Research on shear fracture behavior of bolt and design method for retractable coupler.

To ensure the coupler's adequate retraction in rail vehicle collisions, this study systematically investigates the shear fracture behavior of bolts, focusing on the effects of geometric parameters and loading dynamics. A novel matching design method for retractable coupler shear bolts is proposed and validated. The material model parameters of AISI 1045 steel were calibrated based on the test data, and the validity of the simulation model was verified. Then, combined with the finite element simulation of the shear bolt, the influence of geometric size and applied load on the maximum shear force is discussed, and the parametric equation of the maximum shear force is derived. Finally, the shear bolt matching design is carried out for a type of coupler, and the impact test of the backtracking coupler is carried out. The influence of the vehicle coupling system and bolt arrangement on the impact interface force is discussed. The results show that the maximum shear force of the shear bolt has nothing to do with the diameter of the bolt itself but is directly proportional to the cross-section area of the groove and inversely proportional to the width of the groove. Bolt material has a strain-hardening effect, and the shear force is positively related to the impact velocity. The impact test results are consistent with the design threshold and simulation results, and the vehicle coupling system and bolt arrangement have relatively little influence on the impact interface force of the vehicle.