The coated thermoelastic body within a low-frequency elastodynamic field

A superposition of a longitudinal and a transverse plane elastic wave excit es a small body which is embedded in an infinite elastic medium. The interi or of the body exhibits thermoelastic behaviour of the Biot type and it con tains a core which is also thermoelastic but with different thermal and ela stic parameters. Integral representations for the near as well as the far-h eld are obtained which involve volume integrals over the shell and the core and surface integrals over the surface of the scatterer and the core-shell interface. Complete low-frequency expansions are provided and the scatteri ng problem is reduced to a sequence of transmission problems for the determ ination of the coefficients of these expansions. It is shown that the therm al character of the interior media is observed in the low-frequency approxi mations of order higher or equal to three, when we are close to the scatter er and higher or equal to five, when we are far away from it. Furthermore, the thermoelastic behaviour of the scatterer affects only the radial scatte ring amplitude, which is of the longitudinal type, while the tangential sca ttering amplitudes, which are of the transverse type, coincide with the cor responding expressions for scattering by an elastic body with a penetrable elastic core. (C) 1998 Elsevier Science Ltd. All rights reserved.