Study On Elastic-Plastic Contact Characteristics And Meshing Power Loss Of Helical Gear

Helical gear transmission has been widely used in many industries due to its advantages of smoothness,low noise,high efficiency,etc.However,under the complex working conditions of high speed,heavy load,high viscosity,insufficient oil supply and friction heat generation,gear meshing will often lead to transmission noise,instability,pitting,gluing and other fatigue damage because of lack of oil lubrication and tooth surface elastoplastic deformation;In order to improve the lubrication effect of gear transmission,it is necessary to study the elastoplastic deformation of gear meshing transient and the thermal elastohydrodynamic lubrication of gear transmission under the starvation condition.In this paper,based on the elastic-plastic contact model of cylindrical roller and helical gear,a heat elastohydrodynamic lubrication and power loss model of helical gear was established to study the contact,lubrication characteristics and power loss of helical gear meshing under multiple working conditions.The main contents of this paper are as follows:(1)Elastic-plastic contact characteristics analysis of finite line contact;The influence of the material strengthening and initial residual stress on the surface,secondary surface stress,plastic deformation and other contact characteristics during the contact process is studied.The results show that the contact width of the elastic-plastic model is obviously larger than that of the elastic model.With the increase of the load,the contact width,maximum stress of surface and the secondary surface are both increase,and the distance between the location of the maximum stress of the secondary surface and the surface increases.The distribution of residual stress after unloading is similar along the direction of contact width and depth.Under three different strengthening models,the plastic strain decreases with the strengthening degree.(2)Elastic-plastic contact characteristic analysis of helical gear;Considering the plastic deformation of gear meshing may occur when overloading,a helical gear pair of elastic-plastic contact model is established for study the influence of the the loads,material strengthen on the contact width,surface and subsurface stress distribution,elastic and plastic deformation,etc,the results show that when plastic deformation is taken into account,the contact force of the tooth surface will increase correspondingly.Under the condition of heavy load,plastic deformation has a significant influence on the contact width and the distribution of subsurface stress.Different strengthening models have little influence on the above results.(3)Study on thermal elastohydrodynamic characteristics and power loss of helical gear;According to the meshing characteristics,geometrical and kinematic analysis of helical gear,the elastohydrodynamic lubrication model of helical gear with thermal effect and power loss considered was established by using the parameters of helical gear in the previous chapter.Study the impacts of thermal effect,torque,rotational speed,the geometric parameters,the surface roughness on helical gear meshing characteristics and power loss with different transmission ratio,at the same time to carry out the tooth root tip temperature rise test and the theory and experimental results were analyzed,research has shows that heat effect has great influence on friction coefficient and sliding power loss;torque and rotational speed have obvious effects on the lubrication performance under different working conditions,selecting proper geometric parameters can improve the lubrication conditions and improve the meshing efficiency;Theoretical addendum and root temperature rise was consistent with experimental addendum and root temperature rise.(4)Study on the thermal elastohydrodynamic characteristics and meshing power loss of helical gear with starvation;A lubrication model of helical gear with both thermal effect and starved condition is established to study the effects of thermal effect and starved factors,input torque,speed,oil supply film thickness and surface roughness on the lubrication characteristics and power loss of helical gear with fixed transmission ratio.The results show that under the of starved condition,considering the thermal effect,the film thickness and friction coefficient will be significantly reduced,and the sliding friction power loss will be greatly reduced.The rotational speed is proportional to the film thickness.When the torque is variable,the oil film thickness is decreased,while the friction coefficient in the middle layer of the oil film is increased.When the speed and torque are increased,the power loss is increased.The thickness of oil supply film has significant influence on the friction coefficient and power loss.The surface roughness will obviously increase the power loss.