旋转磁场作用下光学材料的磁性混合流体超精密抛光机理研究

There is a significantly increasing demand on the optical materials (such as optical glass and optical polymers) with nano-precision surface in scientific and industrial fields, including optical systems, aeronautics and astronautics, semiconductor industry, etc. However, traditional polishing methods are costly, time consuming and easily result in surface damages. Besides, polishing efficiency and quality are hardly improved in static magnetic field assisted polishing using magnetic fluids (MFs) or magnetorheological (MR) fluids. In this study, a magnetic compound fluid (MCF) slurry polishing method under a rotary magnetic field is proposed. First, dynamic distributions of magnetic field and magnetic line of force, MCF slurry behaviors and its shape self-restoring ability will be studied; Macro morphology and microstructure characteristics of MCF slurry in the interacting area will be analyzed; Then, the coupling action of magnetic field, MCF slurry and abrasive particle and its influence on abrasive particle distribution and surface morphology will be explained. Secondly, the micro-actions and distributions of pressure and shear stress will be obtained; dynamic shape, macro morphology and microstructure characteristics of MCF slurry cross-section in the interacting area will be analyzed; Accordingly, relationship among magnetic field, MCF slurry behaviors, abrasive particle distribution and polishing force action, material removal will be clarified and an material removal rate model involving critical process parameters will be established; Based on the above work, the mechanism of ultrafine polishing of optical materials with MCF slurry under a rotary magnetic field will be clarified. Finally, aiming to obtain both excellent surface roughness and high efficiency, process parameters will be optimized for materials with different characteristics. This study will provide an effective way for ultra-fine polishing of optical materials with high efficiency.

光学系统、航空航天、半导体产业等科研和工业领域需要大量纳米精度表面的光学材料。然而，传统抛光技术成本高、效率低且易产生表面损伤。另外，静磁场辅助磁性流体或磁流变液抛光方法的抛光质量和效率难以进一步提高。本项目提出一种旋转磁场作用下磁性混合流体抛光方法。首先，研究磁场强度和磁力线的动态分布、抛光液的动态行为及形状自恢复能力，分析抛光区域抛光液表面的宏观形貌和微观结构特征，明确磁场、流体和磨粒的耦合作用及其对磨粒行为和加工表面形貌的影响机制；其次，研究抛光正压力和剪切应力的分布及微观作用规律，分析抛光区域抛光液横截面的动态形状、宏观形貌和微观结构特征，揭示磁场分布、抛光液行为和磨粒分布与抛光力作用和材料去除的映射机制，建立包含关键工艺参数的材料去除模型，系统地阐明旋转磁场作用下磁性混合流体抛光机理；最后，在材料去除率和表面粗糙度多目标下优化工艺参数，为不同特性光学材料的高效超精密抛光提供支持。

磁场辅助抛光技术在光学材料的低/无损伤、高效率、纳米精度抛光的优势很明显，然而磁场、流体和磨粒的耦合作用及其对磨粒行为、高质量表面创成、抛光力作用及材料去除行为的影响机制研究尚不足。另外，静磁场作用下，磁力线的空间分布不变，因而抛光液的行为被动，易导致抛光力作用不稳定，限制加工表面质量和抛光效率的进一步提高。.针对以上研究现状，本项目提出一种旋转磁场作用下磁性混合流体抛光方法。将永磁铁相对其旋转轴心设计偏心距，永磁铁将做公转运动，产生磁场强度不变、但磁力线公转的旋转磁场。明确了旋转磁场作用下磁力线带动抛光液做公转运动，抛光液具有动态行为及较强的形状自恢复能力；旋转磁场作用下加工表面的抛光痕方向接近随机的，抛光液分布更均匀，抛光簇的尺寸更细小，磨粒分布更均匀，揭示了抛光区域磁场、流体和磨粒的耦合作用及其对磨粒行为（运动方式、分布规律等）的影响机制；分析了加工表面形貌、抛光痕作用方向与抛光液行为、磨粒分布之间的映射关系，阐明了旋转磁场作用下的高质量表面创成机理。.设计实验获得了抛光正压力和剪切应力的分布，明确了抛光力的微观作用机制，建立了包含关键工艺参数的抛光正压力和剪切应力与材料去除率的映射机制，揭示了旋转磁场作用下的材料去除机理，发现剪切应力发挥主要的材料去除作用。观测了抛光液横截面的外观形貌，分析了抛光液微观构成粒子的分布，研究了抛光区域横截面处的磁场、流体和磨粒耦合作用下的磨粒行为，从而解释了抛光力作用和材料去除行为的发生机理，综合宏观力学和微观磨粒分布，明确了旋转磁场作用下光学材料的磁性混合流体抛光机理。.采用线性规划、遗传算法等方法，开展了在材料去除率和表面粗糙度双目标下优化抛光液成分、磁铁偏心距、加工间隙、抛光液载板旋转速度等关键工艺参数；针对不同特性材料或异形面的抛光，设计新型抛光头，控制抛光路径及驻留时间，将旋转磁场推广应用到自由曲面和模具材料的高效高质量抛光。