An elastodynami`c hybrid boundary element study for elastic guided wave interactions with a surface breaking defect

Elastic guided wave interactions with various defects are explored for investigating defect characterization possibilities by using a hybrid boundary element method (BEM) in combination with an elastodynamic boundary integral equation and the Lamb wave normal mode expansion technique. The BEM code accuracy is verified based on energy conservation and available bench marking data for guided wave scattering problems. Through two-dimensional (2-D) parametric studies for an arbitrarily shaped defect, from a surface breaking crack model to a round surface defect, a waveguide cross-section including a defect is locally selected as a model for a given incident mode, frequency and a specific set of material properties. Mode reflection and transmission factors are numerically calculated to evaluate mode sensitivities and to obtain the potentially good classification features. It turns out that the guided wave scattering profiles show quite different behaviors as functions of incident mode, frequency, defect shape and size in providing us with enough rich feature extraction information for defect classification and sizing analysis. The theoretical analysis can be used to establish efficient guidelines for both data acquisition and feature selection in a pattern recognition analysis program of study. Sample results are presented.