Fatigue-Induced Micro-damage Characterization of Austenitic Stainless Steel 316 Using Innovative Nonlinear Acoustics

We present innovative nonlinear acoustics for characterizing fatigue-induced micro-damage of austenitic stainless steel 316 subjected to high-cycle fatigue. Various fatigue-driven deformations are accumulated at several positions near the middle of hourglass-shaped specimens. A bell-shaped curve of acoustic nonlinearity as a function of position is observed, and the variation in acoustic nonlinearity is attributed to the evolution of a lattice defect (dislocation) and stress-induced martensite based on transmission electron microscopy (TEM) observations. An oblique incidence technique using a longitudinal waveform is a potentially viable method for characterizing the high-cycle fatigue deformation of austenitic stainless steel 316 alloys.