宏微观表面纹理的润滑及摩擦性能研究

发布时间：2018-06-10 19:06

本文选题：表面纹理 + 流体动压润滑　；参考：《中国矿业大学》2013年博士论文

【摘要】：近年来，表面纹理作为一种可以显著改善表面摩擦学性能的方法得到国内外学者的广泛关注，成为当前摩擦学领域热点研究方向之一。为了寻找具有优异润滑性能的纹理几何形貌和参数组合，最大可能的改善摩擦性能，申请人利用理论分析和数值模拟的方法，针对宏观纹理表面动压润滑问题，围绕Reynolds方程的有效性评价、纹理表面动压润滑形成机理、几何形貌和参数对纹理表面动压润滑性能的影响规律、纹理表面的优化设计四个方面展开了系统讨论。首先基于Reynolds方程和Navier-Stokes方程在流体动压润滑条件下建立了纹理表面的润滑模型。通过理论分析和数值模拟发现Reynolds方程有效性的两个决定性因素是缩减的雷诺数和油膜厚度与纹理特征长度比。只有当这两个因素同时趋近于零时，Reynolds方程才不至于造成不可接受的误差；对于矩形微坑纹理表面，Reynolds方程有效性的评价准则为：油膜厚度与纹理特征长度的比值小于0.015，并且缩减的雷诺数小于0.20。推导出了基于Reynolds方程的矩形纹理表面动压润滑的解析解；得到了使润滑性能全局最优的无量纲微坑深度和宽度的解析表达，最优的无量纲深度和宽度组合为~0.87和~0.72。数值模拟验证了这一结果。进一步研究表明，即使在Reynolds方程不能有效使用的情况下，理论预测的最优微坑深度也能与数值计算结果相一致；这为工程应用中矩形纹理的优化设计提供了可靠、高效的理论依据。其次，提出和论证了单个微坑和整体轴承两个层面的纹理表面动压润滑形成机理，分析了纹理参数和工况条件对润滑形成机理的影响规律。并绘制了矩形沟槽纹理表面润滑机理“相图”。基于动压润滑形成机理和参数的影响规律，分析了润滑性能的提高对纹理形状的需求，由此设计了具有优异润滑性能的楔形纹理表面。通过与矩形、三角形、圆弧形、椭圆形纹理的对比发现楔形纹理在低雷诺数下具有最优的动压润滑性能；在此基础上，构建了楔形微坑的多纹理轴承，并分析了几何参数对其动压润滑性能的影响规律。压印方法在45#钢表面制备了阵列排布的球冠状微坑纹理表面，并采用销-盘实验和数值模拟方法评价了其摩擦性能。实验表明，只有合适的纹理尺寸才能够在特定的载荷下起到降低摩擦的作用，不适当的纹理尺寸不但起不到减摩的作用，，甚至会起到反作用。数值模拟与该实验结果基本保持一致。最后，建立了具有纹理表面和光滑表面的单晶硅纳米薄膜的分子动力学模型，研究了单晶硅纳米薄膜纹理表面和光滑表面纳米力学性能和摩擦行为。结果表明纳米纹理的引入增加了摩擦力，降低了薄膜硬度，改变了摩擦法则，即：摩擦力与载荷的关系将从光滑表面的超线性关系转变为纹理表面的线性关系；纹理表面的摩擦力与载荷随纹理做周期性的振荡；摩擦力频谱包含了丰富的结构信息。纳米压痕中，相变是单晶硅纳米薄膜塑性变形唯一的机理；金刚石结构的Si-I转变为体心结构的Si-II和BCT5相是单晶硅纳米薄膜纳米压痕加载过程主要的相变机制；BCT5相的出现领先于Si-II相；卸载过程中高压Si-II和BCT5相全部转变为非晶相。
[Abstract]:In recent years, surface texture has been widely concerned by scholars both at home and abroad as a method to improve the tribological properties of the surface. It has become one of the hot research fields in the field of tribology. In order to find the best possible lubricating properties, the most likely to improve the friction performance is to use the theory. In view of the dynamic lubrication problem of the macroscopic texture surface, the method of analysis and numerical simulation is focused on the effectiveness evaluation of the Reynolds equation, the formation mechanism of the dynamic pressure lubrication of the texture surface, the influence of the geometric morphology and parameters on the dynamic lubrication performance of the texture surface, and the four aspects of the optimization of the texture surface.
Based on the Reynolds equation and the Navier-Stokes equation, the lubrication model of the texture surface is established under the hydrodynamic lubrication condition. Through theoretical analysis and numerical simulation, it is found that the two decisive factors of the validity of the Reynolds equation are the reduced Reynolds number and the oil film thickness and the texture feature length ratio. Only when these two factors are approaching at the same time At zero, the Reynolds equation does not cause unacceptable error. For the rectangular micropits texture surface, the evaluation criterion for the effectiveness of the Reynolds equation is that the ratio of the oil film thickness to the texture feature length is less than 0.015, and the reduced Reynolds number is less than 0.20..
The analytical solution of the dynamic pressure lubrication of the rectangular texture surface based on the Reynolds equation is derived. The analytical expression of the depth and width of the dimensionless pit for the global optimum lubrication performance is obtained. The optimal dimensionless depth and width combination is verified by the numerical simulation of ~0.87 and ~0.72.. Further research shows that even in the Reynolds square The optimal micro pit depth predicted by theory can also be consistent with the numerical results, which provides a reliable and efficient theoretical basis for the optimization design of rectangular texture in engineering applications.
Secondly, the formation mechanism of the dynamic lubrication of the texture surface on two layers of a single micro pit and a whole bearing is presented and demonstrated. The influence of the texture parameters and working conditions on the lubrication mechanism is analyzed. The phase diagram of the lubrication mechanism of the rectangular groove texture surface is drawn. Based on the mechanism of the dynamic lubrication and the influence of the parameters, the mechanism of the dynamic lubrication and the parameters are analyzed. A wedge texture surface with excellent lubrication performance is designed to improve the texture shape. By comparing with the rectangle, triangle, arc and ellipse texture, it is found that the wedge texture has the best dynamic lubrication performance at low Reynolds number, and on this basis, the multi texture bearing of the wedge micro pit is constructed. The influence of geometric parameters on hydrodynamic lubrication performance is also analyzed.
The texture surface of the ball coronal micro pits was prepared on the surface of 45# steel on the surface of the array, and the friction performance was evaluated by the pin disk experiment and the numerical simulation method. The experiment shows that only the suitable texture size can reduce the friction under the specific load, and the inappropriate texture size can not reduce the friction effect. It may even be counterproductive. Numerical simulation is basically consistent with the experimental results.
Finally, the molecular dynamics model of monocrystalline silicon Nanothin films with texture surface and smooth surface was established. The nanomechanical properties and friction behavior of the smooth surface were studied. The results showed that the introduction of the nano texture increased the friction force, reduced the hardness of the film, and changed the friction rule, that is, friction. The relationship between force and load changes from the superlinear relationship of the smooth surface to the linear relationship of the texture surface; the frictional force and load of the texture surface oscillate with the texture, and the friction spectrum contains rich structural information. In the nano indentation, the phase transition is the only mechanism of the plastic deformation of the monocrystalline silicon thin film; the diamond structure is the only mechanism. The transformation of Si-I into the Si-II and BCT5 phase of the body core structure is the main phase transition mechanism in the nano indentation loading process of monocrystalline silicon Nanothin films, and the appearance of the BCT5 phase is leading to the Si-II phase, and the high pressure Si-II and the BCT5 phase are all transformed into amorphous phase during the unloading process.
【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TH117

【参考文献】