COMPARISON OF ELASTIC-CONSTANT DETERMINATION IN ANISOTROPIC MATERIALSFROM ULTRASONIC GROUP AND PHASE-VELOCITY DATA

A comparative analysis of elastic constant determination from the angu lar dependence of group and phase velocity data in orthotropic and tra nsversely isotropic materials is performed. A nonlinear least-squares optimization procedure is used for inversion. The method allows the us e of group velocity data in a cuspidal region, where for a given ray d irection there are more than three distinct wave modes propagating wit h different velocities. Exact analytical equations are derived relatin g group velocities to elastic constants for arbitrary planes in transv ersely isotropic materials. Approximate relations for nonsymmetry plan es in orthotropic materials are obtained. The procedure is generalized for determination of elastic constants from group velocities measured in arbitrary incident planes in orthotropic materials. (C) 1997 Acous tical Society of America. [S0001-4966(97)01312-X].