Ultrasonic Sensing of Internal Temperature Distributions in Heated Materials

An ultrasonic technique for sensing internal temperature distributions in heated materials is presented. The principle for measuring internal temperature of material is based on temperature dependence of the velocity of the ultrasonic wave propagating through the material. A single side of a steel plate of 30 mm thickness is heated up to about 75 degC and ultrasonic pulse-echo measurements are then performed during heating. The propagation time of ultrasonic wave in the heated steel is monitored and used to determine the temperature distribution in the steel. The internal temperature distribution determined ultrasonically almost agrees with that obtained using thermocouples installed in the steel