A MODEL OF FATIGUE CUMULATIVE DAMAGE UNDER STEP BLOCKS SPECTRUM

In view of the materials fatigue life prediction problem under step blocks specturm,especially the calculation parameters of the existing nonlinear models depend on a large number of test data or it is difficult to select a suitable reference value,which leads to the limitation in practical engineering application.A new effect coefficient αi=(Si+1/Si)1/b lg K based on adjacent load was proposed,in which the two parameters b,K were derived from the fatigue life relation S=KN-b.The fatigue damage models and the results which combined with the previous experimental results of two-,three-and four-stage loading were calculated and compared.The results show that the new model has better fatigue life/damage predicted results than Miner model,Manson model,Subramanyan model and Hashin model,which can be predicted more accurately in fatigue life/damage under step blocks spectrum.