Coupling of Lamb waves with the aperture between two elastic sheets

The interaction between ultrasonic Lamb waves and the region of rigid contact between two elastic layers is explored analytically. This problem is a model of two sheets welded in this region, and is of great practical importance in a nondestructive evaluation of welds. To uniquely define the dimensions of the region on the basis of the transmitted ultrasonic signal, the experimental conditions are selected in such a manner as to avoid resonance in the region of contact. Our experiments show that there exists a one-to-one relationship in the form of T∼d3 between the transmission coefficients T of the wave through a region of contact having diameter d.