基于流场聚焦的磁流变抛光原理与技术研究

Magnetorheological finishing is a most commonly used ultra-precision surface finishing method currently, but it is not applicable for concave structures with small radii of curvature, since the machining region is limited by the size of magnet part due to its mechanism. In this project, a new method based on flow focusing mechanism is proposed for the first time to constrain the magnetized high viscous region. Consequently, the method will be used to manipulate the abrasive particles in a more precise manner, and to generate magnetized region much smaller than the magnet part. Therefore, the method will be applied to machine concave structures with small radii of curvature using dual polishing modes. The multiphysics flow focusing mechanism will be studied using numerical simulation and experiments, and the competing effects from fluidic field, magnetic field and inertia will be examined. The nozzle with combined jetting apparatus and magnet part will be fabricated, and the platform for experiments will be constructed. The position and abrasive function for each of the two polishing regions, i.e. one for jet machining and another for magnetorheological finishing, will be identified. The parameters for the polishing process will be optimized based on the material and shape of work piece. The proposed method will expand the scope of application for magnetorheological finishing, and is instrumental for the ultra-precision machining of brittle materials with irregular shapes in aerospace and aviation industry.

磁流变抛光技术是目前最常用的一种超精密抛光方法，但是其原理上的缺点是加工区域受到励磁抛光头尺寸的限制，无法加工小曲率半径凹面结构。本项目首次提出一种使用流场聚焦的方法来约束磁流变抛光中的磁化高粘度抛光液，实现对流场中磨粒的精确控制，使磁化区直径远远小于励磁抛光头的直径，从而实现对小曲率凹面结构的双重模式抛光。本项目将研究多物理场耦合中流场聚焦的机理，对聚焦过程进行数值模拟与实验研究，确定流场、磁场、惯性相互竞争的关系；制作喷射头+励磁头复合结构，搭建实验平台；研究射流抛光与磁流变抛光双重抛光模式下不同抛光区的位置分布及其去除函数；研究与工件材料、表面形状相对应的优化抛光工艺参数。本项目研究成果可大大拓展磁流变抛光技术的适用范围，对航空航天领域中硬脆材料异形结构的超精密加工具有重要指导意义。

磁流变抛光技术是目前最常用的一种超精密抛光方法，但是其原理上的缺点是加工区域受到励磁抛光头尺寸的限制，无法加工小曲率半径凹面结构。本项目提出一种使用流场聚焦的方法约束磁流变抛光中的磁化高粘度抛光液，通过数值模拟与实验研究流场聚焦的机理，研发基于流场聚焦的磁流变抛光装置，聚焦后磁化高粘度区直径≤500µm，远小于目前最小的4mm励磁头，可加工的凹面结构曲率半径≤1mm，确定流场+磁场复合作用下的材料去除机理与去除函数，探究主轴转速、加工间隙、聚焦流速、加工时长等工艺参数对抛光效果的影响，并通过正交实验衡量与优化各工艺参数。针对狭小曲折内孔内腔的光整加工需求，研发一种基于旋转磁场的光整加工装置，利用励磁装置对磁性抛光介质进行非接触式驱动，实现了对直径≤3mm的内孔内腔表面的光整加工。针对液体在颗粒孔隙间的流动，确定重力对孔隙渗流的影响，发现新的渗流长度随时间变化的幂率指数，探讨孔隙边缘处的渗流界面振荡现象，提出并验证振荡周期的预测模型。本项目研究成果可大大拓展磁流变抛光技术的适用范围，对航空航天领域中硬脆材料小曲率凹面结构及内孔内腔结构的超精密加工具有重要指导意义。