Research Progress of Crystal Plastic Fatigue Indicator Parameters

Fatigue failure of metal materials and structures is considered as a "cancer" in engineering field and the result of gradual deterioration of microstructure.Therefore,quantifying this behavior is crucial in predicting fatigue crack initiation.Fatigue indicator factor（FIP） based on crystal plastic finite element can better characterize fatigue crack driving force dominated by shear strain from a micro perspective.At present,FIP models such as cumulative plastic slip,strain energy dissipation and fatigue indicator factor improved by multi-axial fatigue life prediction criteria have been proposed.The first one within the framework of dislocation slip theory demonstrated the success of the model in describing the phenomenon of fatigue persistent slip band and stress concentration at the trigeminal grain boundary with a relatively simple formulation and few materials parameters.The second approach is based on energy theory without distinguishing the load mode and the preferred direction of crack growth.It is more reliable than cumulative plastic slip under high strain amplitude or complex loading conditions.The last one improved by Fatemi-Socie criterion,Dang-Van criterion,as well as Tanaka-Mura criterion has been widely used in engineering,but a large number of experimental parameters are needed for empirical model.In fact,the relationship between critical plane and dislocation slip plane is not clear enough.As the above summaries,it is pointed out that the research on the physical consistency between the critical plane of multiaxial fatigue damage and the slip plane of crystal plasticity,the direct construction of crystal plasticity FIP model based on grain rotation data,and the analysis of the characteristics of crystal plasticity FIP by fuzzy mathematics are the future development directions,which have important theoretical significance and practical value for the supplement and improvement of crystal plasticity FIP method.