2011 Volume 47 Issue 10 Pages 422-429
Lamb waves have been used for non-destructive inspection of thin-plate-like structures. However, the conventional time-of-flight technique is not reliable for locating the defects even in isotropic plates because of the dispersiveness in the Lamb wave propagation. Avoiding difficulties caused by the dispersiveness, this paper proposes a novel dynamic shear strains analysis which has an ability to localize defects with reconstructing near-field images. The proposed imaging method utilizes the determinant of the dynamic shear strains covariance matrix which are defined over the object surface. The determinant denotes the distribution of correlated intensity modulation of the incident wave fronts with scattered ones. The value of the determinant, therefore, increases significantly in the near-field of the defects. In this study, the computational process in the wave field near the defects is discussed and their physical meanings are investigated through FDTD-simulations and acoustic experiments.
