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 veri®ed 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 speci®c set of material properties. Mode re¯ection and transmission factors are numerically calculated to evaluate mode sensitivities and to obtain the potentially good classi®cation features. It turns out that the guided wave scattering pro®les show quite di€erent behaviors as functions of incident mode, frequency, defect shape and size in providing us with enough rich feature extraction information for defect classi®cation and sizing analysis. The theoretical analysis can be used to establish ecient guidelines for both data acquisition and feature selection in a pattern recognition analysis program of study. Sample results are presented