STUDY ON MIXED LUBRICATION MECHANISMS OF FRACTAL SURFACES

该项目旨在为理解基于表面粗糙度分形表示的完全流体动力到混合润滑状态下的膜形成和接触机制奠定理论基础。进行了规则微槽混合润滑试验、膜厚和微腔的荧光显微镜测量以及分形表面流体动力润滑的理论分析。用光刻法制备规则微沟槽的铜试样进行混合润滑试验表明，当沟槽纵向与运动方向的夹角在0 ~ 90度之间变化时，摩擦系数和局部接触起始的膜参数在中间夹角处最大。采用喷丸法制备随机粗糙度的钢球和玻璃盘进行了点接触混合润滑试验。从荧光显微镜上的荧光图像和反射图像，定量地得到了表面相对间隙减小和局部粗糙接触面积增加的结果。3 .采用球盘结构进行了滑动和滚动试验，结果表明，微空腔是在较低的宏观动水压力下产生的，磨合套管对表面粗糙度的改变增加了局部动水压力，导致了微空腔的生长。建立了基于微扰方法的分形表面流体动力润滑理论，揭示了分形表面对流体动力润滑的影响。采用傅立叶滤波方法对无限宽倾斜滑块轴承进行了数值计算，结果与理论一致。采用512X512网格尺寸对有限宽倾斜轴承进行了模拟面压力数值计算，得到了分形结构对轴承承载能力的影响。少

This project was aimed at establishing a theoretical ground for understanding mechanisms of film formation and contact in full hydrodynamic to mixed lubrication regimes on the basis of fractal representation of surface roughness. Mixed lubrication tests with regular microgrooves, measurements of film thickness and microcavity using a fluorensent microscope, and theoretical analyzes of hydrodynamic lubrication for fractal surfaces were conducted.1.Mixed lubrication tests using copper specimens with regular microgrooves made by photoetching revealed that, when the angle between longitudinal direction of the grooves and the direction of motion was changed between 0 and 90 degrees, the friction coefficient and the film parameter for the onset of partial contact took on maximum at intermediate angles.2.Point contact mixed-lubrication tests were conducted using a glass disk and steel balls having random roughness made by shot-blast. From fluorescent images and reflection images on the fluore … More scent microscope, decrease in the relative gap between the surfaces and increase in local asperity contact areas were obtained quantitatively.3.Sliding and rolling tests were conducted with the ball/disk configuration, which showed that microcavities are generated under low macroscopic hydrodynamic pressure, and that modification of surface asperities by running-in cased increase in local hydrodynamic pressure leading to growth of microcavities.4.A theory of hydrodynamic lubrication of fractal surfaces based on a perturbation method was established to show effects of fractal surcture on hydrodynamic lubrication. Numerical computations for an infinitely-wide inclined slider bearing were also conducted using simulated profiles created with the Fourier filtering method, and the results agreed with the theory.5.Numerical computations of pressure for a finite width inclined bearing with simulated surfaces were conducted using a grid size of 512X512, which showed effects of fractal structures on load carrying capacity of the bearing. Less