Measurement of Elastic Nonlinearities Using the Fundamental Edge Wave Mode

Measurement of the nonlinear elastic properties of materials represents a great interest in engineering and materials science. Changes of these properties are often related to mechanical damage and applied stresses, which are paramount for maintaining integrity and safety of structures. Current ultrasonic techniques typically utilise bulk, Lamb, or Rayleigh waves to measure material nonlinearities, however, spatial and velocity dispersion make this a very difficult task, and the use of several (empirical) correction factors is usually required. In this work we suggest using the fundamental edge wave mode – a natural analogue of the classical Rayleigh wave propagating in a finite thickness plate – for the purpose of measuring elastic nonlinearities. Edge waves naturally avoid spatial dispersion as they are guided by the apex of a plate, thus avoiding the need for correction factors. Additionally, the fundamental edge wave mode can propagate long distances without significant attenuation under certain conditions. The outcomes of this study demonstrate that the measurement of material nonlinearities is achievable using the fundamental edge wave mode. A linear trend between the nonlinearity parameter and propagation distance is experimentally observed, which is predicated by theoretical studies. Therefore, potential applications of the fundamental edge wave mode are very promising for the evaluation of mechanical damage and measurement of applied or residual stresses.