Thermal elastohydrodynamic lubrication analysis for roller enveloping end face worm drive considering fractal roughness

ZHOU Guangqian; LIAO Honghui; LI Jinkuan

doi:10.16578/j.issn.1004.2539.2026.06.009

Abstract：[Objective]The thermal elastohydrodynamic lubrication performance of roller enveloping end face worm drives is closely related to surface micro-morphology.However,the influence of fractal micro-morphology on the thermal elastohydrodynamic lubrication characteristics of this type of drive has not been investigated.Therefore a thermal elastohydrodynamic lubrication analysis method for roller enveloping end face worm drive considering fractal roughness was proposed,aiming to reveal the corresponding influence mechanism and provide a reference for the lubrication performance optimization of this novel drive.[Methods]Firstly,a thermal elastohydrodynamic lubrication analysis model for roller enveloping end face worm drive pairs was established based on the fractal mechanism of surface micro-morphology and the thermal elastohydrodynamic lubrication mechanism,which provided support for subsequent numerical calculations.Secondly,a tooth surface micro-morphology model was constructed using the anisotropic Weierstrass-Mandelbrot fractal function to characterize the anisotropic features of ground tooth surfaces.Then,the calculation formulas for entrainment velocity and induced normal curvature at meshing points were derived,and the dimensionless treatment of the basic equations for thermal elastohydrodynamic lubrication was completed.Finally,the multigrid method was adopted for solution.The lubrication performances under smooth and rough conditions were compared,and the influence laws of fractal parameters were investigated.[Results]The results show that surface micro-morphology has a significant influence on the thermal elastohydrodynamic lubrication performance of the drive pair.The fractal dimension D is negatively correlated with the maximum oil film pressure,the minimum oil film thickness and the interlayer temperature rise of the oil film.When D increases from 1.3 to 1.7,the maximum oil film pressure decreases from 1.56 GPa to 0.73 GPa,and the maximum temperature rise of the intermediate oil film decreases by 76.9%.The characteristic scale coefficient G is positively correlated with the above indicators.When G increases from 0.000 1 to 0.001,the maximum oil film pressure increases from 0.689 GPa to 0.986 GPa,and the maximum temperature rise of the intermediate oil film increases by 116.6%.To obtain better lubrication performance,the fractal dimension D should not be too small,and the characteristic scale coefficient G should not be too large.