Study On The Friction And Wear Mechanism Of MoS₂ Film For Space Rolling Bearings Based On Molecular Dynamics

Space rolling bearing as one of the key parts of the spacecraft,when the operation of the bearing problems will affect the stability,reliability and safety of the spacecraft in the process of mission execution,serious will endanger the life safety of space personnel.Therefore,the study on the failure mechanism of space rolling bearings is of great significance for improving the operating life of space rolling bearings,extending the in-orbit service time of spacecraft and improving the stability of spacecraft.Due to the limitation of space environment and spacecraft conditions,space rolling bearings usually use molybdenum disulfide for solid lubrication.During the lubrication process of molybdenum disulfide film in space,the film is subjected to the combined action of high vacuum,ultra-low temperature,radiation,cosmic dust and other bad factors.As a result,the wear evolution law of molybdenum disulfide film in bearing in space is not clear,and the friction lubrication mechanism has not been fully studied.Therefore,a molecular dynamics simulation method was proposed in this paper to construct a molecular dynamics model of molybdenum disulfide film nano friction from atomic scale,and to explore the friction and wear characteristics of molybdenum disulfide film in space state.Through the molecular dynamics simulation of the friction of molybdenum disulfide film in space state,the relationship between the wear state of molybdenum disulfide film and the load,friction velocity and temperature was revealed.Through molecular dynamics simulation of molybdenum disulfide film in special working conditions,the wear evolution process and lubrication characteristics of molybdenum disulfide film in reciprocating motion in space were investigated.The three-body contact friction and wear mechanism of molybdenum disulfide film was explored through molecular dynamics simulation of the scene in which foreign bodies invaded and interfered with the lubrication of molybdenum disulfide film in long-term operation.The above molecular dynamics research on the friction and wear mechanism analysis of molybdenum disulfide film of space rolling bearing provides an understanding on the atomic scale for the lubrication of molybdenum disulfide film,and provides a certain theoretical basis for exploring the lubrication failure mechanism of space rolling bearing.The main research contents of this paper are as follows:(1)A three-dimensional atomic model of molybdenum disulfide thin films was constructed,utilizing Fe-Ni-Cr alloy as its substrate,based on an atomic scale analysis of the lattice structure and lubrication principle of molybdenum disulfide,in conjunction with the material characteristics of space rolling bearings.A mixed potential function scheme was then proposed to explain the interaction between atoms in molybdenum disulfide using REBO potential function,and the interaction between atoms in Fe-Ni-Cr alloy using MEA.The Lennard-Jones potential function is employed to elucidate the interplay between atoms in diverse materials;parameters such as potential function,ensemble,and boundary conditions are then established for the MD simulation procedure.(2)In view of the unclear friction and wear mechanism of molybdenum disulfide film in space state,the molecular dynamics simulation of friction of molybdenum disulfide film was carried out.The effects of load,friction velocity and alternating temperature on the friction and wear characteristics of molybdenum disulfide films were investigated.(3)The friction and wear characteristics of molybdenum disulfide film are not clear in space reciprocating operation.The molecular dynamics simulation of the reciprocating friction of molybdenum disulfide film was carried out.The effects of load and temperature on wear evolution and friction characteristics of molybdenum disulfide films during repeated friction were investigated.(4)The friction and wear mechanism of molybdenum disulfide film in the state of foreign body invasion is not clear.The molecular dynamics simulation of three-body contact friction of molybdenum disulfide film in space state was carried out.The effects of load,abrasive rotation speed and substrate surface structure on friction and wear mechanism of molybdenum disulfide film under three-body contact condition were investigated.