Lamb wave scattering by a pair of surface-breaking inclined cracks in a plate

Lamb wave scattering in an infinite, isotropic, homogeneous and linear elastic plate which contains a pair of surface-breaking inclined notch is evaluated. An inclined crack can be approached by vanishing the width of the inclined notch. The scattering of Lamb waves from geometric discontinuities involves all these wave modes which contain a finite number of propagating modes having real wave-numbers, a finite number of non-propagating modes having imaginary wave-numbers and an infinite number of in-homogeneous modes having complex wave numbers in order to satisfy the boundary conditions. The scattering field is expanded in terms of complex Lamb wave modes with unknown amplitudes. The complex mode expansion and vector projection (CMEP) method is used to deduce the solving process about these unknown amplitudes. We discuss the influences of the different length of the symmetric and asymmetric crack on the amplitudes of lamb wave scattering fields respectively. Results provide theoretical guidance for Structural Health Monitoring (SHM) using the lamb wave generation devices.