聚酰亚胺薄膜超湿滑刀具时变切削的减摩抗粘机理与技术研究

Polyimide film is an ideal material for the construction of large-aperture space-borne Fresnel lens system. During cutting of the polyimide film, chip-sticking phenomenon is so serious that the obtained surface roughness is poor. Although the mechanism is not so clear, chip adhesion could be reduced by strengthening cooling/lubrication at tool tip. In view of this, a tool-tip-varying cutting method is proposed, in which the position of cutting point is varying along the arc-shaped tool edge. Meanwhile, an ultra-slippery micro-textured tool is also going to be developed by imitating the microstructures on the peristome surface of Nepenthes alata. The directional transport of lubrication film up to the tool tip could be expected. By combination of super-slippery micro-textured tool with the tool-swinging cutting method, the chip-sticking problem could be solved and the high-quality cutting of polyimide film could be achieved. It is known that the molecular structure of polyimide is totally different from the lattice structures of metal and semiconductor. Therefore, the micro-mechanical behaviors under the influence of shear stress such as the fracture, the tear, and the extraction of molecular chains will be studied. The mechanisms in plastic deformation and brittle fracture of polyimide will be established, and the fundamental cutting theory could be enriched. The achievements obtained in this project could also be used in the development of medical surgical instruments, flat panel display, solar photovoltaic system and other high value-added products.

聚酰亚胺薄膜是建造未来空间环境下服役的大型菲涅尔衍射镜的理想材料。近年来超精密切削已发展成为菲涅尔衍射镜的高效加工方法之一。但因材料的特殊性，金刚石刀具切削聚酰亚胺薄膜时会发生强烈的切屑粘结和堆积，严重影响切削表面质量。鉴于此，本项目提出通过刀具摆动实现刀具与工件接触区（刀触区）在大圆弧刀刃上的周期性往复迁徙，创建刀触区时变切削方法。同时，借鉴猪笼草口缘区的微观结构，试制切削液定向输送至切削点的仿生织构刀具，并将其装备于刀触区时变切削系统，揭示刀触区时变与超湿滑织构表面协同作用下刀-屑界面的切削液浸润机制和减摩抗粘机理。聚酰亚胺是典型的聚合物材料，其长链状分子结构对切屑形成、表面质量影响巨大，研究剪切应力作用下分子链的断裂、滑脱、扯离等纳米力学行为，揭示聚酰亚胺材料的塑性变形和脆性断裂机制。本项目的研究成果还可提升我国医用手术器械、柔性显示、空间太阳能电池光伏系统等高附加值产品的制造水平。

微纳结构光学元件具有广泛的应用前景，但大面积、高精度、高均一性的微纳结构表面加工依然具有技术瓶颈。同时，薄膜光学元件正在突破传统的范畴，愈来愈广泛地从液晶显示渗透到空间探测、生物芯片、激光器件、集成光学等光电信息领域。因而薄膜光学元件的制造已经成为科技发展的关键技术之一。鉴于此，本项目以实现聚酰亚胺薄膜的低阻湿滑超精密切削为目标，开展大口径聚酰亚胺薄膜基底衍射元件的制造技术研究。通过超精密切削机床误差检测与在位补偿、微织构刀具的加工与应用、连续型菲涅尔结构的超精密切削加工、聚酰亚胺薄膜基底上的菲涅尔透镜复制等多个方面研究，实现了聚合物材料表面的微细加工和相关技术创新，显著提升了聚酰亚胺薄膜的平面度和微纳结构表面质量。本项目自2018年1月启动以来，总体运行情况良好，按计划较好地完成了各项研究内容，并实现了考核指标。近年来，国内外学者对硬脆材料（硅、锗、光学陶瓷、玻璃等）的超精密切削开展了详细研究，形成了完善的超精密切削理论与技术。但是，对于低硬度、高延性的聚合物光学材料的研究相对较少。因此，本项目研究的聚酰亚胺薄膜材料的切削性能，将丰富我国在超精密切削的基础理论工作，具有重要的科学意义。本项目的技术成果也有利支撑和推动了国家重点研发计划“宽波段平面超表面太阳能聚光器”、空间引力波探测“太极计划”检验质量、星载激光雷达2米口径主镜等高端光学元件研制项目。