Thesis (Ph. D.)--University of Michigan, 1930. / Caption title. From Transactions of the American society of mechanical engineers, 1930. Applied mechanics.

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Inaug.-diss.-Rostock.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Les objectifs visés dans ce travail sont de: i) Concevoir et fabriquer des bétons à très haute résistance, ayant une résistance en compression simple comprise entre 60 et 120 MPa, En effet, on dispose de très peu de données scientifiques sur les caractéristiques des bétons à très haute résistance dans cette plage de résistance. ii) Échantillonner ces différents bétons pour déterminer: 1) leur résistance en compression simple (f’c) à ld, *7d, 28d, 91d et1 an;2) leur module d'élasticité;3) leur résistance en flexion (f’r à 7d, 28d et 91 d. iii) Essayer d'établir des corrélations entre:1) la résistance en compression simple et le module d'élasticité;2) la résistance en compression simple et la résistance en flexion (module de rupture);3) la résistance en compression simple et le coefficient de Poisson. iv) Étudier la microstructure des bétons à très haute résistance. * Id = 1 jour

Le but de ce travail, est d'étudier certaines méthodes de détermination du module dynamique d'élasticité en fonction de la fréquence, à partir d'éprouvettes soumises à des vibrations transversales.

The oscillation of a column subjected to periodic axial end excitation was analytically and experimentally investigated. The initial crookedness of the column and the longitudinal inertia of a column element give rise to coupled, longitudinal-flexural oscillations. A snap-thru phenomenon and complex subharmonics of natural flexural modes of oscillation also occur at certain axial end excitation frequencies. Furthermore; at certain excitation frequencies, a coupling between longitudinal and torsional oscillations is found to exist. A theory providing qualitative and quantitative information about coupled longitudinal-flexural oscillations and complex subharmonics was developed for a column with hinged ends. In order to test the validity of the theory an experimental apparatus was set up to excite the column axially, with transducers monitoring the response of the column. The experimental results were in very good agreement with the theoretical predictions. A column with built-in ends was also tested and its response was similar to the column with hinged ends. Thus, the results of the experimental investigation suggest that the results of the theory developed for a column with hinged ends are also applicable to a column with built-in ends. Coupled longitudinal-flexural oscillations were observed when the axial end excitation frequency was equal to the natural longitudinal frequency of the column. Large amplitude oscillations in both longitudinal and flexural vibration modes occurred at this frequency. When the frequency of axial end excitation was equal to the natural flexural frequencies of the column, large amplitude flexural oscillations resulted, Flexural oscillations were also observed when the frequency of the axial end excitation was one half, one third, …. up to one eighth of the natural flexural frequencies of the column, A spectrum analysis of the strain signal showed that the flexural response then comprised two fundamental motions, one with the frequency of the axial excitation and one with frequency equal to the associated natural frequency. The resulting amplitudes of flexural oscillations at these frequencies were smaller than those observed when the frequency of the axial end excitation was equal to the natural flexural frequencies of the column. The flexural oscillations occurring at these axial end excitation frequencies were identified as the complex subharmonics of natural flexural frequencies, A snap-thru phenomenon occurred when the axial end excitation frequency was twice the frequency of natural flexural frequencies. Under certain circumstances the column then oscillated flexurally with one half of the excitation frequency. The amplitudes of flexural oscillations were comparable to those occurring when the frequency of the axial end excitation was equal to natural flexural frequencies of the column. Large amplitude flexural oscillations occurring at natural flexural frequencies, complex subharmonics and snap-thru phenomena, though excited by the axial end excitation, did not cause appreciable increase in amplitudes of longitudinal oscillations. Finally, large amplitude torsional oscillations occurred when the axial end excitation was of the same frequency as the predicted torsional natural frequencies. Again no appreciable increase in amplitudes of longitudinal oscillations was observed. Flexural oscillation phenomena here described, also occurred during flexural in-plane oscillation of a column. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The effect of vibration upon the rate of sublimation from horizontal circular cylinders has been studied previously in several investigations. However, no satisfactory overall correlation has been obtained up to the present time. In the present investigation, data have been obtained for mass transfer from naphthalene to air and phenol to air for horizontal cylinders vibrated vertically over a wide range of Reynolds number. It is shown that these data and the data of all previous investigations, including liquid systems, lie on or near a single smooth curve provided that an appropriate system of coordinates is selected. Further, for high Reynolds number and high Schmidt number, the data approach the theoretical equation of Jameson derived using boundary-layer theory. The author has found that the mass transfer coefficient for sublimation can be increased by a factor of 30 over that which prevails for the stationary (non-vibrating) case. For mass transfer to gaseous media only, the following correlation is proposed, having an average deviation of ±17 % : Sh = 0.261 Sc¹/³Revº•⁷¹⁷( H/d )º•²³³ This equation is believed to be valid over the following range of the variables: Diameter: 0.07 - 1.1 cm Frequency: 100 - 7000 RPM Amplitude (double): 0.05 - 4.0 cm Vibrational Reynolds number: 9 - 2000 Ratio of amplitude to diameter: 0.2 - 5.7 / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The behaviour of the quasi-harmonic type frictional oscillation for steel sliding surfaces was investigated both experimentally and theoretically. The kinetic coefficient of friction, which was expressed as a function of sliding velocity, was represented by a polynomial. The slowly varying amplitude and phase method of Kryloff and Bogoliuboff was used to solve the non-linear differential equation of motion. The calculations were carried out on the computer. The theoretical analysis suggests that the amplitude of the quasi-harmonic oscillation increases almost linearly as the driven surface velocity increases until a critical velocity is reached where the friction-velocity curve begins to flatten out. Beyond this point the oscillation diminishes to zero. Experiments were carried out mainly on unlubricated surfaces at driven surface velocities ranging from 0.5 in/sec to 25 in/sec. The results revealed that for short running distances frictional oscillation of the stick-slip type could occur. Frictional oscillation of the quasi-harmonic type existed in the system when negative slope appeared in the low velocity region of the friction-velocity curve after a run-in period. The growth and decay of the vibration amplitude with variation in driven surface velocity has been observed and this substantiates the findings of the theoretical analysis. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

A study has been made of the behaviour of a hydraulic-ally driven system subject to friction induced oscillations. An experimental apparatus consisting of a heavy mass driven by a hydraulic ram was constructed. A mathematical model for the system was derived, and its validity was shown by comparison with experimental results. Studies were subsequently carried out with the mathematical model to determine the effects of varying system parameters and to verify the validity of simplifications in the governing equations. It was found that in general the effect of leakage at the piston should be negligible, and that the variation in behaviour with piston location can be predicted by a simple system stiffness correction. The effect of changing most parameters is to change the rate of tangential load application for a given average velocity of traverse, and the resulting behaviour can be predicted from the static friction relationship that has been proposed. A detailed study was made of the nature of the friction forces in effect during a stick-slip process. A relation, for the variation of the static coefficient of friction which appears more accurate than previous time of contact dependent formulations has been found. In the case of the kinetic coefficient of friction, a gradual decrease from the static value was found at the inception of slip. This has been observed before but generally it has not been recognized by investigators of stick-slip. Simple models have been given for both the static and kinetic friction behaviour. These may be useful as guide in further research into the fundamental nature of friction. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate