混合润滑状态下结合面的法向接触刚度研究

针对润滑条件下机械结合面的接触特性受油膜影响的问题,基于结合面接触刚度由油膜接触刚度和固体表面接触刚度组成的思想,建立混合润滑状态下结合面的法向接触刚度模型。采用三维的Weierstrass-Mandelbrot函数获得具有分形特征的粗糙表面,并基于统计学方法建立干摩擦条件下结合面的法向接触刚度模型,考虑了微凸体的完全弹性变形、弹塑性变形以及完全塑性变形过程。在此基础上,求解了油膜的等效厚度并建立油膜的接触刚度模型。结果表明:结合面的法向接触刚度随法向载荷的增加而增加,且混合润滑状态下结合面的接触刚度大于干摩擦条件下结合面的接触刚度;该模型避免了油膜厚度测量难的问题,为机械结构的润滑状态预测提供了帮助。

Normal contact stiffness of machine joint surfaces under mixed lubrication state

Aiming at the problem of contact characteristics of machine joint surfaces being affected by oil film under lubrication conditions, based on the idea of a joint surface’s contact stiffness consisting of oil film contact stiffness and solid surface contact stiffness, the joint surface’s normal contact stiffness model was established under mixed lubrication state.The 3-D Weierstrass-Mandelbrot function was used to obtain a rough surface with fractal feature to build a joint surface’s normal contact stiffness model under dry friction condition using the statistics method and considering a micro-convex body’s full elastic deformation process, elastoplastic one and full plastic one.Furthermore, the equivalent thickness of an oil film was solved and its contact stiffness model was built.The results showed that a joint surface’s contact stiffness increases with increase in normal load; a joint surface’s contact stiffness under mixed lubrication state is larger than that under dry friction condition; the proposed model avoids the problem of measuring oil film’s thickness being difficult and provides a help for predicting lubrication state of mechanical structures.