2 – FATIGUE DAMAGE THEORIES

Predicting fatigue damage for structural components subjected to variable loading conditions is a complex issue. The first, simplest, and most widely used damage model is the linear damage. This rule is often referred to as Miner’s rule (1945). However, in many cases the linear rule often leads to nonconservative life predictions. The results from this approach do not take into account the effect of load sequence on the accumulation of damage due to cyclic fatigue loading. Since the introduction of the linear damage rule many different fatigue damage theories have been proposed to improve the accuracy of fatigue life prediction. A comprehensive review of many fatigue damage approaches can be found elsewhere (Fatemi and Yang, 1998). This chapter addresses (1) underlying fatigue damage mechanisms, (2) fatigue damage models commonly used in the automotive industry, and (3) postulations and practical implementations of these damage rules.