Investigations on Reliability Analysis of Fatigue Lives of Carbon Steels and Reliability-based Design Safe Lives

Abstract

Firstly, it is discussed in this paper how to estimate statistically the shape and scale parameters in the fatigue life distribution assumed to be a two-parameter Weibull type. As the result, the former is found to be well estimated by TOSE, i, e., the two-ordered-statistic estimator first developed by I.C. Whittaker, et al., and the latter by MLE, that is, the maximum likelihood estimator.
Secondly, the method is discussed for determining the design safe life to meet the desired reliability goal.
Further, the actual fatigue life distribution and the dependency of the shape parameter upon the testing conditions are considered by applying the aforementioned reliability analysis technique to the empirical fatigue life data on S25C, S35C, S45C and S50C carbon steels under constant amplitude stressing, programmed loading or superposed stressing. The importance is also pointed out that the design safe life in the structure has to be determined on the basis of TTFF, that is, the time to the first failure of a component.