DETERMINATION OF THE ELASTIC-CONSTANTS OF ANISOTROPIC SOLIDS FROM GROUP VELOCITIES MEASURED IN SYMMETRY DIRECTIONS

We present in this article a novel method of determining all three ela stic constants of cubic crystals from a single broadband waveform prop agating in the [001] direction. The method can be easily extended to m edia of orthorhombic symmetry whose symmetry plane quasitransverse (QT ) group velocity sheet is folded across the symmetry axis. The usefuln ess of these formulas lies in providing a very convenient and easy met hod of determining all the elastic constants of a medium from the rays propagating in the principal symmetry directions of the medium. Parti cular emphasis is given to the so-called oblique-mode QT rays with gro up velocity lying along a symmetry axis but with wave normal lying awa y from that axis in a symmetry plane. Through the use of these oblique modes the need to make off-axis measurements to obtain a complete set of elastic constants is circumvented. Moreover, we describe a method of clarifying the ambiguity that arises; with which symmetry plane is the wave normal of an oblique-mode QT ray propagating in the symmetry axis associated. Further, we show how the effect of a finite rise time source can be corrected for in the determination of a mixed index ela stic constant.