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Title:Effect of stress amplitude on statistical variability in fatigue life of 75S T6 aluminum alloy
Author(s):Sinclair, G.M.; Dolan, Thomas J.
Subject(s):Stress Amplitudes
Alloy Fatigue
Aluminum Alloy
Fatigue Life Scatter
Abstract:Recent studies indicate that most of the "scatter" observed in finite fatigue life testing of metals is an inherent characteristic of the material and does not necessarily indicate poorly adjusted machines or improper testing techniques. In the present study, groups of 17 to 57 specimens of 758-T6 aluminum alloy were tested in rotating bending at six different stress levels. The smallest stress used was 30,000 psi and the greatest was 62,500 psi. A statistical analysis was made of fatigue life data obtained at each of the six stresses. The distribution of the fatigue lifetimes, for each stress, was found to be approximately logarithmic-normal. The standard deviation (which is a measure of scatter in the fatigue life) was related to the stress amplitude and could be represented within the stress range investigated by a simple exponential function. Constants of an S-N relation recently proposed by W. Weibull were evaluated for a probability of failure P = 0.50. Results of the study are summarized in two equations and in a composite S-N diagram showing lines of equal probability of failure.
Issue Date:1952-07
Publisher:Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report:TAM R 31
Genre:Technical Report
Sponsor:Office of Naval Research 52/07 Contract N6 ORI 71 TO 4 52/07 TR 31
Rights Information:Copyright 1952 Board of Trustees of the University of Illinois
Date Available in IDEALS:2021-11-04

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  • Technical Reports - Theoretical and Applied Mechanics (TAM)
    TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.

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