Dynamic Modeling And Characteristic Analysis Of Bolted Connections Subjected To Torsional Vibration

Bolt connections can be used for connecting,fastening,load transferring,sealing,etc..As fundamental components,bolt connections are widely used in aerospace,shipbuilding,machinery and equipment,automobiles and other industries due to the advantages of simplicity,easy disassembly ad low cost.However,in practical conditions,bolt connections are often subjected to vibration,variable load,impact load or temperature change.These kinds of loads would lead to gradual reduction of anti-loosening friction and clamping fore,resulting in the thorough failure of loosening and poor reliability of mechanical equipment.From the perspectives of equipment safety and economic benefit,clarifying the mechanism of bolt connection loosening,building its dynamic model,acquiring its loosening rules,thus predicting of is loosening and realizing its anti-loosening,are of great importance for the reliable operation of mechanical equipment,production accident rate reduce and economic prosperity.In order to solve the problem of bolt connection loosening under vibration environment,methods of theoretical analysis,dynamic modeling and experimental validation were adopted to analyze the mechanism of bolt connection loosening due to torsional vibration excitation.A MDOF lumped mass model of the connecting bolt subjected to torsional vibration was proposed and validated by a specifically designed test bench.Simulations were conducted to analyze the dynamic response of bolt connection when subjected to torsional vibration excitation and the influences of factors,such as friction coefficient,pre-force,excitation etc.on the bolt loosening characteristics.Finally,a clamping force controlling based anti-loosening method of bolt connections was proposed.The main research work is summarized as follows:(1)Reasons responsible for the loosening of bolt connection under vibration environment were summarized.And the loosening process were divided into two stages: fretting wear stage and rotating stage.Especially,the loosening mechanism of bolt connection subjected to torsional vibration was emphasized and clarified.(2)A MDOF dynamic model of the bolt connection was built using the lumped mass method.In order to validate the built model,a bolt connection torsional vibration test bench was designed.The comparison between tested and simulated results showed the correctness of the proposed model.(3)Influences of factors such as friction coefficient,pre-force,excitation etc.,on the dynamic responses of the bolt connection were analyzed using the proposed dynamic model.And the laws of how these factors influence the loosening of bolt connection was obtained.(4)An anti-loosening method based on clamping force controlling was proposed.The proposed method has the advantages of whole-process anti-loosening over traditional methods.