Some comments about fatigue crack initiation in relation to cyclic slip irreversibility

In the present work, an overview of recent measurements of plastic strain irreversibility obtained with atomic force microscopy (AFM) is used to discuss the opportunity to define fatigue crack initiation in terms of a critical value of plastic strain irreversibility. We illustrate the fact that the critical value of height emergency associated with deformation band, necessary to crack initiation, is a decreasing function of the plastic strain localization in band. This phenomenon can be understood in terms of an excess of elastic energy associated with mobile dislocations and an interaction between vacancy mobility and oxygen diffusion.