Volume 5, Issue 4 (July 1977)
A Concept for Fatigue Analysis of Complex Components
Recently, a two-step procedure that determines local stresses and strains as functions of loading and that assesses the fatigue damage they cause in terms of smooth specimen laboratory test data has shown promise in making consistently accurate life to crack initiation predictions of notched specimens. However, this procedure, which accounts for notch effects by using a single parameter, is less accurate in predicting the fatigue life for complex components than that for simple notched specimens. The present paper examines the problems of predicting the fatigue life of complex components and structures. It is shown that fatigue life in such structures is governed by the multiplicity of initiation locations and crack initiation mechanisms. An approach is outlined whereby the role of each potential initiation location and mechanism is accounted for in fatigue analysis of the structures by using the two-step procedure. Fatigue life predictions are made for a hypothetical complex component to illustrate the approach and its application. The accuracy of the approach is then assessed by comparing the results of actual test data for a built-up box beam with those simulated by using the approach outlined in this paper.