BEM ANALYSIS OF LAMB WAVE SCATTERING BY LAYERED PLATE DEBONDING

抄録

 This paper presents an analysis of reflection and transmission coefficients as boundary element solutions of guided Lamb wave scattering in a two-dimensional, isotropic, and linear elastic layered plate. A scatterer, defined as a debonding, is located on the interface between layers. The numerical model is formulated based on the boundary element method with elastodynamic traction and displacement fundamental solutions in frequency domain, where the boundary integral equations, including artificial boundaries, are discretized with constant elements. Lamb wave modal functions in each layer can be calculated by using the partial wave technique. Wave fields on the artificial boundaries, which are set long enough from the debonding to neglect near-field evanescent scattering modes, are treated as the superposition of incident wave and possible scattered waves. Then, the traction boundary condition on the artificial boundary can be expressed by unknown total displacement fields. In addition to the artificial boundary condition, the continuity condition of layer interface and the traction-free boundary conditions yield a system of linear equations that can be solved by the efficient indirect solver. The reflection and transmission coefficients are obtained from the total displacement fields after solving the system of linear equations. Various configurations of problems, including materials and length of the debonding are considered. Furthermore, the mode conversion and resonance phenomena of scattering coefficients can be seen directly related to the length of the debonding.