Notice of Removal: Characterizing micro-crack distributions with nonlinear acoustic surface and wedge waves

Abstract

Pre-fatigue damage can have drastic effects on the elastic nonlinearity of solid materials, offering the possibility of extracting spatially resolved information on the pre-fatigue state from nonlinear effects on guided waves, like harmonic generation [1]. Of particular interest are surface and wedge acoustic waves. They are sensitive to surfaces and edges and are non-dispersive in homogeneous media, at planar surfaces and — in the case of wedge waves — perfect wedge tips on the scale of the wavelength. This favors nonlinear effects. Our current investigations focus on the nonlinearity generated by micro-cracks with the goal of extracting information about their spatial and orientational distribution from the efficiency of second harmonic generation and its dependence on amplitude and frequency of the input wave [2]. The linear dispersion arising from a spatially inhomogeneous distribution of the micro-cracks is accounted for in the propagation of the second harmonic.