蓝宝石光学曲面柱形宽缎带磁流变抛光仿真分析及实验研究

目的 针对目前光滑无损伤光学曲面蓝宝石加工成本高、效率低的问题，对加工过程中磁流变抛光缎带进行流体仿真，进而优化抛光轮表面结构。方法 设计并提出3种表面结构柱形宽缎带磁流变抛光轮，介绍了磁流变抛光轮加工的基本原理，建立了磁流变抛光垫Bingham流体特性加工仿真模型，分析了3种抛光轮表面结构对工件表面磁通密度模、流场流速、流场压力分布的影响。同时对3种抛光轮的抛光效果进行了实验探究，探究了抛光轮表面结构对材料去除率和抛光后表面粗糙度的影响规律。结果 仿真结果表明，抛光轮表面槽型结构具有能增强磁通密度模、增大流体流速和流体压力的特性。实验结果表明，螺旋槽抛光轮的抛光效果最好，在螺旋抛光轮作用下，材料去除率为0.22 mg/h，抛光后蓝宝石表面粗糙度为1.08 nm。最终抛光轮近壁区总压力和速度的乘积结果与抛光轮实验去除率结果具有较好的一致性。结论 槽型结构可以提高抛光液在抛光轮表面的固着效果，影响工件表面流场运动状态，增强工件表面受到抛光垫的作用力。相较于光滑和横条槽抛光轮，螺旋槽抛光轮的抛光效率最高，表面粗糙度最低，可有效提高抛光效果。

Simulation and Experimental Study on Optical Surface Wide Ribbon Wheel Magnetorheological Polishing of Sapphire

At present, the processing of smooth and non-destructive optical curved sapphire has problems of high cost and low efficiency. Magnetorheological polishing technology has advantages of real-time update of abrasives, non-wear polishing tools, easy computer control, stable removal function and controllable performance of magnetorheological microgrinding head, etc. and is suitable for polishing processing of various types of complex surfaces. In order to optimize the surface structure of the polishing wheel, increase the fixing force of the polishing wheel on the magnetorheological polishing pad, and improve the polishing effect, it is necessary to simulate the fluids of the magnetorheological polishing ribbon during processing. According to the actual processing process of the cylindrical wide ribbon magnetorheological polishing wheel, Solidworks was used to model the polishing wheel in three dimensions, and then the simulation software COMSOL was imported for multiphysics coupling simulation. A machining simulation model for controlling the fluid characteristics of magnetorheological polishing pad Bingham was established, and the effects of the surface structure of the three polishing wheels on the magnetic flux density mode, flow velocity and flow field pressure distribution in the surface processing area of the workpiece were analyzed. At the same time, the polishing effect of the three polishing wheels was experimentally explored, and the influence of the surface structure of the polishing wheel on the material removal rate and surface roughness after polishing was explored. The simulation results showed that the geometric structure on the surface of the polishing wheel had the characteristics of enhancing the magnetic flux density mode in the polishing area, increasing the fluid flow velocity and fluid pressure. Compared with the smooth wheel machining area, the magnetic flux density mode increased by 18.5%, the average flow rate of the flow field increased by 7%, the total surface pressure increased by 54.4%, and the shear force increased from 250 Pa to 850 Pa. The experimental results showed that the roughness Sa of the smooth wheel, horizontal bar wheel and spiral wheel reached 1.6, 1.57, 1.08 nm, respectively, the scratch depth decreases from 60 nm to 11 nm, 9 nm and 5.5 nm, and the material removal rate was 0.145, 0.155, and 0.22 mg/h, respectively. Compared with smooth wheels, polishing wheels with grooved structures had better surface quality and higher material removal rate after polishing, among which the polishing effect of spiral wheels was the best. The product result of the total pressure and velocity in the near wall area of the final polishing wheel had good consistency with the experimental removal rate of the polishing wheel, and the error was within 10%. The groove structure can improve the fixing effect of the polishing liquid on the surface of the polishing wheel, affect the flow field motion state of the workpiece surface, and enhance the force of the polishing pad on the surface of the workpiece. Compared with smooth and transverse groove polishing wheels, spiral groove polishing wheels have the highest polishing efficiency and the lowest surface roughness, which can effectively improve the polishing effect.