Research On Loosening Mechanism Of Bolt Connection Under Transverse Load

With the continuous development of the power grid,the voltage level of transmission lines is constantly increasing,and the types and quantities of transmission towers are also increasing.Under the harsh ice and wind load conditions,there are more and more problems on the transmission tower.As a truss structure connected by bolts,the loosening of bolts on the transmission tower has become an important cause of failure of the transmission line.Therefore,it is particularly important to study the bolted joints in the transmission tower,especially the connecting bolts of the main material components of the transmission tower bearing larger loads.In practical engineering,the bolted joints are often subjected to alternating dynamic loads.Under the transverse load,the preload of bolt will be reduced and loosened,thus changing the inherent mechanical properties of the bolted joint and even the entire structure.The tower collapse accident jeopardizes the safe operation of the power system.In this paper,the critical loosening load of the bolt under different models is given by theoretical derivation and numerical calculation for bolted joints of main components of transmission towers,and the influence law of the bolt parameters on the critical loose load is given.Based on the bolted joints as the model,the experimental device of transverse vibration was designed and processed.The critical loose load of the bolted joint was experimentally studied.The accuracy of the calculation method was verified by comparing the theoretical calculation results with the test results.The model of bolted joint considering thread refinement is established.The loosening process of bolted joint under cyclic load is analyzed by finite element simulation.The influence of different contact conditions on bolt loosening process is given.Finally,the finite element simulation is used to compare the theoretical calculation and simulation of the thread load distribution,and then the theoretical method is modified.It provides a theoretical basis for studying the mechanism of bolt loosening and bolting anti-loose.