PLANE HARMONIC-WAVES FOR 3 THERMOELASTIC THEORIES

Plane harmonic thermoelastic waves predicted by two theories, which in corporate second sound effects, are investigated. An isotropic solid i s assumed and the theories are linear, consequently the strain is infi nitesimal and temperature changes are small compared with the referenc e temperature. Results from the two theories, for material properties representative of aluminum, are compared with those obtained from the classical theory that has been treated in detail by Chadwick One purpo se of the paper is to investigate the validity of one of the second so und theories, which is based on the Principle of Local State and the M axwell-Cattaneo relation. This theory violates a consequence of the Cl ausius-Duhem relation but it is shown that, for the relaxation time co nsidered, this violation is negligible for plane harmonic waves, excep t for frequencies of order of magnitude of 10 GHz or greater. The rela tionship between characteristic theory and the theory of plane harmoni c waves, for the thermoelastic wave problem, discussed.