Influence Of Residual Stress And Interfacial Wear On The Initiation Of Bending Fretting Fatigue Cracks

Fretting fatigue widely exists in the fastening parts in aerospace,railway,automobile,machinery,nuclear reactor and other fields,which greatly reduces the service life of the parts and even threatens people’s life safety.In recent years,scholars at home and abroad have made some achievements in the research of tension and compression fretting fatigue,but the research on bending fretting fatigue mainly focuses on experimental research,lacking of numerical research.In this thesis,the bending fretting fatigue of 316 L stainless steel will be simulated by finite element model,focusing on the effects of the residual stress and wear of contact interface on fretting fatigue crack initiation.The main contents of this thesis include the following parts:(1)Introduction of residual stress field.Through the finite element simulation of the quenching heat treatment process of the flat sample,the variation of the temperature field and stress field of the sample with the cooling time under the cooling media of water and oil is obtained,and the residual stress field of the sample after complete cooling is obtained.The distribution form of the residual stress field shows that the surface of the flat has compression stress and the center has tension stress,which represents a typical residual stress field of heat treatment,and can be used as the initial stress field of the bending fretting fatigue simulation.(2)Effects of the residual stress on fatigue crack initiation of bending fretting.Considering different friction coefficients,normal loads and bending loads,the effects of the residual stress on the bending fretting fatigue crack initiation of 316 L stainless steel was systematically studied by using SWT critical surface method,including the effects on the crack initiation position,angle and life.The research results provide a theoretical guidance for the surface technology to the prevent bending fretting fatigue failure.(3)Effects of the contact interface wear on the fatigue crack initiation of the bending fretting.The user subroutine umeshmotion based on energy wear method is written via FORTRAN language,and combined with adaptive mesh technology,the variation of wear profile of contact interface with loading cycles under fretting fatigue condition is studied;Furthermore,the SWT critical surface method and cumulative damage criterion are used to reveal the influence of the interface wear in the contact area on the bending fretting fatigue crack initiation,including the changes of the damage value SWT and cumulative damage value D at different positions with cycle times.The research results have certain significance for improving the accuracy of finite element method in predicting the bending fretting fatigue crack initiation.