Magnetorheological finishing of an irregular-shaped small-bore complex component using a small ball-end permanent-magnet polishing head

A novel magnetorheological finishing(MRF)process using a small ball-end permanent-magnet polishing head is proposed,and a four-axes linkage dedicated MRF machine tool is fabricated to achieve the nanofinishing of an irregularψ-shaped small-bore complex component with concave surfaces of a curvature radius less than3 mm.The processing method of the complex component is introduced.Magnetostatic simulation during the entire finishing path is carried out to analyze the material removal characteristics.A typicalψ-shaped small-bore complex component is polished on the developed device,and a fine surface quality is obtained with surface roughness Raof 0.0107μm and surface accuracy of the finished spherical surfaces of 0.3320μm(PV).These findings indicate that the proposed MRF process can perform the nanofinishing of a kind of small-bore complex component with small-curvature-radius concave surfaces.

Magnetorheological finishing of low-gradient curved surfaces based on four-axis linkage technique

Based on the distribution characteristic of magnetic field along the polish wheel,the four-axis linkage technique is advanced to replace a standard five-axis one to figure low-gradient optical surfaces with a raster tool-path in magnetorheological finishing(MRF).After introducing the fundaments of such simplification,the figuring reachability of a four-axis system for the low-gradient optics was theoretically analyzed.Further validation including magnetic field intensity and influence function characteristic was performed to establish its application.To demonstrate the correctness,feasibility and applicability of such technique,a K4 spherical part was figured by two iterations of MRF with surface form error improved to 0.219λPV and 0.027λRMS.Meanwhile,the surface roughness was also improved a lot in MRF process.These theoretical analyses and experimental results both indicate that high form accuracy and excellent surface quality can be obtained by using the four-axis linkage technique in the process of figuring low-gradient optical elements,and the four-axis linkage system undoubtedly is much more easy to control and much more economical.

The Synthetic Effect of Magnetorheological Finishing Technology:Analysis,Modeling,and Control

The controllable key factors in magnetorheological finishing device were studied to determine their influence on efficiency of magnetorheological finishing(MRF)and surface of MRF,as well as interaction between efficiency and surface.Based on theoretical and experimental research,the law of material removal was explored and a new process variable based material removal model(PVMR)was proposed.The experimental findings demonstrate that PVMR reveals the law of the material removal with introduction of three concepts and makes a material removal function z(y i)where the magnetorheological finishing process parameters are considered since they are easy to control and adjust.So the material function of this model is quadratic curve function which is readily suitable for stability and online control magnetorheological finishing.

First order sensitivity analysis of magnetorheological fluid damper based on the output damping force

With many features,the magnetorheological fluid( MRF) damper is widely applied in the semiactive vibration control system. And sensitivity analysis is an important method to study the influence weight of various parameters on damping force characteristics. A mathematical model of the output damping force on the MRF damper is established by the mechanism modeling method,a first order output sensitivity equation is deduced and the expression of the first order output sensitivity function is obtained. The first-order sensitivity functions of ten design parameters are solved,and the influence degree of system parameters change on the output force of MRF damper is analyzed by comparing the sensitivity index of the parameters. Two sensitivities of vibration velocity and control current are obtained through experiment to prove the other parameters sensitivity analysis conclusion by analogy verification,which provides guidance for the structure optimization design of MRF damper.

Advanced nonlinear rheology magnetorheological finishing: A review

High-performance devices usually have curved surfaces, requiring high accuracy of shape and low surface roughness. It is a challenge to achieve high accuracies for form and position on a device with low surface roughness. However, due to the unique nonlinear rheology, magnetorheological fluids with hard abrasives are widely applied in ultra-precision surface finishing. Compared with conventional mechanical finishing, magnetorheological finishing displays obviously advantages, such as high precision shape of machined surface, low surface roughness and subsurface damage, and easy control for finishing processes. However, finishing performance depends on various factors, e.g. volume fraction and distribution of magnetic particles, types of hard abrasives and additives, strength of magnetic field, finishing forms. Therefore, a comprehensive review on related works is essential to understand the state-of-the-art of magnetorheological finishing and beneficial to inspire researchers to develop lower cost, higher machining accuracy and efficient approaches and setups, which demonstrates a significant guidance for development of high-performance parts in fields of aerospace, navigation and clinical medicine etc. This review starts from the rheological property of magnetorheological fluids, summarizing dynamically nonlinear rheological properties and stable finishing approaches. Then, the effect of components in magnetorheological fluids is discussed on finishing performance, consisting of magnetic particles, carrier fluid, additives and abrasives. Reasonable configuration of magnetorheological fluids, and different magnetorheological finishing methods are presented for variously curved surfaces. In addition, the current finishing forms and future directions are also addressed in this review.

Restraint of mid-spatial frequency error in magnetorheological finishing (MRF) process by maximum entropy method

In order to restrain the mid-spatial frequency error in magnetorheological finishing (MRF) process, a novel part-random path is designed based on the theory of maximum entropy method (MEM). Using KDMRF-1000F polishing machine, one flat work piece (98 mm in diameter) is polished. The mid-spatial frequency error in the region using part-random path is much lower than that by using common raster path. After one MRF iteration (7.46 min), peak-to-valley (PV) is 0.062 wave (1 wave =632.8 nm), root-mean-square (RMS) is 0.010 wave and no obvious mid-spatial frequency error is found. The result shows that the part-random path is a novel path, which results in a high form accuracy and low mid-spatial frequency error in MRF process.

磁流变抛光（MRF）技术的发展

对磁流变抛光技术20多年来的发展作了简要的回顾，介绍了磁流变液的组成、抛光机理及磁流变抛光技术的产生、发展和最新研究情况，并对其发展未来进行了展望。

一阶不连续光学元件MRF流体动力学分析方法

一阶不连续光学元件的磁流变抛光问题是制约我国高精高效光学制造领域发展的难题之一,其涉及锥形、矩形等几何形貌元件的光学元件加工问题以及常见光学元件的边缘效应控制问题。提出了基于一阶不连续光学元件的磁流变抛光流体动力学方法,建立了该类元件抛光区域流体动力分析的理论方法和数值手段。首先,对磁流变抛光工况下的流场进行了合理假设,其次,从微元流体动力方程出发,建立了适用于一阶不连续面形的流场分析方法,最后,基于有限差分法和数值迭代方法建立了流场控制方程的数值计算方法。通过对切入距离为1～18mm的抛光过程进行数值仿真,发现该方法所获取的一阶不连续面形的压力分布形态是正确的,产生的不连续压降与实验观测一致。

Material removal model of magnetorheological finishing based on dense granular flow theory

Magnetorheological finishing(MRF)technology is widely used in the fabrication of high-precision optical elements.The material removal mechanism of MRF has not been fully understood because MRF technology involves the integration of electromagnetics,contact mechanics,and materials science.In this study,the rheological properties of the MR polishing fluid in oscillation model have been investigated.We propose that the shear-thinned MR polishing fluid over the polishing area should be considered a dense granular flow,based on which a new contact model of MRF over the polishing area has been constructed.Removal function and processing force test experiments were conducted under different working gaps.The normal pressure and effective friction equations over the polishing area were built based on the continuous medium and dense granular flow theories.Then,a novel MRF material removal model was established.A comparison of the results of the theoretical model with actual polishing results demonstrated the accuracy of the established model.The novel model proposed herein reveals the generation mechanism of shear force over a polished workpiece and realizes effective decoupling of the main processing parameters that influence the material removal of MRF.The results of this study will provide new and effective theoretical guidance for the process optimization and technology improvement of MRF.

光学元件磁流变加工不确定度误差工艺方法

为减少磁流变抛光过程中误差对加工精度的影响,实现光学元件磁流变高精度加工,采用一种不确定度误差工艺方法对加工中的误差进行抑制。通过对磁流变加工过程中的位置误差和去除函数误差进行不确定度分析,在理论分析与实验分析的基础上进行验证实验。由仿真与实验结果可知,加工中面形误差与中频误差均存在3.5 nm的不确定度误差值,通过验证实验,得到了加工后的面形误差RMS值为20 nm,中频误差RMS值为14 nm。结果表明,采用误差不确定度的方法可优化加工工艺流程,减少误差对加工过程的影响,可以达到不确定度下的面形精度。该方法为磁流变高精度确定性加工以及面形误差与中频误差的抑制问题提供了一种解决方案。

磁流变抛光技术研究进展

表面质量是精密零部件最重要的性能之一,零件的表面质量主要是由加工过程中不同的工艺参数和方法决定的。传统的磨抛工艺由于作用在工件上的力很大、嵌入的磨料颗粒、对工艺的控制有限等原因很难使表面粗糙度降低到精密零部件的要求精度。磁流变抛光(MRF)提供了一种新型高效的方法使工件加工质量达到预期的精度水平。MRF对工艺控制具有更大的灵活性,并且可以在不破坏表面形貌的情况下完成加工。综述了磁流变抛光液组分对加工效果的影响、材料去除模型的建立和发展、不同的MRF加工方式和未来磁流变抛光技术发展的新方向,最后总结了目前MRF技术存在的问题总结,并提出了MRF技术未来可能的发展方向。

光学材料研磨亚表面损伤的快速检测及其影响规律

提出了一种光学材料研磨亚表面损伤的非破坏性快速检测方法。基于印压断裂力学理论建立了亚表面损伤深度与表面粗糙度的关系模型。使用磁流变抛光斑点技术测量了K9玻璃在不同研磨条件下的亚表面损伤深度,并验证了上述模型。最后,分析了研磨加工参数对亚表面损伤深度的影响规律,提出了高效率的研磨加工策略。研究表明:光学材料研磨后亚表面损伤深度与表面粗糙度成单调递增的非线性关系,即SSD^SR4/3。磨粒粒度对亚表面损伤深度的影响最显著,研磨盘硬度的影响次之,而研磨压力和研磨盘公转速度的影响基本可以忽略。利用建立的亚表面损伤深度与表面粗糙度间的关系模型能够实现亚表面损伤深度的快速、准确和非破坏性检测。

磁流变抛光消除磨削亚表面损伤层新工艺

针对传统光学加工技术难于精确测量和控制亚表面损伤的特点,提出用磁流变抛光替代研磨工序并直接衔接磨削的新工艺流程。采用自行研制的磁流变抛光机床KDMRF-1000和水基磁流变抛光液KDMRW-2进行了磁流变抛光去除磨削亚表面损伤层的实验研究。结果显示,直径为100mm的K9材料平面玻璃,经过156min的磁流变粗抛,去除了50μm深度的亚表面损伤层,表面粗糙度Ra值进一步提升至0.926nm,经过17.5min磁流变精抛,去除玻璃表面200nm厚的材料,并消除磁流变粗抛产生的抛光纹路,表面粗糙度Ra值提升至0.575nm。由此表明,应用磁流变抛光可以高效消除磨削产生的亚表面损伤层,提出的新工艺流程可以实现近零亚表面损伤和纳米级精度抛光两个工艺目标。

磁流变光整加工技术研究进展

介绍了近年来磁流变光整加工(MRF)技术的研究状况及最新进展,对磁流变光整加工机理研究、加工机床与相关装置的开发、加工工艺试验研究、加工算法与模型研究、磁流变液流体开发与应用等五个方面进行了详细的综述与分析。最后探讨了磁流变光整加工中的关键技术与存在的问题,并对其发展趋势进行了展望。

基于研磨加工参数的亚表面损伤预测理论和试验研究

为实现研磨亚表面损伤深度的无损、快速和准确检测,并预测研磨参数对亚表面损伤深度的影响规律,针对光学材料研磨加工过程建立基于研磨加工参数的亚表面损伤深度预测模型。使用磁流变抛光斑点技术测量K9玻璃在不同研磨条件下的亚表面损伤深度,对上述预测模型进行试验验证。最后,提出以提高光学零件加工效率为目的的研磨加工策略。研究表明:建立的研磨亚表面损伤深度预测模型能够通过研磨加工参数对亚表面损伤深度进行有效的预测;研磨亚表面损伤深度与磨粒粒度、研磨盘硬度和研磨压强成正比关系,与研磨速度和研磨液浓度成反比关系;磨粒粒度对亚表面损伤深度的影响最显著,研磨压强的影响次之,研磨盘硬度、研磨速度和研磨液浓度的影响较小;为提高光学零件加工效率,建议在研磨过程中选取较高的研磨速度和较浓的研磨液,以在降低亚表面损伤深度的同时提高材料去除效率。

高精度光学表面磁流变修形

系统研究了确定性磁流变抛光高精度光学表面的关键技术及应用。介绍了自行研制的KDMRF-1000F磁流变抛光机床及其基本工作原理,给出了抛光过程中建立材料去除模型的两种方法和如何根据驻留时间完成路经规划的过程。采用KDMRF-1000F磁流变抛光机床和KDMRW-1水基磁流变抛光液对直径80mm的K4材料平面反射镜和直径145mm的K9材料球面反射镜进行修形实验。实验显示,样件一面形收敛到PV值55.3nm,RMS值5.5nm;样件二面形收敛到PV值40.5nm,RMS值5nm;样件的表面粗糙度均有显著改善。结果表明,磁流变修形技术具有高精度、高效率、高表面质量的特点。

磁流变抛光技术

对磁介质辅助抛光技术２０ 年来的发展作了简要的回顾，进而介绍了磁流变抛光技术的产生和发展背景、抛光机理及微观解释、数学模型，同时提出了这种抛光技术的关键所在，并对其发展未来进行了展望。

光学镜面磁流变抛光的后置处理

分析了自行研制的磁流变抛光机床KDMRF-1000的拓扑结构以及坐标变换关系,对其进行了运动求解,建立了光学镜面的磁流变抛光后置处理算法模型。针对机床四轴联动的特点,对建立的磁流变抛光后置处理模型进行了近似处理。以球面镜的后置处理为例,推导了具有普适性的以光栅扫描方式加工光学镜面的后置处理算法,同时分析了这种近似处理引入的误差,仿真了其对不同口径和不同相对口径球面镜的影响,得到了这种近似处理算法对球面镜的加工范围。最后,对一块口径为200mm,相对口径为1∶1.6的K9材料球面镜进行了磁流变抛光实验,在不考虑边缘效应的情况下其面形误差的PV值和RMS值分别达到了65nm和9nm以下,有效地验证了后置处理算法模型的准确性以及四轴联动近似处理的可行性。该算法对各类形状和大小的光学镜面加工均有参考意义。

光学元件精密加工中的磁流变抛光技术工艺参数

为了充分掌握磁流变抛光中磁场强度、浸入深度、抛光轮转速、磁流变液水分含量等工艺参数对抛光结果的影响规律,以期提高元件的面形精度和表面的质量,在研究了磁流变抛光材料的去除数学模型的基础上,结合实验室的PKC100-P1型抛光设备,对上述的关键工艺参数分别进行了研究,设置了一系列的实验参数,进行了详细的实验探索,分析了单因素条件下材料的去除量以及元件表面质量同关键工艺参数的内在联系,得出了相应影响关系曲线。从关系曲线表明:工艺参数对抛光斑的去除效率以及被加工元件表面质量存在着明显的影响规律,掌握这些影响关系就能用于分析和优化磁流变加工的结果,为高精度光学表面的加工提供可靠的保障,同时实验的结果也很好地验证了磁流变抛光材料去除理论的正确性。

磁流变抛光系统去除函数的原点位置标定

为了实现磁流变抛光的确定性加工,对磁流变抛光去除函数的原点位置进行了标定。分析了磁流变抛光去除函数的产生过程及其去除率分布。利用标准圆柱,建立了抛光轮最低点与数控加工中心测头的相对位置坐标变换关系,实现了光学元件在机床坐标系中的精确对准。通过在光学元件的特征点上进行去除函数实验测试,实现了抛光轮最低点对应的去除函数原点位置标定,对标定误差进行了分析。选择圆形平面光学元件,应用以金刚石颗粒为抛光粉的水基磁流液,对抛光轮直径为360mm的磁流变抛光系统进行去除函数原点标定,单次标定精度达到0.030mm。实验结果表明:本文提出的去除函数原点标定方法简单可靠,能够满足磁流变抛光技术的修形需求,可为磁流变抛光在光学制造中的应用提供有力支持。