Experimental Study On Looseness Of Bolt Connection Structure Under Transverse Vibration Condition

The bolt connection structure is widely used in all kinds of connection structures.In general,the bolt connection has become loosened before fatigue damage.Loosening of bolt connection structure means that with the increase of working hours,the loosening of bolted connection components will cause loosening of preload.In the early stage of loosening,it may not affect the normal operation of the whole system,but with the decrease of clamping force,the loosening will intensify,and the overall stiffness of the whole bolted connection system will decrease,which will cause bolt breakage and cause major accidents.This paper takes the bolt of the transmission tower M20 × 90 as the research object,and studies the loosening mechanism of the bolt connection structure under the transverse vibration condition through the experimental method.First of all,theoretical calculation is done through theoretical models which have been put forward by predecessors.The slip between thread surfaces is analyzed,and the slip process during lateral vibration is expounded.Then,the transverse vibration test on the FPD-200 fastener test machine is carried out.The single factor and three level research method is adopted to analyze the effects of preload,lateral amplitude and vibration frequency on bolt loosening respectively.At last,the optimum three groups of pretension,lateral amplitude and vibration frequency are obtained.Orthogonal experiment is used to make orthogonal experiment on three factors,and a better combination is obtained.Through experimental analysis,the transverse vibration condition,the vibration frequency of the pretightening force and transverse amplitude,affect the structure of bolt connection looseness,suitable locking parameters: initial preload 55 kN,transverse amplitude 0.4mm,vibration frequency is 12Hz;available by comparing the structure: amplitude is the main effect the factors of loose bolt structure,the pretightening force of the frequency,the weakest,and orthogonal method and single factor experiment research method correlation.