In this paper, a three-dimensional modified boundary element method (BEM) is proposed to solve the guided wave scattering problem by cavity-type flaws in an infinite plate. The aim of modification is to correct the artificial scattering introduced by inevitable modal truncation at far-field in the traditional BEM model. The far-field wave displacement fields beyond the BEM model are assumed to be the summation of orthogonal propagating guided wave patterns, and are finally incorporated into BEM equation sets as the modified items to account for the contribution of infinite boundaries traditionally omitted. With this improvement, the spurious reflected waves are eliminated. The method is formulated for a three-dimensional homogeneous, isotropic, elastic plate and its implementation is discussed in details. The formulation is finally validated for several benchmark problems.

本文提出了一种三维修正边界元方法（BEM），以解决无限板中空腔型缺陷引起的导波散射问题。修改的目的是纠正传统BEM模型中不可避免的模态截断在远场引入的人工散射。假设超出BEM模型的远场波位移场是正交传播的导波图的总和，最后将其作为修正项并入BEM方程组中，以解决传统上忽略的无限边界的贡献。通过这种改进，消除了寄生反射波。该方法是为三维均质各向同性弹性板制定的，并详细讨论了其实现方法。