Some theoretical and experimental aspects of surface waves for elastic constant determination

摘要

This thesis discusses the utility of surface waves for the determination of effective elastic constants of anisotropic materials. Theoretical analysis of surface wave propagation in anisotropic materials is presented. Computer software to calculate the velocities of surface waves on an arbitrarily oriented free surface of a generally anisotropic material is developed. The dependence of the surface wave velocities on the variations of the elastic constants of the materials and the azimuthal angles of the propagation is studied. An ultrasonic technique which combines measurements of bulk waves, subsurface longitudinal waves, and surface waves to determine the elastic constants of materials with monoclinic, orthotropic or transversely isotropic symmetry is investigated. A computer aided evaluation (CAE) system is proposed to offer an alternative method to a non-linear curve fitting algorithm to convert the surface wave measurement data to a partial set of elastic constants of a material. The CAE system is applied to the evaluation of CCSS material with columnar grain structure. The effect of experimental error on the reconstruction of elastic constants with respect to bonds of elastic constants for the stability study of the CAE system is demonstrated on a synthetic set of data. Sample measurement protocols on the determination of elastic constants of transversely isotropic and orthotropic materials from one-sided access wave measurements are summarized and discussed. Finally, a finite element method is suggested for further studies of and insight into surface wave propagation, especially involving material inhomogeneities.