Investigating the critical aspects of evaluating the material nonlinearity in metal plates using Lamb waves: Theoretical and numerical approach

Abstract

The present study focuses on critical analysis of various aspects related to the evaluation of amplitude based material nonlinearity parameter γamp through the numerical simulations and theoretical justifications. Two different materials with distinct nonlinearities are interrogated using Lamb waves in the numerical simulations. The effects of input force amplitude, number of cycles in the tone burst, tone burst windowing functions, material model parameters, excitation frequency, and wave propagation distance on γamp are studied in detail. Also, γamp estimated for the data obtained from the numerical simulations considering S0-S0 mode pair at low frequencies and resonant S1-S2mode pair at higher frequencies are compared with the physics based material nonlinearity parameter γphy. The difference between the results is marginal. Thus, the nonlinear Lamb wave technique can be effectively used even at low frequencies to estimate the actual material nonlinearity of the (metallic) plate materials with fair accuracy using the proposed nonlinearity models.