Numerical simulation of laser ultrasonics for detecting subsurface lateral defects

Abstract

Non-contact and nondestructive monitoring of subsurface defects are urgently required especially in the line production of such products. In this paper a two-dimensional plane stress finite element model with absorbing boundary condition has been developed to investigate the ultrasonic wave generated by nanosecond pulsed laser propagation in two-layer material. The pulsed laser is assumed to be transient heat source, and the Surface acoustic wave is computed based on the thermoelastic theory, which propagated on the top surface of the plate. The defects located on the interface can be modeled as the subsurface slits of the Al/Cu layers. The numerical results include the three cases which the subsurface slit located in different positions of the interface of the Al/Cu layers. After performing Wigner-Ville analysis on the displacement data, frequency domain feature analysis is done. This study of the SAW was demonstrated to be promising in evaluating the bond quality as well as identifying the location of subsurface lateral defects.