Development of a friction sensor for hot forging

Abstract

A friction sensor that can detect both pressure and frictional stress on the tool’s surface during hot forging has been developed. The detection principle was introduced in 2004 by the present author; however, a sensor suitable to be installed in the forging die has not been created until now. In this study, a hot forging sensor prototype is presented, and its design method is described in detail. The sensor comprises two beams connected to the thin plate part of the top surface of the sensor pin, and a thin plate connects the base of the two beams. According to the friction applied on the sensor surface, the two beams incline to deform the thin plate at the base of the beams. The frictional stress on the sensor surface corresponds to the difference between the two strains on the thin plate surface. The main dimensions of the sensor structure are determined according to the expected applied pressure and frictional stress. Additionally, a new calibration test equipment is developed to obtain the calibration coefficient. Finally, the pressure and the frictional stress are measured in hot forging, as illustrated in an example, and the validity of the output of the friction sensor is confirmed.