Numerical modeling of local residual stress detection in thin plates using the fundamental antisymmetric mode of ultrasonic Lamb waves

Residual stresses occur in different processes such as plastic deformation, temperature variation and structural changes. Welding and metal deformation are conventional processes which lead to residual stress. Residual stress plays a key role in the characterization of welded structures, and it has a significant effect on fatigue behavior as well as the lifespan of loaded structures. Therefore, at the first step, measuring residual stress, and in the next level taking action to reduce or eliminate it by usual methods are of extreme significance. In this study, Lamb waves were applied to evaluate the local residual stress in thin steel plates. A two-dimensional hyperelastic nonlinear model on which a Lamb wave propagated was simulated in ABAQUS CAE finite element software. In order to create residual stress, loading was applied to the thin plate either perpendicular or parallel to the wave motion direction. In different frequencies and stresses, the behavior of A0 mode was scrutinized. Results indicated that A0 mode was sensitive to stress changes, and its changes against the residual stress followed a specific trend. In addition, sensitivity to residual stress decreases with increasing frequency. Hence, the frequency of 50 kHz is selected as the optimal frequency in local residual stress evaluation in thin steel plates.