Investigation of Stud Bolt with Fiber Bragg Grating Sensor Under Different Bolt Tightening Torque

Abstract

This study presents an investigation of stud bolt with embedded Fiber Bragg Grating (FBG) sensor under different tightening torque. The use of FBG sensor enables the precise quantification of the actual strain caused by any loading acting on bolts, as well as the detection of potential harm arising from an excessive working load to the flange. The objective of this work is to monitor the axial strain of M18 stud bolts on a standard flange for pipe connections using multiplexed FBG sensors that are integrated into the bolts. A connection was established between two carbon steel pipes using a series of flanges secured by four bolts. The testing results demonstrated a clear and direct relationship between the tightening torque and the wavelength of the FBG sensor. The strain reading showed an acceptable level of linearity. It is revealed that, although bolts were tightened with the same torque, each bolt experienced a different level of tension. The methodology outlined in this research presents an alternative approach to monitoring the extension of bolted gaps and assessing the degree of bolt looseness.