超声椭圆振动磨削的光学非球面亚表面损伤抑制及其对中频误差的影响机制

The application and development of optical aspheric glass lens are restricted by the efficiency of traditional ultra precision manufacturing technology of optical aspheric lens. Ultrasonic technology is applied to the precision grinding of the optical aspheric glass according to its superiority. However, the mechanisms of subsurface damage and mid-spatial-frequency error on optical aspheric glass lens in this machining method are not clear. The generation mechanisms of the subsurface damages on the optical glass, including subsurface crack and subsurface residual stress, are researched to explore the influence relationship between the subsurface damage and the mid-spatial-frequency error in terms of grinding parameters. Firstly, the generation mechanisms of the subsurface crack and subsurface residual stress are modeled for the elliptical ultrasonic assisted grinding. Secondly, the effects of aspheric machining path on the subsurface crack and the subsurface residual stress are analyzed and the growth of subsurface damage is modeled. Thirdly, the mid-spatial-frequency error of the optical aspheric lens in the elliptical ultrasound assisted grinding is modeled to explore the internal relation between the subsurface damage and the mid-spatial-frequency. Finally, the processing control technologies of the subsurface damage and the mid-spatial-frequency error of the optical aspheric lens in the elliptical ultrasound assisted grinding are researched by a series of machining and detecting experiments. This research can be used as basic theory of the surface/subsurface qualities of optical aspheric glass in ultrasound assisted grinding and improve the technology of precision manufacture of the optical aspheric lens. It has great theoretical and practical significance.

光学非球面超精密加工技术一直受加工效率的制约，由于超声振动在脆硬性材料加工方面的优势，将其应用于光学玻璃非球面精密磨削加工是一种极具吸引力的技术改良，但该加工方式对光学元件极为关注的亚表面损伤和中频误差的影响规律尚不明确。本课题以超声椭圆振动磨削下光学玻璃非球面元件亚表面损伤机理为研究对象，探索亚表面损伤抑制过程中工艺参数对中频误差的影响机制。首先研究高频脉冲磨削力对磨粒压痕应力场的影响，掌握亚表面裂纹与残余应力初始形成机理；其次研究非球面加工轨迹拐点处裂纹尖端应力应变耦合作用关系，掌握磨削过程亚表面裂纹与残余应力相互影响的扩展规律；然后建立中频误差磨削参数预测模型，掌握中频误差与亚表面损伤的内在联系；最后通过实验研究获得低亚表面损伤和中频误差的控制方法。本研究可为光学非球面超声振动磨削表面/亚表面质量控制方法研究奠定理论基础，推动光学非球面精密制造技术发展，具有重要的理论和实践指导意义。

光学非球面元件精密、超精密制造技术作为极具竞争的技术之一，一直受到许多国家的重点关注，它是尖端技术产业发展不可缺少的关键技术，是衡量一个国家制造技术水平高低的重要标志之一，如何提高其加工制造技术一直是光学制造行业和机床行业的重要课题。由于光学技术领域的迅猛发展，光学玻璃因其夹杂物较少透明度高，物理及化学性质稳定，且机械强度和热稳定性都较高等特点，在许多如日常生活、科研医疗、航空航天、国防工业等关键领域都扮演越来越重要的角色。而光学元件在加工过程中引起的亚表面损伤会导致材料的强度下降、折射系数变化等，直接影响到光学零件的使用性能、长期稳定性、抗激光损伤阈值和寿命等重要性能指标，对光学系统的性能造成很大的影响。.项目以超声椭圆振动磨削下光学玻璃非球面元件亚表面损伤为研究对象，理论结合实验调查了超声振动磨削下光学玻璃材料去除机理及损伤机制。首先建立单颗磨粒在高频脉冲运动下对光学玻璃材料的压痕应力场模型，创新性地提出一种适应于描述超声振动压痕区域的力学参数——等效平均接触应力，揭示了等效平均接触应力与超声振动压痕下光学玻璃亚表面损伤的联系；其次建立超声振动辅助磨削的表面粗糙度、亚表面损伤深度和磨削力预测模型，基于传统脆硬材料去除机理研究基础上提出一项新的评价指标——材料脆性去除比，并实验调查了材料脆性去除比率与材料表面粗糙度、亚表面损伤深度及磨削力的内在联系；构建超声振动磨削力模型，系统地分析了超声振动磨削加工材料去除机制对光学非球面元件制造过程中能量消耗与加工时间减少的影响。通过理论和实验上的深入研究，实现低亚表面损伤的光学玻璃非球面超声椭圆磨削最优参数条件，改进光学非球面磨削技术，改善后续抛光的初始工件质量，为大幅度提高后续抛光效率创造前提条件，并为整套光学玻璃非球面超精密加工技术的改良提供理论基础与指导依据。