单晶硅微纳结构的空间多频自适应铣削原理及损伤抑制研究

单晶硅微纳结构表面是现代光学和光电系统关键元件的核心元素，具有非连续、多层次、跨尺度等复杂几何特征，在加工中极易出现微裂纹损伤和面型精度低等问题，严重制约了高能强光和光电信息装备的性能和寿命。本项目从空间多频运动铣削系统的设计理论和运动学规律解析出发，研究一种可在加工中针对微纳结构局部形貌变化快速动态调制多个切削参量（包含切屑厚度、切削前角、刀痕残留结构、刀具旋转轨迹形状等）的微纳结构自适应加工原理，以达到提高面型精度和表面质量一致性的目的，并实现纳米级和微米级结构的跨尺度加工。为有效抑制微裂纹损伤，依据离散位错动力学和应变梯度理论，建立单晶硅微纳结构加工的跨尺度关联耦合仿真模型，揭示塑性变形驱使的微裂纹损伤机理，探明瞬变切削参量、冲击载荷、微纳结构几何约束、微缺陷等对微裂纹萌生与演化的影响机制，最终形成一种兼顾面型精度、微裂纹抑制、效率的微纳结构加工工艺，促进单晶硅微纳结构的广泛应用。

Micro/nanostructures of single-crystal silicon featuring complicated geometrical shapes are the key parts of the advanced optical and optoelectronic systems with function integration and minimization. However, the existing machining technologies can easily cause the crack damage and low form accuracy of the machined micro/nanostructures due to the inherent low fracture toughness of silicon, which highly restricts the performance and the life of energetic light and electro-optical information systems. This project will begin with the deep investigation on the design principles and the kinematics of a novel diamond milling system featuring spatial motions with multiple frequencies, based on which a new machining mechanism that can dynamically and self-adaptively tune different cutting parameters according to the local topographies of the machined micro/nanostructures will be developed. It is worth to note that through flexibly tuning the cutting parameters including chip thickness, cutting rake angle, tool residual structures and the shape of tool trajectory, the finished surface quality and the form accuracy will be improved. Besides, the proposed machining mechanism is able to fabricate nano- and micro-structures in one-step operation. To efficiently suppress the crack damage, a multiscale correlative coupling model will also be built according to the discrete dislocation dynamics and strain gradient theory, based on which the damage mechanism of the cracks induced by the plastic deformation of silicon will be learned, and the influence mechanism of the cutting conditions, high-speed impact, geometric constraint of micro/nanostructures and micro-defects on the crack damage will be studied. Finally, a new low-damage machining technology of micro/nanostructures will be built with the full consideration of the form accuracy, crack damage suppression and efficiency, to promote the wide-spread application of micro/nanostructures of single-crystal silicon.