Modeling And Analysis Of Normal Contact Stiffness Of Joint Surface In Mixed Lubrication

The joint surface is the contact surface between machine tool structural components,and its contact stiffness is an important part of the overall rigidity of the machine tool structure and a weak link.The contact of two surfaces are the contact of the asperities scattered over the whole rough surface actually.Due to the different actual working conditions,the contact of the asperities will bring wear,so they will do great harm to the mechanical equipment,at the same time,under the action of external loads,the interaction between asperity will occur,generally,some bonding surfaces of machine tools often use lubricating film to reduce friction,reduce wear and increase the service life of the machine tool.Therefore,studying the contact stiffness of the joint surface under lubrication conditions has an important role in the analysis and prediction of machine tool performance.However the existing researches neglect the mixed lubrication and asperity interaction,which has important effect on the mechanical contact characteristics.In view of this,the influence of the mixed lubrication wear of the asperities and the interaction between the asperities on the contact characteristics of the interface is studied in this paper.The main works about this research is as followed.(1)Based on the theory of contact mechanics,the deformation of a single asperity due to asperity interaction under the action of normal loads is further analyzed,and a two-dimensional fractal calculation model of the normal contact stiffness of the combined lubrication joint surface considering the asperity interaction is established.The effects of the fractal parameters of the joint surface and the lubrication medium on the normal contact stiffness of the joint surface were revealed through simulation.The contact stiffness fractal model is compared and analyzed,which further reveals the normal contact stiffness variation law of the mixed lubrication joint surface and importance of considering the effects of asperities interaction.(2)Based on the three-dimensional W-M function,a fractal model of the normal contact stiffness of the joint surface under mixed lubrication wasestablished.The numerical simulation of the model was used to reveal the influence of the joint surface morphology parameters and the lubrication medium on the normal stiffness of the joint surface,and compared with the two-dimensional fractal model of the joint surface under mixed lubrication.(3)Based on the above model and the fractal contact theory of the joint surface,the influence of the interaction between asperities is considered,then established the three-dimensional fractal model of normal contact stiffness of the joint surface considered asperity interaction in the mixed lubrication state.The influence law of the joint surface morphology parameters and the lubrication medium on the normal contact stiffness is simulated and compared with the above two-dimensional fractal model considering the normal contact stiffness of the interface of the asperity.