Abstract
The nonlinear ultrasonic testing is expected to be an effective technique for detection of closed cracks which cannot be detected by the linear ultrasonic testing. However, although the nonlinear ultrasonic waves such as higher- and sub-harmonics are considered as generated by the interaction of the crack faces such as clapping motion or friction, the mechanism of generation has not been understood clearly from theoretical viewpoints yet. Therefore, the boundary integral equation for an interface crack with nonlinear boundary conditions in 3-D is formulated, and numerically solved using the convolution quadrature time-domain boundary element method (CQ-BEM) in order to investigate the behavior of nonlinear ultrasonic generation.
