Thermal characterization of viscoelastic materials using sonothermography

The "Sonothermography" technique consists in measuring temperature field during vibrations or ultrasonic wave propagation in viscolelastic material. If the level of energy is sufficient, the temperature field can be acquired with an infrared camera and exploited for nondestructive evaluation and testing. This paper proposed to use sonothermography as volumic heat source in order to characterize the thermal properties (ie thermal diffusivity) of a homogeneous viscoelastic sample. A new method. based on a Low Order Weak Formulation (LOWF) of the heat equation is used. In this formulation, the spatial derivatives of temperature are substituted by an analytical expression using virtual test function. By this way, LOWF leads to a more robust estimation of the thermal diffusivity. LOWF method is numerically and experimentally applied to the temperature field generated by acoustic wave propagation in a thin viscoelastic sample.