Generation of higher harmonics with the fundamental edge wave mode

Abstract

The measurement and evaluation of nonlinear elastic properties represents a great interest in materials science and engineering. These measurements can be conducted using the internal resonance of higher harmonics generated with ultrasonic bulk, Rayleigh, and Lamb waves. However, these waves are spatially dispersive, making the evaluation very difficult. In this paper, we present the outcomes of an experimental study on the generation of higher harmonics with the fundamental mode of edge waves. This wave mode - an analog of the Rayleigh wave - propagates along the apex of an elastic plate, where the lateral plate surfaces naturally avoid spatial dispersion. In addition, this mode is weakly dispersive in the frequency domain enabling approximate internal resonance, which is required for the measurement of material nonlinearities. The current experimental results indicate that the second harmonic of the fundamental edge wave mode grows linearly with the propagation distance. The linear rate of accumulation of this harmonic can then be related to the nonlinear elastic properties as procured by previous theoretical studies.