New ultrasonic thermometry and its applications to temperature profiling of heated materials

In the fields of materials science and engineering, there are growing demands for monitoring temperature and its distribution of heated materials. This is basically because temperature is one of the most important factors that dominate the material properties and behavior. Such temperature monitoring is required for not only the surface but also the inside of heated materials. In this work, a new ultrasonic method for monitoring temperature gradients of materials during heating or cooling is presented. The method consists of ultrasonic pulse-echo measurements and an inverse analysis for determining one-dimensional temperature distributions along the direction of ultrasound propagation in or on the material. To demonstrate the practical feasibility of the method, several experiments with heated materials have been made and successful results of internal temperature profiling are obtained. In addition, laser ultrasonic techniques that provide non-contact monitoring of surface temperature distributions of heated materials are proposed and their potentials are demonstrated. Thus, it is highly expected that the ultrasonic thermometry is a promising means for on-line temperature profiling of industrial materials processed at high temperatures.