| Damage and fracture of steel-cored aluminium strand(ACSR)occur frequently at the joint of ACSR.It is mainly manifested in the influence of residual stress,dynamic bending stress amplitude of breeze vibration and vibration fatigue of steel-cored aluminium strand splicing sleeve after compression,which are prone to fatigue damage.Therefore,the fretting fatigue of steel-cored aluminium strand connector under compression residual stress can be studied,which can control compression residual stress,reduce vibration stress amplitude and improve fatigue life.In order to study fretting fatigue life of steel-cored aluminium strand connector.The mathematical model of wind-induced fatigue response of the splicing sleeve under compression residual stress is established.The mathematical model is solved by numerical simulation software.Finally,the mathematical model is validated by the splicing sleeve fatigue test.The following studies were carried out:Firstly,the influence of three factors,i.e.the size of the butt side,the length of the die and the chamfer shape of the splicing sleeve,on the residual stress of the splicing sleeve is studied.Taking LGJ-240/30 steel-cored aluminium strand splicing sleeve as the research object,a mathematical model of residual stress in splicing sleeve compression was established.COMSOL software is used to establish the physical model of splicing sleeve crimping.Different crimping factors are set as boundary conditions.The generalized data are obtained by calculating different crimping combinations,and the mathematical model is solved by fitting.The mathematical model can calculate the residual stress of the pipe body and the strand after the joint is pressed.Secondly,the influence of compression residual stress on the stress amplitude of joint pipe under breeze vibration is studied.Based on the energy method,the mathematical model of the influence of compression residual stress on the dynamic bending stress amplitude of joint pipe is established.COMSOL simulation software is used to establish the physical model of the splicing sleeve breeze vibration.By changing the coefficient of calculation formula of the software core,the mathematical model is input into the software.The wind speed and frequency of a single steel-cored aluminium strand connector under lock-in effect are calculated.The wind speed input is taken as the boundary condition,and the stress amplitude of the steel-cored aluminium strand under different tension is calculated based on the energy balance method.Thirdly,the fatigue life of splicing sleeves under the influence of compressive residual stress is calculated.Based on the plastic flow method and the intensity factor theory,the fatigue life mathematical model of splicing sleeves at the damage and fracture stages is established.The S-N curve of splicing sleeve material and the generalized data in the calculation of breeze vibration are used to simulate the fatigue of the same physical model.The cumulative fatigue of damage and fracture stages is used to calculate the boundary conditions.The corresponding coefficients in the steady-state formula of the foundation are modified,and the plastic flow method and the intensity factor theory are input into the calculation core to calculate the fatigue usage rate and strain change rate of the splicing sleeve.Finally,the fretting fatigue damage caused by the fatigue source zone of the steel-cored aluminium strand joint after pressing was verified,and fretting fatigue test of the joint was carried out.The LGJ-240/30 steel-cored aluminium strand splicing sleeve was used as the test material,and the conditions were as follows: the dimension of the opposite side was 30 mm,the length of the die was 30 mm,and the fillet of the splicing sleeve of the splicing sleeve was chamfered.The dynamic bending strain of the pipe body and the strand at the splicing sleeve during the splicing sleeve vibration was collected by applying load on the high frequency fatigue testing machine,and the crack length in the splicing sleeve damage was collected by scanning electron microscopy(SEM).After the experiment,the data were sorted out and compared with the simulation results,the coincidence was 84.6%.The results show that the influence of the size,length and the chamfer of the splicing sleeve on the formation of the residual stress decreases in turn.The fatigue source area caused by compression residual stress forms larger dynamic bending stress amplitude under the condition of breeze vibration,which accelerates the fatigue damage of the splicing sleeve.Therefore,the service life of the splicing sleeve can be improved by controlling the pressure conditions of the splicing sleeve. |
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