Multimodal Sparse Reconstruction In Lamb Wave Based Structural Health Monitoring

Lamb waves are utilized extensively for structural health monitoring of thin structures, such as plates and shells. Normal practice involves fixing a network of piezoelectric transducers to the structural plate member for generating and receiving Lamb waves. Using the transducers in pitch-catch pairs, the scattered signals from defects in the plate can be recorded. In this paper, we propose an l(1)-norm minimization approach for localizing defects in thin plates, which inverts a multimodal Lamb wave based model through exploitation of the sparseness of the defects. We consider both symmetric and anti-symmetric fundamental propagating Lamb modes. We construct model-based dictionaries for each mode, taking into account the associated dispersion and attenuation through the medium. Reconstruction of the area being interrogated is then performed jointly across the two modes using the group sparsity constraint. Performance validation of the proposed defect localization scheme is provided using simulated data for an aluminum plate.