An experimental investigation is carried out to study the effects of nonproportional loading in the plastic range on a buckling load. The discrepancy between experimental and theoretical results points to some principal shortcoming in the analysis. The problem has been simplified by applying axial tensile load and external press to simple cylindrical shell specimen and observing the buckling load for various nonproportional load-paths. Results are compared to numerical predictions (BOSOR5) using classical type plasticity models such as J\u2082 deformation and J\u2082 incremental theory. Significant discrepancy was found an attributed to inadequate modeling of the nonlinear material behavior. The effects of geometrical imperfections and large deflections were found to insignificant, thereby leading to an idea how much of the discrepancy between test and theory is due to a use of inadequate plastic model. The introduction of the Southwell plot into elastic shell buckling problem reduced the already minor effects of geometric imperfections.
\r\n\r\nThe Christoffersen-Hutchinson corner theory model was introduced into BOSAR5 in its simplest form as presented by Poh-Sang Lam. Results obtained with this model, which allows corners to form on an initially smooth yield surface, displayed better agreement with experimental data. However, increased computational time and problems related to abrupt changes in load-path at the corner are a major concern at this present time.
\r\n", "doi": "10.7907/ycv3-kp17", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4421", "collection": "thesis", "collection_id": "4421", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-080516", "type": "thesis", "title": "On the Collapse of Long Thick-Walled Circular Tubes under Biaxial Loading", "author": [ { "family_name": "Madhavan", "given_name": "Raghu", "clpid": "Madhavan-Raghu" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" } ], "thesis_committee": [ { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" }, { "family_name": "Hall", "given_name": "John F.", "clpid": "Hall-J-F" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Rosakis", "given_name": "Ares J.", "clpid": "Rosakis-A-J" }, { "family_name": "Singer", "given_name": "Josef", "clpid": "Singer-J" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The collapse phenomenon of long, thick-walled tubes subjected to axial tension and external pressure is investigated. A combined experimental and analytic approach is adopted. The diameter to thickness ratio (DA) of the tubes studied is in the range 10-40.
\r\n\r\nA series of collapse tests are conducted using thick-walled, small diameter tubes of two different materials. Careful measurements of geometrical and material parameters are carried out before each collapse test. Tension-Pressure collapse envelopes are obtained for tubes of different D/t and loading paths. Collapse tests involving initially ovalized tubes are also carried out. The results show that collapse strength is strongly influenced by initial ovality.
\r\n\r\nA two-dimensional model is used for predicting the collapse strength. The limit point behavior of a long tube with initial geometric imperfections has been modeled. The tube is assumed to be under generalized plane strain conditions and the possible variations of material and geometric parameters along the length are not considered. Hill's anisotropic plasticity theory involving a quadratic yield function is used to model the anisotropies in yield shown by drawn tubes. A power law creep model is employed to assess the effect of primary creep on collapse strength.
\r\n\r\nThe interaction between collapse pressure and tension is found to depend on both material and geometric parameters. The yield behavior of the tube material strongly affects the collapse phenomenon. Initial ovality of the tube is shown to be a very important geometric parameter that influences collapse strength. The effect of primary creep on collapse is shown to be not very significant, for the type of materials used (304 stainless steel and 6061-O aluminum).
\r\n", "doi": "10.7907/VPAC-QV51", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4415", "collection": "thesis", "collection_id": "4415", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062003-092741", "primary_object_url": { "basename": "Waas_am_1988.pdf", "content": "final", "filesize": 26765568, "license": "other", "mime_type": "application/pdf", "url": "/4415/1/Waas_am_1988.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Compression Failure of Fibrous Laminated Composites in the Presence of Stress Gradients: Experiment and Analysis", "author": [ { "family_name": "Waas", "given_name": "Anthony Marius", "orcid": "0000-0002-5258-2749", "clpid": "Waas-Anthony-Marius" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" } ], "thesis_committee": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Rosakis", "given_name": "Ares J.", "clpid": "Rosakis-A-J" }, { "family_name": "Hall", "given_name": "John F.", "clpid": "Hall-J-F" }, { "family_name": "Lorenz", "given_name": "Jens", "clpid": "Lorenz-Jens" }, { "family_name": "Singer", "given_name": "Josef", "clpid": "Singer-J" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "A series of experiments were performed to determine the mechanism of failure in compressively loaded laminated plates in the presence of stress gradients generated by a circular cutout. Real time holographic interferometry and in-situ photomicrography of the hole surface, were used to observe the progression of failure.
\r\n\r\nThe test specimens are multi-layered composite flat plates, which are loaded in compression. The plates are made of two material systems, T300/BP907 and IM7/8551-7. Two different lay-ups of T300/BP907 and four different lay-ups of IM7/8551-7 are investigated.
\r\n\r\nThe load on the specimen is slowly increased and a series of interferograms are produced during the load cycle. These interferograms are video-recorded. The results obtained from the interferograms and photo-micrographs are substantiated by sectioning studies and ultrasonic C-scanning of some specimens which are unloaded prior to catastrophic failure, but beyond failure initiation. This is made possible by the servo-controlled loading mechanism that regulates the load application and offers the flexibility of unloading a specimen at any given instance in the loadtime history.
\r\n\r\nAn underlying objective of the present investigation is the identification of the physics of the failure initiation process. This required testing specimens with different stacking sequences, for a fixed hole diameter, so that consistent trends in the failure process could be identified.
\r\n\r\nIt is revealed that the failure is initiated as a localized instability in the 0\u00b0 plies at the hole surface, approximately at right angles to the loading direction. This instability emanating at the hole edge and propagating into the interior of the specimen within the 0\u00b0 plies is found to be fiber microbuckling. The microbuckling is found to occur at a local strain level of \u2243 8600 \u00b5strain at the hole edge for the IM material system. This initial failure renders a narrow zone of fibers within the 0\u00b0 plies to loose structural integrity. Subsequent to the 0\u00b0-ply failure, extensive delamination cracking is observed with increasing load. The through thickness location of these delaminations is found to depend on the position of the 0\u00b0 plies.
\r\n\r\nThe delaminated portions spread to the undamaged areas of the laminate by a combination of delamination buckling and growth, the buckling further enhancing the growth. When the delaminated area reaches a critical size, about 75-100% of the hole radius in extent, an accelerated growth rate of the delaminated portions is observed. The culmination of this last event is the complete loss of flexural stiffness of each of the delaminated portions leading to catastrophic failure of the plate. The levels of applied load and the rate at which these events occur depend on the plate stacking sequence.
\r\n\r\nA simple mechanical model is presented for the microbuckling problem. This model addresses the buckling instability of a semi-infinte layered half-plane alternatingly stacked with fibers and matrix, loaded parallel to the surface of the half-plane. The fibers are modelled using Bernoulli-Navier beam theory, and the matrix is assumed to be a linearly elastic foundation. The predicted buckling strains are found to overestimate the experimental result. However, the dependence of the buckling strain on parameters such as the fiber volume fraction, ratio of Youngs moduli of the constituents and Poisson's ratio of the matrix are obtained from the analysis. It is seen that a high fiber volume fraction, increased matrix stiffness, and perfect bonding between fiber and matrix are desirable properties for increasing the compressive strength.
", "doi": "10.7907/PP86-PE50", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4425", "collection": "thesis", "collection_id": "4425", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-092509", "type": "thesis", "title": "Response and Failure of Fluid-Filled Tanks under Base Excitation", "author": [ { "family_name": "Natsiavas", "given_name": "Sotirios", "clpid": "Natsiavas-Sotirios" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "An analytical model is developed that leads to better understanding of the response of fluid-filled tanks whose bottom may separate from and lift off the foundation, during base excitation. First, the hydrodynamic problem is solved in closed form, for the most general motion of the structure. This eliminates the fluid response unknowns and therefore only the structural degrees-of-freedom need to be considered. Then, application of Hamilton's Principle in the structural domain sets up the system equations of motion. During this procedure, the uplifting behavior is modeled by an appropriate rotational spring, placed between the foundation and the bottom of the tank. Equivalent springs are also used for modeling the ground/structure interaction. Moreover, shell flexibility and liquid sloshing effects are also incorporated and investigated.
\r\n\r\nUsing this model, results are obtained and compared with experimental data. This comparison reveals some interesting effects of the base uplift on the system response. Ground flexibility is found to reduce the effective beam-type stiffness of the structure, but this reduction is much smaller than the substantial stiffness reduction induced by the possibility of uplifting. For the cases examined, the stiffness reduction due to the base uplift changes dramatically the dynamics of the system, which in turn alters the developed hydrodynamic loads, through the fluid/structure coupling process. Also, the shell flexibility effects - which can be important for the anchored tank case - are found to be negligible for an unanchored tank. Knowledge of the structural response leads to direct calculation of the hydrodynamic loads and consequently to prediction of failure. Buckling phenomena observed experimentally at the top and the bottom of scale model tanks are studied and explained.
\r\n", "doi": "10.7907/CNWT-V417", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1100", "collection": "thesis", "collection_id": "1100", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03242008-104934", "primary_object_url": { "basename": "Freeman_je_1986.pdf", "content": "final", "filesize": 4117164, "license": "other", "mime_type": "application/pdf", "url": "/1100/1/Freeman_je_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Design of One-Kilometer-Long Antenna Sticks and Support Structure for a Geosynchronous Satellite", "author": [ { "family_name": "Freeman", "given_name": "Janet Elizabeth", "clpid": "Freeman-Janet-Elizabeth" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "This study develops a preliminary structural design for three one-kilometer-long antenna sticks and an antenna support structure for a geosynchronous earth-imaging satellite. On each of the antenna sticks is mounted a linear array of over 16,000 antenna elements. The antenna sticks are parallel to each other, and are spaced 1 km apart so that they form the corners of an imaginary triangular tube. This tube is spinning about its long axis. Antenna performance requires that the position of each antenna element be known to an accuracy of 0.5 cm, and that the spacecraft's spin axis be parallel to the earth's spin axis within one degree. Assuming that the position of each joint on each antenna stick is known, the antenna sticks are designed as beams under a uniformly distributed acceleration (due to spacecraft spin) to meet the displacement accuracy requirements for the antenna elements. Both a thin-walled round tube and a three-longeron double-laced truss are considered for the antenna stick structure. A spacecraft spinrate is chosen by considering the effects of environmental torques on the precession of a simplified spacecraft. A preliminary truss-like support structure configuration is chosen, and analyzed in quasi-static equilibrium with control thrusters firing to estimate the axial loads in the structural members. The compressive loads found by this analysis are used to design the support structure members to be buckling-critical three-longeron double-laced truss columns. Some tension-only members consisting of Kevlar cord are included in the design to eliminate the need for bulkier members. The lateral vibration modes of the individual structural members are found by conventional analysis -- the fundamental frequencies are as low as 0.0066 Hz. Finite element dynamic analyses of the structure in free vibration confirm that simplified models of the structure and members can be used to determine the structural modes and natural frequencies for design purposes.", "doi": "10.7907/0cpe-gh28", "publication_date": "1986", "thesis_type": "engd", "thesis_year": "1986" }, { "id": "thesis:4597", "collection": "thesis", "collection_id": "4597", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11182004-161353", "primary_object_url": { "basename": "Elyada_d_1985.pdf", "content": "final", "filesize": 7735025, "license": "other", "mime_type": "application/pdf", "url": "/4597/1/Elyada_d_1985.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Structural Analysis of Imperfect Three-Legged Truss Columns for Large Space Structures Applications", "author": [ { "family_name": "Elyada", "given_name": "Dov", "clpid": "Elyada-Dov" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Cohen", "given_name": "Donald S.", "clpid": "Cohen-D-S" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Roshko", "given_name": "Anatol", "clpid": "Roshko-A" }, { "family_name": "Rosakis", "given_name": "Ares J.", "orcid": "0000-0003-0559-0794", "clpid": "Rosakis-A-J" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Three-legged truss columns are basic structural components of many envisioned large outer-space structures. They constitute three longerons ('legs') forming, in the column cross-section, the vertices of an equiliateral triangle. Their longerons are held together by uniformly spaced battens while a shear web, usually made of diagonals, restrains shear deformation.
\r\n\r\nThis work deals with configurations characterized by having relatively stiff battens, longerons which are pinned to the battens and prestressed string diagonals. Considered are only simply-supported slender columns having slender longeron segments and relatively thin and lightly preloaded diagonals. The columns are allowed to have global (overall) as well as local (longeron segment) geometrical imperfections - not necessarily small ones.
\r\n\r\nInvestigated is the static structural behavior of such columns when loaded by purely axial compressive concentrated forces acting at the supports. Addressed are the topics of global and local buckling, post-buckling, imperfection sensitivity, global-local mode interaction, complete non-linear response, limit loads and diagonals slackening and post-slackening.
\r\n\r\nThe approach is a theoretical one; a system of non-linear, ordinary differential equations is set up which represents the column, and results, mostly in closed form, are obtained by solving that system for a variety of cases of varying generality.
\r\n\r\nFirst, a highly idealized case is studied in detail, in which the diagonals are removed and infinite shear rigidity is postulated instead. The results exhibit most of the essential features of the more complicated cases. Next, the case of the undeflected or only-slightly deflected column is considered. Results include the prebuckling behavior, slackening and local buckling loads, global buckling load, initial post-buckling behavior and imperfection sensitivities. Diagonals slackening in a deflecting column is studied next. This is done by means of slackening loci constructed in the load-deflection plane. Solutions are obtained for some special cases of a deflecting column. These include a complete analysis of the locally-perfect case and the cases of small load and high defection. Also obtained is an engineering-oriented load-deflection working relation valid for the most general case but based on generalization rather than on rigorous solution. A torsion-compression mode, dominant in post-slackening, is also analyzed. The work is concluded by investigating the error committed in treating continuous longerons as if they were discontinuous-pinned.
\r\n", "doi": "10.7907/YXNE-YE65", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:3354", "collection": "thesis", "collection_id": "3354", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-082416", "primary_object_url": { "basename": "Magaldi_t_1983.pdf", "content": "final", "filesize": 10867749, "license": "other", "mime_type": "application/pdf", "url": "/3354/1/Magaldi_t_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Low Velocity Impact Damage and its Propagation Under Compressive Load in Curved, Graphite/Epoxy Panels", "author": [ { "family_name": "Magaldi", "given_name": "Anthony", "clpid": "Magaldi-Anthony" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "An experimental study was conducted to investigate the influence of plate curvature on low-velocity impact damage and its propagation under compressive load in thick, Graphite/Epoxy laminates. High-speed photography coupled with the oblique-shadow moire technique indicates that initial impact damage and its subsequent propagation through delamination buckling act as separate mechanisms during the catastrophic failure process.\r\n\r\nResults of an initial-postbuckling analysis for the buckling of thin cylindrical plates in axial compression were used to assess the effect of plate curvature on the conditions necessary for delamination buckling. Although curvature was found to increase the buckling load at the expense of a greater imperfection sensitivity, the effect is insignificant in thin shells if the plate width (i.e. initial delamination width) is small compared to the plate's radius.\r\n\r\nWhen compared with the experimental and analytic findings of similar studies involving flat Gr/Ep laminates, results reveal that the 15 inch plate radius used for this series of experiments had a negligible influence on the inital damage and delamination propagation mechanisms.", "doi": "10.7907/ekat-8g08", "publication_date": "1983", "thesis_type": "engd", "thesis_year": "1983" }, { "id": "thesis:1366", "collection": "thesis", "collection_id": "1366", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04132004-084629", "type": "thesis", "title": "The Growth of Impact Damage in Compressively Loaded Laminates", "author": [ { "family_name": "Chai", "given_name": "Herzl", "clpid": "Chai-Herzl" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" }, { "family_name": "Miklowitz", "given_name": "Julius", "clpid": "Miklowitz-J" }, { "family_name": "Housner", "given_name": "George W.", "clpid": "Housner-G-W" }, { "family_name": "Corcoran", "given_name": "William Harrison", "clpid": "Corcoran-W-H" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "The thesis is divided into two chapters. The first chapter describes an experimental program carried out to determine the phenomenological aspects of composite panel failure (graphite/epoxy laminate) under simultaneous in-plane compression and low velocity transverse impact (0-250 ft/sec). High-speed photography and the shadow moire technique were used to record a full-field surface deformation history of the impacted plate. The information gained from these records, supplemented by plate sectioning and observation for interior damage, has shown that the predominant failure mechanism is the coupled effect of delamination and buckling.
\r\n\r\nIn chapter 2, this process of failure is modelled by delamination buckling wherein the local delamination stability, growth or arrest are governed by an energy release rate criterion. Various degrees of problem simplifications are employed, starting with a one-dimensional, delaminated-beam model. In the most sophisticated treatment, it is assumed that the damaged area has an elliptical shape. It was found that this model is capable of describing the growth conditions and the growth behavior of the damaged area. It was also found that the predominant parameter controlling delamination growth or arrest is the fracture energy associated with delamination.
\r\n\r\nIn the appendix at the end of this work, the fracture energy of a composite laminate is considered. A modified cleavage analysis is developed, and is applied to evaluate this quantity for two composite materials of current interest. The test results are then examined with reference to impact damage tolerance data available for these materials. A viscoelastic characterization of the two resins used to fabricate the two composites mentioned above is also provided. The results of these measurements are then examined with reference to long-term applicability of the matrix material.
", "doi": "10.7907/58D3-ZZ41", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:10805", "collection": "thesis", "collection_id": "10805", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04132018-090928397", "primary_object_url": { "basename": "Shih_C-F_1981.pdf", "content": "final", "filesize": 82437175, "license": "other", "mime_type": "application/pdf", "url": "/10805/1/Shih_C-F_1981.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Failure of Liquid Storage Tanks Due to Earthquake Excitation", "author": [ { "family_name": "Shih", "given_name": "Choon-Foo", "clpid": "Shih-Choon-Foo" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Housner", "given_name": "George W.", "clpid": "Housner-G-W" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Miklowitz", "given_name": "Julius", "clpid": "Miklowitz-J" }, { "family_name": "Wu", "given_name": "Theodore Yao-tsu", "clpid": "Wu-T-Y-T" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Above ground liquid storage tanks have suffered serious damage during earthquakes. The damage of tanks can vary from local yielding or buckling of the tank wall, to loss of contents, or to collapse which leads to an unrepairable tank. Considerable work has been carried out on this problem with varying degree of success. However, the results are largely directed toward response rather than failure prediction. The information on failure mechanisms is very limited. The present work consists of scale model testing, correlation with existing analysis and failure prediction with laboratory verification. The scale model testing incorporates dynamic similarity of the fluid/structure interaction problem. The model study shows that small plastic models can be useful in studying the dynamics and buckling of liquid-filled tanks under ground excitation even though the model does not display complete similitude. The buckling criterion proposed in this study is based upon static considerations and the complex stress field in the shell wall is supplanted by a simple field for which analytical/experimental results are available. Harmonic buckling tests demonstrate that the static buckling criterion is satisfactory even though the prebuckling stress field is time dependent. The harmonic buckling tests, when correlated with the stresses from a response analysis, also indicate that the buckling is largely dependent upon the n = 1 response, Transient buckling tests are also carried out and the results show that the linear analysis together with the static buckling criterion gives a good prediction of the failure of a full fluid-filled tank. The test parameters in these buckling tests include water depth, title angle, thickness of tank wall, top end condition, ground excitation pattern, etc. In addition, buckling tests of unanchored tanks are conducted to study the influence of changing the anchorage of the tank base. An analytical model is suggested to predict the response of an unanchored tank due to overturning moment. The current design criterion of an un\u00adanchored tank is also assessed in this study. The results of this investigation, in addition to those carried out previously, provide a better understanding of the forced vibration problem, failure criterion and appropriate design procedure for a liquid storage tank.
\r\n", "doi": "10.7907/m0v8-hs31", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:4300", "collection": "thesis", "collection_id": "4300", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10292003-134840", "primary_object_url": { "basename": "Kyriakides_s_1980.pdf", "content": "final", "filesize": 14032300, "license": "other", "mime_type": "application/pdf", "url": "/4300/1/Kyriakides_s_1980.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "On the Propagating Buckle and Its Arrest", "author": [ { "family_name": "Kyriakides", "given_name": "Stelios", "clpid": "Kyriakides-Stelios" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "If an offshore pipeline locally buckles in the presence of sufficiently large external pressure, a propagating buckle is initiated. The buckle propagates along the pipeline until it encounters a region of adverse conditions -- low pressure or an arresting device. The lowest pressure at which a buckle propagates is defined as the Propagation Pressure. An experimental study of this quantity is presented and a semiempirical expression derived by examining various models of the phenomenon. The dynamics of the Propagating Buckle are also examined and a parametric study of the steady state velocity of Propagation is carried out. A systematic way of empirically deriving the parametric dependence of arresting devices is presented and experimental results of two such arrestors are discussed. During this study a unique \"flip-flop\" mode of propagation was discovered and studied. An explanation of the phenomenon is also attempted.", "doi": "10.7907/c81x-nk02", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:4394", "collection": "thesis", "collection_id": "4394", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11032006-091936", "primary_object_url": { "basename": "Oey_kt_1979.pdf", "content": "final", "filesize": 16269340, "license": "other", "mime_type": "application/pdf", "url": "/4394/1/Oey_kt_1979.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Leading Edge Flutter of a Supercavitating Hydrofoil", "author": [ { "family_name": "Oey", "given_name": "Nicolaus Kiam Thian", "clpid": "Oey-Nicolaus-Kiam-Thian" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" } ], "thesis_committee": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" }, { "family_name": "Liepmann", "given_name": "Hans Wolfgang", "clpid": "Liepmann-H-W" }, { "family_name": "Davis", "given_name": "Leverett", "clpid": "Davis-Leverett" }, { "family_name": "Wu", "given_name": "Theodore Yao-tsu", "clpid": "Wu-T-Y-T" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Leading edge flutter is a problem that is unique to a super-cavitating hydrofoil. At high speed, the leading edge portion has been observed to oscillate while the trailing edge remains motionless.
\r\n\r\nIn this study, several flat plate hydrofoils were tested. The experimental results indicate that the phenomenon is a complex function of speed, angle of attack, cavitation number and mass ratio. Leading edge flutter was also observed to cause cavity pinching. A theoretical study was also conducted. Two mathematical models are presented here. The first one models the flexible chord foil as a rigid chord foil hinged at the trailing edge; the second model treats the fluid-structure interaction problem of a flexible chord foil cantilevered at the trailing edge. Both models resemble leading edge flutter near zero cavitation number in some respects. At short and moderate cavity lengths, leading edge flutter phenomenon is influenced by the cavity closure condition.
\r\n", "doi": "10.7907/9DGB-DW93", "publication_date": "1979", "thesis_type": "phd", "thesis_year": "1979" }, { "id": "thesis:4533", "collection": "thesis", "collection_id": "4533", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11132006-080224", "primary_object_url": { "basename": "Wojcik_gl_1977.pdf", "content": "final", "filesize": 3029411, "license": "other", "mime_type": "application/pdf", "url": "/4533/1/Wojcik_gl_1977.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Self-Similar Elastodynamic Solutions for the Plane Wedge", "author": [ { "family_name": "Wojcik", "given_name": "Gregory Lynn", "clpid": "Wojcik-Gregory-Lynn" } ], "thesis_advisor": [ { "family_name": "Sechler", "given_name": "Ernest Edwin", "clpid": "Sechler-E-E" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Sechler", "given_name": "Ernest Edwin", "clpid": "Sechler-E-E" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Miklowitz", "given_name": "Julius", "clpid": "Miklowitz-J" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Wave propagation in a two-dimensional elastic wedge is fundamental to a large class of problems in elastodynamic theory, however until now analytical solutions to all but certain degenerate cases were unknown. In this thesis a general elastodynamic solution is derived for the wedge in a state of plane strain. Surface tractions are, restricted to uniform normal and shear loads spreading from the wedge vertex at constant velocity. The geometry and loading then allow self-similar solutions of the governing differential equations and boundary conditions in hyperbolic and elliptic domains. Hyperbolic solutions are found in terms of the elliptic solutions by the method of characteristics, while elliptic solutions are reduced using analytic function theory to two independent Fredholm integral equations of the second kind in one dimension. Although numerical solutions are beyond the scope of the investigation, the integral equations are solvable by standard techniques. Such solutions can be used to solve a number of plane elastodynamic problems involving an edge.", "doi": "10.7907/E1D3-0T11", "publication_date": "1977", "thesis_type": "phd", "thesis_year": "1977" }, { "id": "thesis:6067", "collection": "thesis", "collection_id": "6067", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09282010-112038866", "primary_object_url": { "basename": "Bremmer_df_1975.pdf", "content": "final", "filesize": 1209015, "license": "other", "mime_type": "application/pdf", "url": "/6067/1/Bremmer_df_1975.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "An Efficient Approximate Solution Method for Predicting the Buckling of Axially Compressed Imperfect Cylindrical Shells", "author": [ { "family_name": "Bremmer", "given_name": "David Franklin", "clpid": "Bremmer-David-Franklin" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" }, { "family_name": "Sechler", "given_name": "Ernest Edwin", "clpid": "Sechler-E-E" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": " A theoretical investigation of an efficient numerical solution scheme to solve approximately the nonlinear Donnell equations for imperfect isotropic cylindrical shells with edge restraints and under axial compression was carried out.\r\n\r\n The nonlinear partial differential equations have been reduced to an equivalent set of nonlinear ordinary differential equations. The resulting two-point boundary value problem was solved, first, by using \"Newton's Method of Quasilinearization\" to obtain a set of linearized differential equations for the correction terms and, secondly, these differentials were approximated as finite differences to cast the linearized system of equations into the form of a block tridiagonal matrix equation. The Potters' Method solution scheme was used to solve efficiently the block tridiagonal matrix equation. By successive iterations a solution to the set of nonlinear ordinary differential equations was obtained.\r\n\r\n The use of this method makes it possible to investigate how the axial load level at the limit point is affected by the following factors: the choice of inplane boundary conditions, the prebuckling growth caused by the radial edge constraint, the orientation and shape of the axisymmetric and asymmetric imperfection components, and the finite length of the shell.", "doi": "10.7907/S3M9-NT50", "publication_date": "1975", "thesis_type": "engd", "thesis_year": "1975" }, { "id": "thesis:6057", "collection": "thesis", "collection_id": "6057", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09272010-093909310", "type": "thesis", "title": "Optimization of Arch and Shell Structures", "author": [ { "family_name": "Moronval", "given_name": "Marc Jules", "clpid": "Moronval-Marc-Jules" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Structural optimization of structures with respect to their shape and thickness distribution is studied using a variational approach. The behavioral constraint is either the state of stress or the stiffness.\r\nThe boundary value problems, derived using Optimal Control theory, are solved with the parallel shooting technique. For statically determinant arches subjected to a uniform pressure, the contribution of the shear force is included in the behavioral constraints to prevent the problems from being singular. For the case of membrane shells of revolution supporting a combined pressure and end traction loading case, solutions were obtained up to a critical value of the load coefficient. A physical interpretation of the singularity is obtained by including the possibility\r\nof discrete rings in the formulation. A set of optimality conditions for shells of revolution described by the bending theory, satisfying a stiffness constraint, is derived. The problem is found to be ill posed when the shear contribution is not included in the structural operator.\r\n", "doi": "10.7907/EMCP-7017", "publication_date": "1975", "thesis_type": "phd", "thesis_year": "1975" }, { "id": "thesis:6047", "collection": "thesis", "collection_id": "6047", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09242010-083549862", "primary_object_url": { "basename": "Kendall_f_1973.pdf", "content": "final", "filesize": 21757045, "license": "other", "mime_type": "application/pdf", "url": "/6047/1/Kendall_f_1973.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "An Experimental Investigation of the Nonlinear Vibration of Cylindrical Shells", "author": [ { "family_name": "Kendall", "given_name": "Frank, III", "clpid": "Kendall-Frank-III" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "An experimental investigation of the nonlinear vibrations of\r\ncylindrical shells was undertaken. An aluminum shell was vibrated by means of an induction shaker. An optical device was used to obtain radial displacement measurements. Several modes of vibration were studied in detail. Various nonlinear effects were observed. These included nonlinearity in the driven mode frequency response\r\ncurve, the participation of the companion mode, and the participation of axisymmetric response at twice the driven frequency. The experimental results indicated only a softening type nonlinearity. The response of the companion mode was significant in several of the modes studied and was of a more complex nature than was predicted by previous theoretical work.\r\n", "doi": "10.7907/Q4F6-C984", "publication_date": "1974", "thesis_type": "engd", "thesis_year": "1974" }, { "id": "thesis:6000", "collection": "thesis", "collection_id": "6000", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08192010-160559026", "primary_object_url": { "basename": "Mahale_nk_1973.pdf", "content": "final", "filesize": 44111624, "license": "other", "mime_type": "application/pdf", "url": "/6000/1/Mahale_nk_1973.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Failure of Precracked Fiber Reinforced Composite Plate", "author": [ { "family_name": "Mahale", "given_name": "Narayan Krishna", "clpid": "Mahale-Narayan-Krishna" } ], "thesis_advisor": [ { "family_name": "Knauss", "given_name": "Wolfgang Gustav", "clpid": "Knauss-W-G" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "In the following pages a theoretical and experimental investigation of the fracture of a precracked carbon fiber reinforced composite is presented. The work deals mainly with a unidirectional composite having the crack aligned parallel to the fibers. We put forth some ideas on how to extend the failure criterion of the above restricted case to a more general one of multidirectional composites.\r\nThe failure criterion proposed is based on an energy argument similar to that proposed by Griffith for isotropic solids. For the purpose of stress analysis the material under consideration is assumed to be homogeneous and orthotropic. Lekhnitskii's complex variable method\r\nof stress analysis of the two dimensional elasticity problems for anisotropic bodies is used in the theoretical investigation.\r\n", "doi": "10.7907/DPK2-YA94", "publication_date": "1973", "thesis_type": "engd", "thesis_year": "1973" }, { "id": "thesis:5431", "collection": "thesis", "collection_id": "5431", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12092009-105825918", "primary_object_url": { "basename": "Tamura_ys_1973.pdf", "content": "final", "filesize": 2786696, "license": "other", "mime_type": "application/pdf", "url": "/5431/1/Tamura_ys_1973.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Dynamic Stability of Cylindrical Shells Under Step Loading", "author": [ { "family_name": "Tamura", "given_name": "Yukio Stephen", "clpid": "Tamura-Yukio-Stephen" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "A study has been made to determine the dynamic stability of an imperfect circular cylindrical shell subject to a step loading in the axial direction. In the analysis, the radial displacement of the shell is approximated by a finite degree of freedom system. To assure that the created model is proper, its static buckling behavior was studied. It was found that the model gives the proper imperfection sensitivity behavior.\r\n\r\nThe dynamic analysis includes not only the effect of the radial inertia, but also that due to the axial inertia in an approximate manner. The critical loads are determined by numerical integration of the equation of motion. In addition a study is carried out to consider the effects of wave number of the radial mode shape, mass on the loaded edge of the shell and damping of the axial motion. Compared with the static case, there is a significant reduction of the dynamic buckling load for the high wave numbers of the radial modes. Also, there is a critical clamping value, above which the dynamic buckling load is close to the static buckling load. The dynamic buckling load approaches half of the static buckling load with increasing mass on the loading edge. Through the parametric studies of the wave number, mass, and damping factor it is concluded that due to frequency coupling between axial and radial motions, the axial inertia plays an essential role in characterizing the dynamic instability of a finite length shell.\r\n", "doi": "10.7907/MSMN-N280", "publication_date": "1973", "thesis_type": "engd", "thesis_year": "1973" }, { "id": "thesis:6016", "collection": "thesis", "collection_id": "6016", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08302010-162439924", "primary_object_url": { "basename": "Bhatia_p_1973.pdf", "content": "final", "filesize": 13561343, "license": "other", "mime_type": "application/pdf", "url": "/6016/1/Bhatia_p_1973.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Buckling of Imperfect Circular Cylindrical Shells", "author": [ { "family_name": "Bhatia", "given_name": "Prem", "clpid": "Bhatia-Prem" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "In this project, the buckling of imperfect circular cylindrical shells under uniform axial compression has been investigated. The imperfection considered is prismatic and is in the form of flat spots along the complete length of the shell. The problem is solved by considering it as an interaction problem between curved and flat panels. Shell equations are satisfied in the curved portions of the shell while flat plate equations are used in the flat spot regions. At the common edge between two adjacent panels, forces and displacements are matched to arrive at the eigenvalue problem for the critical load of the shell. Two flat spot configurations have been studied. In the first case, a single flat spot along the complete length of the shell is considered. Curved and flat panels join to form sharp corners at their common edges. Numerical results are presented to show the effect of the width of the flat spot, thickness ratio and length to radius ratio of the shell, on the buckling load of the shell. In the second case, the imperfection is in the form of two or more identical flat spots distributed uniformly along the circumference of the shell. Between two consecutive flat spots is a uniform radius cylindrical panel joining smoothly to the flat panels. This analysis is valid for any integral number of identical flat spots. Numerical results are presented for 2, 3, 4, 8-flat spots. The effect of width of flat spots, radius of curved panels, thickness ratio of the shell has been investigated. The results, presented in this paper, clearly demonstrate a very significant reduction in the buckling load of the shell below its classical value. This is true even in the presence of relatively small flat spots. This reduction becomes more severe with a decrease in the thickness of the shell or an increase in the width of the flat spot. ", "doi": "10.7907/FS7M-8D46", "publication_date": "1973", "thesis_type": "phd", "thesis_year": "1973" }, { "id": "thesis:6046", "collection": "thesis", "collection_id": "6046", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09232010-145835690", "primary_object_url": { "basename": "Ditchey_rl_1973.pdf", "content": "final", "filesize": 1777952, "license": "other", "mime_type": "application/pdf", "url": "/6046/1/Ditchey_rl_1973.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Effect of Imperfections on the Buckling of Thin Walled Cylindrical Shells", "author": [ { "family_name": "Ditchey", "given_name": "Robert Louis", "clpid": "Ditchey-Robert-Louis" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "A theoretical study of the effect of imperfections on the buckling load of a circular cylindrical shell under axial compression was carried out. The nonlinear shell equations of Donnell are solved in an approximate manner using the Potential Energy Theorem. The method of derivation and the resulting algebraic equations are com-pared to previous derivations which use a different method of solution. It was found that the resulting equations are identical to the ones derived by Galerkin's procedure, lending credence to that method. A parametric study of an imperfection model was carried out numerically. The imperfection model is similar to that originally used by Donnell, having amplitude decay with increasing wave number. The results show the effect of various rates of decay of amplitude with wave number, as well as the effect of various assumed amplitudes. Using these parameters, it is shown when shell buckling is dominated by long wave imperfections as opposed to classical short wave imperfections. It was found that if the decay of asymmetric imperfections with axial wave number is sufficiently high, that long wave imperfections can dominate. In the range of values chosen for these parameters, changes in the axisymmetric imperfection model had little effect on buckling behavior as compared to the changes in sensitivity to long waves which occur as the asymmetric model is varied.", "doi": "10.7907/TPE9-EM80", "publication_date": "1973", "thesis_type": "engd", "thesis_year": "1973" }, { "id": "thesis:6049", "collection": "thesis", "collection_id": "6049", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09242010-085617930", "primary_object_url": { "basename": "Chen_jc_1972.pdf", "content": "final", "filesize": 4632497, "license": "other", "mime_type": "application/pdf", "url": "/6049/1/Chen_jc_1972.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Nonlinear Vibration of Cylindrical Shells", "author": [ { "family_name": "Chen", "given_name": "Jay-Chung", "clpid": "Chen-Jay-Chung" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "The large amplitude vibrations of a thin-walled cylindrical shell are analyzed using the Donnell's shallow-shell equations. A perturbation method is applied to reduce the nonlinear partial differential equations into a system of linear partial differential equations. The simply-supported boundary condition and the circumferential periodicity condition are satisfied. The resulting solution indicates that in addition to the fundamental modes, the response contains asymmetric modes as well as axisymmetric modes with the frequency twice that of the fundamental modes. In the previous investigations in which the Galerkins procedure was applied, only the additional axisymrnetric modes were assumed.\r\nVibrations involving a single driven mode response are investigated. The results indicate that the nonlinearity is either softening or hardening depending on the mode. The vibrations involving both a driven mode and a companion mode are also investigated. The region where the companion mode participates in the vibration is obtained and the effects due to the participation of the companion mode are studied.\r\nAn experimental investigation is also conducted. The\r\nresults are generally in agreement with the theory. \"Non-stationary4 response is detected at some frequencies for large amplitude response where the amplitude drifts from one value to another. Various nonlinear phenomena are observed and quantitative comparisons with the theoretical results are made.\r\n", "doi": "10.7907/CBC4-MP23", "publication_date": "1972", "thesis_type": "phd", "thesis_year": "1972" }, { "id": "thesis:6142", "collection": "thesis", "collection_id": "6142", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10132010-094217970", "primary_object_url": { "basename": "Giraudbit_jn_1972.pdf", "content": "final", "filesize": 1199012, "license": "other", "mime_type": "application/pdf", "url": "/6142/1/Giraudbit_jn_1972.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Optimal Simple Structures with Bending and Membrane Stresses", "author": [ { "family_name": "Giraudbit", "given_name": "Jean-No\u00ebl", "clpid": "Giraudbit-Jean-No\u00ebl" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Structural optimization of elastic solid structures with membrane and bending stresses is studied. A necessary and sufficient optimality condition for maximum stiffness is derived using an energy formulation (minimum potential energy). In the case of pure membrane or pure bending stress states, maximum stiffness and maximum strength are governed by the same optimality condition (uniform strength design). For mixed stress states (membrane and bending), this result is not true, and a general method of approach to find a necessary condition for maximum strength is developed by means of the calculus of variation. Two particular statically indeterminate problems with one design variable to be optimized (clamped-clamped beam, clamped-clamped arch) are treated by this method, and, in both examples, maximum. strength is achieved by a uniform strength design.", "doi": "10.7907/29PJ-3X76", "publication_date": "1972", "thesis_type": "engd", "thesis_year": "1972" }, { "id": "thesis:6010", "collection": "thesis", "collection_id": "6010", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08262010-162507540", "primary_object_url": { "basename": "Van_Dillen_de_1972.pdf", "content": "final", "filesize": 4836520, "license": "other", "mime_type": "application/pdf", "url": "/6010/1/Van_Dillen_de_1972.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Vibrations of a Three-Layer Beam with a Viscoelastic Middle Layer", "author": [ { "family_name": "Van Dillen", "given_name": "David Edwin", "clpid": "Van-Dillen-David-Edwin" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "The equations governing a three-layer beam in which the middle layer is viscoelastic were derived by means of a variational principle. These equations were solved subject to arbitrary time dependent boundary conditions of both the simply-supported and cantilever type. In the simply-supported case, an eigenfunction expansion was constructed after the governing equations had been transformed through operation by a differential operator. In the cantilever case, the solution was obtained by Fourier transform with respect to time, and inversion by residue theory. An analysis of the theoretical response of the cantilever beam to steady state sinusoidal loading was carried out, and an experiment was conducted for comparison.", "doi": "10.7907/P2BD-K350", "publication_date": "1972", "thesis_type": "engd", "thesis_year": "1972" }, { "id": "thesis:1235", "collection": "thesis", "collection_id": "1235", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03312009-153153", "primary_object_url": { "basename": "Liu_t_1970.pdf", "content": "final", "filesize": 2983549, "license": "other", "mime_type": "application/pdf", "url": "/1235/1/Liu_t_1970.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "An Energy Approach to the Dynamic Buckling of Spherical Caps", "author": [ { "family_name": "Liu", "given_name": "Ting-Lung", "clpid": "Liu-Ting-Lung" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "An experimental study to determine the dynamic buckling load of a spherical cap under impulsive loading was carried out. Impulsive loading was realized experimentally by use of a spray deposited explosive (Silver Acetylide-Silver Nitrate). The experimental dynamic buckling loads were compared to the dynamic buckling loads as calculated by using an energy criterion. The critical load from the energy criterion was determined by the conducting static pressure volume tests on the spherical caps. It was found that experimental results were consistently below the dynamic buckling load as predicted by the energy criterion. It was thought that this inconsistency resulted from the fact that transition state found in the static experiment was not the same as the dynamic transition state.", "doi": "10.7907/8JD0-W843", "publication_date": "1971", "thesis_type": "engd", "thesis_year": "1971" }, { "id": "thesis:1569", "collection": "thesis", "collection_id": "1569", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05012008-155801", "primary_object_url": { "basename": "Imbert_j_1971.pdf", "content": "final", "filesize": 2558460, "license": "other", "mime_type": "application/pdf", "url": "/1569/1/Imbert_j_1971.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Effect of Imperfections on the Buckling of Cylindrical Shells", "author": [ { "family_name": "Imbert", "given_name": "Jean-Fran\u00e7ois", "clpid": "Imbert-Jean-Fran\u00e7ois" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "A theoretical investigation of the effect of general imperfections on the buckling of a cylindrical shell under axial compression was carried out. A limit point analysis was performed to determine the buckling loads using a simplified imperfection and displacement model consisting of one axisymmetric and two asymmetric components with the same circumferential wave number.\r\n\r\nThe wave number dependence of imperfections for a class of shells obtained by the same manufacturing processes was characterized by using an imperfection model to fit the experimental imperfection coefficients available. Buckling load calculations were performed using both experimental and fitted data as imperfection coefficients.\r\n\r\nFor the experimental data available the three-mode solution was found to have only a small additional effect with respect to the two-mode solution. In addition, by extrapolating imperfection coefficients for high wave numbers by means of the imperfection model, it was found that a strong interaction effect would exist between a low wave number axisymmetric mode and two classical asymmetric modes.", "doi": "10.7907/RHXA-BJ33", "publication_date": "1971", "thesis_type": "engd", "thesis_year": "1971" }, { "id": "thesis:7491", "collection": "thesis", "collection_id": "7491", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02212013-152121344", "primary_object_url": { "basename": "El Raheb-ms-1970.pdf", "content": "final", "filesize": 18248654, "license": "other", "mime_type": "application/pdf", "url": "/7491/1/El Raheb-ms-1970.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Some Approximations in the Dynamic Shell Equations", "author": [ { "family_name": "El Raheb", "given_name": "Michel Sadek", "clpid": "El-Raheb-Michel-Sadek" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "A theoretical analysis was performed on the linear dynamic\r\nequations of thin cylindrical shells to find the error committed by the\r\nDonnell assumption and the neglect of inplane inertia.
\r\n\r\nThe Donnell approximation was found to be valid at high\r\nfrequencies as compared to the ring frequencies, for all admissible\r\nsets of boundary conditions for finite length thin shells.
\r\n\r\nThe error from neglecting tangential inertia is appreciable for\r\nlong circumferential and axial wave lengths, independent of shell\r\nthickness.
\r\n\r\nThe effect of boundary conditions was investigated from an\r\nexact solution of the linear eigenvalue problem. The inplane boundary\r\nconditions proved to be very influential in the neighborhood of the\r\nminimum frequency. An approximate technique which accounts for the\r\ninplane boundary conditions was then developed and shown to be in good\r\nagreement with the exact solution.
\r\n\r\nFinally, the effect of an elastic end ring on the eigenfrequencies\r\nwas studied. The out-of-plane and torsional rigidities of the ring were\r\nfound to govern the overall shell stiffness. Considerable mode inter action\r\nwas noticed at low circumferential wave numbers for low values\r\nof ring stiffness. The computed eigenfrequencies were found to be in\r\ngood agreement with the experimental results.
\r\n\r\n", "doi": "10.7907/ejzn-dy90", "publication_date": "1970", "thesis_type": "phd", "thesis_year": "1970" }, { "id": "thesis:4570", "collection": "thesis", "collection_id": "4570", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11152005-104435", "primary_object_url": { "basename": "Delph_tj_1969.pdf", "content": "final", "filesize": 1740996, "license": "other", "mime_type": "application/pdf", "url": "/4570/1/Delph_tj_1969.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Dynamic Stability Under Impulsive Loading of Shallow Arches with Elastic End Restraints", "author": [ { "family_name": "Delph", "given_name": "Terry Joseph", "clpid": "Delph-Terry-Joseph" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "A theoretical and experimental study of the buckling under impulsive load of an arch with rotational end restraints was carried out.\r\n\r\nImpulsive loading was realized experimentally by use of the spray deposited explosive silver nitrate-silver acetylide. The experimental buckling loads were compared to those obtained by a theoretical analysis. It was found that the theoretical analysis yields a quite conservative lower bound on the magnitude of load necessary for buckling. Both uniform and nonuniform loadings were considered.\r\n\r\nIt was found that there exists a critical value of rotational spring constant above which dynamic buckling may not occur in the rigorous mathematical sense. An expression for this critical value was found.", "doi": "10.7907/GRVF-AN95", "publication_date": "1969", "thesis_type": "engd", "thesis_year": "1969" }, { "id": "thesis:4585", "collection": "thesis", "collection_id": "4585", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11162005-081618", "primary_object_url": { "basename": "Cheung_mc_1969.pdf", "content": "final", "filesize": 3112978, "license": "other", "mime_type": "application/pdf", "url": "/4585/1/Cheung_mc_1969.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Static and Dynamic Stability of Clamped Shallow Circular Arches", "author": [ { "family_name": "Cheung", "given_name": "Man Cheong", "clpid": "Cheung-Man-Cheong" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nAn experimental investigation of the relationship between the dynamic buckling and the static buckling phenomenon was carried out.\r\n\r\nThe first half of the paper studies the stability of shallow arches subjected to lateral forces. Concentrated static and step loads were applied to circular arches with geometric parameters 7 < [...] < 20. Equilibrium path and the dynamic response at the loading position were recorded. Dynamic buckling is distinct. Supercritical and subcritical responses were separated by [...] of the total load. The sensitivity of the arch to loading imperfection was studied. The effect was pronounced in the static tests but moderate in the dynamic responses.\r\n\r\nThe second half of the paper studies the response of clamped circular arches under lateral impulse. The motion of the arch was recorded by a high speed camera and the deflected arch shape was measured in detail. The response was expressed in terms of the average displacement and three generalized displacement coordinates representing the amplitudes of the assumed mode shapes. The critical impulse is defined as the impulse level at the inflection point of the curve of maximum response versus impulse.", "doi": "10.7907/8MXG-DE89", "publication_date": "1969", "thesis_type": "phd", "thesis_year": "1969" }, { "id": "thesis:4510", "collection": "thesis", "collection_id": "4510", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11112005-152910", "primary_object_url": { "basename": "Majumdar_s_1968.pdf", "content": "final", "filesize": 1525332, "license": "other", "mime_type": "application/pdf", "url": "/4510/1/Majumdar_s_1968.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Buckling of Thin Annular Plates Due to Radial Compressive Loading", "author": [ { "family_name": "Majumdar", "given_name": "Suarindranath", "clpid": "Majumdar-Suarindranath" } ], "thesis_advisor": [ { "family_name": "Sechler", "given_name": "Ernest Edwin", "clpid": "Sechler-E-E" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nBuckling of circular annular plates with the outer edge clamped and the inner edge free loaded with a uniform radial compressive force applied at the outside edge has been studied both theoretically and experimentally. A differential equation of equilibrium of the buckled plate has been developed for any general deflection pattern and solutions corresponding to the buckled form [...] Cos n 0 have been sought. The differential equation has been solved exactly for n = 0 and n = l and approximately for higher values of n as well as for n = 0 and 1. The solutions indicate that, for small ratios of inner to outer radius, the plates buckle into a radially symmetric buckling mode, but for the ratio of inner to outer radius exceeding a certain minimum value the minimum buckling load corresponds to buckling modes with waves along the circumference, the number of which depends on the particular ratio of the inner and outer radii. Tests were carried out using thin aluminum plates and the results agreed reasonably well with the theoretical predictions.", "doi": "10.7907/QAE9-G437", "publication_date": "1968", "thesis_type": "engd", "thesis_year": "1968" } ]