CaltechDATA: Monograph
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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenThu, 28 Mar 2024 10:48:45 -0700Correlation of Existing Design Information on Sandwich Construction
https://resolver.caltech.edu/CaltechETD:etd-02112009-154609
Year: 1949
DOI: 10.7907/F4C5-0536
The problem considered is one of survey and correlation of existing design information on sandwich construction. The subject matter deals with the types of sandwiches, advantages, buckling and stress analysis, published test data, design methods, core materials, weight comparisons, current applications and the manufacture, repair and inspection of sandwich construction.
Suggestions for extensions needed are given and where obvious improvements in analysis could be seen, these modified methods were suggested.
Suggested further work - Every phase of sandwich construction considered in the present thesis shows need for further development. Particularly useful fields for further work are the development of more adequate stress analysis methods for the core, more general correlation of existing formulas and the development of better means of attachment, inspection and repair.https://resolver.caltech.edu/CaltechETD:etd-02112009-154609The Effect of pH on the Workability of Concrete
https://resolver.caltech.edu/CaltechTHESIS:12042017-111708147
Year: 1952
DOI: 10.7907/C141-5S39
<p>It was believed that the pH of concrete would affect
the workability. The effect of pH on the workability was
determined experimentally by adding chemical admixtures
to a cement mortar mix, measuring the pH and workability.</p>
<p>pH was measured by a Beckman Glass Electrode pH
Meter equipped with a standard Calomel electrode and a
special type "42" glass electrode. The use of the type "42"
glass electrode made it possible to place the electrodes in
wet cement mortar without damage.</p>
<p>The workability was determined by measuring the
penetration of a three inch diameter cylinder with a
hemispherical tip. This ball penetration measure of workability
has a linear relationship to that measured by the slump test.</p>
<p>From these tests it was found that the pH has no effect
on the workability of cement mortar. The admixtures changed
both the pH and the workability, however, the variations in pH
and workability were independent of each other. It is believed
that the major factor which affects the workability of concrete
is the dispersing effect of the admixture on the cement.</p>https://resolver.caltech.edu/CaltechTHESIS:12042017-111708147The Effect of Surface Roughness upon 25 ST Aluminum Alloy Subjected to Repeated Tensile Stresses Above the Proportional Limit
https://resolver.caltech.edu/CaltechETD:etd-02022009-093120
Year: 1949
DOI: 10.7907/WH57-T868
Utilizing the Repeated Load Hydraulic Testing Machine at the Daniel Guggenheim Aeronautical Laboratory, California Institute of Technology, Pasadena, California, the author, in collaboration with Lt. Comdr. D. J. Hardy, U. S. Navy, investigated the effects of surface roughness upon the cyclic life of 25 ST aluminum alloy when subjected to repeated constant tensile stresses in the region above the proportional limit.
The stress impulses are of such low frequency as to allow consideration of single impulses. The rate of build-up of the impulse and the duration of the impulsive load are such as to create an equivalent static load of substantially the same magnitude as the peak of the impulse loading.
It was found that surface roughness has some effect upon the cyclic life. In the lower stress regions, the greater the degree of surface roughness, the shorter the life appears to be. However, for the range of roughness investigated, 5μ to 200μ, the effect is not so pronounced as is usually found below the proportional limit.
Where the applied stresses reached far up into the plastic range the effect of surface roughness does not seem to follow quite as specific a pattern. Since the loading impulse featured a 0.33 second duration of maximum load, the effects of creep may well have taken over in shaping the life cycle curve with little regard for surface roughness.https://resolver.caltech.edu/CaltechETD:etd-02022009-093120The Effect of Surface Roughness upon 25 ST Aluminum Alloy Subjected to Repeated Tensile Stresses Above the Proportional Limit
https://resolver.caltech.edu/CaltechETD:etd-01272009-083535
Year: 1949
DOI: 10.7907/Q6A7-1796
Fatigue tests were conducted on 54 specimens of 25 ST aluminum alloy for the purpose of determining the effect of surface roughness on the fatigue life of the material when subjected to constant repeated tensile stresses above the proportional limit. In addition, the basic stress vs. cycle curve for 25 ST aluminum alloy was extended to include the range of cycles below 100,000.
A machine capable of applying repeated pure tension loads at a rate of 52 cycles per minute, without shock but with a high rate of loading, was used to obtain this data.
It was found that the rate of build-up and the duration of the impulse created an equivalent static load equal to the peak of the impulse loading.
For the material tested, it was found that as the surface roughness increased from 5μ to 200μ, the life expectancy of the alloy in general was reduced. However, the experimental results revealed a larger degree of scatter in the cyclic range below 40,000 cycles as opposed to the relatively consistent data obtained at the higher cycles. Therefore, no general conclusions could be ascertained as to the effect of roughness on the fatigue life of the material in the high stress region.https://resolver.caltech.edu/CaltechETD:etd-01272009-083535A Study of the Effect of Vertical Sand Drains as a Means for the Rapid Consolidation of Soils of Low Permeability
https://resolver.caltech.edu/CaltechETD:etd-10062005-131350
Year: 1947
DOI: 10.7907/FB0G-N523
The phenomenon of consolidation or the settlement of soils under load is well known to civil engineering practice in all works dealing with earth movement and foundations. Unlike true elastic materials, this deformation takes place at a variable rate over an extended period of time and is especially apparent in clays saturated with water. This phenomenon was first explained by K. Terzaghi who assumed the soil mass to be an elastic porous medium with voids filled with water or the concept of a saturated rubber sponge. The deformation of such a mass upon application of a load would then be variable, depending upon the rate at which water was forced from the voids. The application of mathematical analysis to this concept led to the complete solution by Terzaghi for the one dimensional process to be followed by the studies of M. A. Biot, L. Rendulic and N. Carillo dealing with the three dimensional case.https://resolver.caltech.edu/CaltechETD:etd-10062005-131350A Rational Design Procedure for Machine Foundations
https://resolver.caltech.edu/CaltechTHESIS:12012017-090837077
Year: 1952
DOI: 10.7907/MZVV-X944
<p>The problem involved in the design of machine foundations are
discussed, followed by a short review of the literature of the subject.
The general theory of vibration for single and multiple degree of freedom
systems is briefly reviewed, with special emphasis on its application
to machine foundation design. A procedure for the analysis of machine
foundations is then developed on the basis of a simplified equivalent
system. Procedures for determining the elastic coefficients and the
inertia parameters of the soil are next considered.</p>
<p>The purpose and extent of the experimental investigations are
discussed, followed by a description of the instrumentation used and
the nature and accuracy of the data obtained. The data is then
analyzed and checked against the theory presented. The data required for
the design of machine foundations is discussed, and a procedure for
design and analysis is recommended. In conclusion recommendations for
further study and research are made.</p>https://resolver.caltech.edu/CaltechTHESIS:12012017-090837077A Fourier Integral Approach to an Aeolotropic Medium
https://resolver.caltech.edu/CaltechETD:etd-04142009-143250
Year: 1949
DOI: 10.7907/CTQV-V186
Chapter I: The equations of equilibrium in terms of the displacement components for an axially symmetric aeolotropic medium are developed from the strain-energy function of the medium. Then follows a discussion of the literature of the subject, and an outline of the scope of the present thesis.
Charter II: The solution is carried through using Fourier Integral technique for the two dimensional plane strain case. Stresses and displacements are obtained for a concentrated line load.
Chapter III: The results of Chapter II are applied to determine the surface settlements, vertical pressures, and shears for a symmetrically loaded strip called "the unit strip" of width two units. The following special load distributions are investigated: concentrated, uniform, parabolic, inverted parabolic, hollow wall, and rigid wall. Extension is then made to a strip of any arbitrary width 2a, and settlements are obtained by means of influence factors, (Graph I). An examination is made of the influence of the type of load distribution, demonstrating St. Venant's principle of equipollent loads.
Chapter IV: The equations of Chapter I are solved for an axially symmetric loading by transforming to polar co-ordinates and using Fourier-Bessel Integral technique. The solution is carried through for the concentrated load case, and the results check those given by Mitchell (6).
Chapter V: An investigation similar to that made in Chapter III is made for a loaded circular area of unit radius. The results are then extended to a circle of any arbitrary width a. Surface settlements are obtained quickly by means of influence factors (Graph II). In the latter part of the Chapter series expansions are obtained for the stresses and displacements at any point in the mass, and application is made to some of the more practical load distributions.
Chapter VI: Corresponding results for an elastic isotropic medium, to those given in above chapters, are obtained by the application of a limiting technique to above results. The ease with which the results are obtained is striking. A discussion is given of the infinite surface displacements that are usually obtained in two-dimensional problems.
Chapter VII: In this chapter a review is made of the literature of the three constant medium. The physical significance of the assumptions and the measure of fulfillment of these assumptions by some types of wood, and by some crystals, is examined. Some errors are noted, and corrected. Finally all are shown to be just particular cases of the medium of Chapter II, without having the redeeming feature of simplicity over the more general theory.
Chapter VIII: Results for Orthotropic plates are deduced from those given in Chapter II by a change of constants.
Chapter IX: Typical problems in soil mechanics connected with a loaded column, and with a loaded wall, are worked out in detail. Graph III shows for a particular case the effect aeolotropy may have on the vertical stress distributions in a loaded soil. A brief outline is made of some other problems in an aeolotropic medium capable of solution by the methods of this thesis.
Appendix F: Practical methods are given for the determination of the required constants. The value of skew samples is shown. The results obtained in this thesis for an aeolotropic medium, apart from the concentrated case given by Mitchell(6), are new. A good test of the accuracy of the work is provided by the known isotropic elastic results obtained by a limiting procedure in Chapter VI. As far as the author is aware, some of the results of Chapter VI are new also. The direct application of Fourier Integral technique to the displacement equations of equilibrium is very rare in elastic problems. This thesis illustrates the power and simplicity of such an approach. Finally, as shown in Chapter IX the results are very readily adapted to practical use.https://resolver.caltech.edu/CaltechETD:etd-04142009-143250