The Research On Prediction Method Of Fretting Fatigue Life Between The Contact Surface Of The Body Bolt Connector

With the increase of diesel engine power and strengthening degree,fretting fatigue life of internal combustion engine block becomes one of the factors which must be considered in design.In this paper,the fretting fatigue failure between the engine block and the main bearing cap of a diesel engine is studied by means of experiment,numerical simulation and theoretical research.A set of models for predicting fretting fatigue life of block's is proposed.The main contents of this paper are as follows:(1)The fretting wear of surface /surface model contact pairs is studied.The curve of contact surface wear profile and contact pressure in the process of contact pair wear is obtained by using the Umeshmotion subroutine of finite element software Abaqus and the adaptive mesh technology.The effects of wear zone factor and stroke amplitude on the wear profile and contact pressure of contact surface are analyzed.(2)The fretting wear of surface /surface model contact pairs is studied.The curve of contact surface wear profile and contact pressure in the process of contact pair wear is obtained by using the Umeshmotion subroutine and the adaptive mesh technology of finite element software Abaqus.The effects of wear zone factor and stroke amplitude on the wear profile and contact pressure of contact surface are analyzed.(3)The fretting fatigue life of the specimen is predicted by using multi-axial fatigue model and fracture mechanics model respectively.Six fatigue damage parameters and Farris life assessment model are used to predict the fretting fatigue life of the specimens.Compared with the experimental results,the predicted results of the Ruiz parameters are closest to the experimental values.The fracture mechanics model first determines the crack initiation position according to the multi-axial stress / strain method,and then determines the initial crack size by comparing the crack nucleation rate and the crack growth rate.Finally,the Basquin formula is used to calculate the crack nucleation life and the Paris formula is used to calculate the crack growth life.The final fretting fatigue life is the sum of the crack nucleation life and the crack growth life.(4)the three-dimensional solid and finite element model of diesel engine block is established,and the fretting fatigue characteristics of diesel engine block are analyzed.The multiaxial fatigue model and fracture mechanics model are applied to predict the fretting fatigue life of diesel engine block.The life prediction results of multiaxial fatigue model show that the Ruiz parameter can accurately predict the crack initiation position,and the life prediction error is within 2.3 times the tolerance zone factor,which is suitable for the life prediction of fretting fatigue.The life prediction results of fracture mechanics model show that the extended finite element method based on Paris formula is suitable for prediction of fretting fatigue life of block's,and the life prediction error is within the range of 2.2 times tolerance zone factor.