Theoretical and numerical investigations of the nonlinear acoustic response of feature guided waves in a welded joint

Abstract The propagation characteristics of feature guided waves (FGWs) in topographical waveguides, such as welded joints, have been widely investigated. However, most of these investigations analyzed linear acoustic characteristics. Considering the high sensitivity of nonlinear ultrasonic techniques in the nondestructive evaluation of microscopic defects in materials, such as identifying micro-defects at an early stage, it is particularly relevant to investigate the nonlinear acoustic response of FGWs in topographical waveguides. In this paper, we use a theoretical analysis and numerical simulation to investigate the second-harmonic generation (SHG) of FGWs in a welded joint. The theoretical framework is firstly expounded based on the reciprocity relation and modal expansion with the nonlinear semi-analytical finite element (SAFE) method and perfectly matched layers. Numerical models are implemented to predict the effect of SHG of FGWs in a welded joint. Two families of FGW propagation in a welded joint are analyzed. The results obtained demonstrate that mode conversion and the cumulative effect of the generated second harmonics can be observed in the welded joint. This investigation provides new physical insights into SHG for FGW propagation.