Research On High Temperature Friction And Solid Film Lubrication Characteristics Of Tapered Roller Bearings

In the dissertation,metal-nitride thin film is designed for the high temperature lubrication of tapered roller bearing.The friction characteristic,wear mechanism and thermal-elastic interface mechanics of metal-nitride coatings serving at high temperature are studied.And,this study will be a basis for the structure optimization and lubrication design of high temperature served mechanical components.To study the variation of friction coefficient at high temperature on the running characteristic of tapered roller bearing,the frictional torque model of the solid film lubricated tapered roller bearing is built.In this model,effect of roller skewing on the internal load distribution and running torque of the tapered roller bearing is emphasized,the load and relative speed at each contact pair are obtained,and the selection of cage pocket clearance according to friction coefficient is further developed for solid film lubricated tapered roller bearing.To investigate the surface/interface stress for the lubrication coating under sliding contact,the interface mechanics analysis is performed for the coating-substrate system.Based on the method of imaging,the Green's function of the coating-substrate system about surface normal load,tangential load and frictional heat are gained in the semi-analytical form.Thereby,the semi-analytical solution of thermo-elastic contact mechanics for the coating-substrate system are finished.The developed thermo-elastic contact model of the coating-substrate system can provide comprehensive information,such as stresses,temperature rising which are essential for tribological design.To investigate load bearing capacity and the friction characteristic of the lubrication coating at serving high temperature,a high temperature adaptive indentation/scratch device is developed.High temperature indentation test are performed on the coating-substrate system,and obtain the high temperature mechanical parameters of the coating and substrate material.By employing the progressive load scratch test,effect of temperature on the critical load of the coating-substrate system is studied,besides,transition of failure mode with the applied environment temperature is observed.By adopting the interface mechanics analysis,transition of failure mode is proved to be highly correlated with the variation of mechanical parameters of coating and substrate material at high temperature.By employing ball-on-disk tribological test,the wear behavior of metal-nitride coating is thoroughly studied.Different wear mechanisms are observed with the variation of temperatures and loads.The main parameters which governing the transition of wear behavior for metal-nitride coating is proposed.Based on the above study,the boundary of failure parameter are analyzed.Finally,with the requirements of serving temperatures and external loads,a metal-nitride film lubricating tapered roller bearing is proposed.The high temperature performance of thin metal-nitride film lubricated tapered roller bearing is evaluated by on the designed test rig under required high temperature conditions,proving the effectiveness of the proposed high temperature lubrication designing method in this dissertation.