive ensemble of in situ diagnostics that are available for simultaneous implementation in every impact experiment. A fast (150,000 fps) camera is used routinely to provide impactor velocimetry. A gated, intensified ultra-high-speed camera is used in conjunction with an optical technique to create shadowgraph images of hypervelocity impact phenomena with very short exposure times (25 ns) and inter-frame times (<1 \u03bcs). This technique uses a constant 532 nm wavelength laser to deliver a collimated, coherent illumination beam orthogonal to the projectile flight direction that provides a 100 mm diameter maximum field of view. The ultra-high-speed camera produces 8 images with exposure and inter-frame times sufficiently short to enable sharp visualization of impact features with little motion blur at the test speeds of 5\u20137 km/s. Additionally, a debris capture system is located behind the target configuration during every experiment. This system is composed of layers of closed-cell foam and plastic film and provides depth of penetration and trajectory measurement for debris particles thrown behind the target. Lastly, the SPHIR facility utilizes two additional high-speed cameras coupled with two spectrographs to characterize the light emitted by the impact event. One spectrograph and its high-speed camera records UV\u2013visible emission spectra in the wavelength range between 300 nm and 850 nm. The other spectrograph uses a high-speed, infrared camera to capture a single full-field image of the near-IR emission in the wavelength range of 0.9 \u03bcm\u20131.7 \u03bcm. These two spectrograph camera systems provide both visual and spectral data of the hypervelocity impact emission; yielding information regarding the molecular composition of both the impact ejecta and debris. The extensive diagnostic capabilities and techniques described can be used with a wide variety of impactors, target materials and target configurations to address a wide variety of engineering and scientific problems.", "doi": "10.1016/j.ijimpeng.2013.05.004", "issn": "0734-743X", "publisher": "Elsevier", "publication": "International Journal of Impact Engineering", "publication_date": "2013-12", "volume": "62", "pages": "13-26" }, { "id": "authors:kag08-dx320", "collection": "authors", "collection_id": "kag08-dx320", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131115-115806236", "type": "article", "title": "Three-dimensional Displacement and Shape Measurement with a Diffraction-assisted Grid Method", "author": [ { "family_name": "Notbohm", "given_name": "J.", "clpid": "Notbohm-J" }, { "family_name": "Rosakis", "given_name": "A.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kumagai", "given_name": "S.", "clpid": "Kumagai-S" }, { "family_name": "Xia", "given_name": "S.", "clpid": "Xia-S" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "The grid method is a full-field optical technique for computing surface displacements and strains of a material by analyzing the phase of grid lines patterned on the specimen. To date, most experiments using the grid method have measured only two-dimensional in-plane deformations. Here, the grid method is extended to three dimensions by using a crossed grid pattern and a diffraction grating which enables acquiring images from multiple viewing angles on a single camera. In-plane displacements and strains are computed using the conventional grid method, and the corresponding three-dimensional (3D) displacements\u2014including out-of-plane displacements or shapes\u2014are computed by analyzing the images collected at different viewing angles. The technique is demonstrated by measuring 3D rigid body motion, the 3D displacements of a membrane in a pressure-bulge experiment, and the out-of-plane curvature of a cylindrical specimen.", "doi": "10.1111/str.12046", "issn": "0039-2103", "publisher": "Wiley-Blackwell", "publication": "Strain: An International Journal for Experimental Mechanics", "publication_date": "2013-10", "series_number": "5", "volume": "49", "issue": "5", "pages": "399-408" }, { "id": "authors:qwsjr-r6q09", "collection": "authors", "collection_id": "qwsjr-r6q09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130619-145739093", "type": "article", "title": "Large scale Optimal Transportation Meshfree (OTM) Simulations of\n Hypervelocity Impact", "author": [ { "family_name": "Li", "given_name": "B.", "orcid": "0000-0002-8019-8891", "clpid": "Li-Bo" }, { "family_name": "Perotti", "given_name": "L.", "clpid": "Perotti-L-E" }, { "family_name": "Adams", "given_name": "M.", "clpid": "Adams-M" }, { "family_name": "Mihaly", "given_name": "J.", "clpid": "Mihaly-J" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Stalzer", "given_name": "M.", "clpid": "Stalzer-M" }, { "family_name": "Ortiz", "given_name": "Michael", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" } ], "abstract": "Large scale three-dimensional numerical simulations of hypervelocity impact of Aluminum alloy 6061-T6 plates by Nylon 6/6 cylindrical\nprojectile have been performed using the Optimal Transportation Meshfree (OTM) method of Li et al. [7] along with the seizing contact\nand variational material point failure algorithm [17, 18]. The dynamic response of the Al6061-T6 plate including phase transition in the\nhigh strain rate, high pressure and high temperature regime expected in our numerical analysis is described by the use of a variational\nthermomechanical coupling constitutive model with SESAME equation of state, rate-dependent J2 plasticity with power law hardening\nand thermal softening and temperature dependent Newtonian viscosity. A polytropic type of equation of state fit to in-house ReaxFF\ncalculations is employed to model the Nylon 6/6 projectile under extreme conditions. The evaluation of the performance of the numerical\nmodel takes the form of a conventional validation analysis. In support of the analysis, we have conducted experiments over a range of\nplate thicknesses of [0.5, 3.0] mm, a range of impact velocities of [5.0, 7.0]km/s and a range of obliquities of [0, 70]\u00b0 at Caltech's Small\nParticle Hypervelocity Range (SPHIR) Facility. Large scale three-dimensional OTM simulations of hypervelocity impact are performed\non departmental class systems using a dynamic load balancing MPI/PThreads parallel implementation of the OTM method. We find\nexcellent full field agreement between measured and computed perforation areas, debris cloud and temperature field.", "doi": "10.1016/j.proeng.2013.05.036", "issn": "1877-7058", "publisher": "Elsevier", "publication": "Procedia Engineering", "publication_date": "2013", "volume": "58", "pages": "320-327" }, { "id": "authors:m8447-nyn62", "collection": "authors", "collection_id": "m8447-nyn62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130305-152759959", "type": "book_section", "title": "A Recursive Division Stochastic Strike-Slip Seismic\n Source Algorithm Using Insights from Laboratory\n Earthquakes", "author": [ { "family_name": "Siriki", "given_name": "H.", "clpid": "Siriki-Hemanth" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Krishnan", "given_name": "S.", "orcid": "0000-0002-2594-1523", "clpid": "Krishnan-Swaminathan" }, { "family_name": "Bhat", "given_name": "H. S.", "clpid": "Bhat-Harsha-S" }, { "family_name": "Lu", "given_name": "X.", "clpid": "Lu-Xiao" } ], "abstract": "There are a sparse number of credible source models available from past earthquakes and a stochastic source\nmodel generation algorithm thus becomes necessary for robust risk quantification using scenario earthquakes.\nWe present an algorithm that combines the physics of fault rupture as imaged in laboratory earthquakes with\nstress estimates on the fault constrained by field observations to generate probability distributions of rise-time\nand rupture-speed for strike-slip earthquakes. The algorithm is validated through a statistical comparison of peak\nground velocity at 636 sites in Southern California from synthetic ground motion histories simulated for 10\nrupture scenarios using a stochastically generated source model against that generated using a kinematic source\nmodel from a finite source inversion. This model, selected from a set of 5 stochastically generated source\nmodels, produces ground shaking intensities in Southern California with a median that is closest to the median\nintensity of shaking from all 5 source models (and 10 rupture scenarios per model).", "publisher": "International Association for Earthquake Engineering", "publication_date": "2012-09" }, { "id": "authors:h0xd7-kna24", "collection": "authors", "collection_id": "h0xd7-kna24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120521-084037755", "type": "article", "title": "A Micromechanics Based Constitutive Model for Brittle Failure at High Strain Rates", "author": [ { "family_name": "Bhat", "given_name": "Harsha S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-Suresh" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Sammis", "given_name": "Charles G.", "clpid": "Sammis-C-G" } ], "abstract": "The micromechanical damage mechanics formulated by Ashby and Sammis, 1990, \"The Damage Mechanics of Brittle Solids in Compression,\" Pure Appl. Geophys., 133(3), pp. 489\u2013521, and generalized by Deshpande and Evans 2008, \"Inelastic Deformation and Energy Dissipation in Ceramics: A Mechanism-Based Constitutive Model,\" J. Mech. Phys. Solids, 56(10), pp. 3077\u20133100. has been extended to allow for a more generalized stress state and to incorporate an experimentally motivated new crack growth (damage evolution) law that is valid over a wide range of loading rates. This law is sensitive to both the crack tip stress field and its time derivative. Incorporating this feature produces additional strain-rate sensitivity in the constitutive response. The model is also experimentally verified by predicting the failure strength of Dionysus-Pentelicon marble over strain rates ranging from ~10^(\u22126) to 10^3s^(\u22121). Model parameters determined from quasi-static experiments were used to predict the failure strength at higher loading rates. Agreement with experimental results was excellent.", "doi": "10.1115/1.4005897", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2012-05", "series_number": "3", "volume": "79", "issue": "3", "pages": "Art. No. 031016" }, { "id": "authors:at0kp-sq105", "collection": "authors", "collection_id": "at0kp-sq105", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120430-133945935", "type": "article", "title": "Rigorous model-based uncertainty quantification with application to terminal ballistics\u2014Part II. Systems with uncontrollable inputs and large scatter", "author": [ { "family_name": "Adams", "given_name": "M.", "clpid": "Adams-M" }, { "family_name": "Lashgari", "given_name": "A.", "clpid": "Lashgari-A" }, { "family_name": "Li", "given_name": "B.", "clpid": "Li-B" }, { "family_name": "McKerns", "given_name": "M.", "clpid": "McKerns-M" }, { "family_name": "Mihaly", "given_name": "J.", "clpid": "Mihaly-J" }, { "family_name": "Ortiz", "given_name": "M.", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Owhadi", "given_name": "H.", "orcid": "0000-0002-5677-1600", "clpid": "Owhadi-H" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Stalzer", "given_name": "M.", "clpid": "Stalzer-M" }, { "family_name": "Sullivan", "given_name": "T. J.", "clpid": "Sullivan-T-J" } ], "abstract": "This Part II of this series is concerned with establishing the feasibility of an extended data-on-demand (XDoD) uncertainty quantification (UQ) protocol based on concentration-of-measure inequalities and martingale theory. Specific aims are to establish the feasibility of the protocol and its basic properties, including the tightness of the predictions afforded by the protocol. The assessment is based on an application to terminal ballistics and a specific system configuration consisting of 6061-T6 aluminum plates struck by spherical 440c stainless steel projectiles at ballistic impact speeds in the range of 2.4\u20132.8 km/s. The system's inputs are the plate thickness, plate obliquity and impact velocity. The perforation area is chosen as the sole performance measure of the system. The objective of the UQ analysis is to certify the lethality of the projectile, i.e., that the projectile perforates the plate with high probability over a prespecified range of impact velocities, plate thicknesses and plate obliquities. All tests were conducted at Caltech's Small Particle Hypervelocity Range (SPHIR), which houses a two-stage gas gun. A feature of this facility is that the impact velocity, while amenable to precise measurement, cannot be controlled precisely but varies randomly according to a known probability density function. In addition, due to a competition between petalling and plugging mechanisms for the material system under consideration, the measured perforation area exhibits considerable scatter. The analysis establishes the feasibility of the XDoD UQ protocol as a rigorous yet practical approach for model-based certification of complex systems characterized by uncontrollable inputs and noisy experimental data.", "doi": "10.1016/j.jmps.2011.12.002", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2012-05", "series_number": "5", "volume": "60", "issue": "5", "pages": "1002-1019" }, { "id": "authors:tzqke-b1x63", "collection": "authors", "collection_id": "tzqke-b1x63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120222-085327488", "type": "article", "title": "Off-fault tensile cracks: A link between geological fault observations, lab experiments, and dynamic rupture models", "author": [ { "family_name": "Ngo", "given_name": "D.", "clpid": "Ngo-Duc" }, { "family_name": "Huang", "given_name": "Y.", "clpid": "Huang-Y" }, { "family_name": "Rosakis", "given_name": "A.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Griffith", "given_name": "W. A.", "clpid": "Griffith-W-A" }, { "family_name": "Pollard", "given_name": "D.", "clpid": "Pollard-D" } ], "abstract": "We examine the local nature of the dynamic stress field in the vicinity of the tip of a semi-infinite sub-Rayleigh (slower than the Rayleigh wave speed, c_R) mode II crack with a velocity-weakening cohesive zone. We constrain the model using results from dynamic photoelastic experiments, in which shear ruptures were nucleated spontaneously in Homalite-100 plates along a bonded, precut, and inclined interface subject to a far-field uniaxial prestress. During the experiments, tensile cracks grew periodically along one side of the shear rupture interface at a roughly constant angle relative to the shear rupture interface. The occurrence and inclination of the tensile cracks are explained by our analytical model. With slight modifications, the model can be scaled to natural faults, providing diagnostic criteria for interpreting velocity, directivity, and static prestress state associated with past earthquakes on exhumed faults. Indirectly, this method also allows one to constrain the velocity-weakening nature of natural ruptures, providing an important link between field geology, laboratory experiments, and seismology.", "doi": "10.1029/2011JB008577", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2012-01-20", "series_number": "B1", "volume": "117", "issue": "B1", "pages": "Art. No. B01307" }, { "id": "authors:kjrbw-h2e32", "collection": "authors", "collection_id": "kjrbw-h2e32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190828-102318872", "type": "book_section", "title": "Feasibility of Non-Equilibrium Hypersonic Flow Measurements at the Small Particle Hypervelocity Impact Range", "book_title": "50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition", "author": [ { "family_name": "Alexeenko", "given_name": "A. A.", "clpid": "Alexeenko-Alina-A" }, { "family_name": "Kulakhmetov", "given_name": "M.", "clpid": "Kulakhmetov-Marat" }, { "family_name": "Weaver", "given_name": "A.", "clpid": "Weaver-Andrew" }, { "family_name": "Slipchenko", "given_name": "M. N.", "clpid": "Slipchenko-M-N" }, { "family_name": "Mihaly", "given_name": "J.", "clpid": "Mihaly-J-M" }, { "family_name": "Adams", "given_name": "M.", "clpid": "Adams-Marc" }, { "family_name": "Rosakis", "given_name": "A.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Currently used hypersonic flow models, such as high-enthalpy reaction and energy relaxation rates, are based on experiments conducted at relatively low flow enthalpies and are highly uncertain. This paper presents analysis of the feasibility of calibrating hypersonic flow parameters using free-flight experiments at the Small Particle Hypervelocity Range (SPHIR) at Caltech/JPL. Chemically reacting, nonequilibrium flows around a 2-mm diameter spherical projectile are modeled using the Direct Simulation Monte Carlo (DSMC) method. The flowfields generated by DSMC simulations are used to calculate emission spectra in order to determine the observable radiation in UV/vis spectral range. Bayesian calibration and generalized polynomial chaos expansion (gPCE) techniques are used to assess the sensitivity of observable flow properties to key reaction rates. These techniques are then used to predict how experimental resolution would affect the uncertainty in the calibrated parameters.", "doi": "10.2514/6.2012-596", "isbn": "9781600869365", "publisher": "American Institute of Aeronautics and Astronautics", "place_of_publication": "Reston, VA", "publication_date": "2012-01-09", "pages": "Art. No. 2012-0596" }, { "id": "authors:w1c0b-nxa29", "collection": "authors", "collection_id": "w1c0b-nxa29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111212-072520072", "type": "article", "title": "The Micromechanics of Westerley Granite at Large Compressive Loads", "author": [ { "family_name": "Bhat", "given_name": "H. S.", "clpid": "Bhat-H-S" }, { "family_name": "Sammis", "given_name": "C. G.", "clpid": "Sammis-C-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The micromechanical damage mechanics formulated by Ashby and Sammis (Pure Appl Geophys 133(3) 489\u2013521, 1990) has been shown to give an adequate description of the triaxial failure surface for a wide variety of rocks at low confining pressure. However, it does not produce the large negative curvature in the failure surface observed in Westerly granite at high confining pressure. We show that this discrepancy between theory and data is not caused by the two most basic simplifying assumptions in the damage model: (1) that all the initial flaws are the same size or (2) that they all have the same orientation relative to the largest compressive stress. We also show that the stress\u2013strain curve calculated from the strain energy density significantly underestimates the nonlinear strain near failure in Westerly granite. Both the observed curvature in the failure surface and the nonlinear strain at failure observed in Westerly granite can be quantitatively fit using a simple bi-mineral model in which the feldspar grains have a lower flow stress than do the quartz grains. The conclusion is that nonlinearity in the failure surface and stress\u2013strain curves observed in triaxial experiments on Westerly granite at low loading rates is probably due to low-temperature dislocation flow and not simplifying assumptions in the damage mechanics. The important implication is that discrepancies between experiment and theory should decrease with increased loading rates, and therefore, the micromechanical damage mechanics, as formulated, can be expected to give an adequate description of high strain-rate phenomena like earthquake rupture, underground explosions, and meteorite impact.", "doi": "10.1007/s00024-011-0271-9", "issn": "0033-4553", "publisher": "Springer", "publication": "Pure and Applied Geophysics", "publication_date": "2011-12", "series_number": "12", "volume": "168", "issue": "12", "pages": "2181-2198" }, { "id": "authors:69vcc-ygz09", "collection": "authors", "collection_id": "69vcc-ygz09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-132645095", "type": "book_section", "title": "In-situ Optical Investigations of Hypervelocity Impact Induced Dynamic Fracture", "book_title": "Dynamic Behavior of Materials", "author": [ { "family_name": "Lamberson", "given_name": "Leslie E.", "clpid": "Lamberson-L-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Eliasson", "given_name": "Veronica", "clpid": "Eliasson-V" } ], "contributor": [ { "family_name": "Proulx", "given_name": "Tom", "clpid": "Proulx-T" } ], "abstract": "Two independent optical methods are used to analyze the dynamic material behavior of Mylar and Homalite-100 subjected to hypervelocity impact. Birefringent targets are loaded in tension inside a two-stage light-gas gun vacuum chamber, and are impacted with a 5 mg nylon slug at velocities between 3 and 6 km/s. Caustics and photoelasticity combined with high-speed photography are used to determine dynamic stress intensity behavior around the crack tip during and after impact. Homalite-100 lower crack tip speeds are subjected to reflecting boundary shear waves from the nylon impact, and thereby the crack path exhibits distinct kinks; whereas Mylar higher crack tip speeds provides distinguishable isochromatic patterns and an unadulterated fracture surface. Shear wave patterns in the target from photoelastic effects are compared to results from numerical simulations using the Overture Suite, which solves linear elasticity equations on overlapping curvilinear grids by means of adaptive mesh refinement.", "doi": "10.1007/978-1-4419-8228-5_6", "isbn": "978-1-4419-8227-8", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "2011-01-25", "pages": "31-37" }, { "id": "authors:0qmj4-bxd18", "collection": "authors", "collection_id": "0qmj4-bxd18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110104-111925811", "type": "article", "title": "Rupture modes in laboratory earthquakes: Effect of fault prestress and nucleation conditions", "author": [ { "family_name": "Lu", "given_name": "Xiao", "clpid": "Lu-Xiao" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" } ], "abstract": "Seismic inversions show that earthquake risetimes may be much shorter than the overall rupture duration, indicating that earthquakes may propagate as self-healing, pulse-like ruptures. Several mechanisms for producing pulse-like ruptures have been proposed, including velocity-weakening friction, interaction of dynamic rupture with fault geometry and local heterogeneity, and effect of bimaterial contrast. We present experimental results on rupture mode selection in laboratory earthquakes occurring on frictional interfaces, which were prestressed both in compression and in shear. Our experiments demonstrate that pulse-like ruptures can exist in the absence of a bimaterial effect or of local heterogeneities. We find a systematic variation from crack-like to pulse-like rupture modes with both (1) decreasing nondimensional shear prestress and (2) decreasing absolute levels of shear and normal prestress for the same value of nondimensional shear prestress. Both pulse-like and crack-like ruptures can propagate with either sub-Rayleigh or supershear rupture speeds. Our experimental results are consistent with theories of ruptures on velocity-weakening interfaces, implying that velocity-weakening friction plays an important role in governing the dynamic behavior of earthquake ruptures. We show that there is no measurable fault-normal stress decrease on the fault plane due to the nucleation procedure employed in experiments, and hence, this is not a factor in the rupture mode selection. We find that pulse-like ruptures correspond to the levels of nondimensional shear prestress significantly lower than the static friction coefficient, suggesting that faults hosting pulse-like ruptures may operate at low levels of prestress compared to their static strength.", "doi": "10.1029/2009JB006833", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2010-12-01", "volume": "115", "pages": "Art. No. B12302" }, { "id": "authors:hpgmj-0yq23", "collection": "authors", "collection_id": "hpgmj-0yq23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101220-143207573", "type": "article", "title": "Identifying the unique ground motion signatures of supershear earthquakes: Theory and experiments", "author": [ { "family_name": "Mello", "given_name": "M.", "orcid": "0000-0003-2129-9235", "clpid": "Mello-M" }, { "family_name": "Bhat", "given_name": "H. S.", "orcid": "0000-0003-0361-1854", "clpid": "Bhat-Harsha-S" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kanamori", "given_name": "H.", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "abstract": "The near field ground motion signatures associated with sub-Rayleigh and supershear ruptures are investigated using the laboratory earthquake experiment originally developed by Rosakis and coworkers (Xia et al., 2004, 2005a; Lu et al., 2007; Rosakis et al., 2007). Heterodyne laser interferometers enable continuous, high bandwidth measurements of fault-normal (FN) and fault-parallel (FP) particle velocity \"ground motion\" records at discrete locations on the surface of a Homalite test specimen as a sub-Rayleigh or a supershear rupture sweeps along the frictional fault. Photoelastic interference fringes, acquired using high-speed digital photography, provide a synchronized, spatially resolved, whole field view of the advancing rupture tip and surrounding maximum shear stress field. Experimental results confirm that near field ground motion records associated with the passage of a sub-Rayleigh rupture are characterized by a FN velocity swing which dominates over the FP velocity swing. The situation is shown to reverse in the supershear rupture speed regime whereby the motion along the shear Mach front is characterized by a FP particle velocity swing which dominates over the FN velocity swing.\n\nAdditional distinguishing particle velocity signatures, consistent with theoretical and numerical predictions, and repeatedly observed in experimental records are (1) a pronounced peak in the FP velocity record, induced by the leading dilatational field, which sweeps the measurement station just prior to the arrival of the shear Mach front, and (2) a pronounced velocity swing in the FN record associated with the arrival of a \"trailing Rayleigh disturbance\", which sweeps the measurement station following passage of the shear Mach front. Each of these features are addressed in detail. We conclude by reexamining the 2002, M_w 7.9 Denali fault earthquake and the remarkable set of ground motion records obtained at Pump Station 10 (PS10), located approximately 85 km east of the epicenter and 3 km north of the fault along the Alaska Pipeline. Motivated by the analysis and thorough interpretation of these records by Dunham and Archuleta (2004, 2005), we attempt to replicate the Denali ground motion signatures using a laboratory earthquake experiment. The experiments feature a left (west) to right (east) propagating right lateral rupture within the Homalite test specimen with particle velocity data collected at a near-field station situated just above (north of) the fault, (on the compressional quadrant) in order to simulate the PS10 scenario. Both sub-Rayleigh and supershear laboratory earthquake experiments are conducted using the \"Denali PS10\" configuration in order to compare and contrast the resulting particle velocity signatures. Results from the supershear experiment capture the prominent FN and FP ground motion signatures and corresponding sense of particle motion revealed in the PS10 ground motion records. Most notably, the particle velocity records feature a dominant FP component coinciding with the arrival of the shear Mach front, followed by a pronounced velocity swing in the FN component coinciding with the passage of a trailing Rayleigh disturbance, as independently confirmed by the presence of these features and their noted arrival times in the synchronized photoelastic image sequence.", "doi": "10.1016/j.tecto.2010.07.003", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2010-10-18", "series_number": "3-4", "volume": "493", "issue": "3-4", "pages": "297-326" }, { "id": "authors:r1cgd-y6303", "collection": "authors", "collection_id": "r1cgd-y6303", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101220-093824979", "type": "article", "title": "The effect of asymmetric damage on dynamic shear rupture propagation II: With mismatch in bulk elasticity", "author": [ { "family_name": "Bhat", "given_name": "H. S.", "clpid": "Bhat-H-S" }, { "family_name": "Biegel", "given_name": "R. L.", "clpid": "Biegel-R-L" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Sammis", "given_name": "C. G.", "clpid": "Sammis-C-G" } ], "abstract": "We investigate asymmetric rupture propagation on an interface that combines a bulk elastic mismatch with a contrast in off-fault damage. Mode II ruptures propagating on the interface between thermally shocked (damaged) Homalite and polycarbonate plates were studied using high-speed photographs of the photoelastic fringes. The anelastic asymmetry introduced by damage is defined by 'T' and 'C' directions depending on whether the tensile or compressive lobe of the rupture tip stress concentration lies on the damaged side of the fault. The elastic asymmetry is commonly defined by '+' and '\u2212' directions where '+' is the direction of displacement of the more compliant material. Since damaged Homalite is stiffer than polycarbonate, the propagation directions in our experiments were 'T+' and 'C\u2212'. Theoretical and numerical studies predict that a shear rupture on an elastic bimaterial interfaces propagates in the '+' direction at the generalized Rayleigh wave speed or in some numerical cases at the P-wave speed of the stiffer material, P_(fast). We present the first experimental evidence for propagation at P_(fast) in the '+' direction for the bimaterial system undamaged Homalite in contact with polycarbonate. In the '\u2212' direction, both theory and experiments find ruptures in elastic bimaterials propagate either at sub-shear speed or at the P-wave speed of the softer material, P_(slow), depending on the loading conditions. We observe that the off-fault damage effect dominates the elastic bimaterial effect in dynamic rupture propagation. In the 'C\u2212' direction the rupture propagates at sub-shear to supershear speeds, as in undamaged bimaterial systems, reaching a maximum speed of P_(slow). In the 'T+' direction however the rupture propagates at sub-shear speeds or comes to a complete stop due to increased damaged activation (slip and opening along micro-cracks) which results in a reduction in stored elastic potential energy and energy dissipation. Biegel et al. (2010-this issue) found similar results for propagation on the interface between Homalite and damaged Homalite where rupture speeds were slowed or even stopped in the 'T\u2212' direction but were almost unaffected in the 'C+' direction.", "doi": "10.1016/j.tecto.2010.03.016", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2010-10-18", "series_number": "3-4", "volume": "493", "issue": "3-4", "pages": "263-271" }, { "id": "authors:xpgdv-d3k74", "collection": "authors", "collection_id": "xpgdv-d3k74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101220-094237516", "type": "article", "title": "The effect of asymmetric damage on dynamic shear rupture propagation I: No mismatch in bulk elasticity", "author": [ { "family_name": "Biegel", "given_name": "R. L.", "clpid": "Biegel-R-L" }, { "family_name": "Bhat", "given_name": "H. S.", "clpid": "Bhat-H-S" }, { "family_name": "Sammis", "given_name": "C. G.", "clpid": "Sammis-C-G" }, { "family_name": "Rosakis", "given_name": "A .J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "High-speed digital photography was used to study rupture propagation on the interface between transparent damaged and undamaged photoelastic plates. Bilateral ruptures were nucleated on pre-machined faults at an angle \u03b1 to the uniaxial loading axis. Stress concentration at the crack tips produced fringes in polarized laser light that allowed their positions to be measured in successive photos. We found that fracture damage introduces a strong asymmetry in propagation speed different from that expected due to the lower elastic stiffness in the damaged material alone. When the tensile lobe of a rupture tip propagated through the damaged material the velocity of that rupture was reduced or stopped. By contrast, when the compressive lobe of a rupture tip passed through the damage, the velocity of that rupture was unaffected by the damage. A physical interpretation is that passage of a tensile lobe through the damage expends energy by lowering the normal stress on pre-existing cracks thus allowing frictional sliding along the crack surfaces. When the compressive lobe of the rupture passes through the damage, compressive stresses prevent sliding, only minor energy is dissipated, and the damage has almost no effect on the velocity. This effect can produce asymmetric propagation for earthquake ruptures on slip surfaces near the edge of a highly damaged fault zone.", "doi": "10.1016/j.tecto.2010.03.020", "issn": "0040-1951", "publisher": "Elsevier", "publication": "Tectonophysics", "publication_date": "2010-10-18", "series_number": "3-4", "volume": "493", "issue": "3-4", "pages": "254-262" }, { "id": "authors:ffqs6-wcg77", "collection": "authors", "collection_id": "ffqs6-wcg77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101026-111445870", "type": "article", "title": "Experimental investigation of converging shocks in water with various confinement materials", "author": [ { "family_name": "Eliasson", "given_name": "V.", "clpid": "Eliasson-Veronica" }, { "family_name": "Mello", "given_name": "M.", "orcid": "0000-0003-2129-9235", "clpid": "Mello-M" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Dimotakis", "given_name": "P. E.", "clpid": "Dimotakis-P-E" } ], "abstract": "Fluid-solid coupling typically plays a negligible role in confined converging shocks in gases because of the rigidity of the surrounding material and large acoustic impedance mismatch of wave propagation between it and the gas. However, this is not true for converging shocks in a liquid. In the latter case, the coupling can not be ignored and properties of the surrounding material have a direct influence on wave propagation. In shock focusing in water confined in a solid convergent geometry, the shock in the liquid transmits to the solid and both transverse and longitudinal waves propagate in the solid. Shock focusing in water for three types of confinement materials has been studied experimentally with schlieren and photoelasticity optical techniques. A projectile from a gas gun impacts a liquid contained in a solid convergent geometry. The impact produces a shock wave in water that develops even higher pressure when focused in the vicinity of the apex. Depending on the confining material, the shock speed in the water can be slower, faster, or in between wave speeds in the solid. For solid materials with higher wave speeds than the shock in water, regions in the water is put in tension and cavitation occurs. Materials with slower wave speeds will deform easily.", "doi": "10.1007/s00193-010-0276-9", "issn": "0938-1287", "publisher": "Springer", "publication": "Shock Waves", "publication_date": "2010-10", "series_number": "5", "volume": "20", "issue": "5", "pages": "395-408" }, { "id": "authors:n7kpe-sfs51", "collection": "authors", "collection_id": "n7kpe-sfs51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100713-095100144", "type": "article", "title": "Pulse-like and crack-like dynamic shear ruptures on frictional interfaces: experimental evidence, numerical modeling, and implications", "author": [ { "family_name": "Lu", "given_name": "Xiao", "clpid": "Lu-Xiao" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Destructive large earthquakes occur as dynamic frictional ruptures along pre-existing interfaces (or faults) in the Earth's crust. One of the important issues in earthquake dynamics is the local duration of relative displacement or slip. Seismic inversions show that earthquakes may propagate as self-healing pulse-like ruptures, with local slip duration being much shorter than the overall rupture duration. Yet many classical models produce crack-like ruptures, with local slip durations comparable to the overall rupture duration. We study rupture modes in an experimental set up designed to mimic a fault prestressed both in compression and in shear. Our experiments demonstrate systematic variation from crack-like to pulse-like rupture modes as nondimensional shear prestress is decreased. The results of our experiments are consistent with theories of ruptures on interfaces with velocity-weakening friction. To consider the possibility that slip-weakening friction can also result in such rupture mode transition in the presence of the dynamic nucleation procedure employed by the experimental setup, we conduct numerical simulations with linear slip-weakening friction. In the simulations, we use the parameter regimes that were shown in previous studies to reproduce supershear transition distances obtained in the same experimental setup. We find that simulations with linear slip-weakening friction are unable to reproduce pulse-like ruptures, even in the presence of the dynamic initiation procedure. Our experimental results and simulations imply that velocity-weakening friction plays an important role in dynamic behavior of shear ruptures and needs to be included in earthquake models.", "doi": "10.1007/s10704-010-9479-4", "issn": "0376-9429", "publisher": "Springer", "publication": "International Journal of Fracture", "publication_date": "2010-05", "series_number": "1-2", "volume": "163", "issue": "1-2", "pages": "27-39" }, { "id": "authors:9sc8a-nxq87", "collection": "authors", "collection_id": "9sc8a-nxq87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091019-101819617", "type": "article", "title": "Effects of Off-fault Damage on Earthquake Rupture Propagation: Experimental Studies", "author": [ { "family_name": "Sammis", "given_name": "Charles G.", "clpid": "Sammis-C-G" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Bhat", "given_name": "Harsha S.", "clpid": "Bhat-H-S" } ], "abstract": "We review the results of a recent series of papers in which the interaction between a dynamic mode II fracture on a fault plane and off-fault damage has been studied using high-speed photography. In these experiments, fracture damage was created in photoelastic Homalite plates by thermal shock in liquid nitrogen and rupture velocities were measured by imaging fringes at the tips. In this paper we review these experiments and discuss how they might be scaled from lab to field using a recent theoretical model for dynamic rupture propagation. Three experimental configurations were investigated: An interface between two damaged Homalite plates, an interface between damaged and undamaged Homalite plates, and the interface between damaged Homalite and undamaged polycarbonate plates. In each case, the velocity was compared with that on a fault between the equivalent undamaged plates at the same load. Ruptures on the interface between two damaged Homalite plates travel at sub-Rayleigh velocities indicating that sliding on off-fault fractures dissipates energy, even though no new damage is created. Propagation on the interface between damaged and undamaged Homalite is asymmetric. Ruptures propagating in the direction for which the compressional lobe of their crack-tip stress field is in the damage (which we term the 'C' direction) are unaffected by the damage. In the opposite 'T' direction, the rupture velocity is significantly slower than the velocity in undamaged plates at the same load. Specifically, transitions to supershear observed using undamaged plates are not observed in the 'T' direction. Propagation on the interface between damaged Homalite and undamaged polycarbonate exhibits the same asymmetry, even though the elastically \"favored\" '+' direction coincides with the 'T' direction in this case. The scaling properties of the interaction between the crack-tip field and pre-existing off-fault damage (i.e., no new damage is created) are explored using an analytic model for a nonsingular slip-weakening shear slip-pulse and verified using the velocity history of a slip pulse measured in the laboratory and a direct laboratory measurement of the interaction range using damage zones of various widths adjacent to the fault.", "doi": "10.1007/s00024-009-0512-3", "issn": "0033-4553", "publisher": "Springer", "publication": "Pure and Applied Geophysics", "publication_date": "2009-10", "series_number": "10-11", "volume": "166", "issue": "10-11", "pages": "1629-1648" }, { "id": "authors:amscn-j3j41", "collection": "authors", "collection_id": "amscn-j3j41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090930-120351492", "type": "article", "title": "Dynamic rupture experiments elucidate tensile crack development during propagating earthquake ruptures", "author": [ { "family_name": "Griffith", "given_name": "W. Ashley", "clpid": "Griffith-W-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Pollard", "given_name": "David D.", "clpid": "Pollard-D-D" }, { "family_name": "Ko", "given_name": "Chi Wan", "clpid": "Ko-C-W" } ], "abstract": "We used optical experiments and high-speed photography to interpret the origins of tensile fractures that form during dynamic shear rupture in laboratory experiments. Sub-Rayleigh (slower than the Rayleigh wave speed, c_R) shear ruptures in Homalite-100 produce damage zones consisting of an array of tensile cracks. These cracks nucleate and grow within cohesive zones behind the tips of shear ruptures that propagate dynamically along interfaces with frictional and cohesive strength, simulating a \"strong\" fault. The tensile cracks are produced only along one side of the interface where transient, fault-parallel, tensile stress perturbations are associated with the growing shear rupture tip. Results of this study represent an important potential bridge between geological observations of structures preserved along exhumed faults and theoretical models of earthquake propagation, potentially leading to diagnostic criteria for interpreting velocity, directivity, and static prestress states associated with past earthquakes on exhumed faults.", "doi": "10.1130/G30064A.1", "issn": "0091-7613", "publisher": "Geological Society of America", "publication": "Geology", "publication_date": "2009-09", "series_number": "9", "volume": "37", "issue": "9", "pages": "795-798" }, { "id": "authors:8211c-4pr05", "collection": "authors", "collection_id": "8211c-4pr05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090828-231034340", "type": "article", "title": "Finite element simulations of dynamic shear rupture experiments and dynamic path selection along kinked and branched faults", "author": [ { "family_name": "Templeton", "given_name": "Elizabeth L.", "clpid": "Templeton-E-L" }, { "family_name": "Baudet", "given_name": "Aur\u00e9lie", "clpid": "Baudet-A" }, { "family_name": "Bhat", "given_name": "Harsha S.", "clpid": "Bhat-H-S" }, { "family_name": "Dmowska", "given_name": "Renata", "clpid": "Dmowska-R" }, { "family_name": "Rice", "given_name": "James R.", "clpid": "Rice-J-R" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Rousseau", "given_name": "Carl-Ernst", "clpid": "Rousseau-C-E" } ], "abstract": "We analyze the nucleation and propagation of shear cracks along nonplanar, kinked, and branched fault paths corresponding to the configurations used in recent laboratory fracture studies by Rousseau and Rosakis (2003, 2009). The aim is to reproduce numerically those shear rupture experiments and from that provide an insight into processes which are active when a crack, initially propagating in mode II along a straight path, interacts with a bend in the fault or a branching junction. The experiments involved impact loading of thin Homalite-100 (a photoelastic polymer) plates, which had been cut along bent or branched paths and weakly glued back together everywhere except along a starter notch near the impact site. Strain gage recordings and high-speed photography of isochromatic lines provided characterization of the transient deformation fields associated with the impact and fracture propagation. We found that dynamic explicit 2-D plane-stress finite element analyses with a simple linear slip-weakening description of cohesive and frictional strength of the bonded interfaces can reproduce the qualitative rupture behavior past the bend and branch junctions in most cases and reproduce the principal features revealed by the photographs of dynamic isochromatic line patterns. The presence of a kink or branch can cause an abrupt change in rupture propagation velocity. Additionally, the finite element results allow comparison between total slip accumulated along the main and inclined fault segments. We found that slip along inclined faults can be substantially less than slip along the main fault, and the amount depends on the branch angle and kink or branch configuration.", "doi": "10.1029/2008JB006174", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2009-08-13", "series_number": "B8", "volume": "114", "issue": "B8", "pages": "B08304" }, { "id": "authors:4pxam-8wf44", "collection": "authors", "collection_id": "4pxam-8wf44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090828-231034169", "type": "article", "title": "Dynamic path selection along branched faults: Experiments involving sub-Rayleigh and supershear ruptures", "author": [ { "family_name": "Rousseau", "given_name": "Carl-Ernst", "clpid": "Rousseau-C-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Building upon previous laboratory earthquake experiments of dynamic shear rupture growth taking place along faults with simple kinks, new and complex fault geometries involving cohesively held fault branches are studied. Asymmetric impact at the specimen boundaries controls the incoming shear ruptures, which are manipulated to propagate at either sub-Rayleigh or supershear velocities. High-speed photography and dynamic photoelasticity are used with a model material, Homalite-100, to monitor incoming and outgoing rupture propagation, acceleration, deceleration, or arrest at the vicinity of the branch location. Differences and similarities of rupture velocity history between cases involving faults with either simple kinks or branches, on the one hand, and sub-Rayleigh and supershear incoming ruptures, on the other, are highlighted and explained. Results of the experiments show a clear general bias toward large branch inclination, smaller branch angles appearing to be overshadowed and suppressed by the stress field associated with the main fault. Of great interest, also, is the sustenance of rupture propagation along a branch by the Mach cone, when the initial rupture is supershear driven. Generally, higher rupture speeds favors larger arrays of branching angles to be triggered. A companion analysis by Templeton et al. (2009) featuring detailed numerical simulations of these experiments provides further insight into the observed phenomena.", "doi": "10.1029/2008JB006173", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2009-08-13", "series_number": "B8", "volume": "114", "issue": "B8", "pages": "B08303," }, { "id": "authors:q6wv0-50a75", "collection": "authors", "collection_id": "q6wv0-50a75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090430-111534836", "type": "article", "title": "Experimental validation of large-scale simulations of dynamic fracture along weak planes", "author": [ { "family_name": "Chalivendra", "given_name": "Vijaya B.", "clpid": "Chalivendra-V-B" }, { "family_name": "Hong", "given_name": "Soosung", "clpid": "Hong-Soosung" }, { "family_name": "Arias", "given_name": "Irene", "clpid": "Arias-I" }, { "family_name": "Knap", "given_name": "Jaroslaw", "clpid": "Knap-J" }, { "family_name": "Rosakis", "given_name": "Ares", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ortiz", "given_name": "Michael", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" } ], "abstract": "A well-controlled and minimal experimental scheme for dynamic fracture along weak planes is specifically designed for the validation of large-scale simulations using cohesive finite elements. The role of the experiments in the integrated approach is two-fold. On the one hand, careful measurements provide accurate boundary conditions and material parameters for a complete setup of the simulations without free parameters. On the other hand, quantitative performance metrics are provided by the experiments, which are compared a posteriori with the results of the simulations. A modified Hopkinson bar setup in association with notch-face loading is used to obtain controlled loading of the fracture specimens. An inverse problem of cohesive zone modeling is performed to obtain accurate mode-I cohesive zone laws from experimentally measured deformation fields. The speckle interferometry technique is employed to obtain the experimentally measured deformation field. Dynamic photoelasticity in conjunction with high-speed photography is used to capture experimental records of crack propagation. The comparison shows that both the experiments and the numerical simulations result in very similar crack initiation times and produce crack tip velocities which differ by less than 6%. The results also confirm that the detailed shape of the non-linear cohesive zone law has no significant influence on the numerical results.", "doi": "10.1016/j.ijimpeng.2008.11.009", "issn": "0734-743X", "publisher": "Elsevier", "publication": "International Journal of Impact Engineering", "publication_date": "2009-07", "series_number": "7", "volume": "36", "issue": "7", "pages": "888-898" }, { "id": "authors:pz1pb-snr66", "collection": "authors", "collection_id": "pz1pb-snr66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090706-134648271", "type": "article", "title": "Analysis of supershear transition regimes in rupture experiments : the effect of nucleation conditions and friction parameters", "author": [ { "family_name": "Lu", "given_name": "Xiao", "clpid": "Lu-Xiao" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "We consider the effect of the rupture initiation procedure on supershear transition of Mode II ruptures on interfaces governed by linear slip-weakening friction. Our study is motivated by recent experiments, which demonstrated the transition of spontaneous ruptures from sub-Rayleigh to supershear speeds in the laboratory. In these works the experiments were analysed using the Burridge\u2013Andrews model of supershear transition, in which a supershear daughter crack is nucleated in front of the main mother rupture. It was concluded that the critical slip of the linear slip-weakening formulation needs to be pressure-dependent for a good match with experiments. However, the dynamic rupture initiation mechanism in the experiments was conceptually different from the quasi-static one adopted in the numerical work used for comparison. Here, our goal is to determine the effect of the nucleation by numerically modelling the experiments using a rupture initiation procedure that captures the dynamic nature of the wire explosion mechanism used in the experiments. We find parameter regimes that match the experimentally observed transition distances for the entire range of experimental conditions. Our simulations show that the dynamic rupture initiation procedure significantly affects the resulting transition distances, shortening them by about 30\u201350 per cent compared to those predicted through the quasi-static rupture initiation process. Moreover, for some cases, the dynamic initiation procedure changes the very mode of transition, causing a direct supershear transition at the tip of the main rupture instead of the mother\u2013daughter mechanism. We find reasonable parameter regimes which match experimentally determined transition distances with both direct supershear transition at the rupture tip and the Burridge\u2013Andrews (mother\u2013daughter) mechanism, using both pressure-independent and pressure-dependent critical slip. The results show that there are trade-offs between the parameters of the rupture initiation procedure and the properties of interface friction. This underscores the importance of quantifying experimental parameters for proper interpretation of the experiments and highlights the importance of the rupture initiation procedure, in simulations of both experiments and real-life earthquake events.", "doi": "10.1111/j.1365-246X.2009.04091.x", "issn": "0956-540X", "publisher": "Royal Astronomical Society", "publication": "Geophysical Journal International", "publication_date": "2009-05", "series_number": "2", "volume": "177", "issue": "2", "pages": "717-732" }, { "id": "authors:jpsbx-f0g76", "collection": "authors", "collection_id": "jpsbx-f0g76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090618-094221376", "type": "article", "title": "Extension of the Coherent Gradient Sensor (CGS) to the combined measurement of in-plane and out-of-plane displacement field gradients", "author": [ { "family_name": "Mello", "given_name": "M.", "orcid": "0000-0003-2129-9235", "clpid": "Mello-M" }, { "family_name": "Hong", "given_name": "S.", "clpid": "Hong-S" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The Coherent Gradient Sensor (CGS) is extended to the optical differentiation of specular, diffracted wave fronts leading to the combined measurement of in- and out-of-plane displacement field gradients. A derivation of the underlying optical interference principles is presented along with an analysis of the effective instrument sensitivity. In order to demonstrate the capabilities of the technique, experimental measurements of crack-tip deformation fields were conducted under various loading conditions corresponding to mode-I, mode-II, and mixed mode near-tip crack fields. The experimental procedures and results of these tests are presented as validation of the technique.", "doi": "10.1007/s11340-008-9147-z", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2009-04", "series_number": "2", "volume": "49", "issue": "2", "pages": "277-289" }, { "id": "authors:f6dyy-bab31", "collection": "authors", "collection_id": "f6dyy-bab31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ROSjcp08", "type": "article", "title": "Dedication [to Tony Leonard]", "author": [ { "family_name": "Rosakis", "given_name": "Ares", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Pullin", "given_name": "Dale", "orcid": "0009-0007-5991-2863", "clpid": "Pullin-D-I" } ], "abstract": "Over more than 30 years, Tony Leonard's contributions to fluid mechanics, continuum mechanics and numerical methods have been dense and seminal. He has worked in diverse areas including vortex dynamics, vortex-based numerical methods, wall-bounded turbulence, quantized turbulence, Large\u2013Eddy Simulation (LES), Lagrangian mixing, spectral numerical methods, bluff body flows and flow-induced vibrations. Tony's first paper on LES, \"Energy Cascade in Large\u2013Eddy Simulation of Turbulent Fluid Flows\" appeared as an article in a review series, \"Advances in Geophysics\", in 1974. It proposed the concept of spatial filtering that has since been a cornerstone of LES. The idea of numerically simulating the evolution of large scales of turbulence while modeling the small scales was not new in the 1970s but it lacked a firm theoretical framework for the conceptual separation of the resolved or computed scales, and the subgrid or unresolved scales. Tony Leonard's 1974 introduction of the convolution operation of a field with a filter to produce the resolvable-scale function, and its application to the Navier Stokes equations of motion provided the means of identifying \"resolved scales\" while isolating and grouping those filtered products of subgrid fields with themselves and with resolved-scale fields, that required modeling. Tony's filter formalism has had a profound impact on the development of LES methodology and indeed is the starting point for most modern expositions on this topic. There is little doubt that his 1974 paper, which has not been published elsewhere, has become an unquantified citation classic.", "doi": "10.1016/j.jcp.2008.08.006", "issn": "0021-9991", "publisher": "Elsevier", "publication": "Journal of Computational Physics", "publication_date": "2008-11-10", "series_number": "21", "volume": "227", "issue": "21", "pages": "9006-9007" }, { "id": "authors:8m330-50y65", "collection": "authors", "collection_id": "8m330-50y65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:NGOam08", "type": "article", "title": "Multilayer thin films/substrate system with variable film thickness subjected to non-uniform misfit strains", "author": [ { "family_name": "Ngo", "given_name": "D.", "clpid": "Ngo-Duc" }, { "family_name": "Feng", "given_name": "X.", "clpid": "Feng-X" }, { "family_name": "Huang", "given_name": "Y.", "clpid": "Huang-Y" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Current methodologies used to infer thin-film stress from curvature measurements are strictly restricted to stress and curvature states that are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to a single thin film of non-uniform thickness deposited on a substrate and subjected to the non-uniform misfit strain. Such methodologies are extended to multilayer thin films of non-uniform thickness deposited on a substrate in the present study. Each thin film may have its own non-uniform misfit strain and non-uniform thickness. We obtain the film stresses and system curvatures in terms of the misfit strains and thickness in thin films. We derive the film stresses and interface shear stresses in terms of system curvatures and film thicknesses. They all feature a \"non-local\" dependence on curvatures, which make full-field measurement a necessity for the experimental inference of such stresses.", "doi": "10.1016/j.actamat.2008.07.016", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2008-10", "series_number": "18", "volume": "56", "issue": "18", "pages": "5322-5328" }, { "id": "authors:mcbkz-v6577", "collection": "authors", "collection_id": "mcbkz-v6577", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190828-154930296", "type": "article", "title": "Some Practical Issues of Curvature and Thermal Stress in Realistic Multilevel Metal Interconnect Structures", "author": [ { "family_name": "Park", "given_name": "T.-S.", "clpid": "Park-T-S" }, { "family_name": "Dao", "given_name": "M.", "clpid": "Dao-M" }, { "family_name": "Suresh", "given_name": "S.", "clpid": "Suresh-S" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Pantuso", "given_name": "D.", "clpid": "Pantuso-D" }, { "family_name": "Shankar", "given_name": "S.", "clpid": "Shankar-S" } ], "abstract": "This paper presents the results of a systematic study of curvature and stress evolution during thermal loading in single- and multilevel interconnect line structures which have been deposited on a much thicker substrate. Effects of line aspect ratio, passivation geometry, and metal density within a metalization level on thermal stress evolution in the lines are addressed. The current analytical stress model enables us to predict that interaction between lines on the same level, i.e., in the lateral direction, is so strong that it cannot be neglected. A two-dimensional (2-D) finite element method has been used to verify the accuracy of the current model, while available experimental data have been compared with theory. In order to capture the exact variation of the thermal stresses at different metalization levels, and to investigate the effect of the upper level line arrangements on the stress states at the lower level, a three-dimensional (3-D) finite element analysis was employed. It can be seen that the interaction between levels in the vertical direction is quite weak when the thickness of the interlevel dielectric (ILD) layer becomes comparable to that of the metal layer.", "doi": "10.1007/s11664-008-0409-4", "issn": "0361-5235", "publisher": "Springer", "publication": "Journal of Electronic Materials", "publication_date": "2008-06", "series_number": "6", "volume": "37", "issue": "6", "pages": "777-791" }, { "id": "authors:g4047-zmj39", "collection": "authors", "collection_id": "g4047-zmj39", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141027-110121008", "type": "article", "title": "An experimental study of the effect of off-fault damage on the velocity of a slip pulse", "author": [ { "family_name": "Biegel", "given_name": "Ronald L.", "clpid": "Biegel-R-L" }, { "family_name": "Sammis", "given_name": "Charles G.", "clpid": "Sammis-C-G" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The effect of off-fault damage on the speed of ruptures propagating on faults in photoelastic Homalite plates was measured using high-speed digital photography. The off-fault damage was composed of a network of fractures introduced by thermally shocking the Homalite in liquid nitrogen. The mode II rupture speed measured in damaged Homalite was significantly lower than the limiting Rayleigh speed of v_r = 0.92 v_s, even after the shear wave speed v_s was reduced to a value appropriate for the fracture-damaged Homalite. The additional slowing is most likely caused by frictional sliding on preexisting cracks, especially since we did not observe the generation of new fractures. The spatial extent of the interaction between the rupture and the off-fault damage was measured using samples in which the damage was limited to a band of width 2w centered on the fault and also using damaged samples containing a band of undamaged Homalite centered on the fault. By measuring the rupture velocity as a function of w, the interaction between the rupture and off-fault damage was observed to be limited to a distance of about 1 cm from the fault plane. This agrees with the spatial extent of Coulomb failure near the tip of a dynamic slip pulse predicted by the analytic model developed by Rice et al. (2005).", "doi": "10.1029/2007JB005234", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2008-04", "series_number": "B4", "volume": "113", "issue": "B4", "pages": "Art. No. B04302" }, { "id": "authors:yef3z-9cf18", "collection": "authors", "collection_id": "yef3z-9cf18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LUXpnas07", "type": "article", "title": "Pulse-like and crack-like ruptures in experiments mimicking crustal earthquakes", "author": [ { "family_name": "Lu", "given_name": "Xiao", "clpid": "Lu-Xiao" }, { "family_name": "Lapusta", "given_name": "Nadia", "orcid": "0000-0001-6558-0323", "clpid": "Lapusta-N" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Theoretical studies have shown that the issue of rupture modes has important implications for fault constitutive laws, stress conditions on faults, energy partition and heat generation during earthquakes, scaling laws, and spatiotemporal complexity of fault slip. Early theoretical models treated earthquakes as crack-like ruptures, but seismic inversions indicate that earthquake ruptures may propagate in a self-healing pulse-like mode. A number of explanations for the existence of slip pulses have been proposed and continue to be vigorously debated. This study presents experimental observations of spontaneous pulse-like ruptures in a homogeneous linear-elastic setting that mimics crustal earthquakes; reveals how different rupture modes are selected based on the level of fault prestress; demonstrates that both rupture modes can transition to supershear speeds; and advocates, based on comparison with theoretical studies, the importance of velocity-weakening friction for earthquake dynamics.", "doi": "10.1073/pnas.0704268104", "pmcid": "PMC2141885", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2007-11-27", "series_number": "48", "volume": "104", "issue": "48", "pages": "18931-18936" }, { "id": "authors:8qbb1-64n80", "collection": "authors", "collection_id": "8qbb1-64n80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171121-100722120", "type": "article", "title": "Numerical modelling and experimental validation of dynamic fracture events along weak planes", "author": [ { "family_name": "Arias", "given_name": "Irene", "clpid": "Arias-I" }, { "family_name": "Knap", "given_name": "Jaroslaw", "clpid": "Knap-J" }, { "family_name": "Chalivendra", "given_name": "Vijaya B.", "clpid": "Chalivendra-V-B" }, { "family_name": "Hong", "given_name": "Soonsung", "clpid": "Hong-Soonsung" }, { "family_name": "Ortiz", "given_name": "Michael", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The conceptual simplicity and the ability of cohesive finite element models to describe complex fracture phenomena makes them often the approach of choice to study dynamic fracture. These models have proven to reproduce some experimental features, but to this point, no systematic study has validated their predictive ability; the difficulty in producing a sufficiently complete experimental record, and the intensive computational requirements needed to obtain converged simulations are possible causes. Here, we present a systematic integrated numerical\u2013experimental approach to the verification and validation (V&V) of simulations of dynamic fracture along weak planes. We describe the intertwined computational and the experimental sides of the work, present the V&V results, and extract general conclusions about this kind of integrative approach.", "doi": "10.1016/j.cma.2006.10.052", "issn": "0045-7825", "publisher": "Elsevier", "publication": "Computer Methods in Applied Mechanics and Engineering", "publication_date": "2007-08-01", "series_number": "37-40", "volume": "196", "issue": "37-40", "pages": "3833-3840" }, { "id": "authors:33bvd-zt618", "collection": "authors", "collection_id": "33bvd-zt618", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100924-103650164", "type": "article", "title": "Thin film/substrate systems featuring arbitrary film thickness and misfit strain distributions. Part I: Analysis for obtaining film stress from non-local curvature information", "author": [ { "family_name": "Ngo", "given_name": "D.", "clpid": "Ngo-Duc" }, { "family_name": "Feng", "given_name": "X.", "clpid": "Feng-X" }, { "family_name": "Huang", "given_name": "Y.", "clpid": "Huang-Y" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Brown", "given_name": "M. A.", "clpid": "Brown-M-A" } ], "abstract": "Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. Recently Huang, Rosakis and co-workers [Huang, Y., Ngo, D., Rosakis, A.J., 2005. Non-uniform, axisymmetric misfit strain: in thin films bonded on plate substrates/substrate systems: the relation between non-uniform film stresses and system curvatures. Acta Mech. Sin. 21, 362\u2013370; Huang, Y., Rosakis A.J., 2005. Extension of Stoney's Formula to non-uniform temperature distributions in thin film/substrate systems. The case of radial symmetry. J. Mech. Phys. Solids 53, 2483\u20132500; Ngo, D., Huang, Y., Rosakis, A. J., Feng, X. 2006. Spatially non-uniform, isotropic misfit strain in thin films bonded on plate substrates: the relation between non-uniform film stresses and system curvatures. Thin Solid Films (in press)] established methods for film/substrate system subject to non-uniform misfit strain and temperature changes. The film stresses were found to depend non-locally on system curvatures (i.e., depend on the full-field curvatures). The existing methods, however, all assume uniform film thickness which is often violated in the thin film/substrate system. We extend these methods to arbitrarily non-uniform film thickness for the thin film/substrate system subject to non-uniform misfit strain. Remarkably the stress-curvature relation for uniform film thickness still holds if the film thickness is replaced by its local value at the point where the stress is evaluated. This result has been experimentally validated in Part II of this paper.", "doi": "10.1016/j.ijsolstr.2006.10.016", "issn": "0020-7683", "publisher": "Elsevier", "publication": "International Journal of Solids and Structures", "publication_date": "2007-03-15", "series_number": "6", "volume": "44", "issue": "6", "pages": "1745-1754" }, { "id": "authors:eg0na-ydr39", "collection": "authors", "collection_id": "eg0na-ydr39", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100503-140829635", "type": "article", "title": "Thin film/substrate systems featuring arbitrary film thickness and misfit strain distributions. Part II: Experimental validation of the non-local stress/curvature relations", "author": [ { "family_name": "Brown", "given_name": "M. A.", "clpid": "Brown-M-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Feng", "given_name": "X.", "clpid": "Feng-X" }, { "family_name": "Huang", "given_name": "Y.", "clpid": "Huang-Y" }, { "family_name": "\u00dcst\u00fcndag", "given_name": "Ersan", "clpid": "\u00dcst\u00fcndag-E" } ], "abstract": "The classical Stoney formula relating local equibiaxial film stress to local equibiaxial substrate curvature is not well equipped to handle realistic cases where the film misfit strain, the plate system curvature, and the film thickness and resulting film stress vary with in-plane position. In Part I of this work we have extended the Stoney formula to cover arbitrarily non-uniform film thickness for a thin film/substrate system subject to non-uniform, isotropic misfit strains. The film stresses are found to depend non-locally on system curvatures. In Part II we have designed a demanding experiment whose purpose is to validate the new analysis for the case of radially symmetric deformations. To achieve this, a circular film island with sharp edges and a radially variable, but known, thickness is deposited on the wafer center. The plate system's curvatures and the film stress distribution are independently measured by using white beam and monochromatic X-ray microdiffraction (\u03bcXRD) measurements, respectively. The measured stress field (from monochromatic \u03bcXRD) is compared to the predictions of various stress/curvature analyses, all of which have the white beam \u03bcXRD measurements as input. The results reveal the shortcomings of the \"local\" Stoney approach and validate the accuracy of the new \"non-local\" relation, most notably near the film island edges where stress concentrations dominate.", "doi": "10.1016/j.ijsolstr.2006.10.015", "issn": "0020-7683", "publisher": "Elsevier", "publication": "International Journal of Solids and Structures", "publication_date": "2007-03-15", "series_number": "6", "volume": "44", "issue": "6", "pages": "1755-1767" }, { "id": "authors:9hm3f-5t356", "collection": "authors", "collection_id": "9hm3f-5t356", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160726-082744533", "type": "book_section", "title": "Dynamic Shear Rupture in Frictional Interfaces: Speeds, Directionality, and Modes", "book_title": "Reference Module in Earth Systems and Environmental Sciences", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Xia", "given_name": "K.", "clpid": "Xia-K" }, { "family_name": "Lykotrafitis", "given_name": "G.", "clpid": "Lykotrafitis-G" }, { "family_name": "Kanamori", "given_name": "H.", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "abstract": "The goal in designing dynamic frictional experiments simulating earthquake rupture has been to create a testing environment or platform which could reproduce some of the basic physics governing the rupture dynamics of crustal earthquakes while preserving enough simplicity so that clear conclusions can be obtained by pure observation. In this chapter, we first review past and recent experimental work on dynamic shear rupture propagation along frictional interfaces. The early experimental techniques are discussed in relation to recent experimental simulations of earthquakes which feature advanced diagnostics of high temporal and spatial resolution. The high-resolution instrumentation enables direct comparison between the experiments and data recorded during natural earthquakes. The experimental results presented in this chapter are examined in light of seismological observations related to various natural large rupture events and of recent theoretical and numerical development in the understanding of frictional rupture. In particular, the physics and conditions leading to phenomena such as supershear rupture growth, sub-Rayleigh to supershear rupture transition, and rupture directionality in inhomogeneous systems are discussed in detail. Finally, experiments demonstrating the attainability of various rupture modes (crack-like, pulse-like, and mixed) are presented and discussed in relation to theoretical and numerical predictions.", "doi": "10.1016/B978-0-444-53802-4.00072-5", "isbn": "978-0-12-409548-9", "publisher": "Elsevier", "place_of_publication": "Amsterdam", "publication_date": "2007", "pages": "183-213" }, { "id": "authors:grsdq-mpd31", "collection": "authors", "collection_id": "grsdq-mpd31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-172557362", "type": "article", "title": "Dynamic sliding of frictionally held bimaterial interfaces subjected to impact shear loading", "author": [ { "family_name": "Lykotrafitis", "given_name": "G.", "clpid": "Lykotrafitis-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The fast frictional sliding along an incoherent interface of a bimaterial system composed of a Homalite and a steel plate is studied experimentally in a microsecond time-scale. The plates are held together by a static uniform compressive pre-stress while dynamic sliding is initiated by asymmetric impact. The full-field technique of dynamic photoelasticity is simultaneously used with a local technique of velocimetry based on laser interferometry. In the case where the impact loading is applied to the Homalite plate, a shear Mach line originates from a disturbance propagating along the interface supersonically with respect to the dilatational wave speed of Homalite and it crosses the P-wave front. The sliding starts well behind the P-wave front in Homalite and it propagates with a supershear speed with respect to Homalite. A fast interface wave and a wrinkle-like opening pulse (detachment wave) travelling along the interface are observed. When the impact loading is applied to the steel plate, the local sliding velocity measurement reveals that sliding initiates with the arrival of the P-wave front in the steel plate.", "doi": "10.1098/rspa.2006.1703", "issn": "1364-5021", "publisher": "Royal Society of London", "publication": "Proceedings of the Royal Society A: Mathematical, physical, and engineering sciences", "publication_date": "2006-10-08", "series_number": "2074", "volume": "5", "issue": "2074", "pages": "2997-3026" }, { "id": "authors:48806-5zq29", "collection": "authors", "collection_id": "48806-5zq29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110128-152248446", "type": "article", "title": "A Comparison of X-Ray Microdiffraction and Coherent Gradient Sensing in Measuring Discontinuous Curvatures in Thin Film: Substrate Systems", "author": [ { "family_name": "Brown", "given_name": "Michal A.", "clpid": "Brown-M-A" }, { "family_name": "Park", "given_name": "Tae-Soon", "clpid": "Park-Tae-Soon" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "\u00dcst\u00fcndag", "given_name": "Ersan", "clpid": "\u00dcst\u00fcndag-E" }, { "family_name": "Huang", "given_name": "Young", "clpid": "Huang-Young" }, { "family_name": "Tamura", "given_name": "Nobumichi", "orcid": "0000-0002-3698-2611", "clpid": "Tamura-Nobumichi" }, { "family_name": "Valek", "given_name": "Bryan", "clpid": "Valek-B" } ], "abstract": "The coherent gradient sensor (CGS) is a shearing interferometer which has been proposed for the rapid, full-field measurement of deformation states (slopes and curvatures) in thin film-wafer substrate systems, and for the subsequent inference of stresses in the thin films. This approach needs to be verified using a more well-established but time-consuming grain orientation and stress measurement tool, X-ray microdiffraction (XRD). Both CGS and XRD are used to measure the deformation state of the same W film/Si wafer at room temperature. CGS provides a global, wafer-level measurement of slopes while XRD provides a local micromeasurement of lattice rotations. An extreme case of a circular Si wafer with a circular W film island in its center is used because of the presence of discontinuous system curvatures across the wafer. The results are also compared with a theoretical model based on elastic plate analysis of the axisymmetric biomaterial film-substrate system. Slope and curvature measurements by XRD and by CGS compare very well with each other and with theory. The favorable comparison demonstrates that wafer-level CGS metrology provides a quick and accurate alternative to other measurements. It also demonstrates the accuracy of plate theory in modeling thin film-substrate systems, even in the presence of curvature discontinuities.", "doi": "10.1115/1.2150500", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2006-09", "series_number": "5", "volume": "73", "issue": "5", "pages": "723-729" }, { "id": "authors:tbnhx-p8j68", "collection": "authors", "collection_id": "tbnhx-p8j68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110602-132455448", "type": "article", "title": "Sliding along frictionally held incoherent interfaces in homogeneous systems subjected to dynamic shear loading: a photoelastic study", "author": [ { "family_name": "Lykotrafitis", "given_name": "G.", "clpid": "Lykotrafitis-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "An experimental investigation was conducted to study dynamic sliding at high strain rates along incoherent (frictional) interfaces between two identical plates. The plates were held together by a uniform compressive stress, while dynamic sliding was initiated by an impact-induced shear loading. The case of freely-standing plates with no external pressure was also investigated. The dynamic stress fields that developed during the events were recorded in a microsecond time scale by high-speed photography in conjunction with classical dynamic photoelasticity. Depending on the choice of experimental parameters (impact speed and superimposed static pressure), pulse-like and crack-like sliding modes were observed. Visual evidence of sub-Rayleigh, intersonic and even supersonically propagating pulses were discovered and recorded. Unlike classical shear cracks in coherent interfaces of finite strength, sliding areas in frictional interfaces seem to grow at various discrete speeds without noticeable acceleration phases. A relatively broad loading wave caused by the interference between the impact wave and the preexisting static stress field was observed emanating from the interface. There was a cusp in the stress contours at the interface, indicating that the propagation speed was slightly faster along the interface than in the bulk. The observed propagation speeds of the sliding tips were dependent on the projectile speed. They spanned almost the whole interval from sub-Rayleigh speeds to nearly the sonic speed of the material, with the exception of a forbidden gap between the Rayleigh wave speed and the shear wave speed. Supersonic trailing pulses generating Mach lines of different inclination angles, emanating from the sliding zone tips, were discovered. In addition, behind the sliding tip, wrinkle-like opening pulses were observed for a wide range of impact speeds and confining stresses. They always traveled at speeds between the Rayleigh wave speed and the shear wave speed of the material.", "doi": "10.1007/s10704-005-6103-0", "issn": "0376-9429", "publisher": "Springer", "publication": "International Journal of Fracture", "publication_date": "2006-07", "series_number": "1-4", "volume": "140", "issue": "1-4", "pages": "213-233" }, { "id": "authors:732kx-27660", "collection": "authors", "collection_id": "732kx-27660", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150225-152118170", "type": "article", "title": "Dynamic Fracture Properties of Titanium Alloys", "author": [ { "family_name": "Anderson", "given_name": "D. D.", "clpid": "Anderson-D-D" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Fatigue precracked specimens of three titanium alloys (6Al-4V, ELI, and Timetal 5111) were dynamically loaded in a drop weight tower system while the dynamic fracture toughness was inferred using Coherent Gradient Sensing, crack opening displacement, or strain gage methods. A comparison of the initiation toughness of the three materials as a function of loading rate and specimen thickness is made.", "doi": "10.1007/s11340-006-6421-9", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2006-06", "series_number": "3", "volume": "46", "issue": "3", "pages": "399-406" }, { "id": "authors:wjvay-4y903", "collection": "authors", "collection_id": "wjvay-4y903", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110120-101227428", "type": "article", "title": "Spontaneous Mixed-Mode Fracture in Bonded Similar and Dissimilar Materials", "author": [ { "family_name": "Xia", "given_name": "K.", "clpid": "Xia-K" }, { "family_name": "Chalivendra", "given_name": "V. B.", "clpid": "Chalivendra-V-B" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "In this paper, we report on an experimental study of spontaneous, mixed-mode, crack propagation in weakly bonded similar and dissimilar materials. A unique experimental configuration is proposed to induce spontaneous crack growth events along the interfaces. The cracks nucleate from tiny circular holes and are triggered by an exploding wire. They subsequently propagate under the action of a constant, far-field load. Dynamic photoelasticity in conjunction with high speed photography is used to capture the real-time isochromatics associated with crack propagation. In the case of identical materials, crack propagation is anti-symmetric with respect to the crack nucleation point while strong asymmetry is observed for the case of dissimilar materials. In both cases, cracks propagate at constant velocity from the initiation point. The time histories of dynamic stress intensity factors and of energy release rates of the propagating cracks along the bonded similar materials are also reported.", "doi": "10.1007/s11340-006-6423-7", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2006-04", "series_number": "2", "volume": "46", "issue": "2", "pages": "163-171" }, { "id": "authors:en5qx-3vf32", "collection": "authors", "collection_id": "en5qx-3vf32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110714-084450267", "type": "article", "title": "Particle Velocimetry and Photoelasticity Applied to the Study of Dynamic Sliding Along Frictionally-Held Bimaterial Interfaces: Techniques and Feasibility", "author": [ { "family_name": "Lykotrafitis", "given_name": "G.", "clpid": "Lykotrafitis-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "A laser interferometry-based technique was developed to locally measure the in-plane components of particle velocity in dynamic experiments. This technique was applied in the experimental investigation of dynamic sliding along the incoherent (frictional) interface of a Homalite\u2013steel bimaterial structure. The bimaterial specimen was subjected to uniform compressive stress and impact-induced shear loading. The evolution of the dynamic stress field was recorded by high-speed photography in conjunction with dynamic photoelasticity. The combination of the full-field technique of photoelasticity with the local technique of velocimetry was proven to be a very powerful tool in the investigation of dynamic sliding. A relatively broad loading wave with an eye-like structure emanated from the interface. The particle velocity measurements established that sliding started behind the eye-like fringe pattern. It propagated with supershear speed with respect to Homalite. A shear Mach line originating from the sliding tip is visible in the photoelastic images. A vertical particle velocity measurement revealed the existence of a wrinkle-like pulse traveling along the bimaterial interface. The wrinkle-like pulse followed the initial shear rupture tip and propagated at a specific subshear speed.", "doi": "10.1007/s11340-006-6418-4", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2006-04", "series_number": "2", "volume": "46", "issue": "2", "pages": "205-216" }, { "id": "authors:vphz8-7sz10", "collection": "authors", "collection_id": "vphz8-7sz10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110623-134147181", "type": "article", "title": "Laboratory Earthquakes", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Xia", "given_name": "Kaiwen", "clpid": "Xia-Kaiwen" } ], "abstract": "We report on the experimental observation of the phenomenon of, spontaneously nucleated, supershear rupture and on the visualization of the mechanism of subRayleigh to supershear rupture transition in frictionally-held interfaces. The laboratory experiments mimic natural earthquakes. The results suggest that under certain conditions supershear rupture propagation can be facilitated during large earthquakes.", "doi": "10.1007/s10704-006-0030-6", "issn": "0376-9429", "publisher": "Springer", "publication": "International Journal of Fracture", "publication_date": "2006-03", "series_number": "1-4", "volume": "138", "issue": "1-4", "pages": "211-218" }, { "id": "authors:pjwqf-qv757", "collection": "authors", "collection_id": "pjwqf-qv757", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200609-095317554", "type": "book_section", "title": "Validation of large scale simulations of dynamic fracture", "book_title": "III European Conference on Computational Mechanics - Solids, Structures and Coupled Problems in Engineering: Book of Abstracts", "author": [ { "family_name": "Arias", "given_name": "Irene", "clpid": "Arias-I" }, { "family_name": "Knap", "given_name": "Jaroslaw", "clpid": "Knap-J" }, { "family_name": "Chalivendra", "given_name": "Vijaya B.", "clpid": "Chalivendra-V-B" }, { "family_name": "Hong", "given_name": "Soonsung", "clpid": "Hong-Soonsung" }, { "family_name": "Ortiz", "given_name": "Michael", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "contributor": [ { "family_name": "Motasoares", "given_name": "C. A.", "clpid": "Motasoares-C-A" }, { "family_name": "Martins", "given_name": "J. A. C.", "clpid": "Martins-J-A-C" }, { "family_name": "Rodrigues", "given_name": "H. C.", "clpid": "Rodrigues-H-C" }, { "family_name": "Ambr\u00f3sio", "given_name": "Jorge A. C.", "clpid": "Ambr\u00f3sio-J-A-C" }, { "family_name": "Pina", "given_name": "C. A. B.", "clpid": "Pina-C-A-B" }, { "family_name": "Motasoares", "given_name": "C. M.", "clpid": "Motasoares-C-M" }, { "family_name": "Pereira", "given_name": "E. B. R.", "clpid": "Pereira-E-B-R" }, { "family_name": "Folgado", "given_name": "J.", "clpid": "Folgado-J" } ], "abstract": "A novel integrated approach is developed for a systematic validation of large-scale finite element simulations on dynamic crack propagations along a weak plane [1]. A set of well-controlled experimental scheme is specifically designed to provide accurate input data for the numerical simulations as well as to provide metrics for quantitative comparisons between experimental and numerical results. Dynamic photoelasticity with high-speed photography is used to capture experimental records of dynamic crack propagations along a weak plane and to provide the crack propagation history. In the dynamic experiments, a modified Hopkinson bar setup with a notch-face loading configuration is used to obtain controlled loading conditions for the dynamic fracture problem. Also an inverse-problem approach of cohesive zone model is employed to obtain a realistic cohesive law, i.e. a traction-separation law, of the weak plane, from independently measured crack-tip deformation fields using speckle interferometry technique. The experimentally collected data, the loading conditions and the cohesive law, are considered as input for the finite element simulations [2]. We employ finite-deformation cohesive elements to account for crack initiation and growth in bulk finite-element discretizations of the experimental sample. As it is well know, the cohesive elements introduce an additional material-dependent length-scale into the finite element model. The demand of accurately resolving this length-scale by the finite-element discretization, as required for truly mesh-independent results, may often lead to discretizations containing several millions of elements. We therefore resort to massively parallel computing. \n\nA comparison of the metrics from the numerical simulations with those from the experimental measurements is performed to validate the large-scale simulations. The numerical results show good agreements with the experimental results, leading to a successful validation of the large scale simulations of the dynamic crack propagations along the weak plane.", "doi": "10.1007/1-4020-5370-3_252", "isbn": "978-1-4020-4994-1", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "2006", "pages": "252-252" }, { "id": "authors:xsd3w-r4q43", "collection": "authors", "collection_id": "xsd3w-r4q43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-142840770", "type": "article", "title": "Non-uniform, axisymmetric misfit strain: in thin films bonded on plate substrates/substrate systems: the relation between non-uniform film stresses and system curvatures", "author": [ { "family_name": "Huang", "given_name": "Yonggang", "orcid": "0000-0002-0483-8359", "clpid": "Huang-Yonggang" }, { "family_name": "Ngo", "given_name": "D.", "clpid": "Ngo-Duc" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. By considering a circular thin film/substrate system subject to non-uniform, but axisymmetric misfit strain distributions in the thin film, we derived relations between the film stresses and the misfit strain, and between the plate system's curvatures and the misfit strain. These relations feature a \"local\" part which involves a direct dependence of the stress or curvature components on the misfit strain at the same point, and a \"non-local\" part which reflects the effect of misfit strain of other points on the location of scrutiny. Most notably, we also derived relations between the polar components of the film stress and those of system curvatures which allow for the experimental inference of such stresses from full-field curvature measurements in the presence of arbitrary radial non-uniformities. These relations also feature a \"non-local\" dependence on curvatures making a full-field measurement a necessity. Finally, it is shown that the interfacial shear tractions between the film and the substrate are proportional to the radial gradients of the first curvature invariant and can also be inferred experimentally.", "doi": "10.1007/s10409-005-0051-9", "issn": "0567-7718", "publisher": "Springer Verlag", "publication": "Acta Mechanica Sinica", "publication_date": "2005-08", "series_number": "4", "volume": "21", "issue": "4", "pages": "362-370" }, { "id": "authors:k7hng-mzy37", "collection": "authors", "collection_id": "k7hng-mzy37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141111-091822890", "type": "article", "title": "Laboratory earthquakes along inhomogeneous faults: Directionality and supershear", "author": [ { "family_name": "Xia", "given_name": "Kaiwen", "clpid": "Xia-K" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" }, { "family_name": "Rice", "given_name": "James R.", "clpid": "Rice-J-R" } ], "abstract": "We report on the experimental observation of spontaneously nucleated ruptures occurring on frictionally held bimaterial interfaces with small amounts of wave speed mismatch. Rupture is always found to be asymmetric bilateral. In one direction, rupture always propagates at the generalized Rayleigh wave speed, whereas in the opposite direction it is subshear or it transitions to supershear. The lack of a preferred rupture direction and the conditions leading to supershear are discussed in relation to existing theory and to the earthquake sequence in Parkfield, California, and in North Anatolia.", "doi": "10.1126/science.1108193", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2005-04-29", "series_number": "5722", "volume": "308", "issue": "5722", "pages": "681-684" }, { "id": "authors:47bf2-kbq88", "collection": "authors", "collection_id": "47bf2-kbq88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160912-082346787", "type": "article", "title": "Frictional sliding modes along an interface between identical elastic plates subject to shear impact loading", "author": [ { "family_name": "Coker", "given_name": "D.", "orcid": "0000-0001-7385-7089", "clpid": "Coker-Demirkan" }, { "family_name": "Lykotrafitis", "given_name": "G.", "clpid": "Lykotrafitis-G" }, { "family_name": "Needleman", "given_name": "A.", "clpid": "Needleman-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Frictional sliding along an interface between two identical isotropic elastic plates under impact shear loading is investigated experimentally and numerically. The plates are held together by a compressive stress and one plate is subject to edge impact near the interface. The experiments exhibit both a crack-like and a pulse-like mode of sliding. Plane stress finite element calculations modeling the experimental configuration are carried out, with the interface characterized by a rate and state dependent frictional law. A variety of sliding modes are obtained in the calculations depending on the impact velocity, the initial compressive stress and the values of interface variables. For low values of the initial compressive stress and impact velocity, sliding occurs in a crack-like mode. For higher values of the initial compressive stress and/or impact velocity, sliding takes place in a pulse-like mode. One pulse-like mode involves well-separated pulses with the pulse amplitude increasing with propagation distance. Another pulse-like mode involves a pulse train of essentially constant amplitude. The propagation speed of the leading pulse (or of the tip of the crack-like sliding region) is near the longitudinal wave speed and never less than \u221a2 times the shear wave speed. Supersonic trailing pulses are seen both experimentally and computationally. The trends in the calculations are compared with those seen in the experiments.", "doi": "10.1016/j.jmps.2004.11.003", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2005-04", "series_number": "4", "volume": "53", "issue": "4", "pages": "884-922" }, { "id": "authors:fjb37-zyf81", "collection": "authors", "collection_id": "fjb37-zyf81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150306-142747141", "type": "article", "title": "Comparison of three real time techniques for the measurement of dynamic fracture initiation toughness in metals", "author": [ { "family_name": "Anderson", "given_name": "D. D.", "clpid": "Anderson-D-D" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Three techniques for measuring dynamic stress intensity factor time histories of dynamically loaded stationary mode-I cracks are compared as applied to dynamically loaded pre-cracked 6Al\u20134V titanium alloy specimens. The three techniques are crack opening displacement (COD), dynamic strain gage measurement, and coherent gradient sensing (CGS). The stress intensity factor histories are inferred from each measurement technique and are used to obtain the critical dynamic initiation toughness as a function of loading rate (K^(d)_(Ic)(K^\u22c5^(d)_(I))). There are significant differences in implementation and information obtained from each of the three measurement techniques, though for the tests performed all are found to yield very similar results.", "doi": "10.1016/j.engfracmech.2004.04.005", "issn": "0013-7944", "publisher": "Elsevier", "publication": "Engineering Fracture Mechanics", "publication_date": "2005-03", "series_number": "4", "volume": "72", "issue": "4", "pages": "535-555" }, { "id": "authors:dgfwg-4xr60", "collection": "authors", "collection_id": "dgfwg-4xr60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141110-155954031", "type": "article", "title": "Laboratory Earthquakes: The Sub-Rayleigh\u2013to\u2013Supershear Rupture Transition", "author": [ { "family_name": "Xia", "given_name": "Kaiwen", "clpid": "Xia-K" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Kanamori", "given_name": "Hiroo", "orcid": "0000-0001-8219-9428", "clpid": "Kanamori-H" } ], "abstract": "We report on the experimental observation of spontaneously nucleated supershear rupture and on the visualization of sub-Rayleigh\u2013to\u2013supershear rupture transitions in frictionally held interfaces. The laboratory experiments mimic natural earthquakes. The results suggest that under certain conditions supershear rupture propagation can be facilitated during large earthquake events.", "doi": "10.1126/science.1094022", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2004-03-19", "series_number": "5665", "volume": "303", "issue": "5665", "pages": "1859-1861" }, { "id": "authors:e5ew9-jej85", "collection": "authors", "collection_id": "e5ew9-jej85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141027-105249515", "type": "article", "title": "On the influence of fault bends on the growth of sub-Rayleigh and intersonic dynamic shear ruptures", "author": [ { "family_name": "Rousseau", "given_name": "Carl-Ernst", "clpid": "Rousseau-C-E" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Earthquake ruptures are modeled as dynamically propagating shear cracks with the aim of gaining insight into the physical mechanisms governing their arrest or, otherwise, the often-observed variations in rupture speeds. Fault bends have been proposed as being the main cause for these variations. Following this line of reasoning, the existence of deviations from fault planarity is chosen as the main focus of this study. Asymmetric impact is used to generate shear loading and to propagate dynamic mode-II cracks along the bonded interfaces of two otherwise identical homogeneous constituents. Secondary paths inclined at various angles are also introduced to represent fault bends or kinks. The experiments show that certain fault bend inclinations are favored as alternate paths for rupture continuation, whereas others suppress further motion of the incoming rupture. The asymptotic elastodynamic stress fields at the tip of the growing rupture are used to develop two criteria (one energetic and one stress based) for rupture propagation or arrest at the kinked interfaces. These criteria correlate very well with the experimental results. Since most field evidence suggests that the average rupture speeds during crustal earthquakes are sub-Rayleigh, this work first focuses on incoming rupture speeds that are just below the Rayleigh wave speed. Reports of intersonic crustal fault rupture speeds having surfaced recently, experiments and analyses are also performed within that speed regime.", "doi": "10.1029/2002JB002310", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2003-09", "series_number": "B9", "volume": "108", "issue": "B9", "pages": "Art. No. 2411" }, { "id": "authors:6wm47-pf415", "collection": "authors", "collection_id": "6wm47-pf415", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171129-164945762", "type": "article", "title": "3D Modelling of Impact Failure in Sandwich Structures", "author": [ { "family_name": "Yu", "given_name": "C.", "orcid": "0000-0003-4176-0324", "clpid": "Yu-Chengxiang-Rena" }, { "family_name": "Ortiz", "given_name": "M.", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Cohesive theories of fracture are applied to simulate the complex failure modes in sandwich structures subjected to low-speed impact. The particular configuration contemplated in this study refers to the experiments performed by Xu and Rosakis [1], where the model specimens involving a compliant polymer core sandwiched between two metal layers, were adopted to simulate failure evolution mechanisms in real sandwich structures. Fracture has been modeled by recourse to an irreversible cohesive law embedded into three-dimensional cohesive elements. These cohesive elements govern all aspects of the separation of the incipient cracks. The cohesive behavior of the material is assumed to be rate independent and, consequently, all rate effects predicted by the calculations are due to inertia. The fidelity of the model has been validated by several previous simulations [2,3]. The numerical simulations have proved highly predictive of a number of observed features, including: the complex sequences of the failure mode, shear-dominated inter-sonic (a speed that is greater than shear wave speed but less than the longitudinal wave speed of the material) inter-layer cracks, the transition from inter-layer crack growth to intra-layer crack formation and the core branching later on.", "doi": "10.1016/S1566-1369(03)80122-X", "issn": "1566-1369", "publisher": "Elsevier", "publication": "European Structural Integrity Society", "publication_date": "2003", "volume": "32", "pages": "527-537" }, { "id": "authors:f2p55-8w991", "collection": "authors", "collection_id": "f2p55-8w991", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171208-154753672", "type": "article", "title": "Three-dimensional modeling of intersonic shear-crack growth in asymmetrically loaded unidirectional composite plates", "author": [ { "family_name": "Yu", "given_name": "C.", "orcid": "0000-0003-4176-0324", "clpid": "Yu-Chengxiang-Rena" }, { "family_name": "Pandolfi", "given_name": "A.", "orcid": "0000-0002-7084-7456", "clpid": "Pandolfi-A" }, { "family_name": "Ortiz", "given_name": "M.", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Coker", "given_name": "D.", "orcid": "0000-0001-7385-7089", "clpid": "Coker-Demirkan" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "An anisotropic cohesive model of fracture is applied to the numerical simulation of Coker and Rosakis experiments (2001). In these experiments, a unidirectional graphite\u2013epoxy composites plate was impacted with a projectile, resulting in an intersonic shear-dominated crack growth. The simulations account for explicit crack nucleation\u2013\u2013through a self-adaptive remeshing procedure\u2013\u2013crack closure and frictional sliding. The parameters used in the cohesive model are obtained from quasi-static fracture experiments, and successfully predict the dynamic fracture behavior. In keeping with the experiments, the calculations indicate that there is a preferred intersonic speed for locally steady-state growth of dynamic shear cracks, provided that sufficient energy is supplied to the crack tip. The calculations also show that the crack tip can attain speeds in the vicinity of the longitudinal wave speed in the direction of the fibers, if impacted at higher speeds. In addition, a double-shock which emanates from a finite size contact region behind the crack tip is observed in the simulations. The predicted double-shock structure of the near-tip fields is in close agreement with the experimental observations. The calculations additionally predict the presence of a string of surface hot spots which arise following the passage of the crack tip. The observed and computed hot spot structures agree both in geometry as well as in the magnitude of the temperature elevation. The analysis thus suggests intermittent friction as the origin of the experimentally observed hot spots.", "doi": "10.1016/S0020-7683(02)00466-3", "issn": "0020-7683", "publisher": "Elsevier", "publication": "International Journal of Solids and Structures", "publication_date": "2002-12", "series_number": "25", "volume": "39", "issue": "25", "pages": "6135-6157" }, { "id": "authors:01twr-4xm74", "collection": "authors", "collection_id": "01twr-4xm74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141027-104113705", "type": "article", "title": "Subsonic and intersonic shear rupture of weak planes with a velocity weakening cohesive zone", "author": [ { "family_name": "Samudrala", "given_name": "O.", "clpid": "Samudrala-O" }, { "family_name": "Huang", "given_name": "Y.", "clpid": "Huang-Y" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "A substantial effort has been devoted in the past toward modeling earthquake source mechanisms as dynamically extending shear cracks. Most of the attention was focused on the subsonic crack speed regime. Recently, a number of reports have appeared in the seismological literature citing evidence of intersonic rupture speeds during shallow crustal earthquakes. In the first part of this paper, we discuss direct experimental observations of intersonic in-plane shear crack growth along a weak plane joining two homogeneous, isotropic, linear elastic plates. Associated with the primary intersonic crack and at locations behind the propagating shear crack tip, a series of secondary tensile cracks, at a steep angle to the shear crack plane, were also observed. Motivated by these observations, subsonic and intersonic mode II crack propagation with a velocity weakening cohesive zone is analyzed in the main body of the paper. A cohesive law is assumed wherein the cohesive shear traction is either a constant or decreases linearly with the local slip rate, the rate of decrease governed by a slip rate weakening parameter. The cohesive shear traction is assumed to vanish when the crack tip sliding displacement reaches a characteristic breakdown slip. It is shown that a positive energy flux into the rupture front is possible in the entire intersonic regime. The influence of shear strength and of the weakening parameter on the crack propagation behavior is investigated. Crack tip stability issues are also addressed, and favorable speed regimes are identified. Estimates of the slip rate weakening parameter are obtained by using the theoretical model to predict the angle of the secondary cracks. The rest of the parameters are subsequently estimated by comparing the isochromatic fringe patterns (contours of maximum in-plane shear stress) predicted by the solution with those recorded experimentally.", "doi": "10.1029/2001JB000460", "issn": "0148-0227", "publisher": "American Geophysical Union", "publication": "Journal of Geophysical Research B", "publication_date": "2002-08", "series_number": "B8", "volume": "107", "issue": "B8", "pages": "Art. No. 2170" }, { "id": "authors:y3p0p-q2t55", "collection": "authors", "collection_id": "y3p0p-q2t55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:RAVaipcp02", "type": "book_section", "title": "On the Conversion of Plastic Work into Heat During High-Strain-Rate Deformation", "book_title": "Shock compression of condensed matter--2001 : proceedings of the Shock COmpression of Condensed Matter held in Atlanta, Georgia, June 24-29, 2001", "author": [ { "family_name": "Ravichandran", "given_name": "Guruswami", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Hodowany", "given_name": "Jon", "clpid": "Hodowany-J" }, { "family_name": "Rosakis", "given_name": "Phoebus", "clpid": "Rosakis-P" } ], "contributor": [ { "family_name": "Furnish", "given_name": "Michael D." }, { "family_name": "Thadhani", "given_name": "Naresh N." }, { "family_name": "Horie", "given_name": "Yasuyuki" } ], "abstract": "Heat generation in metals during high-strain-rate plastic deformation was investigated. Experiments were designed to measure the partition of plastic work into heat and stored energy during dynamic deformations under adiabatic conditions. A Kolsky pressure bar was used to determine mechanical properties at high strain rates while a servo-hydraulic material testing system was used at low strain rates. For dynamic loading, in-situ temperature changes were measured using a high-speed infrared detector. The dependence of the fraction of plastic work converted to heat on strain and strain rate was determined for an aluminum 2024-T3 alloy and alpha-titanium. The flow stress and the fraction of plastic work converted to heat for 2024-T3 aluminum alloy were found to be a function of strain but not of the strain rate while they were found to be strongly dependent on strain rate for alpha-titanium.", "doi": "10.1063/1.1483600", "isbn": "0735400687", "publisher": "American Institute of Physics", "place_of_publication": "Melville, NY", "publication_date": "2002-07-08", "pages": "557-562" }, { "id": "authors:fde8n-wwd04", "collection": "authors", "collection_id": "fde8n-wwd04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200219-114918280", "type": "book_section", "title": "Experimental and Numerical Investigation of Shear-dominated Intersonic Crack Growth and Friction in Unidirectional Composites", "book_title": "Recent Advances in Experimental Mechanics: In Honor of Isaac M. Daniel", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Yu", "given_name": "C.", "orcid": "0000-0003-4176-0324", "clpid": "Yu-Chengxiang-Rena" }, { "family_name": "Ortiz", "given_name": "M.", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Coker", "given_name": "D.", "orcid": "0000-0001-7385-7089", "clpid": "Coker-D" }, { "family_name": "Pandolfi", "given_name": "A.", "orcid": "0000-0002-7084-7456", "clpid": "Pandolfi-A" } ], "contributor": [ { "family_name": "Gdoutos", "given_name": "Emmanuel E.", "clpid": "Gdoutos-E-E" } ], "abstract": "Dynamic crack growth in unidirectional graphite/epoxy composite materials subjected to in-plane impact loading is investigated experimentally and numerically. The experiments are conducted using CGS (Coherent Gradient Sensing) Interferometry in conjunction with high-speed photography to visualize the crack growth events. Cracks are found to propagate at subsonic speeds in the Mode-I case, whereas in both mixed mode and Mode-II the crack tip speed clearly exceeds the shear wave speed of the laminate. For these intersonically growing shear (Mode-II) cracks a shock wave emanating from the crack tip is observed. This provides direct evidence that the cracks propagate faster than the shear wave speed of the composite. The crack tip speed is initally observed to jump to a level close to the axial longitudinal wave speed along the fibers (7500 m/s) and then to stabilize to a lower level of approximately 6500 m/s. This speed corresponds to the speed at which the energy release rate required for shear crack growth is non-zero as determined from asymptotic analysis. The CGS interferograms also reveal the existence of large-scale frictional contact of the crack faces behind the moving shear cracks. In addition high speed thermographic measurements are conducted that show concentrated hot spots behind the crack tip indicating crack face frictional contact. These experiments are modeled by a detailed dynamic finite element calculation involving cohesive elements, adaptive remeshing using subdivision and edge collapse, composite elements, and penalty contact. The numerical calculations are calibrated on the basis of fundamental material properties measured in the laboratory. The computational results are found to be in excellent agreement with the optical experimental measurements (crack speed record and near tip deformation field structure). For shear crack growth, the numerics also confirm the optical observation of large-scale crack face contact.", "doi": "10.1007/0-306-48410-2_27", "isbn": "978-1-4020-0683-8", "publisher": "Kluwer Academic Publishers", "place_of_publication": "Dordrecht", "publication_date": "2002", "pages": "275-288" }, { "id": "authors:ej9tm-c3704", "collection": "authors", "collection_id": "ej9tm-c3704", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200221-133523276", "type": "book_section", "title": "Dynamic Crack Growth along Interfaces", "book_title": "IUTAM Symposium on Analytical and Computational Fracture Mechanics of Non-Homogeneous Materials", "author": [ { "family_name": "Needleman", "given_name": "A.", "clpid": "Needleman-A" }, { "family_name": "Coker", "given_name": "D.", "orcid": "0000-0001-7385-7089", "clpid": "Coker-Demirkan" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "contributor": [ { "family_name": "Karihaloo", "given_name": "B. L.", "clpid": "Karihaloo-B-L" } ], "abstract": "For remotely loaded cracks in isotropic elastic solids, the energy flux into the crack tip vanishes as the crack speed increases to the Rayleigh wave speed of the material, see [1]. However, theoretical and numerical studies dating back to the mid 1970's, e.g. Andrews [2], Burridge et al. [3] and Broberg [4, 5], have indicated that faster crack speeds should be possible under shear loading conditions.", "doi": "10.1007/978-94-017-0081-8_29", "isbn": "978-90-481-5977-2", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "2002", "pages": "261-270" }, { "id": "authors:gva5x-8ww77", "collection": "authors", "collection_id": "gva5x-8ww77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190826-124740965", "type": "article", "title": "Determination of the yield properties of thin films using enhanced coherent gradient sensing", "author": [ { "family_name": "Singh", "given_name": "R. P.", "clpid": "Singh-R-P" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "This paper describes coherent gradient sensing (CGS) as an optical, full-field, real-time, nonintrusive, noncontact technique for measurement of curvature and curvature changes in single-layered and multilayered thin films deposited on substrates. The sensitivity of the basic CGS technique is enhanced using optical fringe multiplication to map curvature in very flat specimens (k \u2264 0.001 m^(\u22121)). Subsequently, this curvature measurement technique is applied to the determination of the yield properties of thin films subjected to cyclic thermomechanical loading.", "doi": "10.1007/bf02323934", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2001-12", "series_number": "4", "volume": "41", "issue": "4", "pages": "403-411" }, { "id": "authors:rpqss-n9334", "collection": "authors", "collection_id": "rpqss-n9334", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-164301757", "type": "article", "title": "Dynamic shear band propagation and micro-structure of adiabatic shear band", "author": [ { "family_name": "Li", "given_name": "Shaofan", "clpid": "Li-Shaofan" }, { "family_name": "Liu", "given_name": "Wing-Kam", "clpid": "Liu-Wing-Kam" }, { "family_name": "Qian", "given_name": "Dong", "clpid": "Qian-Dong" }, { "family_name": "Guduru", "given_name": "Pradeep R.", "clpid": "Guduru-P-R" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Meshfree Galerkin approximations in both two and three dimensions have been used in simulations of dynamic shear band propagation in an asymmetrically impact-loaded prenotched plate. Failure mode switching and failure mode transitions, which have been reported experimentally, are replicated in numerical computations. For intermediate impact speed (25m/s30m/s), the numerical results show that a dynamic shear band penetrates through the specimen without trace of cleavage-type fracture, which is a ductile failure mode. Overall, with the increase of impact speed, the final failure mode of the impacted plate transits from brittle failure to ductile failure. By introducing a multi-physics model to describe the stress collapse state of the shear band, it has been found that there is a non-uniform temperature distribution inside the adiabatic shear band. Strong evidences indicate that temperature distribution inside the shear band has periodic patterns in both space and time, confirming the latest experimental results of P. Guduru et al. [Mech. Mater. (2000), submitted]. This suggests that there may exist a thermal\u2013mechanical instability within the adiabatic shear band, reminiscent of hydrodynamic instability due to viscous heating.", "doi": "10.1016/S0045-7825(01)00245-6", "issn": "0045-7825", "publisher": "Elsevier", "publication": "Computer Methods in Applied Mechanics and Engineering", "publication_date": "2001-11-09", "series_number": "1-2", "volume": "191", "issue": "1-2", "pages": "73-92" }, { "id": "authors:qp5tz-zhm88", "collection": "authors", "collection_id": "qp5tz-zhm88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:GUDpre01", "type": "article", "title": "Observations of transient high temperature vortical microstructures in solids during adiabatic shear banding", "author": [ { "family_name": "Guduru", "given_name": "P. R.", "clpid": "Guduru-P-R" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "By using a unique infrared high-speed camera especially constructed for recording highly transient temperature fields at the microscale, we are able to reveal the spatial and temporal microstructure within dynamically growing shear bands in metals. It is found that this structure is highly nonuniform and possesses a transient, short range periodicity in the direction of shear band growth in the form of an array of intense \"hot spots\" reminiscent of the well-known, shear-induced hydrodynamic instabilities in fluids. This is contrary to the prevailing classical view that describes the deformations and the temperatures within shear bands as being essentially one-dimensional fields. These observations are also reminiscent of the nonuniform structure of localized shear regions believed to exist, at an entirely different length scale, in the earth's lower crust and upper mantle.", "doi": "10.1103/PhysRevE.64.036128", "issn": "1063-651X", "publisher": "Physical Review E", "publication": "Physical Review E", "publication_date": "2001-09", "series_number": "3", "volume": "64", "issue": "3", "pages": "Art. No. 036128" }, { "id": "authors:dzpd8-ms393", "collection": "authors", "collection_id": "dzpd8-ms393", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150227-142723796", "type": "article", "title": "Dynamic full field measurements of crack tip temperatures", "author": [ { "family_name": "Guduru", "given_name": "P. R.", "clpid": "Guduru-P-R" }, { "family_name": "Zehnder", "given_name": "A. T.", "clpid": "Zehnder-A-T" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "This paper presents a detailed investigation of the evolution of temperature field at the tip of a stationary crack subjected to dynamic loading in two different types of steels. A high speed two-dimensional infrared camera was used to image the temperature fields at the crack tips. In a high strength maraging steel, the thermograms reveal the development of plastic zone and the process of crack initiation and propagation. In ductile HY100 steel, the thermograms are used to estimate the evolution of J integral and its critical value at crack initiation. The temperature images are also used to investigate the dominance of HRR field around the crack tip.", "doi": "10.1016/S0013-7944(01)00045-5", "issn": "0013-7944", "publisher": "Elsevier", "publication": "Engineering Fracture Mechanics", "publication_date": "2001-09", "series_number": "14", "volume": "68", "issue": "14", "pages": "1535-1556" }, { "id": "authors:789kh-kbp41", "collection": "authors", "collection_id": "789kh-kbp41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141027-101750993", "type": "article", "title": "How fast is rupture during an earthquake? New insights from the 1999 Turkey Earthquakes", "author": [ { "family_name": "Bouchon", "given_name": "Michael", "clpid": "Bouchon-M" }, { "family_name": "Bouin", "given_name": "Marie-Paule", "clpid": "Bouin-M-P" }, { "family_name": "Karabulut", "given_name": "Hayrullah", "clpid": "Karabulut-H" }, { "family_name": "Toks\u00f6z", "given_name": "M. Nafi", "clpid": "Toks\u00f6z-M-N" }, { "family_name": "Dietrich", "given_name": "Michel", "clpid": "Dietrich-M" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "We report that during the two devastating 1999 earthquakes in Turkey, rupture propagated over a large part of the nearly 200km long fault zone at supershear speed approaching 5km/s. We present observations and modeling which confirm the original inference of supershear rupture during the Izmit earthquake and we show that supershear rupture also occurred during the D\u00fczce earthquake. We show that the rupture velocity measured\u2014about \u221a2 times the shear wave velocity\u2014is the value predicted by theoretical studies in fracture dynamics. We look for clues to explain these observations.", "doi": "10.1029/2001GL013112", "issn": "0094-8276", "publisher": "American Geophysical Union", "publication": "Geophysical Research Letters", "publication_date": "2001-07-15", "series_number": "14", "volume": "28", "issue": "14", "pages": "2723-2726" }, { "id": "authors:8dp8d-d1k28", "collection": "authors", "collection_id": "8dp8d-d1k28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150227-145757124", "type": "article", "title": "Dynamic shear bands: an investigation using high speed optical and infrared diagnostics", "author": [ { "family_name": "Guduru", "given_name": "P. R.", "clpid": "Guduru-P-R" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "This paper presents an experimental investigation of the initiation and propagation characteristics of dynamic shear bands in C300 maraging steel. Pre-fatigued single edge notched specimens were impacted on the edge under the notch to produce shear dominated mixed mode stress fields. The optical technique of coherent gradient sensing (CGS) was employed to study the evolution of the mixed mode stress intensity factors. Simultaneously, a newly developed two-dimensional high speed infrared (IR) camera was employed to observe the temperature field evolution during the initiation and propagation of the shear bands. Possible criteria for failure mode selection are discussed. The IR images, for the first time, revealed the transition of crack tip plastic zone into a shear band and also captured the structure of the tip of a propagating shear band. These thermographs support the notion of a diffuse shear band tip and reveal \"hot spots\" distributed along the length of a well-developed shear band.", "doi": "10.1016/S0167-6636(01)00051-5", "issn": "0167-6636", "publisher": "Elsevier", "publication": "Mechanics of Materials", "publication_date": "2001-07", "series_number": "7", "volume": "33", "issue": "7", "pages": "371-402" }, { "id": "authors:8sdrd-qey59", "collection": "authors", "collection_id": "8sdrd-qey59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:LEEapl01", "type": "article", "title": "Full-field optical measurement of curvatures in ultra-thin-film\u2013substrate systems in the range of geometrically nonlinear deformations", "author": [ { "family_name": "Lee", "given_name": "Hansuk", "clpid": "Lee-H" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Freund", "given_name": "L. B.", "clpid": "Freund-L-B" } ], "abstract": "This article describes coherent gradient sensing (CGS) as an optical, full-field, real-time, nonintrusive, and noncontact technique for the measurement of curvatures and nonuniform curvature changes in film-substrate systems. The technique is applied to the study of curvature fields in thin Al films (6 mum) deposited on thin circular silicon wafers (105 mum) of \"large\" in-plane dimensions (50.8 mm in diameter) subjected to thermal loading histories. The loading and geometry is such that the system experiences deformations that are clearly within the nonlinear range. The discussion is focused on investigating the limits of the range of the linear relationship between the thermally induced mismatch strain and the substrate curvature, on the degree to which the substrate curvature becomes spatially nonuniform in the range of geometrically nonlinear deformation, and finally, on the bifurcation of deformation mode from axial symmetry to asymmetry with increasing mismatch strain. Results obtained on the basis of both simple models and more-detailed finite-element simulations are compared with the full-field CGS measurements with the purpose of validating the analytical and numerical models.", "doi": "10.1063/1.1364650", "issn": "0021-8979", "publisher": "Journal of Applied Physics", "publication": "Journal of Applied Physics", "publication_date": "2001-06-01", "series_number": "11", "volume": "89", "issue": "11", "pages": "6116-6129" }, { "id": "authors:d6b3w-0fb81", "collection": "authors", "collection_id": "d6b3w-0fb81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:ZEHrsi00", "type": "article", "title": "Million frames per second infrared imaging system", "author": [ { "family_name": "Zehnder", "given_name": "Alan T.", "clpid": "Zehnder-A-T" }, { "family_name": "Guduru", "given_name": "Pradeep R.", "clpid": "Guduru-P-R" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "An infrared imaging system has been developed for measuring the temperature increase during the dynamic deformation of materials. The system consists of an 8\u00d78 HgCdTe focal plane array, each with its own preamplifier. Outputs from the 64 detector/preamplifiers are digitized using a row-parallel scheme. In this approach, all 64 signals are simultaneously acquired and held using a bank of track and hold amplifiers. An array of eight 8:1 multiplexers then routes the signals to eight 10 MHz digitizers, acquiring data from each row of detectors in parallel. The maximum rate is one million frames per second. A fully reflective lens system was developed, consisting of two Schwarszchild objectives operating at infinite conjugation ratio. The ratio of the focal lengths of the objectives determines the lens magnification. The system has been used to image the distribution of temperature rise near the tip of a notch in a high strength steel sample (C-300) subjected to impact loading by a drop weight testing machine. The results show temperature rises at the crack tip up to around 70 K. Localization of temperature, and hence, of deformation into \"U\" shaped zones emanating from the notch tip is clearly seen, as is the onset of crack propagation.", "doi": "10.1063/1.1310350", "issn": "0034-6748", "publisher": "Review of Scientific Instruments", "publication": "Review of Scientific Instruments", "publication_date": "2000-10", "series_number": "10", "volume": "71", "issue": "10", "pages": "3762-3768" }, { "id": "authors:ym4hp-s8w59", "collection": "authors", "collection_id": "ym4hp-s8w59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171213-085245977", "type": "article", "title": "Three dimensional cohesive-element analysis and experiments of dynamic fracture in C300 steel", "author": [ { "family_name": "Pandolfi", "given_name": "A.", "orcid": "0000-0002-7084-7456", "clpid": "Pandolfi-A" }, { "family_name": "Guduru", "given_name": "P. R.", "clpid": "Guduru-P-R" }, { "family_name": "Ortiz", "given_name": "M.", "orcid": "0000-0001-5877-4824", "clpid": "Ortiz-M" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The dynamic drop-weight test is taken as a convenient basis for assessing the fidelity and predictive ability of cohesive models of fracture in applications involving dynamic crack growth. In the experimental phase of the study, coherent gradient sensing (CGS) has been used to study dynamic fracture in C300 maraging steel. The specimens were subjected to three-point bend impact loading under a drop weight tower. High-speed photographs of the CGS interferograms were analyzed to determine the crack tip location, the velocity and the dynamic fracture toughness as a function of time. Post-mortem examination of the specimens revealed the fractography of the fracture surfaces, including the development of shear lips. In a parallel numerical phase of the study, fracture has been modeled by recourse to an irreversible cohesive law embedded into cohesive elements. These cohesive elements govern all aspects of the separation and closure of the incipient cracks. The cohesive behavior of the material is assumed to be rate independent. The finite element model is three dimensional and consists of quadratic ten-noded tetrahedra. The numerical simulations have proven highly predictive of a number of observed features, including: the crack growth initiation time; the trajectory of the propagating crack tip; and the formation of shear lips near the lateral surfaces. The simulations therefore establish the feasibility of using cohesive models of fracture and cohesive elements to predict dynamic crack-growth initiation and propagation in three dimensions.", "doi": "10.1016/S0020-7683(99)00155-9", "issn": "0020-7683", "publisher": "Elsevier", "publication": "International Journal of Solids and Structures", "publication_date": "2000-07", "series_number": "27", "volume": "37", "issue": "27", "pages": "3733-3760" }, { "id": "authors:ca49t-wm037", "collection": "authors", "collection_id": "ca49t-wm037", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180803-080941028", "type": "article", "title": "Dynamic Shear-Dominated, Supersonic Crack Growth in Bimaterial and Layered Systems and Relationship to Earthquake Rupture", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Samudrala", "given_name": "Omprakash", "clpid": "Samudrala-O" }, { "family_name": "Singh", "given_name": "Raman P.", "clpid": "Singh-R-P" } ], "abstract": "This paper describes experimental observations of various phenomena characteristic of dynamic intersonic decohesion of bimaterial interfaces. The optical method of coherent gradient sensing is used in conjunction with high speed photography to explore the nature of the large scale contact formation at the vicinity of a running crack in a PMMA/steel bimaterial system. Theoretical predictions of crack tip speed regimes where large scale contact is implied are confirmed. A physical model for intersonic crack propagation along bimaterial interfaces is presented and ratified in view of most recent experimental observations and theoretical developments.", "doi": "10.1515/JMBM.2000.11.1-3.191", "issn": "0334-8938", "publisher": "De Gruyter", "publication": "Journal of the Mechanical Behavior of Materials", "publication_date": "2000-06", "series_number": "1-3", "volume": "11", "issue": "1-3", "pages": "191-204" }, { "id": "authors:7hhd9-rr083", "collection": "authors", "collection_id": "7hhd9-rr083", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150226-165652488", "type": "article", "title": "Partition of Plastic Work into Heat and Stored Energy in Metals", "author": [ { "family_name": "Hodowany", "given_name": "J.", "clpid": "Hodowany-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Rosakis", "given_name": "P.", "clpid": "Rosakis-P" } ], "abstract": "This study investigates heat generation in metals during plastic deformation. Experiments were designed to measure the partition of plastic work into heat and stored energy during dynamic deformations under adiabatic conditions. A servohydraulic load frame was used to measure mechanical properties at lower strain rates, 10^(\u22123) s^(\u22121) to 1 s^(\u22121). A Kolsky pressure bar was used to determine mechanical properties at strain rates between 10^3 s^(\u22121) and 10^4 s^(\u22121). For dynamic loading, in situ temperature changes were measured using a high-speed HgCdTe photoconductive detector. An aluminum 2024-T3 alloy and \u03b1-titanium were used to determine the dependence of the fraction of plastic work converted to heat on strain and strain rate. The flow stress and \u03b2 for 2024-T3 aluminum alloy were found to be a function of strain but not strain rate, whereas they were found to be strongly dependent on strain rate for \u03b1-titanium.", "doi": "10.1007/BF02325036", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "2000-06", "series_number": "2", "volume": "40", "issue": "2", "pages": "113-123" }, { "id": "authors:bzdz6-0yd40", "collection": "authors", "collection_id": "bzdz6-0yd40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150226-170425585", "type": "article", "title": "A Thermodynamic Internal Variable Model for the Partition of Plastic Work into Heat and Stored Energy in Metals", "author": [ { "family_name": "Rosakis", "given_name": "P.", "clpid": "Rosakis-P" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Hodowany", "given_name": "J.", "clpid": "Hodowany-J" } ], "abstract": "The energy balance equation for elastoplastic solids includes heat source terms that govern the conversion of some of the plastic work into heat. The remainder contributes to the stored energy of cold work due to the creation of crystal defects. This paper is concerned with the fraction \u03b2 of the rate of plastic work converted into heating. We examine the status of the common assumption that \u03b2 is a constant with regard to the thermodynamic foundations of thermoplasticity and experiments. A general internal-variable theory is introduced and restricted to abide by the second law of thermodynamics. Experimentally motivated assumptions reduce this theory to a special model of classical thermoplasticity. The only part of the internal energy not determined from the isothermal response is the stored energy of cold work, a function only of the internal variables. We show that this function can be inferred from stress and temperature data from a single adiabatic straining experiment. Experimental data from dynamic Kolsky-bar tests at various strain rates yield a unique stored energy function. Its knowledge is crucial for the determination of the thermomechanical response in non-isothermal processes. Such a prediction agrees well with results from dynamic tests at different rates. In these experiments, \u03b2 is found to depend strongly on both strain and strain rate for various engineering materials. The model is successful in predicting this dependence. Requiring \u03b2 to be constant is thus an approximation of dubious validity.", "doi": "10.1016/S0022-5096(99)00048-4", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "2000-03", "series_number": "3", "volume": "48", "issue": "3", "pages": "581-607" }, { "id": "authors:px2cr-yjj66", "collection": "authors", "collection_id": "px2cr-yjj66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190930-110457541", "type": "article", "title": "Intersonic shear crack growth along weak planes", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Samudrala", "given_name": "Omprakash", "clpid": "Samudrala-O" }, { "family_name": "Coker", "given_name": "Demirkan", "orcid": "0000-0001-7385-7089", "clpid": "Coker-Demirkan" } ], "abstract": "Classical dynamic fracture theories predict the Rayleigh surface wave speed (c_R ) to be the limiting speed of propagation for mode-I cracks in constitutively homogeneous, isotropic, linear elastic materials subjected to remote loading. For mode-II cracks, propagating along prescribed straight line paths, the same theories, while excluding the possibility of crack growth in the speed regime between c_R and the shear wave speed, c_s , do not exclude intersonic (c_s <\u03c5", "doi": "10.1007/s100190050009", "issn": "1432-8917", "publisher": "Taylor & Francis", "publication": "Materials Research Innovations", "publication_date": "2000-03", "series_number": "4", "volume": "3", "issue": "4", "pages": "236-243" }, { "id": "authors:6c6b8-g8g44", "collection": "authors", "collection_id": "6c6b8-g8g44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150227-095546315", "type": "article", "title": "Dynamic Failure Mechanics", "author": [ { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "Advances in computing as well as measurement instrumentation have recently allowed for the investigation of a wider spectrum of physical phenomena in dynamic failure than previously possible. The current status and potential topics for research in dynamic failure mechanics are described in this article. These include basic research in dynamic crack initiation and growth in brittle materials, elastic\u2013plastic solids, heterogeneous solids, such as layered materials and composites, and adiabatic shear banding in ductile materials. Research that would benefit and advance practical applications such as aircraft hardening, micrometeorite impact shielding and high speed machining is also outlined. For each of the topics, research needs in terms of theory, numerical simulation and validation as well as experimentation are described.", "doi": "10.1016/S0020-7683(99)00097-9", "issn": "0020-7683", "publisher": "Elsevier", "publication": "International Journal of Solids and Structures", "publication_date": "2000-01", "series_number": "1-2", "volume": "37", "issue": "1-2", "pages": "331-348" }, { "id": "authors:jh0sj-st066", "collection": "authors", "collection_id": "jh0sj-st066", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-164322770", "type": "article", "title": "Analysis of intersonic crack growth in unidirectional fiber-reinforced composites", "author": [ { "family_name": "Huang", "given_name": "Y.", "clpid": "Huang-Y" }, { "family_name": "Wang", "given_name": "W.", "clpid": "Wang-W" }, { "family_name": "Liu", "given_name": "C.", "clpid": "Liu-C" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Recent experiments on dynamic fracture of unidirectional fiber-reinforced graphite/epoxy composite materials showed that, in Mode I, the crack tip velocity could never exceed the shear wave speed, while the crack tip velocity in Mode II not only exceeded the shear wave speed but also approached a stable velocity at which the crack grew for a substantial period of time in experiments. The experimentally obtained fringe patterns also clearly showed the existence of shear shock waves when the crack tip velocity exceeded the shear wave speed. In the present study, we have obtained the asymptotic fields near an intersonically propagating crack tip. It is shown that Mode-I intersonic crack propagation is impossible because the crack tip energy release rate supplied by the elastic asymptotic field is negative and unbounded, which is physically unacceptable since a propagating crack tip cannot radiate out energy. For Mode II, however, it is established that there exists a single crack tip velocity (higher than the shear wave speed) that gives a finite and positive crack tip energy release rate. At all other intersonic crack tip speeds the energy release rate supplied by the elastic asymptotic field is identically zero. This critical crack tip velocity agrees well with the stable crack tip velocity observed in experiments. The synthetically obtained fringe patterns based on the asymptotic field also agree with experimentally obtained fringe patterns, particularly on the existence of the shock waves.", "doi": "10.1016/S0022-5096(98)00124-0", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "1999-09", "series_number": "9", "volume": "47", "issue": "9", "pages": "1893-1916" }, { "id": "authors:c77sv-bzv86", "collection": "authors", "collection_id": "c77sv-bzv86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141121-151007117", "type": "article", "title": "Cracks Faster than the Shear Wave Speed", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Samudrala", "given_name": "O.", "clpid": "Samudrala-O" }, { "family_name": "Coker", "given_name": "D.", "orcid": "0000-0001-7385-7089", "clpid": "Coker-Demirkan" } ], "abstract": "Classical dynamic fracture theories predict the surface wave speed to be the limiting speed for propagation of in-plane cracks in homogeneous, linear elastic materials subjected to remote loading. This report presents experimental evidence to the contrary. Intersonic shear-dominated crack growth featuring shear shock waves was observed along weak planes in a brittle polyester resin under far-field asymmetric loading. When steady-state conditions were attained, the shear cracks propagated at speeds close to \u221a2 times the material shear wave speed. These observations have similarities to shallow earthquake events where intersonic shear rupture speeds have been surmised.", "doi": "10.1126/science.284.5418.1337", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1999-05-21", "series_number": "5418", "volume": "284", "issue": "5418", "pages": "1337-1340" }, { "id": "authors:hfsy1-xhq05", "collection": "authors", "collection_id": "hfsy1-xhq05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151124-101329882", "type": "monograph", "title": "Cracks Faster Than the Shear Wave Speed", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Samudrala", "given_name": "O.", "clpid": "Samudrala-O" }, { "family_name": "Coker", "given_name": "D.", "orcid": "0000-0001-7385-7089", "clpid": "Coker-Demirkan" } ], "abstract": "Classical dynamic fracture theories predict the Rayleigh surface wave speed to be the limiting speed for propagation of in-plane cracks in homogeneous, linear-elastic materials subjected to remote loading. However, in the present\nstudy, experimental evidence to the contrary is reported, in which intersonic shear dominated crack growth is seen along weak planes in Homalite-100 under far-field asymmetric loading. It is seen that mode-II (in-plane shear) conditions are essential to attain intersonic crack-tip speeds. The stress field generated by\nthe intersonically propagating crack-tip is recorded using photoelasticity and high speed photography. Intersonic shear cracks, featuring shear shock waves\nand large scale crack face frictional contact, are initially highly unstable and\ncrack-tip speeds vary from the shear wave speed to the dilatational wave speed of the material. As steady state conditions are achieved, the mode-II intersonic\ncracks propagate at a constant speed of \u221a2c_s. These observations have potential implications in geological settings where intersonic rupture velocities have been\nreported for crustal earthquakes.", "doi": "10.7907/fcw8-1577", "publisher": "California Institute of Technology", "publication_date": "1998-12" }, { "id": "authors:kwdf1-3v169", "collection": "authors", "collection_id": "kwdf1-3v169", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150226-154026983", "type": "article", "title": "Dynamic Crack Initiation in Ductile Steels", "author": [ { "family_name": "Guduru", "given_name": "P. R.", "clpid": "Guduru-P-R" }, { "family_name": "Singh", "given_name": "R. P.", "clpid": "Singh-R-P" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "The goal of the work presented here is to study dynamic crack initiation in ductile steels (Ni\u2013Cr steel and 304 stainless steel) at different loading rates and to establish appropriate dynamic failure criteria. A variety of infrared and visible optical methods and high-speed photography are used in this study. Precracked steel specimens are subjected to dynamic three-point bend loading by impacting them in a drop weight tower. During the dynamic deformation and fracture initiation process the time history of the transient temperature in the vicinity of the crack tip is recorded experimentally using a high-speed infrared detector. The dynamic temperature trace in conjunction with the HRR solution is used to determine the time history of the dynamic J-integral J^d(t), and to establish the dynamic fracture initiation toughness, J^d_c. The measurements made using high-speed thermography are validated through comparison with determination of J^d(t) by dynamic optical measurements of the crack tip opening displacement (CTOD). Finally, the micromechanisms of fracture initiation are investigated by studying the fracture surface using scanning electron microscopy.", "doi": "10.1016/S0022-5096(98)00035-0", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "1998-10-01", "series_number": "10", "volume": "46", "issue": "10", "pages": "1997-2016" }, { "id": "authors:ewmvh-h8c20", "collection": "authors", "collection_id": "ewmvh-h8c20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150226-152919848", "type": "article", "title": "On the growth of shear bands and failure-mode transition in prenotched plates: A comparison of singly and doubly notched specimens", "author": [ { "family_name": "Zhou", "given_name": "M.", "clpid": "Zhou-M" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "Recent studies of the initiation and propagation of shear bands using doubly or singly notched plates loaded asymmetrically have yielded valuable insight into this phenomenon. The same experiments also demonstrated that the shear banding mode of failure and a more brittle, \"fracture\", mode of failure can coexist in the impact-loaded specimens and transitions between the two modes were documented. However, different investigators have reported significantly different types of failure mode transitions. Due to the slightly different experimental configurations used in the studies, direct comparisons could not be made to analyze the causes of the different results. This investigation focuses on isolating the cause of this discrepancy by conducting experiments on the same material using both configurations simultaneously. The results suggest that the different types of failure mode transitions are caused by the different material properties used in the studies and the difference in specimen geometry does not seem to be primarily responsible for the differing behaviors.", "doi": "10.1016/S0749-6419(98)00003-5", "issn": "0749-6419", "publisher": "Elsevier", "publication": "International Journal of Plasticity", "publication_date": "1998", "series_number": "4-5", "volume": "14", "issue": "4-5", "pages": "435-451" }, { "id": "authors:fhffm-wbw51", "collection": "authors", "collection_id": "fhffm-wbw51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150226-154819567", "type": "article", "title": "Experimental Determination of Dynamic Crack Initiation and Propagation Fracture Toughness in Thin Aluminum Sheets", "author": [ { "family_name": "Owen", "given_name": "D. M.", "clpid": "Owen-D-M" }, { "family_name": "Zhuang", "given_name": "S.", "clpid": "Zhuang-S" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "An experimental investigation was undertaken to characterize the dynamic fracture characteristics of 2024-T3 aluminum thin sheets ranging in thickness from 1.63\u20132.54 mm. Specifically, the critical dynamic stress intensity factor K^d_c was determined over a wide range of loading rates (expressed as the time rate of change of the stress intensity factor K^d_I) using both a servo-hydraulic loading frame and a split Hopkinson bar in tension. In addition, the dynamic crack propagation toughness, K_D, was measured as a function of crack tip speed using high sensitivity strain gages. A dramatic increase in both K^d_c and K_D was observed with increasing loading rate and crack tip speed, respectively. These relations were found to be independent of specimen thickness over the range of 1.5 to 2.5 mm.", "doi": "10.1023/A:1007439301360", "issn": "0376-9429", "publisher": "Kluwer Academic", "publication": "International Journal of Fracture", "publication_date": "1998", "series_number": "1-2", "volume": "90", "issue": "1-2", "pages": "153-174" }, { "id": "authors:evjkm-ybj38", "collection": "authors", "collection_id": "evjkm-ybj38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200929-143508284", "type": "article", "title": "Investigation of the mechanics of intersonic crack propagation along a bimaterial interface using coherent gradient sensing and photoelasticity", "author": [ { "family_name": "Singh", "given_name": "Raman P.", "clpid": "Singh-Raman-P" }, { "family_name": "Lambros", "given_name": "John", "clpid": "Lambros-J" }, { "family_name": "Shukla", "given_name": "Arun", "clpid": "Shukla-Arun" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "This paper describes the first experimental observations of various phenomena characteristic of dynamic intersonic decohesion of bimaterial interfaces. Two separate but complementary optical methods are used in conjunction with high speed photography to explore the nature of the large scale contact and mach wave formation at the vicinity of running cracks in two different bimaterial systems. Theoretical predictions of crack\u2010tip speed regimes where large scale contact is implied are confirmed. Also, the theoretically predicted mach wave emanating from the intersonically propagating crack\u2010tip is observed. Direct visual evidence is also obtained for another travelling mach wave emanating from the end of the intersonically moving contact zone.", "doi": "10.1098/rspa.1997.0141", "issn": "1364-5021", "publisher": "Royal Society of London", "publication": "Proceedings of the Royal Society A: Mathematical, physical, and engineering sciences", "publication_date": "1997-12-08", "series_number": "1967", "volume": "453", "issue": "1967", "pages": "2649-2667" }, { "id": "authors:vpykk-xqn78", "collection": "authors", "collection_id": "vpykk-xqn78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-161418553", "type": "article", "title": "An experimental study of dynamic delamination of thick fiber reinforced polymeric matrix composites", "author": [ { "family_name": "Lambros", "given_name": "J.", "clpid": "Lambros-J" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "Dynamic delamination of thick fiber reinforced polymeric matrix composite laminates is investigated using optical techniques and high-speed photography. The laminates used in this work are graphite/epoxy fiber reinforced, 65 percent fiber volume fraction, composite plates consisting of 48 plies (6 mm plate thickness). Two different laminate layups are tested: a quasi-isotropic arrangement and a unidirectional arrangement. The experimental setup consists of 152 mm\u00d7152 mm square plates impact loaded in an outof-plane configuration using a high-speed gas gun. Impact speeds range from 1 m/s to 30 m/s. Real-time imaging of the laminate out-of-pane displacement is performed using the lateral shearing interferometer of coherent gradient sensing (CGS) in conjunction with high-speed photography. Onset of dynamic delamination can be observed, and quantities such as delamination speeds (in some cases up to 1800 m/s) are measured and reported. A brief comparison is made with dynamic fracture experiments of the same material conducted in a separate study.", "doi": "10.1007/BF02317432", "issn": "0014-4851", "publisher": "Springer", "publication": "Experimental Mechanics", "publication_date": "1997-09", "series_number": "3", "volume": "37", "issue": "3", "pages": "360-366" }, { "id": "authors:c33gk-64k25", "collection": "authors", "collection_id": "c33gk-64k25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201201-105030731", "type": "book_section", "title": "Dynamically Growing Shear Bands in Metals: A Study of Transient Temperature and Deformation Fields", "book_title": "IUTAM Symposium on Nonlinear Analysis of Fracture", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Zhou", "given_name": "M.", "clpid": "Zhou-M" } ], "contributor": [ { "family_name": "Willis", "given_name": "J. R.", "clpid": "Willis-J-R" } ], "abstract": "The objective of our work is (1) to establish the critical conditions for initiation and growth of shear bands in pre-notched plates subjected to asymmetric impact loading (dynamic mode II, see Fig. 1); and (2) to investigate and characterize the transition in the modes of failure when such plates are subjected to a variety of loading rates (impact velocities). These failure modes which may feature either dynamic shear band growth, dynamic crack propagation or both, (see Fig. 1), have been observed in structural materials such as the high strength steels and heat-resistant titanium alloy considered in the present work. The approach is to study both the dynamic mechanical deformations and the processes of heat generation and thermal softening. This necessitates the simultaneous use of high speed optical and infrared diagnostics in the experiments. In parallel to the experimental study, full-scale thermomechanical finite element simulations are conducted to assist the development of criteria for shear band initiation and propagation. The calculations make use of constitutive parameters measured in house through material testing in a variety of strain rates. Such a combined experimental and numerical approach enables us to make direct comparisons between measurements and predictions obtained using various material constitutive and failure models.", "doi": "10.1007/978-94-011-5642-4_14", "isbn": "978-94-010-6379-1", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1997", "pages": "141-150" }, { "id": "authors:v7jxt-1x377", "collection": "authors", "collection_id": "v7jxt-1x377", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150226-104806715", "type": "article", "title": "Dynamically propagating shear bands in impact-loaded prenotched plates\u2014I. Experimental investigations of temperature signatures and propagation speed", "author": [ { "family_name": "Zhou", "given_name": "M.", "clpid": "Zhou-M" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "The initiation and propagation of shear bands are investigated by subjecting prenotched plates to asymmetric impact loading (dynamic mode-II). The materials studied are C-300 (a maraging steel) and Ti-6Al-4V. A shear band emanates from the notch tip and propagates rapidly in a direction nearly parallel to the direction of impact. When the impact velocity is higher than a critical value, the shear band propagates throughout the specimen. The shear band arrests inside the specimen when the impact velocity is below this critical value. In the latter case and for the C-300 steel, a crack initiates and propagates from the tip of the arrested shear band at an angle to the direction of shear band propagation. Microscopic examinations of the shear band and crack surfaces reveal a ductile mode of shear failure inside the shear band and an opening mode of failure for the crack. The coexistence of shear banding and fracture events in the same specimen signifies a transition in the modes of failure for this material under the conditions described. For Ti-6Al-4V, the only mode of failure observed is shear banding. While the transition is induced by changes in loading conditions, the different behaviors of these two materials suggest it is also related to material properties. The experimental investigation focuses on both the thermal and the mechanical aspects of the propagation of shear bands. Real time temperature histories along lines intersecting and perpendicular to and along the shear band path are recorded by means of a high speed infrared detector system. Experiments show that the peak temperatures inside the propagating shear bands increase with impact velocity. The highest temperature measured is in excess of 1400 \u00b0C or approximately 90% of the melting point of the C-300 steel. For Ti-6Al-4V, the peak temperatures are approximately 450 \u00b0C. In the mechanical part of the study, high speed photography is used to record the initiation and propagation of shear bands. Recorded images of propagating shear bands at different impact velocities provide histories of the speed of shear band propagation for the C-300 steel. A strong dependence of shear band speed on the impact velocity is found. The highest speed observed for the C-300 steel is approximately 1200 ms\u22121 or 40% of its shear wave speed.", "doi": "10.1016/0022-5096(96)00003-8", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "1996-06", "series_number": "6", "volume": "44", "issue": "6", "pages": "981-1006" }, { "id": "authors:5hjjd-6m442", "collection": "authors", "collection_id": "5hjjd-6m442", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:BRUjmr96", "type": "article", "title": "The dynamic compressive behavior of beryllium bearing bulk\n metallic glasses", "author": [ { "family_name": "Bruck", "given_name": "H. A.", "clpid": "Bruck-H-A" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Johnson", "given_name": "W. L.", "clpid": "Johnson-W-L" } ], "abstract": "In 1993, a new beryllium bearing bulk metallic glass with the nominal composition of Zr_(41.25)Ti_(13.75)Cu_(12.5)Ni_(10)Be_(22.5) was discovered at Caltech. This metallic glass can be cast as cylindrical rods as large as 16 mm in diameter, which permitted specimens to be fabricated with geometries suitable for dynamic testing. For the first time, the dynamic compressive yield behavior of a metallic glass was characterized at strain rates of 10^2 to 10^4/s by using the split Hopkinson pressure bar. A high-speed infrared thermal detector was also used to determine if adiabatic heating occurred during dynamic deformation of the metallic glass. From these tests it appears that the yield stress of the metallic glass is insensitive to strain rate and no adiabatic heating occurs before yielding.", "issn": "0884-2914", "publisher": "Materials Research Society", "publication": "Journal of Materials Research", "publication_date": "1996-02", "series_number": "2", "volume": "11", "issue": "2", "pages": "503-511" }, { "id": "authors:dvt7q-77n70", "collection": "authors", "collection_id": "dvt7q-77n70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141203-091643410", "type": "article", "title": "Development of a Dynamic Decohesion Criterion for Subsonic Fracture of the Interface between Two Dissimilar Materials", "author": [ { "family_name": "Lambros", "given_name": "John", "clpid": "Lambros-J" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "We present findings of an experimental study of dynamic decohesion of bimaterial systems composed of constituents with a large material property mismatch. Poly-methylmethacrylate (PMMA)-steel and PMMA-aluminium bimaterial fracture specimens were used. Dynamic one-point bend loading was accomplished with a drop-weight tower device (for low and intermediate loading rates) or a high-speed gas gun (for high loading rates). High-speed interferometric measurements were made using the lateral shearing interferometer of coherent gradient sensing in conjunction with high-speed photography. Very high crack propagation speeds (terminal crack-tip speeds up to 1.5c_s^(PMMA), where c_s^(PMMA) is the shear wave speed of PMMA) and high accelerations (of about 10^7g, where g is the acceleration of gravity) were observed and are reported. Issues regarding data analysis of the high-speed interferograms are discussed. The effects of near-tip three-dimensionality are also analysed. Dynamic complex stress factor histories are obtained by fitting the experimental data to avail-able asymptotic crack-tip fields. A dynamic crack growth criterion for crack growth along bimaterial interfaces is proposed. In the subsonic regime of crack growth it is seen that the opening and shearing displacements behind the propagating crack tip remain constant and equal to their value at initiation, i.e. the crack retains a self-similar profile during crack growth at any speed. This forms the basis of the proposed dynamic interfacial fracture criterion.", "doi": "10.1098/rspa.1995.0151", "issn": "0962-8444", "publisher": "Royal Society", "publication": "Proceedings of the Royal Society of London. Series A, Mathematical, Physical and Engineering Sciences", "publication_date": "1995-12-08", "series_number": "1943", "volume": "451", "issue": "1943", "pages": "711-736" }, { "id": "authors:fgw24-b8n42", "collection": "authors", "collection_id": "fgw24-b8n42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150225-164037543", "type": "article", "title": "Full Field Measurements of the Dynamic Deformation Field Around a Growing Adiabatic Shear Band at the Tip of a Dynamically Loaded Notch", "author": [ { "family_name": "Mason", "given_name": "James J.", "clpid": "Mason-J-J" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "The method of Coherent Gradient Sensing (CGS) is used to record the deformation field around an adiabatic shear band emanating from a pre-crack tip in C-300 steel loaded dynamically in mode II. At early times after impact, the resulting fringe pattern surrounding the shear band seems to exhibit the deformation characteristics of a mode II Dugdale plastic zone evolving under small-scale yielding conditions and, as a result, the experimental fringe patterns are fitted to the theoretical Dugdale crack deformation field by using a least squares fitting scheme. This results in values for the shear band length and the average shear stress acting on the shear band as functions of time. The shear band is observed to initiate when K^d_(11)(t) = 140 MPa\u221am and subsequently propagate with an average speed of 320 m s^(\u22121). The average shear stress on the shear band decreases from 1.6 GPa at initiation to 1.3 GPa during the later stages of propagation.", "doi": "10.1016/0022-5096(94)90067-1", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "1994-11", "series_number": "11", "volume": "42", "issue": "11", "pages": "1679-1697" }, { "id": "authors:ha7qw-mgw23", "collection": "authors", "collection_id": "ha7qw-mgw23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150225-162749467", "type": "article", "title": "On the Strain and Strain-Rate Dependence of Plastic Work Converted to Heat: An Experimental Study Using High Speed Infrared Detectors and the Kolsky Bar", "author": [ { "family_name": "Mason", "given_name": "J. J.", "clpid": "Mason-J-J" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "The conversion of plastic work to heat at high strain rates gives rise to a significant temperature increase which contributes to thermal softening in the constitutive response of many materials. This investigation systematically examines the rate of conversion of plastic work to heat in metals using a Kolsky (split Hopkinson) pressure bar and a high-speed infrared detector array. Several experiments are performed, and the work rate to heat rate conversion fraction, the relative rate at which plastic work is converted to heat, is reported for 4340 steel, 2024 aluminum and Ti-6A1-4V titanium alloys undergoing high strain and high strain rate deformation. The functional dependence of this quantity upon strain and strain rate is also reported for these metals. This quantity represents the strength of the coupling term between temperature and mechanical fields in thermomechanical problems involving plastic flow. The experimental measurement of this constitutive function is important since it is an integral part of the formulation of coupled thermomechanical field equations, and it plays an important role in failure mode selection \u2014 such as the formation of adiabatic shear bands \u2014 in metals deforming at high strain rates.", "doi": "10.1016/0167-6636(94)90054-X", "issn": "0167-6636", "publisher": "Elsevier", "publication": "Mechanics of Materials", "publication_date": "1994-03", "series_number": "2-3", "volume": "17", "issue": "2-3", "pages": "135-145" }, { "id": "authors:nnwb0-g7c38", "collection": "authors", "collection_id": "nnwb0-g7c38", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150225-160634772", "type": "article", "title": "The Conversion of Plastic Work to Heat around a Dynamically Propagating Crack in Metals", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Mason", "given_name": "J. J.", "clpid": "Mason-J-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "Investigations of the temperature rise at a dynamically propagating crack\ntip using an infrared detector array are reported. Also, a measurement of the\nfraction of plastic work converted to heat using a split hopkinson bar apparatus\nin conjunction with an infrared detector array is summarized. For 4340 steel\nit is seen that \u224885% of the plastic work is converted to heat leading to a\ntemperature rise of 300\u00b0C at a crack tip propagating 600 m/s in steel. This\nresults is compared to earlier studies that report a 450\u00b0C temperature rise at a\ncrack tip propagating 900 m/s in steel. In a titanium alloy the temperature rise\nis higher than that in steel for equal plastic work rate densities. The conditions at\nthe crack tip are shown to be adiabatic, and, as a result, this effect is due to the\ndifference in density, heat capacity and crack tip speed. Thermal conductivity has\nno effect.", "doi": "10.1515/JMBM.1993.4.4.375", "issn": "0334-8938", "publisher": "Freund Publishing House", "publication": "Journal of Mechanical Behavior of Materials", "publication_date": "1993-09", "series_number": "4", "volume": "4", "issue": "4", "pages": "375-385" }, { "id": "authors:rz0hf-4v226", "collection": "authors", "collection_id": "rz0hf-4v226", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150309-093637326", "type": "monograph", "title": "The Conversion of Plastic Work to Heat around a Dynamically Propagating Crack in Metals", "author": [ { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Mason", "given_name": "J. J.", "clpid": "Mason-J-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "Investigations of the temperature rise at a dynamically propagating crack tip using an infrared detector array are reported. Also, a measurement of the fraction of plastic work converted to heat using a split hopkinson bar apparatus in conjunction with an infrared detector array is summarized. For 4340 steel it is seen that \u224885% of the plastic work is converted to heat leading to a temperature rise of 300\u00b0C at a crack tip propagating 600 m/s in steel. This results is compared to earlier studies that report a 450\u00b0C temperature rise at a crack tip propagating 900 m/s in steel. In a titanium alloy the temperature rise is higher than that in steel for equal plastic work rate densities. The conditions at the crack tip are shown to be adiabatic, and, as a result, this effect is due to the difference in density, heat capacity and crack tip speed. Thermal conductivity has no effect.", "doi": "10.7907/f9vk-b551", "publisher": "California Institute of Technology", "publication_date": "1992" }, { "id": "authors:cyp7x-a0095", "collection": "authors", "collection_id": "cyp7x-a0095", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190221-110520688", "type": "book_section", "title": "Crack-tip deformation field measurements using coherent gradient sensing", "book_title": "Second International Conference on Photomechanics and Speckle Metrology", "author": [ { "family_name": "Tippur", "given_name": "Hareesh V.", "clpid": "Tippur-H-V" }, { "family_name": "Krishnaswamy", "given_name": "Sridhar", "clpid": "Krishnaswamy-S" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "contributor": [ { "family_name": "Chiang", "given_name": "Fu-Pen", "clpid": "Chiang-Fu-Pen" } ], "abstract": "A real time, full field, lateral shearing interferometry - coherent gradient sensing (CGS) - has recently been developed for investigating fracture in transparent and opaque solids. The resulting interference patterns are related to the mechanical fields by means of a first order diffraction analysis. The method has been successfully applied to quasi-static and dynamic crack tip deformation field mapping in homogeneous and bimaterial fracture specimens.", "doi": "10.1117/12.49513", "isbn": "9780819406828", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1991-12-01", "pages": "176-191" }, { "id": "authors:ack8r-qbt11", "collection": "authors", "collection_id": "ack8r-qbt11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190221-110520782", "type": "book_section", "title": "Interpretation of optical caustic patterns obtained during unsteady crack growth: an analysis based on a higher-order transient expansion", "book_title": "Second International Conference on Photomechanics and Speckle Metrology", "author": [ { "family_name": "Liu", "given_name": "Cheng", "clpid": "Liu-Cheng" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "contributor": [ { "family_name": "Chiang", "given_name": "Fu-Pen", "clpid": "Chiang-Fu-Pen" } ], "abstract": "The optical caustic method is re-examined considering the presence of transient effects. Based on the higher-order asymptotic expansion provided by Freund and Rosakis, regarding the stress field near a non-uniformly propagating crack tip, the caustic mapping and the initial curve equations are derived. The dynamic stress intensity factor, K^d_I(t), is related to experimentally measurable quantities of the caustic pattern by an explicit expression. It is shown that the classical analysis of caustics is a special case of the new interpretation method. The Broberg problem is used as an example problem to check the feasibility of analysing caustics in the presence of higher-order transient terms. It is shown that the caustic patterns are sensitive to transient effects, and that use of the classical analysis of caustics in the interpretation of the optical patterns for this problem may result in large errors in the value of the stress intensity factor, especially at short times after initiation.", "doi": "10.1117/12.49532", "isbn": "9780819406828", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1991-12-01", "pages": "814-825" }, { "id": "authors:6xgdj-ghr74", "collection": "authors", "collection_id": "6xgdj-ghr74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190221-110520608", "type": "book_section", "title": "Experimental investigation of dynamic mixed-mode fracture initiation", "book_title": "Second International Conference on Photomechanics and Speckle Metrology", "author": [ { "family_name": "Lambros", "given_name": "J.", "clpid": "Lambros-J-M" }, { "family_name": "Mason", "given_name": "J. J.", "clpid": "Mason-J-J" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "contributor": [ { "family_name": "Chiang", "given_name": "Fu-Pen", "clpid": "Chiang-Fu-Pen" } ], "abstract": "The use of a coherent gradient sensing (CGS) apparatus is explored in dynamic fracture mechanics investigations. The ability of the method to accurately quantify mixed-mode crack tip deformation fields is tested under dynamic loading conditions. The specimen geometry and loading follow that of Lee and Freund who give the theoretical and numerical mixed mode K values as a function of time for the testing conditions. The CGS system's measurements of KI and KII are compared with the predicted results, and good agreement is found.", "doi": "10.1117/12.49481", "isbn": "9780819406828", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1991-12-01", "pages": "70-83" }, { "id": "authors:1fb46-hns36", "collection": "authors", "collection_id": "1fb46-hns36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150225-160203923", "type": "article", "title": "On the Extent of Dominance of Asymptotic Elastodynamic Crack-tip Fields: Part II - Numerical Investigation of Three Dimensional and Transient Effects", "author": [ { "family_name": "Krishnaswamy", "given_name": "Sridhav", "clpid": "Krishnaswamy-S" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" } ], "abstract": "In Part I of this paper, the question of the extent of dominance of the mode I asymptotic elastodynamic crack-tip field (the K d I -field) was studied experimentally. Here, the results of two and three-dimensional elastodynamic finite element simulations of the drop-weight experiments are reported. The load records as obtained from the impact hammer and supports of the drop-weight loading device were used as boundary tractions in the numerical simulations. For the laboratory specimen studied, the results of the simulations indicate that the asymptotic elastodynamic field is not an adequate description of the actual fields prevailing over any sizeable region around the crack tip. This confirms the experimental results of Part I which showed that three-dimensional and transient effects necessarily have to be taken into account for valid interpretation of experimental results.", "doi": "10.1115/1.2897185", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "1991-03", "series_number": "1", "volume": "58", "issue": "1", "pages": "95-103" }, { "id": "authors:8q9mf-r9g94", "collection": "authors", "collection_id": "8q9mf-r9g94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170830-085454047", "type": "article", "title": "Dynamic crack propagation in elastic-perfectly plastic solids under plane stress conditions", "author": [ { "family_name": "Deng", "given_name": "Xiaomin", "clpid": "Deng-Xiaomin" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "the phenomenon of steady-state dynamic crack propagation in elastic-perfectly plastic solids under mode I plane stress, small-scale yielding conditions is investigated numerically. An Eulerian finite element scheme is employed. The materials are assumed to obey the von Mises yield criterion and the associated flow rule. The ratio of the crack tip plastic zone size to that of the element nearest to the crack tip is of the order of 1.6 \u00d7 104. Two subjects of general interest are discussed. These are the asymptotic structure of the crack tip stress and deformation fields, and the appropriateness of a crack growth fracture criterion based on the far-field dynamic stress intensity factor. The crack-line solution by achenbach and li (Report NU-SML-TR-No. 84-1, Dept. of Civil Engineering, Northwestern University, Evanston, IL 60201, 1984a; in Fundamentals of Deformation and Fracture (edited by B.A. Brilby et al.). Cambridge University Press, 1984b) is discussed and compared to the numerical solution. The results of this study strongly indicate that the crack tip strain and velocity fields possess logarithmic singularities, which is consistent with the assumptions in the asymptotic analysis by Gao (Int. J. Fracture 34, 111, 1987). However, it is revealed that the crack tip field variations in Gao's solution present features often contrary to the numerical findings. To this end, a preliminary asymptotic analysis is performed in an effort to resolve certain issues. Finally, the critical plastic strain criterion (mcclintock and irwin, in Fracture Toughness Testing and Its Applications, ASTM STP 381, p. 84, 1964) is adopted to obtain theoretical relations between the critical dynamic stress intensity factor and the crack propagation speed. These relations are found to agree well with experimental measurements by Rosakis et al. (J. Mech. Phys. Solids 32, 443, 1984) and by zehnder and rosakis (Int. J. Fracture, to appear 1990), performed on thin 4340 steel plates whose material characteristics match those of the calculation. The results seem to support the existence of a one-to-one relationship between the dynamic fracture toughness of the material and the crack propagation speed, for materials which fail in a locally ductile manner.", "doi": "10.1016/0022-5096(91)90047-R", "issn": "0022-5096", "publisher": "Elsevier", "publication": "Journal of the Mechanics and Physics of Solids", "publication_date": "1991", "series_number": "5", "volume": "39", "issue": "5", "pages": "683-722" }, { "id": "authors:wqb80-31122", "collection": "authors", "collection_id": "wqb80-31122", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141103-084331857", "type": "article", "title": "On the Scale of the Nonlinear Effect in a Crack Problem", "author": [ { "family_name": "Knowles", "given_name": "J. K.", "clpid": "Knowles-J-K" }, { "family_name": "Rosakis", "given_name": "A. J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "abstract": "When crack problems are analyzed on the basis of nonlinear\ntheories, such as finite elasticity or deformation theory of\nplasticity, it is inevitable that nonlinear effects will\npredominate near a crack-tip, even if the loads are small. The\nmost favorable circumstance in this regard occurs when the\nloads are so small that the zone of significant nonlinearity lies\nwithin the region of validity of the near-tip approximation to\nthe global solution of the associated linearized crack problem.\nThis situation - called small-scale yielding for crack problems\nin plasticity - permits simplifications in analysis which are\noften decisive; see, e.g., Knowles (1977) and Rice (1968).\nInsofar as we know, there are no analytical estimates\navailable of the level of load below which nonlinear effects are\nguaranteed to be small-scale in the above sense. Indeed, even a\nprecise version of the question seems to be lacking. In the present\nnote we formulate and answer such a question for an\nespecially cooperative crack problem; that corresponding to\nfinite anti-plane shear of an infinite medium containing a\ncrack of finite length for an elastic material of Neo-Hookean\ntype. The associated boundary value problem is a linear one\nfor Laplace's equation and thus can be solved globally. Nevertheless,\nthere is a significant nonlinear effect of Kelvin type in\nthe stress field. We give a condition under which this nonlinear\nresponse occurs on a small scale near the crack tips.", "doi": "10.1115/1.3171808", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "1986-09", "series_number": "3", "volume": "53", "issue": "3", "pages": "545-549" } ]