基于微裂纹主动调控的硬脆单晶材料椭圆振动辅助飞切高效创成机理与方法

Along with the development of optical technology, the demands of the complex optical surface elements are increasing. The hard-brittle monocrystalline materials, represented by Si, are widely used in various fields such as imaging, lighting and energy systems. However, the characteristics of high hardness, anisotropy, as well as the low fracture toughness, make them susceptible to brittle fracture, which is a typical difficult-to-cut materials. In addition, it is difficult to predict and control the surface and subsurface damage and it is easy to brittle fracture during machining. Therefore, an active control method for nucleation and propagation of microcracks based on elliptical vibration-assisted fly cutting was proposed, we focus on design and optimization problem of elliptical-vibration-based spatial motion modulation servo mechtronic system; studying material damage mechanism and nucleation and propagation of microcracks under the impact of varying load assisted by elliptical vibration fly cutting in different dimensions (one-dimensional vibration, oblique vibration and three-dimensional vibration), revealing the mechanism of microcrack nucleation and propagation active control based high efficiency, ductilie and low cost fabrication method. The completion of the project will provide key theoretical basis and technical support for the high efficiency, precision and low-cost fabrication of optical surfaces elements and the improvement of the machinability of hard-brittle monocrystalline materials.

硬脆单晶材料复杂光学曲面元件的需求日益增大，以单晶硅为代表的硬脆单晶材料在成像、照明和能源系统等领域有着广泛的应用前景，但该类材料具有高硬度、各向异性、低断裂韧性的特点，使其在加工过程中极易产生脆性断裂，是典型的难加工材料。因此，针对硬脆单晶材料加工易脆裂且表面及亚表面损伤难以预测和控制的问题，本项目提出一种基于椭圆振动辅助飞切的微裂纹形核与扩展主动调控方法，重点研究空间椭圆振动主动调制伺服机电系统设计与协调优化；不同维度（二维、斜角、三维）椭圆振动辅助飞切变载荷冲击作用下硬脆单晶材料损伤机制和微裂纹形核与扩展规律，揭示基于主动调控微裂纹形核与扩展行为的高效、延性、低成本创成机理。本项目的完成将为高效精密低成本地创成复杂光学曲面元件、改善硬脆单晶材料的切削加工性等方面提供关键理论基础和技术支撑。

硬脆单晶材料在光学、能源系统等领域有着重要的应用前景，然而其高硬度、各向异性和低断裂韧性等特点使其在加工成本和加工质量方面很难兼得。针对上述问题，本项目以硬脆单晶材料高效、延性、低成本创成为目标，针对单晶硅这一典型的硬脆单晶材料，提出了一种基于椭圆振动辅助切削的微裂纹主动调控方法，实现面向形面加工的硬脆单晶材料高效、延性、低成本创成。本项目的主要研究进展包括：（1）研制了压电致动可转位三自由度解耦高频伺服机电系统，建立了柔性运动机构的静力学、运动学和动力学模型，开展了柔性运动机构的多目标参数协调优化，建立了其伺服控制策略，研制的伺服驱动系统工作带宽可以达到5kHz,运动分辨率可以达到3nm，具有良好的运动解耦能力。（2）基于研制的伺服机电系统，开展了正交、斜角和三维椭圆振动辅助变切深刻划实验，探究了不同参数对单晶硅脆塑转变临界切深的影响规律，通过试验和仿真揭示了材料以相变为主的塑性去除机理，揭示了微裂纹的形核和扩展机制，建立了面向形面加工的延性去除切削模型。（3）确定了调控裂纹扩展的有效工艺参数，结果表明基于角度和三维刀具轨迹调制的椭圆振动辅助切削均能够实现对微裂纹扩展的调控，该方法为基于硬脆单晶材料连续走刀的高效、延性、低成本面形加工提供了一种新的途径，研究成果将丰富硬脆单晶材料纳米加工理论体系，为面向复杂形面的金刚石超精密切削系统和高效、延性创成方法提供理论基础和技术支持。