Boundary element solution for the bidimensional scattering of guided waves in laminated plates

The boundary element method (BEM) in the frequency domain based on the full space fundamental solution is used in this paper to study bidimensional plate wave scattering problems. When some purely elastic waveguides are present, the BEM cannot be applied directly because energy can travel without attenuation through the waveguide towards infinity in the form of travelling (or propagating) guided waves. Since the accurate calculation of the far field is an essential information for remote sensing applications, the mesh truncation approach cannot be applied. In this paper, semi-analytical consistent absorbing boundaries which accurately model the dynamic response of semi-infinite plates are used to replace the actual waveguides. The resulting hybrid boundary element–finite element method is described and applied to study several Lamb and guided SH wave scattering problems for which some results are available in the literature. Ultrasonic guided waves are being successfully applied to remotely detect defects in large metallic elements. These components are commonly coated for corrosion protection or insulation purposes. Since the coating materials are usually viscoelastic, the inspection range is severely reduced unless an adequate combination of mode and frequency with low attenuation are chosen. The hybrid boundary element–finite element method is applied to study the scattering of low-attenuated modes by hidden corrosion defects. Some trends in the mode conversion factors are highlighted that could be used in long-range NDE applications for defect sizing.