In Situ Monitoring of Temperature Rise in Friction Surface Using Ultrasonic Technique

Abstract

In this work, the feasibility of the use of ultrasonic thermometry for in situ monitoring of temperature rise in friction surface has been examined. The ultrasonic thermometry that is a method providing internal temperature measurements by ultrasound is applied to temperature measurements of a friction surface at which temperature rise occurs due to friction, and an attempt is made to demonstrate in situ monitoring of transient variations in the friction surface temperature and temperature distribution beneath the surface. Those temperatures near the friction surface are quantitatively determined by an effective method consisting of ultrasonic pulseecho measurements and a finite difference calculation for estimating a one-dimensional temperature distribution along the direction of ultrasound propagation. The advantage of the method is that no boundary condition at the friction surface is needed. To demonstrate the practical feasibility of the method, the ultrasonic pulse echo measurements at 5 MHz are performed for a steel plate of 30 mm thickness whose single side is being rubbed with a felted fabric plate. The temperature at the friction surface and internal temperature distribution of the steel plate are measured during the rubbing process and the transient variations of the measured temperatures are obtained. Quick temperature rise of approximately 30 K at the friction surface is observed within a few seconds after the rubbing starts. It is noted that the temperatures measured by the ultrasonic method almost agree with those measured using thermocouples inserted into the steel plate. Thus, it has been demonstrated that the ultrasonic thermometry is a promising sensing means for in situ monitoring of temperatures at friction surface as well as beneath the surface.