Research On Fatigue Life For Stator Rubber Of PCP By Simulation Test

Oil extraction progressing cavity pump(PCP)is a commonly used mechanical oil extraction equipment in the oil field.Stator rubber fatigue is one of the most important reasons to lead to the failure of PCP according to the failure statistics of PCP well.In order to improve the checking period and increase the service life of PCP,to study the fatigue life of stator rubber is particularly necessary.The test method is an effective method to study the fatigue of the stator rubber of PCP.However,the fatigue test of PCP takes a long time,a large amount of work,great difficulty and many influencing factors.Therefore,based on the analysis of the mechanical characteristics of oil extraction PCP and the structural parameters of the stator and rotor of PCP,a set of equivalent accelerated fatigue simulation test device for PCP is developed,and its fatigue life is studied.According to the uniaxial tensile test results of the stator rubber material under different temperatures,oil immersion and non-oil immersion conditions,the Mooney-Rivlin constitutive model was selected and the model constants were calculated.The PCP finite element analysis model was established by means of element type selection,meshing,parameter setting,etc,and mechanical properties were analyzed to obtain the distribution law of contact stress and equivalent stress,the position of rubber fatigue hazard section of PCP stator rubber is determined to be the position of semi-circular belt 1 near helical belt4.Changing the interference between stator and rotor in PCP model,the maximum contact stress under different interference amounts is determined,which lays a foundation for the design of accelerated fatigue simulation test device.According to the structural parameters of PCP,the contact method of the stator and rotor,and the analysis results of the mechanical properties,determining the 16-tooth plum metal rotor and the rubber block stator are used to simulate the stator and rotor of PCP.The finite element analysis of the simulated structure was carried out to calculate the contact pressure value of the contact surface and determine the equivalent load.According to the actual operating conditions of PCP,the adjustment devices such as the interference amount,temperature,and medium were designed,finally,a set of simulated fatigue test device of PCP is developed,which can accelerate fatigue 240 times under different working conditions.According to the criterion of rubber fatigue failure,the static stiffness loss rate is selected as the basis for fatigue failure of rubber specimen.The fatigue test under the conditions of water and oil medium,different temperatures and different interference amounts was carriedout by the accelerated fatigue test device,calculate the static stiffness loss rate of rubber specimen before and after each time period test,and judge whether the rubber specimen has fatigue,determine the end time of the test under each working condition.According to the total fatigue test time,combined with the multiple acceleration of the device,the fatigue life of PCP under different conditions is calculated equivalently,which is basically in agreement with the actual life of PCP.