Ultrasonic measurement of elastic constants of anisotropic materials with laser source and laser receiver focused on the same interface

A noncontact laser-ultrasonic technique is described that allows determination of material properties of anisotropic platelike samples. The method requires access to only one side of the sample. Plane waves are synthesized by scanning the surface with a laser line source at judiciously chosen intervals. By doing so, the intricacies associated with the reflection of an acoustic ray off an interface of an anisotropic medium are avoided. The plane-wave reflections off the opposite free surface of the plate are simply governed by Snell's law. The identification of the stiffness-tensor components is based on the inversion of the phase velocities of these reflected plane waves. The procedure developed is presented and applied to both simulated and experimental signals. The method is easy to implement, and provides a means for noncontact measurement of elastic properties where there is limited access to test specimens. (C) 2001 American Institute of Physics.