Determination of elastic constants of anisotropic materials by multiple mode surface waves

An efficient inversion technique to determine elstic constants of anisotropic solids from the leaky surface acoustic wave (LSAW) is presented. In the present inversion two types of LSAW velocities, the leaky Rayleigh mode and the pseudo-leaky Rayleigh mode, have been used as knewn parameters. Both the velocities in specified directions on the solid surface can be obtained from either the phase change or the amplitude change of the ultrasonic reflection coefficient of the surface. The elastic constants are determined from the directional variations of both the LSAW velocities using an optimization procedure. Based on the investigations of the stability and accuracy of the solution in inverse problems defined on a cubic crystal, it has been shown (that the use of dual mode LSAWs enables us to make better elastic constants determination with a high precision than the use of a single mode LSAW. In addition, it has been confirmed that, by performing a series of numerical simulations using a synthetic data and an experiment, all the elastic constants of the crystal can be determined accurately by the present inversion with the knowledge of the crystallographic orientation and the density.