磁流变动压复合抛光基本原理及力学特性

目的探究磁流变动压复合抛光基本原理及抛光力学特性。方法通过建立磁流变动压复合抛光过程中流体动压数学模型,分析抛光盘面结构化单元对抛光力学特性的影响规律,并优化其结构。搭建磁流变动压复合抛光测力系统,探究工作间隙、抛光盘转速、工件盘转速和凸轮转速对抛光力的影响规律,基于正交试验,优化抛光效果。结果抛光盘面结构化单元的楔形区利于流体动压效应的产生,且流体动压随楔形角和工作间隙的增大而减少,随楔形区宽度的增大而增大。结构化单元较为合理的几何参数为:楔形角3°~5°,工作间隙0.2~1.0 mm,楔形区宽度15~30 mm。法向力Fn随工作间隙的增大而减小,随工件盘转速的增大而增大,随抛光盘和凸轮转速的增大而先增大后减小;剪切力Ft随工作间隙的增大而减小,随工件盘、抛光盘和凸轮转速的增大均呈现先增大后减小的规律。通过正交试验获得优化工艺参数为:抛光盘转速60 r/min,工件盘转速600 r/min,凸轮转速150 r/min。在羰基铁粉(粒径3μm、质量分数35%)、SiC磨料(粒径3μm、质量分数5%)、工作间隙0.4 mm和磁感应强度0.1 T工况下,抛光2 in单晶硅基片4 h后,表面粗糙度Ra由20.11 nm降至2.36 nm,材料去除率为5.1 mg/h,初始大尺度纹理被显著去除。结论磁流变动压复合抛光通过在抛光盘面增设结构化单元,以引入流体动压效应,强化了抛光力学特性,并利用径向往复运动的动态磁场实现柔性抛光头的更新和整形,最终达到了提高抛光效率和质量的目的。

Basic Principle and Mechanical Property of Magnetorheological Hydrodynamic Compound Polishing

The work aims to investigate the basic principle and mechanical properties of magnetorheological hydrodynamic compound(MRHC)polishing.Effects of structured element of the polishing disk on the mechanical properties of polishing were analyzed according to the mathematical model for hydrodynamic pressure of MRHC and the structure was optimizedaccordingly. Then, effects of working gap and rotating speed of polishing disk, workpiece and cam on the polishing force werestudied. Furthermore, the orthogonal test was carried out to obtain the optimal polishing efficiency. The hydrodynamic pressurecould be generated in the wedge region of structured element on the polishing disk and decreased with the increase of wedgeangle and working gap and increased with the increase of width of wedge region. The reasonable geometrical parameters ofstructured element were wedge angle of 3°~5°, working gap of 0.2~1.0 mm and width of wedge region of 15~30 mm. Thenormal force Fn decreased with the increase of working gap and the decrease of rotating speed of workpiece, and increased firstand then decreased with the increase of rotating speed of polishing disk and cam. The shear force Ft decreased as working gapincreased, increased first and then decreased as the rotating speed of workpiece, polishing gap and cam increased. Finally, theoptimal polishing parameters were obtained through orthogonal test: the rotating speed of polishing disk, workpiece and camwas 60, 600, and 150 r/min, respectively. After 2 in single-crystal silicon was polished for 4 h under the conditions of carbonyliron powder (size 3 μm, mass fraction 35%), SiC abrasive (size 3 μm, mass fraction 5%), working gap of 0.4 mm andmagnetic induction strength of 0.1 T, the surface roughness Ra decreased from 20.11 nm to 2.36 nm, the material removal ratewas 5.1 mg/h, and the initial large-scale scratches were obviously removed. Hydrodynamic pressure can be induced according tothe structured element on the polishing disk of MRHC to strengthen the polishing mechanical properties. In addition, the updateand truing of flexible polishing head can be realized with the drive of moving magnetic field in radial direction, thus finallyimproving the polishing efficiency and quality.