Scattering of fundamental Lamb wave modes obliquely incident on a surface breaking crack in a plate

The use of guided Lamb waves for non-destructive evaluation of metal and composite plates has been investigated in numerous studies. In order to locate and size defects with Lamb waves, it is important to develop a quantitative understanding of their interaction. When Lamb waves are obliquely incident on a transverse crack in a plate, they are subject to scattering. This study develops analytical solutions for the reflection and transmission energy coefficients of the waves scattered by the fundamental anti-symmetric Lamb mode incident obliquely on surface breaking cracks. The modal decomposition technique coupled with the method of collocation is used to determine the energy coefficients. These coefficients are shown to depend on the crack depth and the incident frequency. Experiments were conducted to verify the analytical results. Two different crack depths and frequencies were used. The experimental results follow the trends seen in the analytical results.