Numerical Analysis Of Tangential Fretting Wear Based On Rough Surface

Tangential fretting is one of the four basic fretting modes and exists in a large number of actual engineering projects.Its amplitude of motion is very small and the impact of tangential fretting is hard to observe.However,it cannot be ignored that wear and fatigue damage caused by tangential fretting lead parts to wear and failure.At present,the research of tangential fretting wear has attracted widespread attention.Whether it is experimental research or numerical simulation research,most of the fretting conditions or single influencing factor(such as initial rough surface and frictional heat)in fretting wear process are considered.Thereby,revealing the wear law and the wear mechanism of tangential fretting.Nevertheless,the surface geometry evolution has an important influence on the mechanical behavior of fretting wear contact surface and subsurface,and the surface morphology is of great importance on the elasto-plastic deformation and the thermal contact,that is,it has an important influence on the friction,wear and the temperature rise.Therefore,this thesis focused on the influence of comprehensive factors and carried out numerical analysis of tangential fretting based on the finite element method.Through the user subroutines embedding the heat source model and the wear model related to the stress field,the tangential fretting prediction model of coupled thermo-mechanical and rough surface was established,and then the numerical analysis of fretting temperature field and stress field were implemented to explore the corresponding material response behavior.The main research work is as follows:1.In the rough contact numerical model,the modified M-B contact model(Y-K model)was selected,and the dimensionless load and the dimensionless contact area of finite element solution were compared with those of the analytical solution.The two are in good agreement,which verifies the reasonability of the model.2.Based on the rough contact theory and the finite element method,a ball/plate tangential fretting numerical model was established using UMESHMOTION user subroutine which introduced wear criteria to study influences of initial surface roughness and different load conditions on the geometric evolution and the stress-strain distribution of the rough contact surface.The results show that the fretting diagram of operating conditions is greatly affected by the initial surface roughness,that is,the surface roughness can affect the transitions from partial slip to full slip.Random distribution of microconvex bodies result in obvious stress singularity and greater wear depth in comparison to the smooth surface.Moreover,the variation of initial surface roughness and load conditions have great influences on the evolution of the wear morphology and the wear depth.3.The coupled thermo-mechanical prediction model of tangential fretting for rough surface was established,and hence the temperature rise and the stress distribution under different initial roughness and load conditions were analyzed.Consequently,the law of temperature rise distribution in tangential fretting wear and the influence of the temperature rise on microdynamic behavior and wear behavior could be revealed.The results showed that the discrete distribution of rough peaks leads to obvious temperature rise and the stress singularity of the rough surfaces,and the highest temperature is not at the contact center.The frictional heat generation rate in the contact area increases with the increasing of the roughness and load conditions.Moreover,the temperature rise on the rough contact surface also increases.In addition,due to the friction heat,the equivalent plastic strain increases which can aggravate the material damage.