分形粗糙面的主轴承弹流脂润滑分析

为探究弹性流体动压润滑(弹流润滑)状态下RV减速器主轴承接触表面之间的润滑特性,基于润滑脂的非牛顿特性以及粗糙表面分形理论,提出一种主轴承的点接触弹流脂润滑数值模型。首先,对该模型进行数值求解,得到脂膜压力、脂膜厚度的分布规律；然后,将其分别与其他点接触弹流润滑模型的数值结果和实验结果进行对比,验证了所建模型的正确性；最后,分析了主轴承表面光滑和粗糙状态下流变指数、分形维数、卷吸速度、载荷和润滑脂黏度对润滑性能的影响。结果表明:润滑脂的非牛顿性越明显,脂膜厚度越小且颈缩现象愈加不明显,接触区附近脂膜压力越符合赫兹压力分布,二次压力峰逐渐消失；考虑主轴承分形粗糙表面的弹流润滑特征更切合实际,增大分形维数,接触区真实接触面积增大,有利于降低脂膜压力,增加脂膜厚度；卷吸速度、载荷和润滑脂黏度对脂膜厚度分布的影响显著,对脂膜压力分布的影响较小；脂膜厚度以及最小膜厚越大,主轴承接触区脂膜不易破坏且越容易形成动压润滑。

Elastohydrodynamic lubrication analysis of main bearing with fractal rough surface

To explore the lubrication characteristics between the contact surfaces of the main bearings of RV reducer under the condition of elastohydrodynamic lubrication(EHL), a numerical model for point contact EHL of main bearings is proposed based on the non-Newtonian characteristics of grease and the fractal theory of rough surface. Firstly, the model is numerically solved to obtain the distribution of grease film pressure and grease film thickness. Then, the model is compared with the numerical results and experimental results of other point contact elastohydrodynamic lubrication models to validate the accuracy of the proposed model. Finally, the effects of rheological index, fractal dimension, entrainment velocity, load and grease viscosity on the lubrication performance of the main bearing under smooth and rough conditions are analyzed. The research shows that the more obvious the non-Newtonian property of the grease, the smaller the thickness of the grease film is and the less obvious the necking phenomenon. The pressure of the grease film near the contact area is more consistent with the Hertz pressure distribution, and the secondary pressure peak gradually disappears. Considering the elastohydrodynamic lubrication characteristics of the fractal rough surface of the main bearing is more realistic. Increasing the fractal dimension increases the real contact area of the contact area, which is beneficial to reduce the pressure of the grease film and increase the thickness of the grease film. The entrainment velocity, load and grease viscosity have significant impact on the thickness distribution of the grease film, while their influence on the pressure distribution of the grease film is comparatively smaller. Larger grease film thickness and the minimum film thickness contribute to the resistance of grease film breakdown and promote het formation of hydrodynamic lubrication.