Reconstruction of internal temperature distributions in heat materials by ultrasonic measurements

An improved method for reconstructing internal transit temperature distribution in a heat material is presented in this paper. This method combines the advantages of the ultrasonic measurement and inverse analysis. Firstly, a numerical model of sensing interior temperature field is obtained based on temperature dependence of the velocity of ultrasonic wave (acoustic velocity) propagating through heated materials. Then, an inverse analysis by the sensitivity method for estimating equivalent thermal boundary conditions are developed to determine the non-uniform temperature fields. Experiments are referred to validate the feasibility and reliability of the presented method, whose robustness and accuracy is also analyzed through a comprehensive parameter analysis. Numerical results reveal that internal temperature gradient and its variation estimated by the developed method agree well with the measured values using thermocouples installed in the steel. Besides, this method can be helpful for solving the problems of transient state boundary using the quasi-steady approximation. It demonstrates that the method presented in this work is a promising means for high-accurately determining internal transient temperature distributions in heat materials by ultrasonic pulse-echo measurements.