The Modified Boundary Element Method For The Problem Of Scattering Of Ultrasonic Lamb Wave With A Defect In Flat Plate

The boundary element method(BEM)has the advantages of fast modeling speed and high calculation efficiency for solving the scattering problem of elastic waves in elastic half-space,elastic plate and other structures with infinite boundaries.However,when modeling the structure with BEM,false reflection waves are generated due to boundary truncation,introducing errors in the calculation results of scattering wave field.In the proposed method,the far-field characteristics of the scattered wave,expressed as the summation of a series of guided wave modes,are introduced in the basic BEM matrix as correction items,The numerical examples show that the method can effectively eliminate the spurious reflection wave.In this paper,the elastodynamic reciprocity theorem is applied to convert it into an integral on the boundary of finite length in the near field and the programming difficulty is greatly simplified without affecting the computational accuracy.In this paper,the modified BEM method is used to solve the elastic guided wave scattering problems in various single-and multi-layered plate structures.In order to verify the correctness of the modified BEM method,the convergence test was carried out for typical defects in single-layer and multi-layer plates.In this paper,the results of modified BEM method and the existing numerical algorithm are compared with some examples.The results are consistent with each other,and the modified BEM method is more efficient.The modified BEM proposed in this paper can accurately and efficiently calculate the problem of guided wave scattering by thinning defects in a plate,And it can be used as the theoretical basis and numerical simulation method of ultrasonic guided wave quantitative nondestructive testing.