Analytical and numerical modeling of non-collinear shear wave mixing at an imperfect interface.

Non-collinear shear wave mixing at an imperfect interface between two solids can be exploited for nonlinear ultrasonic assessment of bond quality. In this study we developed two analytical models for nonlinear imperfect interfaces. The first model uses a finite nonlinear interfacial stiffness representation of an imperfect interface of vanishing thickness, while the second model relies on a thin nonlinear interphase layer to represent an imperfect interface region.

Finite element analysis of Rayleigh wave interaction with finite-size, surface-breaking cracks.

The interaction of surface acoustic waves with finite-size, surface-breaking, semi-circular cracks is studied numerically, and experimentally. We focus on the behavior of the reflection coefficient of the Rayleigh wave from such cracks in the far field of the crack, when the depth of the crack is comparable to the wavelength of the interrogating surface wave. The cases in which the depth of the crack is much smaller or much larger compared to the wavelength have been extensively investigated by many authors and are not considered here except for validating the numerical and experimental results in these regimes.