Two-dimensional monitoring of surface temperature distribution of a heated material by laser-ultrasound scanning

Abstract

A non-contact method with a laser-ultrasonic technique for measuring two-dimensional temperature distribution on a material surface is presented. The method consists of a laser-ultrasonic measurement of a one-dimensional temperature distribution on a material surface and its two-dimensional area mapping. The surface temperature is basically determined from a temperature dependence of the velocity of the surface acoustic wave (SAW) propagating on a material surface. One-dimensional surface temperature distributions are determined by an inverse analysis consisting of a SAW measurement and a finite difference calculation. To obtain a two-dimensional distribution of surface temperature on a material surface, SAW measurements within the area of a square on the surface are performed by a pulsed laser scanning with a galvanometer system. The inverse analysis is then applied to each of the SAW data to determine the surface temperature distribution in a certain direction, and the obtained one-dimensional distributions are combined to construct a two-dimensional distribution of surface temperature. It has been demonstrated from the experiment with a heated aluminum plate that the temperature distributions of the area of a square on the aluminium surface determined by the ultrasonic method almost agree with those measured using an infrared camera.