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Reversed bending fatigue properties of 25 S-T, 75 S-T, and 76 S-T aluminum alloys

Citation

Cooley, J. S. (1949) Reversed bending fatigue properties of 25 S-T, 75 S-T, and 76 S-T aluminum alloys. Engineer's thesis, California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-01262009-110934

Abstract

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The problem of this investigation was to determine the effects of surface roughness and surface stressing on the reversed bending fatigue properties of 25 S-T, 75 ST and 76 S-T aluminum alloys.

Tests were conducted in a stress range from 37,700 psi, to that stress giving a fatigue life of 500,000,000 cycles.

Surface roughness was varied from five micro-inches to 400 micro-inches. Two different machining tools were used to obtain the various degrees of surface roughness: 1/8" radius tool, and a sharp pointed tool.

Surface stressing was obtained by shot peening with 0[...]028 diameter shot at .010/.012 A-2 intensity, and cold rolling at 100 lbs. and 200 lbs. pressure.

It was determined that fatigue life decreased as surface roughness increased in a similar manner for specimens machined with both types of tool; but that endurance limit was not affected by the sharp tool, whereas it was decreased by the 1/8" radius tool.

Shot peening increased fatigue life of 25 S-T by about 500%; it had but slight effect on 76 S-T.

Cold rolling increased fatigue life of 25 S-T and 76 S T by about 2500%. 75 S-T was neither shot peened nor cold rolled.

This work was carried out by the author at the Guggenheim Aeronautical Laboratory, California Institute of Technology under the supervision of Dr. E. E. Sechler.

Item Type:Thesis (Engineer's thesis)
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:
  • Sechler, Ernest Edwin (chair)
  • Hudson, Donald E.
  • Clark, Donald S.
Defense Date:1 January 1949
Record Number:CaltechETD:etd-01262009-110934
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-01262009-110934
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:359
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:26 Jan 2009
Last Modified:26 Dec 2012 02:29

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