Experimental study of thermo-acoustic wave modulation in a cracked plate

This paper presents a study on nonlinear elastic wave modulation due to an applied pe-riodic thermal field. The experimental study is performed with a thermal analogy of the vibro-acoustic wave modulation (VAM) technique. The aim is to identify sources of nonlin-ear effects appearing in the response signal of a damaged structure. Assigning specific non-linear effects to their corresponding sources is a key challenge for most nonlinear acoustic methods. Separation of nonlinear effects into those related to damage dynamics and those related to other sources, e.g., material nonlinearity or boundary conditions, is very impor-tant for practical applications of nonlinear acoustic methods. In this study, an aluminum plate with a localized fatigue crack is investigated. The plate is excited simultaneously with a high-frequency acoustic wave and a low-frequency thermal field generated by a modulated laser source. The response vibration signal is acquired at different locations (near and far from the damage) using a Laser Doppler Vibrometer (LDV). Signal processing is applied to extract the nonlinear effects in the form of modulation sidebands. (c) 2021 Elsevier Ltd. All rights reserved.