Bolt Pretightening Force Measurement Based on Strain Distribution of Bolt Head Surface

Abstract

To monitor bolt connection status and detect bolt looseness in engineering structures, a bolt pretightening force sensor was designed and fabricated with a strain gauge bonded on the top surface of a bolt head. The stress–strain states of the top surface of the bolt head under different pretightening forces were analyzed using the finite element method (FEM). It was found that the radial strain on the top surface of the bolt head and the pretightening force of the bolt have a good linear relationship. A bolt sensor integrated with the designed radial strain gauge on the top surface of the bolt head was designed and fabricated, and an experimental device was also set up. The experimental results showed a good linearity between the radial strain on the top surface of the bolt head and the bolt pretightening force. The FEM and experimental results demonstrate that the proposed method and the designed sensor can effectively measure the bolt pretightening force. The proposed method and sensor are a new way to monitor bolt connection status and detect bolt looseness. The proposed method is easy to implement and has good application prospects.