Line source representation for laser-generated ultrasound in an elastic transversely isotropic half-space

Theoretical and experimental results are presented for a laser line source in an elastic, transversely isotropic half-space. The thermoelastic source (laser source) is represented as an appropriately weighted shear stress dipole applied at the sample surface. The plane of isotropy coincides with the half-space boundary. Analytical expressions representing the out-of-plane displacements for the surface wave and for the epicentral cases are given for all crystal classes that exhibit elastic transverse isotropy. In addition, quasianalytical results are given for observation points off the epicentral axis. Theoretical wave forms for all of the source/observation geometries considered are compared with experimental wave forms generated in single crystal zinc samples. The close comparison between experiment and theory confirms, for this particular line source orientation and crystal symmetry, that a laser line source is accurately modeled using an equivalent boundary stress. (C) 2004 Acoustical Society of America.