Experimental observation of static component generation by Lamb wave propagation in an elastic plate

The experimental observation of acoustic radiation induced static component (SC) generation by Lamb wave propagation in an elastic plate is first reported. An experimental approach to directly detect the generated SC of primary Lamb wave propagation in an elastic plate is proposed, where a low-frequency wedge transducer is used to detect the SC pulse generated by primary Lamb wave tone-burst that is excited by a high-frequency wedge transducer. The basic requirements are that the group velocity of primary Lamb wave needs to be equal to that of the s₀ mode at zero frequency (i.e., the SC), and that the central frequency of the low-frequency wedge transducer needs to be near the center of the main lobe frequency range of the generated SC pulse. For this purpose, the S₄ mode whose group velocity is equal to that of the generated SC is selected as the primary Lamb wave, and then the specific mode pair S₄-s₀ is focused and analyzed. Accompanying propagation of the S₄ mode tone-burst, the generated SC pulse detected with the low-frequency wedge transducer is clearly observed. Through respectively measuring the amplitudes of the S₄ mode and the generated SC for different spatial separation between the transmitting and receiving wedge transducers, the quantitative relationship of the relative nonlinear acoustic parameter with propagation distance is obtained. The experimental results show that the proposed approach can be used to directly detect the generated SC of Lamb wave propagation, and that the said SC does have a cumulative growth effect with propagation distance.