Evaluation of early stage local plastic damage induced by bending using quasi-static component of Lamb waves

Abstract

This paper investigates an experimental technique for evaluating early stage material damage in an aluminum plate using quasi-static component of Lamb waves, which is a simpler version of the nonlinear Lamb wave measurement technique. Different levels of material nonlinearities were induced by local plastic bending. A pair of piezoelectric ceramics transducers (PZTs) were used to excite and detect the fundamental Lamb waves and quasi-static component, respectively. The quasi-static component was extracted from received signals through signal processing with a low-pass filter. The effectiveness of PZT was validated through laser inspection. The results show that the measured acoustic nonlinearity parameter (ANP) monotonically increases with bending time before the generation of macro-cracks, and Fast Fourier Transform (FFT) is a good and efficient choice to demonstrate the intensity of the quasi-static component. Compared with the established framework of the second harmonic generation technique, this study reveals that the quasi-static component method is a more powerful technique in evaluating early stage local plastic damage.