Study of fatigue damage accumulation and fatigue reliability based on rotating bending test data

To investigate how fatigue damage is accumulated, experimental work was conducted in the present study. Aside from the regular tensile test, the experiment includes constant-amplitude, two-stress-level, three-stress-level and random-amplitude fatigue tests using a rotating bending test machine. Considerable large number of tests were carried out for some cases with the purpose of studying the so-called 'fatigue reliability' of the tested material. After all tests were completed, analytical work was performed. The analytical work includes construction of the P-S-N curve, investigating the probability distribution of the fatigue life, examining the applicability of different fatigue damage accumulation rules, and development of simple formulas to predict the fatigue damage and life of components when random loading is concerned. After careful study, several conclusions are drawn in the present paper for the tested material. First, the fatigue life follows a normal probability distribution. Secondly, the Corten-Dolan and Marco-Starkey rules provide better fatigue damage prediction than the others. Thirdly, the proposed fatigue damage prediction algorithm can be extended from two-stress-level, three-stress-level to multi-stress-level as well as random loading conditions, although more experimental study is needed for the last case. It is believed that the above results are helpful for engineers in the reliability-based design of fatigue vulnerable components.