Research On Micro-elastohydrodynamic Lubrication Properties For Modified Helical Gear

Gear transmission is one of the important forms of mechanical transmission,lubricant film rupture when gear meshing,making the tooth surface contact directly,lead to pitting and gluing of gear surface,which may affect the mechanical performance of gear.The current gear design is mostly based on classical mechanical design of Hertz contact theory,and the contact stress is corrected by a large amount of experimental data.However,this design method does not analyze the contact of the tooth surface and the lubrication of tooth surface from the micro level,and it is hard to reveal the mechanism of the tooth surface failure.To improve the wear resistance and life expectancy of gears,it's need to consider the tribological design of the gear from the point of lubrication.Firstly,the time-varying isothermal elastohydrodynamic lubrication(EHL)of helical gears was studied.In this study,a finite line contact EHL model was established by using the equivalent meshing contact model of helical gears.The model was solved numerically by using multi-grid integral method and progressive mesh densification(PMD)method.Isothermal elastohydrodynamic lubrication characteristic properties were obtained.Secondly,the thermal effect of the oil film was considered,a time-varying elastohydrodynamic lubrication model of helical gear was established.The solid-state heat transfer method was proposed to solve the oil film temperature.The effects of power,rotational speed,initial viscosity,viscous pressure coefficient,normal pressure angle and the helix angle on gear lubrication were discussed and analyzed.In addition,the time-varying elastohydrodynamic lubrication model based on rough surface was established,and the roughness direction,the basic parameters of roughness including amplitude,wavelength and texture influence on the lubrication performance were analyzed.At last,the time-varying micro-elastohydrodynamic lubrication model based on surface modification was established.In this paper,the helical gear was modified along the time-varying contact line,The effects of two-end modification and the helical gears lubrication under drum modification were studied,and the effects of different modified parameters on their lubrication properties were analyzed.