Equivalent life distribution and fatigue failure probability prediction

Abstract

Equivalent fatigue life distributions under two-level cyclic stress are analyzed experimentally, and a model of describing equivalent life distribution is presented. Based on the equivalent life distribution model, an “equivalent damage – equivalent life distribution” method is developed to predict fatigue failure probability under variable amplitude loading. The underlying principles are fatigue damage accumulation rule and “load cycles – fatigue life” interference theorem. In the equivalent damage – equivalent life distribution method, two parameters, i.e. mean and standard deviation of the (equivalent) life distribution are used to describe cumulative fatigue damage effect. A basic feature of the equivalent damage – equivalent life distribution method is its capability of reflecting the loading history dependent change of the equivalent life distribution. Tests under multi-level stress show a good agreement between predicted fatigue failure probability and the test results.