Noncontact temperature profiling of rotating cylinder by laser-ultrasound

Abstract

In the fields of engineering and manufacturing industries, it is often required to know quantitative information about surface and internal temperatures of rotating objects. In this work, a new ultrasonic method for measuring such temperatures of a heated rotating cylinder is presented. A laser-ultrasonic technique which provides noncontact ultrasonic measurements is employed in the present method. To make a quantitative evaluation of the internal temperature distribution in the radial direction of a heated rotating cylinder having axisymmetric temperature distribution, an effective method consisting of surface temperature measurements with a laser-ultrasonic technique and one-dimensional unsteady heat conduction analyses with a finite difference calculation is developed. To demonstrate the feasibility of the method, experiments with heated steel cylinders of 100 mm and 30 mm in diameter rotating at 300 min− 1 are conducted. 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. The estimated temperature distributions during heating almost agree with those measured by an infrared radiation camera. Thus, it has been shown that the noncontact temperature measurement technique with laser ultrasound is a promising tool for on-line monitoring of heated rotating cylinders.