Study of axial force sensor for bolt

Abstract

Conventional methods such as torque method are mainly used for tightening control. However, it is often difficult to tighten bolt with the required axial force by effect of the friction between both bearing and the thread surfaces. Usually bolts are loosened due to heat, vibration and impact in circumstances. In this study, an axial force sensor using PZT element is proposed. The new developed sensor can estimate the axial force of bolts by measuring the difference of the ultrasonic wave propagation time before and after bolt's tightening. Moreover, a bolt loosing test machine which can control vibration and impact is proposed. In this paper, it is clarified that, the proposed sensor for tightening control is reliable enough to be applied in practical use. Furthermore, the axial force sensor for detecting the loosening of bolt is proved its reliability using bolt loosening test machine.