A non-contact temperature sensing with ultrasound and the potential for monitoring heated materials

A new non-contact method for measuring both surface and internal temperature distributions of heated materials is presented. A laser-ultrasound technique that enables non-contact ultrasonic pulse-echo measurements is employed in this work. An effective inverse method is developed to determine the temperature distributions quantitatively. To demonstrate the practicability of the developed method, some experiments with aluminum and steel plates heated up to 150°C are carried out. Using the laser-ultrasound, surface acoustic waves and longitudinal waves of heated plates are measured to estimate the surface and internal temperature distributions, respectively. It is verified that the ultrasonically determined results almost agree with those measured using an infrared radiation camera or thermocouples. Thus, the ultrasonic method is believed to be effective in the in-situ or in-process monitoring of temperature distributions of materials being processed at high temperatures.