2-D SIMULATION OF SUB-HARMONIC GENERATION DUE TO CRACKS WITH CONTACT-BOUNDARY CONDITIONS

Abstract

The nonlinear ultrasonic testing has attracted notice as a new technique for detection of closed cracks which cannot be found by the linear one. However, the generation mechanism of sub-harmonic wave, which is one of the nonlinear ultrasonic waves, has not been understood clearly from theoretical point of view yet although it is considered as caused by the dynamic interaction of crack faces such as clapping or friction. In this paper, the boundary integral equation for two-dimensional crack problems is formulated and numerically solved to investigate the behavior of the sub-harmonic wave. Some numerical results of sub-harmonic generation are obtained and discussed.