Study On Fretting Wear Mechanism Of Fixed Joint Surface

The equipment manufacturing industry is an indispensable and important factor to support my country's modern development.Among them,CNC machine tools and CNC technology are an important part of supporting the rapid development of my country's equipment manufacturing industry.As the processing mother machine of modern manufacturing,CNC machine tools have formed a professional and intelligent industry development model.And at the same time,it also provides the possibility for the processing of various types of high-precision mechanical parts.There are many fixed joint surfaces in CNC machine tools.As the most important form of mechanical joint surfaces in CNC machine tools,their main function is to transfer the load and kinetic energy between mechanical parts.The relative position of the fixed joint surface will move in the micron level during the processing,which will cause the removal of the material on the contact surface and the generation of fatigue cracks.It is precisely because of the occurrence of fretting wear and fatigue cracks on the fixed joint surface that the dynamic characteristics of the machine tool during operation are extremely complicated,which seriously affects the stability,efficiency,and machining accuracy of the machine tool.Therefore,the research on fretting wear and crack initiation of fixed interface is of great significance to the development of CNC machine tools and CNC technology.This paper establishes the spherical/spherical contact model and the cylindrical/planar contact model in the ABAQUS finite element simulation software to study the fretting wear and fretting fatigue crack initiation of the fixed joint surface.The main research contents are as follows:(1)Theoretical research on fixed joint surface.The accuracy of the contact model established in this paper is verified by comparing the positive pressure and tangential force data obtained by ABAQUS finite element simulation with Hertz contact theory,the asymptotic solutions of contact pressure and shear force derived by Dini and Hills,and the PQ space loading curve proposed by Barber et al.in the case of elastic contact.(2)Analysis of fretting wear of fixed joint surface.In order to solve the problem of collecting and processing a large amount of data when the energy consumption model is used for fretting wear research,the UMESHMOTION subroutine used in this paper is written based on the FORTRAN language and the finite element contact model in this paper to realize the node update in the fretting wear process.Because the fretting will cause the finite element mesh to deform too much,which will lead to the non-convergence of the simulation results,this paper uses the adaptive mesh technology in the ABAQUS software to solve the problem of non-convergence of the results.To obtain contact characteristic data such as stress and relative slip in the contact area,different boundary conditions and loads are applied to the finite element model,and then a large amount of data obtained is analyzed to obtain the change curve of the wear depth of the contact area.In this way,the influence of different materials' friction coefficient,displacement load amplitude,normal load,fretting cycles,model contact angle,etc.on fretting wear is analyzed.(3)Prediction of crack initiation position on fixed joint surface.At the same time,the position of crack initiation caused by fretting wear is studied based on the cylindrical/planar finite element model and Ruiz parameters.This paper analyzes the influence of different load conditions and phase difference between different periodic loads on the value of crack initiation parameter,and then get the crack initiation position and development trend in the fretting process.