Effect of Preload on Tensile Fracture of Variable Cross-Section Bolts: Experiment and Simulation

Abstract

High-strength bolts are widely used in structural connections, and the preload affects the failure behavior of bolts. In this paper, a variable cross-section bolt (VCSB) with weakened strength to induce fracture is designed. Quasi-static tensile experiments with different preload torque values were performed on the VCSB. The preload torques of 0, 430, 610, and 820 N·m were applied to the VCSB connection structures before the test. The load–displacement curves obtained by the test could be divided into three stages: the initial elastic phase, the yield phase, and the rapidly necking phase. As the preload increased, the stiffness of the initial elastic phase increased from 101.21 kN/mm to 270.64 kN/mm and the fracture displacement DC decreased from 10.54 mm to 8.42 mm. Finite element models were developed to simulate the failure process of VCSB under tensile loads. The difference between the FB and DC values in the simulation results and the test is within 2%. The simulations were carried out by adjusting the prestress from 0 to 650 MPa. The results show that the value of preload force has no effect on the FB of VCSB, but greatly influences the DC and FC of the connection.