A Confrontation of Mathematical Models for Fatigue Life with Actual Service Data
Final rept. 15 Sep 1974-15 Sep 1975
WASHINGTON STATE UNIV PULLMAN DEPT OF PURE AND APPLIED MATHEMATICS
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From a collection of over a thousand different groups of qualified aluminum fatigue data, an empiric distribution is obtained which can serve as a standard for comparison of various mathematical models for fatigue. On this basis several commonly used parametric models, as well as some mathematical suppositions, can be discarded if good predications are desired of the earliest fatigue failures. One of the models not disqualified, which contains sufficient flexibility to fit the actual data, is a distribution of the log-life with three parameters, namely, location, scale and flexure. Because maximum likelihood estimation of all three parameters cannot be accomplished simultaneously, the location parameter is posited as being calculated on the basis of a cumulative damage rule known a priori while the scale parameter is determined from the material and the flexure parameter describes the presence of flaws andor the time to crack initiation. These relations with the physics of materials provide a design basis for calculation of reliability.
- Metallurgy and Metallography