Experimental observation of cumulative second harmonic generation of Lamb wave modes

Abstract

Non-linear Lamb waves have been employed in recent years to monitor microstructural changes in thin-walled metallic plate and shell structures. The extreme sensitivity of this technique is advantageous for detection, but also leads to high variability in measurements taken. The measurement of the material nonlinearity is complicated by several factors, such as the nonlinearity present in measurement equipment, transducer position and angle, as well as the coupling conditions at the transducer-specimen interface. The present article reports experimental results obtained for the inherent material nonlinearity in a large undamaged and unloaded Aluminium plate. The need for improved robustness of the experimental procedure is identified.