Multi‐scale fatigue crack propagation in 304 stainless steel: experiments and modelling

Abstract

Abstract The stages of fatigue crack initiation and small crack propagation usually occupy most part of fatigue life. The multi‐scale fatigue crack propagation mechanism of 304 stainless steel using in situ optical microscopy was investigated in this paper. An analytical model was also proposed to predict the multi‐scale crack growth rate. Results indicated that grain boundaries inhibit the small crack propagation and lead to the fluctuation of crack growth rate when the applied stress is relatively low. The prediction results using the proposed model agree well with the experimental result. The effect of grain size distribution on crack growth rate can be identified by the present model. Moreover, the prediction capacity of the proposed model is further verified by using another two materials, for example 7075‐T6 and U720Li.