Noncontact temperature profiling of rotating cylinder by laser-ultrasonic sensing

There are growing demands for measuring surface and internal temperature profiles of rotating objects in the fields of engineering and manufacturing industries. In this work, a new noncontact method for measuring such temperature profiles of a heated rotating cylinder is presented. A laser-ultrasonic technique which provides noncontact ultrasonic measurements of heated objects is employed in the method. Surface temperature measurements for a heated cylinder using the laser-ultrasonic technique and a heat conduction analyses with a finite difference calculation are combined together for making a quantitative evaluation of the internal temperature profile in the radial direction of the cylinder. To demonstrate the feasibility of the combined method, an experiment with a heated steel cylinder (100 mm dia.) rotating at 300 min-1 is carried out. A pulsed laser generator and a laser Doppler vibrometer are used for generating and detecting surface acoustic waves (SAWs) on the steel cylinder, respectively. Measured SAWs are used for determining both surface and internal temperatures of the cylinder. As a result, the estimated temperature distributions during heating almost agree with those measured by an infrared radiation camera. In addition, the influence of the rotating speed of the cylinder on the error in ultrasonically estimated surface temperatures is examined.