Mutual interactions between bulk waves and guided waves in a quadratic nonlinear elastic medium

Abstract

The high sensitivity of nonlinear ultrasonic waves to the early stages of local material deteriorations makes them ideal candidates for nondestructive material characterization. Guided elastic waves, which can be emitted and received on the same surface, expand the possibilities to inspect inaccessible domains to test and monitor existing structures. The pure measurement of the amplitude of the second harmonic has only limited significance, since it is difficult to distinguish between the rather weak material nonlinearity and the nonlinearities from the technical equipment. This can be avoided by mixing two ultrasonic waves of different frequencies, which results in superposed harmonics at these frequencies. In this study, the mutual interactions between bulk waves and guided waves in a quadratic nonlinear elastic medium are investigated by highly efficient computations. In addition, numerical examples for the wave interaction in a finite area with nonlinearity in an otherwise linearly elastic host medium are presented and discussed to explore the effects of individual parameters as well as possible experimental implementation.