磨合过程界面结构演化规律与调控的研究

Running-in is the initial friction and wear stage that tribo-elements experienced during operation. During the running-in process, contacting interfaces of machine elements evolute gradually in a complicated way in the aspects of the contacting geometry, topography and interface microstructure, which affects the friction, wear, lubrication and interface damage behavior of the machine element in the following operation stage enormously. A lot of experimental work has been done on the changes in surface topography, boundary film generation and subsurface microstructures after running-in, and by optimizing the running-in conditions it has been utilized to improve the tribological performance of machine elements. However, the previous researches are lack of investigation on the evolution process of interface microstructures, insufficient in effective techniques to control the running-in process, and of limited capability of modeling and numerical simulation of the running-in processes. In this project, the evolutions of surface topography and microstructure will be investigated with in situ measurement techniques, the microtribological properties of tribofilms and subsurface layers will be characterized with the aid of advanced instruments, models of mixed lubrication and boundary lubrication will be improved and computation programs for numerical simulation of the running-in process will be developed. In addition, new techniques for controlling the running-in process will be proposed, including the surface texturing, application of external electric and/or magnetic fields and nanoparticles as lubricant additives. The research results to be obtained will be applied to improve the performance of the main shaft bearings of jet engines made in china. The aim of the project is at exploring the evolution model of interface structure during running-in processes and at extending its application in industry.

磨合是机械零件运行时初期经历的摩擦磨损阶段，接触状态、表面形貌以及界面结构会发生复杂的演化，对其后续工作阶段的摩擦、磨损、润滑和界面失效行为有决定性影响。人们对磨合前后接触表面的形貌变化、边界膜的生成以及亚表面材料组织结构的改变已进行了大量实验研究，並利用磨合工艺优化改善零件的摩擦学性能。但以往的研究对磨合过程中界面结构动态演化规律缺乏深入了解，主动调控磨合过程技术手段不足，定量分析模型水平和数值模拟能力有限。本项目将对磨合过程中表面和界面结构演化开展动态原位检测与分析；对磨合过程中生成的边界膜及亚表面变质层开展纳米摩擦学特性的测量与表征；发展混合润滑和边界润滑的计算分析模型，开发磨合过程数值模拟的计算程序；探索利用表面织构、外加电磁场和纳米颗粒添加剂调控磨合过程的新技术；将磨合的研究成果应用于改善国产航空发动机轴承性能。旨在充分揭示磨合过程中界面结构的演化规律、拓展其工程应用范围。

磨合是磨损的起始阶段，机械零部件耐磨性好坏不仅取决于设计、材料和制造过程，也依赖于其磨合阶段发生的界面结构演化过程。工程实践中主要依赖经验摸索合适的磨合工艺，同时发展高效减摩抗磨润滑添加剂技术；磨合机理实验研究关注磨损量、形貌、反应膜和磨屑随工况条件与时间的变化，宏观理论分析大多基于Archard磨损模型或损伤、疲劳和断裂力学理论，微观实验借助原子力显微镜、扫描和透射电子显微镜。由于磨损问题固有的系统依赖、时间依赖、跨尺度和多因素交互影响的复杂性，磨合理论尚未成熟，磨合调控技术仍基于工程经验。本项目围绕磨合诱发界面结构和边界膜演化过程的检测、表征与分析，混合润滑与磨损耦合计算模型的发展以及磨合过程的主动调控技术展开，目标是解决机械零件磨合过程中摩擦和磨损的定量预测以及主动调控的难题，丰富和完善摩擦学理论与技术体系。通过研究取得了以下几项重要结果：1）修正了Archard磨损模型并与混合润滑统计计算模型相结合，建立了能够预测磨合过程中表面轮廓曲线演化的计算方法，进而提出利用数值磨合优化轴承滚子修形的方法，成功应用于圆柱、圆锥滚子修形设计和球轴承滚道磨损预测；2）提出了粘着磨损磨屑生成判据并与混合润滑确定性计算模型相结合，首次实现了磨屑尺寸、表面粗糙度、润滑膜厚和压力分布随磨合过程变化的仿真；3）用分子动力学模拟揭示出纳米尺度下表面能对金属摩擦磨损的重要影响，从原子尺度为所提出的磨屑生成判据提供了支撑，并与国际上透射电镜下金属单粗糙峰摩擦磨损观测和测试结果相符；4）揭示了表面纹理、外加电场与添加剂的交互作用对边界润滑膜减摩抗磨影响的机理，发展了磨合过程主动调控技术。该项目从理论和实验方面充分揭示了表面能、粘附功是磨屑生成和磨损控制的关键因素，将新的磨损模型与混合润滑理论相结合，建立了磨损表面轮廓、形貌以及磨屑生成的定量预测算法，提出的数值磨合修形设计和主动调控磨合技术可用于指导工程实践。