微织构棘轮效应对转移润滑的作用机制及其可控设计

Transfer lubrication plays a key role in the realization of self-lubricity for solid lubricant containing composites. Aside from the effect of intrinsic properties of material on the process, the influence of plastic ratchetting caused by the surface morphology (i.e. roughness, waviness, wave orientation, etc.) of tribo-counterpart is also significant. To obtain regulative ratchetting effect, micro-textured counter-face will be adopted in the project. The aim is to shorten the run-in period and extend the life of lubricating transfer film, so as to optimize tribological properties of the composite. Two key issues in connection with micro-texture, namely the interface contact stress distribution and the strain accumulation in subsurface, and the rheological behavior of lubricating transfer film, will be considered in the project. The effect of various texture parameters on the friction and wear behavior of graphite-containing copper based composite will be observed through friction test combined with finite element modelling. The corresponding design criteria for micro-texture will be developed based on deep understanding in the effect and mechanism of plastic ratchetting introduced by micro-texture in transfer lubrication. The work will enriches and perfects transfer lubrication theory of self-lubricating composites, and offers a new approach to optimize tribological properties on the basis of material design. Further, the research will provides theoretical and experimental foundation for the tribology design of solid lubricating materials.

转移润滑是含固体润滑剂复合材料实现其自润滑性的关键过程。除材料本征性能外，由摩擦对偶表面形貌（粗糙度、波纹度、纹路取向等）引起的塑性棘轮效应对该过程有重要影响。项目拟针对含石墨铜基复合材料，在其对偶表面引入微织构，通过摩擦实验结合有限元模拟，研究织构参数与摩擦磨损行为之间的联系，重点关注并解决两个关键科学问题：（1）微织构引入对界面接触应力分布及亚表层应变累积的影响；（2）微织构对界面转移润滑膜流变行为的影响；揭示微织构棘轮效应在转移润滑中的作用机制，并据此提出相应的微织构设计准则以实现棘轮效应可控化，达到缩短跑合时间和延长界面转移润滑膜存续寿命的目的。本项目的实施将丰富和完善自润滑复合材料的转移润滑理论，在材料设计基础上为摩擦学性能的优化开辟新思路，并为固体润滑材料的摩擦学设计提供理论和实验依据。

自润滑材料的摩擦学表现一方面取决于材料本征性能，另一方面也受控于其它外部工况，尤其是影响到具体转移润滑行为的对偶表面形貌。本项目系统研究了对偶表面微织构棘轮效应对自润滑材料转移润滑行为的影响机制，具体研究内容包括：（1）微织构对自润滑复合材料摩擦磨损性能的影响；（2）微织构对复合材料表面转移润滑膜“构建-破坏-修复”和亚表层变形机制的影响；（3）微织构对摩擦界面接触应力分布和亚表层应变累积的影响；（4）微织构表面转移润滑膜流变行为研究；建立了微织构特征参数与复合材料摩擦磨损行为之间的基本规律和联系，初步阐明了微织构棘轮效应在复合材料亚表层变形、界面转移润滑膜建立和材料磨损等方面的作用机制，探讨了微织构形状、滑动方向、载荷等因素对微织构摩擦界面接触应力应变影响机制。另外，制备了微观组织均匀、力学性能优异的Fe-Co-Ni-Cr-Mo系自润滑高熵合金，并考察了其常温摩擦磨损行为，拟在接下来的研究中结合微织构进一步提升其高温摩擦学表现。项目取得的研究成果在磁头-磁盘、内燃机活塞-气缸系统、车辆制动盘和轮轨摩擦、仿生减摩等方面具有较好的应用前景。