表面微造型技术改善物体表面摩擦性能的研究

物体表面的微细形貌深刻影响和改变着物体表面的摩擦性能，这就促使人们利用各种加工手段在物体表面进行微细造型改变表面状况以达到所需要的表面摩擦性能。本文首先论述了微造型的几何参数及其对摩擦性能的影响，接着阐述了近年来物体表面微细形貌加工方法以及表面微造型技术的应用领域，最后提出了表面微造型技术的可能发展方向。     

微造型在机械密封作用机理研究中若干关键问题的探讨

为探讨端面微造型在机械密封中的作用机理,以形成动压效应的几何楔空间为切入点,分析了端面微造型在摩擦副表面中的几何构成。分析结果表明:端面微造型使摩擦副表面几何形貌不平,并借助压差流和剪切流形成动压效应,而表面微观几何形貌是一种特殊的微造型。实验结果的分析表明,表面微观几何形貌不平可影响动压效应,经电化学光整加工的表面微观几何形貌使润滑膜增厚。机械密封中的摩擦副表面微造型不仅具有润滑与密封的作用,而且还具有速度式泵送与容积式泵送的效应。表面微造型的不平度、分布密度以及形状等因素对润滑膜厚度及其稳定性等影响的研究将有助于机械密封理论和技术的进一步发展。     

激光微造型技术中表面微形貌的数值模拟研究

近年来研究发现,具有规则凹凸的非光滑表面,具有良好的摩擦润滑性能.而激光表面微造型技术由于具有良好的可操控性,被广泛认为是具有较好的实现规则凹凸非光滑表面的表面微细加工技术.为了预测激光微细造型所得表面形貌的几何特征,本文采用有限元分析软件ANSYS对激光微造型中的烧蚀温度场和弹坑进行数值模拟.在此基础上详细分析了激光功率密度、激光脉宽对烧蚀弹坑表面形貌的影响和变化规律,为快速有效地加工出所设计的规则凹凸非光滑表面奠定了基础.     

表面微观几何形貌对液膜形成及其影响的研究

针对磨削加工和电化学光整加工后的表面微观几何形貌对液膜厚度影响的实验结果,结合表面微观几何形貌的构型分析,基于流体润滑理论,采用有限差分法进行了数值分析。分析结果表明:表面微造型使表面几何形态呈凹凸不平状,有助于动压效应的形成;在同样的条件下,与磨削加工相比,电化学光整加工后表面微观几何结构可产生更强的动压效应,有利于润滑;使微观几何结构在摩擦副表面分布,可使液膜压力分布不均,使摩擦副表面的膜压具有波动性,形成泵送效应。     

微细铣削表面形貌形成分析

基于最小切削厚度的概念,提出了微细铣削过程槽底表面几何形貌仿真模型。通过微细铣削表面形貌的仿真和表面粗糙度Ra值的计算以及微细铣削实验,对微细铣削表面粗糙度随着每齿进给量变化的规律进行了分析和描述。     

飞机舵机组合O形密封件密封性能与摩擦热效应的数值分析

飞机舵机一般采用橡胶-聚四氟乙烯组合O形密封件密封活塞杆高压端面,舵机工作时的摩擦发热会导致密封件的密封性能下降。为研究密封性能的热效应,利用ABAQUS软件建立考虑三重非线性(材料非线性、几何非线性以及边界非线性)的热-结构耦合效应的组合O形密封件有限元模型,分析密封件在不同油压下的接触压力分布及密封性能。开发ABAQUS的重启动功能,研究不同油压、滑动速度以及摩擦因数3种因素对密封件在活塞杆滑动过程中的摩擦生热影响,得到密封件的局部温度场分布,探讨3种因素对温度场的影响规律。分析结果表明:密封件在活塞杆滑动过程中的最高温度随着油压、滑动速度和摩擦因数的增大而增大,其中摩擦因数的影响最为显著。     

基于摩擦磨损特性的激光表面造型试验研究

通过球墨铸铁材料圆环端面的激光造型,对比光滑表面、点圆和网格造型图案对材料摩擦磨损性能影响,发现同样分布率的网格造型图案有较好的抗磨损特性和承载性能.通过比较不同激光加工参数和网格几何参数的激光造型表面的形貌和摩擦磨损特性,找到激光造型的优选方案.     

油润滑对微动摩擦特性影响的研究

研究了钢摩擦副在油润滑工况下不同位移幅值对微动润滑摩擦特性的影响,分析了表面形貌。研究表明微动过程中表面之间的油介质会被驱除出接触区域,而滑动过程中表面之间的油介质始终保持在接触区域;润滑油的存在对接触区域起到了遮盖的作用,减少了氧化反应;由于油的流动性,在微动过程中容易再次渗透到接触区域,降低了表面摩擦与磨损。     

微细切削毛刺的有限元仿真

在微细加工精密微小零件的过程中,存在的主要问题之一是有微型毛刺产生。利用有限元软件Abaqus对铝2024-T3微细切削进行仿真,运用Johnson-Cook(J-C)模型建立工件材料模型,用网格自适应技术(arbitrary Lagrangian Eulerian,ALE)实现切屑和工件的分离,切屑和刀具的接触摩擦模型采用修正的库仑摩擦定律,动态模拟微型毛刺的形成过程,分析不同刀具几何参数及切削参数对毛刺形成的影响,得到微细加工过程中不同刀具几何参数及切削参数对微型毛刺形成影响的一般规律。分析结果为优化刀具几何参数及切削参数、减少微细切削中的毛刺和提高表面加工质量等提供指导。     

表面织构化对摩擦学性能影响的研究进展

表面织构技术是通过微细加工技术在材料表面加工出具有一定几何形貌与尺寸,且排列规律的图案,从而改善材料表面摩擦学性能的新型表面改性技术。表面织构因在改善材料摩擦学特性方面具有的突出优势而在机械摩擦配副中发挥着重要的作用。介绍了常见的表面织构加工技术,阐述了不同工况下表面织构的减磨机理,总结了表面织构形貌及其几何参数对耐磨性能的影响,并展望了表面织构技术的未来发展方向。     

柴油机滑动轴承热流体动力润滑仿真研究

根据径向滑动轴承热流体动力润滑理论,基于JFO理论提出的质量守恒边界条件,建立同时包含油膜完整区和空 穴压力变化的单缸柴油机滑动轴承热流体动力润滑模型,采用有限差分法求解模型方程,仿真分析滑动轴承的油膜厚度、油膜压力、润滑油流量和温度等参数对润滑性能的影响,分析内燃机滑动轴承润滑特性,为轴承润滑可靠性设计提供一定的理论依据.     

Grooved surface texturing by electrical discharge machining (EDM) under different lubrication regimes

The aim of the present research work was to investigate the effectiveness of grooved surface texturing with a rhombic geometry under different lubrication regimes. Tribological investigation under unidirectional sliding was focused on the effect of texturing parameters including pattern area density on the coefficient of friction under different lubrication regimes, achieved by varying sliding speed and lubricant viscosity. Grooved patterns with different textured area densities were produced on steel samples by electrical discharge machining. Results of this investigation showed that under boundary lubrication, textures resist sliding thus resulting in increased friction. The largest improvement of friction reduction was observed under hydrodynamic lubrication, for low‐viscosity oil when using the textured disc with 21% pattern area density. The reduction of the coefficient of friction if compared with the untextured surface was of approximately 24%. Examination of the sliding surfaces has not shown any quantifiable wear for the contact conditions studied.     

密封环圆台型织构化粗糙表面对润滑性能的影响

针对密封环接触面之间的润滑问题,基于Reynolds方程,考虑粗糙度的影响,建立在流体动压润滑状态下圆台型表面织构的数学模型,对密封环接触表面在不同织构参数、不同粗糙度参数下润滑膜压力大小及分布情况进行研究。采用有限差分法、牛顿迭代法研究不同润滑介质下,圆台型微凹坑的几何参数及粗糙度参数对润滑膜平均压力的影响,并与理论数值结果进行对比验证。结果表明:密封环端面的平均膜压随圆台型织构间距、小径的增大而减小,随织构大径的增大而增大;存在最佳织构深度使平均膜压最大;润滑介质黏度越大,密封环端面平均膜压越大;粗糙峰峰高越大,端面平均膜压越小,而粗糙峰波长对端面平均膜压的影响较小,因此粗糙峰应尽可能小;存在织构参数、粗糙度参数的最优组合使润滑膜平均压力值达到最大。     

Effects of micro-wedges formed between parallel surfaces on mixed lubrication – Part II: modeling

The hydrodynamic effects of micro-wedges formed by asperities on two parallel surfaces in parallel sliding have been proved to be significant on mixed lubrication in the Part I of the present research. In this part of study, a theoretical model for the concept of micro wedges is proposed and used for calculating the hydrodynamic load and friction. The results show that the main influential factor on hydrodynamic effects was the separation of the two rough surfaces. Such a separation governed by the heights of highest asperities determined the minimum gaps of the micro-wedges and so thus the hydrodynamic effects. The calculated results were consistent with experimental evidence, especially, in mixed friction.     

A slip line field analysis of the transition from local asperity contact to full contact in metallic sliding friction

Under normal well-lubricated sliding conditions the contact is at the tips of asperities and the real area of contact is many times smaller than the apparent area of contact. When the lubrication is poor or the normal pressure between the contacting surfaces is very high the real area of contact approaches and in the limit equals the apparent area of contact. The purpose of this paper is to investigate the transition between these two extremes. The investigation is made using rigid-perfectly plastic slip line field theory and the paper concludes with a consideration of how real material properties such as strain hardening might be expected to modify the results obtained.     

An interferometric study of lubricated rotary face seals

Ineffective lubrication of rotary face seals can lead to rapid wear and failure. This paper is concerned primarily with the conditions under which effective lubrication can be achieved, rather than with sealing. Following a preliminary study of the lubrication of a rubber cylinder, an optically smooth toroidal seal running against a glass plate was investigated. For well aligned surfaces, it appears that the source of pressure generation in the lubricant film is small asperities and other surface defects: radial misalignment promotes the formation of a relatively thick, stable elastohydrodynamic film. The results indicate that controlled roughness and misalignment should enable rotary face seals to operate satisfactorily in the presence of lubricants of adequate viscosity     

Geometric Shape Effects of Surface Texture on the Generation of Hydrodynamic Pressure Between Conformal Contacting Surfaces

Micro-surface texturing design is becoming an important part of surface engineering since engineering practices and analyses have indicated that surface textures may significantly affect the tribological performance of contact interfaces. Advances in the manufacturing technologies of surface finishing and micro-machining, such as laser surface texturing, photolithography, and etching, LIGA process, have made it possible to fabricate different fine structures on various engineering surfaces. Though the influence of micro-surface texturing on hydrodynamic lubrication has been widely investigated over the last decade, such an influence may be complicated and difficult to characterize with only a few statistic surface parameters. Thus, very little attention has been paid to the effects of different textural shapes and orientations on hydrodynamic lubrication, which is the main topic of this article. A theoretical model based on a single dimple was established to investigate the geometric shape and orientation effects on the hydrodynamic pressure generated between conformal contacting surfaces. Using the Successive Over Relaxation method, the average hydrodynamic pressure generated by the texture pattern with the dimples in shapes of circle, ellipse, and triangle at different orientations to the direction of sliding are obtained. The results indicate that geometric shape and orientation have obvious influences on load-carrying capacity of contacting surfaces. With the same dimple area, area ratio and dimple depth given in this research, ellipse dimples perpendicular to the sliding direction showed the best load-carrying capacity. This result agrees with previous experimental results very well.     

表面织构特征对其摩擦润滑特性的影响

为研究织构阵列的形貌、排布方式对织构化滑动摩擦副摩擦学特性的影响,利用三维CFD仿真方法,基于Navier-Stokes(N-S)方程建立不同形貌、排布的织构阵列摩擦副的润滑模型,分析不同形貌及排布方式对压力分布和承载特性的影响;在此基础上,研究6种形貌、2种排布方式织构的润滑特性及摩擦性能。结果表明,流体流入收敛楔产生正的流体动压,流入发散楔产生负的流体动压,规则排布的织构单元摩擦性能优于错开排布的织构单元。在最优的雷诺数条件下,不同形貌的织构单元平均摩擦系数随面积率的增加而减少,菱形织构和球冠形织构面积率从4.5%增加到12.5%时,摩擦系数分别降低了81%和76%。因此,合理的选择织构形貌、尺寸有助于改善织构化滑动摩擦副的摩擦学特性。     

锥形缸体球面配流副润滑特性建模及试验验证

配流副油膜的润滑特性对轴向柱塞泵的可靠运行有重要影响。建立了锥形缸体球面配流副油膜润滑特性仿真模型,并通过试验验证了模型的有效性。对锥形缸体进行受力分析,通过对柱塞滑靴组件运动学和受力的分析,求解得到柱塞滑靴组件对锥形缸体的作用力;通过对球面配流副油膜厚度分布和压力分布的分析,求解得到球面配流副对锥形缸体的油膜支承力;采用有限容积法对油膜进行离散化处理,通过牛顿迭代法数值求解球面配流副油膜润滑特性和锥形缸体运动方程;开展轴向柱塞泵高压稳态试验和轮廓扫描试验,获得不同稳态试验时长的球面配流盘磨损形貌,对比球面配流盘磨损轮廓与仿真得到的油膜厚度分布和压力分布。研究结果表明,仿真得到的油膜厚度较小区域与配流盘主要磨损区域相近,验证了锥形缸体球面配流副油膜润滑模型的有效性。     

ISG型混合动力系统滑动轴承液体动力润滑性能探讨

建立了包括滑动轴承、机电耦合轴和发动机缸体在内的混合动力系统轴系数学模型,依此模型对混合动力系统轴承液体动力润滑性能进行分析,分别计算了一个工作周期内不同混合动力工况和不同电机功率情况下滑动轴承的偏心率和油膜压力.计算结果的分析表明,混合动力工况改变和电机功率的增大不会明显影响混合动力系统轴承的偏心率和油膜压力;根据机电耦合轴电机端轴承的油膜压力和偏心率可以优化电机轴承以及电机的选型和设计.