CaltechTHESIS
  A Caltech Library Service

Some studies in the fundamental parameters of fatigue

Citation

Valluri, S. R. (1954) Some studies in the fundamental parameters of fatigue. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-01292004-104442

Abstract

A torsional fatigue testing machine of the resonant vibrator type has been designed in order to investigate the fatigue and internal friction properties of 3S-O aluminum. This machine uses an elastic restraint on an a-c motor to create resonant conditions and uses a photocell electronic system for the measurement of internal friction by the method of measuring the logarithmic decrement of free oscillations.

It has been established that for 3S-O aluminum at torsion stress levels below 112 psi, the stress history does not affect damping and that, for an annealed specimen, the material exhibits a maximum value of internal friction at 375[degrees]F. "Temporary mobility" aspects of the slip bands have been investigated and in addition, variation of internal friction as a function of stress amplitude in repeated torsional loading, temperature, and number of reversals has been obtained. At room temperature (75[degrees]F) the internal friction increases with the number of stress reversals in the 0 to 10[superscript 5] range. This increment in general increases with increasing amplitude of stress. At test temperatures of 225[degrees] and 525[degrees]F it was found that this increment does not show any regular variation with stress. In addition, however, it was found that at 375[degrees]F the internal friction decreases with stress reversals in the 0 to 10[superscript 5] range for all stresses. The variation of internal friction with stress history after a large number of stress reversals of the order 10[superscript 6] cycles, is quite complex, giving rise to random patterns of increase and decrease.

This work is exploratory in nature and suggestions for further work are indicated.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Sechler, Ernest Edwin
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1954
Record Number:CaltechETD:etd-01292004-104442
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-01292004-104442
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:401
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:29 Jan 2004
Last Modified:26 Dec 2012 02:29

Thesis Files

[img]
Preview
PDF (Valluri_sr_1954.pdf) - Final Version
See Usage Policy.

3242Kb

Repository Staff Only: item control page