Numerical Analysis Of Thermal Elastohydrodynamic Lubrication Of Roller Chains Under Intermittent Motion

In this thesis,using the theory of EHL,with roller chain transmission as the research background,the method of numerical analysis is used to study the lubrication state of the sleeve-pin hinge pair contact area from simple to complex.Due to the existence of machining error,there may be an point contact area between the sleeve pins,so the research of this thesis is based on the assumption of point contract.The main research contents include:(1)The mathematical model of Isothermal EHL with point contact under intermittent motion is established,and the complete numerical solution to the problem is obtained.The effects of intermittent motion,ellipse ratio and single surface roughness Valley/peak on the lubrication state of the contact zone were studied.It is found that in the rest stage of intermittent motion,a entrapmented oil film is produced due to the extrusion effect,and the overall film thickness is low.The increase of the ellipse ratio would reduce the pressure of the oil film and the increase of the film thickness to different d egrees.The rough valleys can play the role of oil storage to a certain extent.The existence of rough peak is easy to cause direct contact between the two surfaces and cause lubrication failure.(2)Taking the thermal effect into account,the mathematical model of steady-state thermal EHL of point contact is established,and the complete numerical solution of the problem is obtained.The effects of ellipse ratio,different forms of surface microtopography and equivalent radius of curvature on the lubrication state of the contact area are studied in detail.It is found that as the ellipse ratio increases,the oil film pressure and the film thickness do not change linearly.The existence of a suitable ellipse ratio is beneficial to the lubrication state of the contact area.Appropriate selection of the surface micro-topography and the existence of an appropriate equivalent radius of curvature can also be beneficial to the lubrication state of the contact area.(3)Furthermore,the mathematical model of point-contact thermal EHL under intermittent motion conditions is established,and the complete numerical solution of the problem is obtained.The influence of thermal effect,load,and cycle time on the lubrication state of the contact area is studied.Compared with the isothermal solution,it is found that the thermal effect can significantly reduce the film pressure and film thickness.The oil film pressure is very sensitive to the load,while the film thickness is not sensitive to the load.The length of the cy cle time has a greater impact on the lubrication state of the contact area.When the cycle time is short,the film thickness is thicker in the stop phase.