Study on loosening mechanism and the influence factors of bolted joints under transverse cyclic loads

Bolted joints are widely used in a variety of engineering applications. However, their loosening significantly increases the risk of structural failure. In this work, a refined finite element model of the bolted joint was developed to investigate the initiation and evolution of loosening under transverse cyclic loads. Loss curves of bolt preload and residual torque with different influencing factors, namely bolt preload, transverse load amplitude and thread friction coefficient, were obtained by finite element analysis. The effect of residual torque on the initiation of loosening was revealed based on the analysis of mechanical state. Results showed that the non-uniform stress distribution at the threads tends to become uniformly distributed under transverse cyclic loads. On the contact surface of bolt head, stress distribution and slip state varied periodically with the transverse cyclic loads. The analysis of the evolution of stress and contact state provides a new perspective for elucidating the loosening mechanism of bolted joints.