Experimental investigation on the small-load-omitting criterion

In the present study, the fatigue tests under variable amplitude loading were carried out on the notched elements of 45 steel with non-continuous hardening characteristics to investigate the small-load-omitting criterion (SLOC). Therefore, three load spectra were designed to have a different loading pattern and loading sequence, in particular the pattern of the small load cycles applied to the notched elements of 45 steel. The test results and the statistical analysis of the fatigue life of the notched elements of 45 steel show that the load cycles at the condition of Δσeqv≤(Δσeqv)th, i.e., the equivalent stress amplitude lower than or equal to the fatigue crack initiation (FCI) threshold, can be omitted in life prediction. In other words, the FCI threshold in the expression of the FCI life, i.e., , developed by Zheng, one of the authors, can be taken as the SLOC in life prediction. The load pattern and the load sequence have no significant effects on the above SLOC. Furthermore, and Minerʹs rule can be directly used to predict the fatigue life and its probability distribution of the notched elements of 45 steel with non-continuous strain hardening characteristics under different load spectra.