Investigation on characteristics of tensile damage and microstructure evolution of steel AISI 316L by nonlinear ultrasonic Lamb wave

In view of the high sensitivity to microstructure evolution higher harmonics generated by nonlinear ultrasonic method, tensile damage in stainless steel AISI 316L was evaluated Lamb wave. The effect different degree deformation on response analyzed considering and test results. First, power-law relation parameter plastic strain is proposed. Meanwhile, martensitic transformation increasing dislocation density can be observed micrographs specimens with increase deformation. Then, same variation tendency intergranularly averaged Kernel Average Misorientation (KAM), as well relative parameter, demonstrated that nonlinearity due controlled directly affects order elastic constant 316L. Furthermore, based continuous mechanics, method quantitatively characterizes degradation mechanical properties proposed a functional variable parameter. this study provides theoretical basis for online monitoring status in-service equipment. It great significance residual life assessment, structure integrity service extension