Wavefront modulation and controlling for Lamb waves using surface bonded slice lenses

There is a growing interest in controlling the propagation of Lamb waves to achieve better performance for structural health monitoring and nondestructive evaluation. In this study, we present new methods of controlling Lamb waves using simple slice lenses through wavefront modulation. The lenses are made of metal slices with designed shapes. Once bonded on plates, the lenses modify the effective plate thickness, and therefore change the Lamb wave characteristics such as the wavenumber and phase velocity, providing convenient ways of modulating wavefront and controlling Lamb waves in plates. Numerically and experimentally, we demonstrated that a straight wavefront A(0) mode can be focused on the desired focal point using a plano-concave aspherical lens. We also demonstrated that the A(0) mode can be steered with different frequency components steered to different directions using a simple prism made of metal slices. The work shows that such simple slice lenses provide easy ways for controlling Lamb waves, and have a great potential for Lamb wave based applications. Published by AIP Publishing.