Combined quantitative evaluation on early-stage fatigue damage of coarse-grained austenite stainless steel based on...

The elastic anisotropy and heterogeneity effects of coarse-grained austenite on ultrasonic propagation significantly undermine the effectiveness of ultrasonic property-based fatigue damage evaluation. A discrete method based on electron backscatter diffraction (EBSD) was proposed to decouple the effects between coarse-grained structure and fatigue damage. An orientation-based damage index, local misorientation (M_L), was extracted and macroscopic and microscopic plastic deformations were characterized. The evolution of ultrasonic attenuation coefficient Δα was established with ΔM_L in grain scale. Approximate downward parabolas was observed, and the peak value of Δα in 〈1 1 1〉 orientation was found to be larger and more sensitive to the cyclic damage than that of 〈0 0 1〉 and 〈0 1 1〉. The influences of the heterogeneous substructure and surface roughness were discussed respectively.