Abstract
A quantitative theory for modeling the laser-generated transient ultrasonic Lamb waves propagating along arbitrary directions in orthotropic thin plates is presented by employing an expansion method of the generalized Lamb wave modes. The displacement is expressed by a summation of the symmetric and antisymmetric modes in the surface stress-free orthotropic plate, and it is particularly appropriate for wave form analyses of Lamb wave in thin plates because one needs only to evaluate a few of the lowest order modes. The transient wave forms are analyzed in the thermoelastic regime and the oil coating generation method for a transversely isotropic plate. The results show that the theory provides a quantitative analysis to characterize anisotropic properties and elastic stiffness properties of the orthotropic plates by the laser-generated Lamb wave detection. (C) 1999 American Institute of Physics. [S0003-6951(99)03209-X].