【作者】 张峰；

【导师】 余景池；

【作者基本信息】 中国科学院长春光学精密机械与物理研究所 ， 光学， 2000， 博士

【摘要】 磁流变抛光（MRF）是近十年新兴的一种先进光学制造技术，它特别适合中、小口径（φ50mm以下）光学元件的快速抛光。目前，国外只有美国Rochester大学的一些研究人员在做这方面的工作，国内未见这方面的报道。本论文对磁流变抛光的研究工作在国内是首次进行的，属于国内开创性工作。 磁流变抛光的原理是这样的：在磁场中，发生流变的磁流变抛光液流经工件与运动盘形成的小间隙时，会对工件表面与之接触的区域产生很大的剪切力，从而使工件表面材料被去除。磁流变抛光与传统抛光相比最显著的优点是：在抛光过程中，不存在“磨头”磨损的问题。这样，抛光去除函数始终是恒定不变的。这对控制抛光以至实现数控磁流变抛光是十分有利的。磁流变抛光能够顺利进行的两个前提条件是：1提供适合于磁流变抛光的梯度磁场；2配制出具有良好流变性的磁流变抛光液。 本文立足于磁流变抛光技术的基础研究，首先在对磁流变抛光技术进行综述的基础上，对进行磁流变抛光所必需的两个前提条件进行了研究。在磁场的研制方面，设计了与分析式铁谱仪的磁路相类似的磁路结构。以该磁场中磁性微粒的受力分析为基础，从理论上分析了磁流变抛光液可以形成抛光所需的缎带凸起，并以实验进行了验证。在磁流变抛光液的研制方面，通过对磁流变抛光液的成分、特性以及流变机理的研究，研制出流变性好、初始粘度低、流动性好的磁流变抛光液。这种磁流变抛光液用于磁流变抛光效果很好。 其次研究了磁流变抛光的机理。磁流变抛光机理是这样的，当发生流变的磁流变抛光液流经工件与运动盘之间形成的小间隙时，会在流出区域（抛光区）形成一个附着于运动盘表面上的核心。该核心上表面与工件表面又形成一个更小的间隙，在这个更小间隙内流动的剪切流会对工件表面产生很大的压力（或剪切力），从而使这个区域内工件表面上的材料被高效率地去除。在研究磁流变抛光机理的基础上，根据光学加工中为人们所普遍接受的Preston方程，建立了磁流变抛光的数学模型。从该模型得出的结论与磁流变抛光的实验结果符合得较好。 中国科学院长春光学精密机械与物理研究所博土学位论文 最后在实验的基础上，研究了抛光时间、运动盘的速度、工件与运动盘形成的间隙大小、磁场强度、工件硬度、磁性微粒的浓度、非磁性抛光粉的浓度等参数对磁流变抛光去除函数的影响。同时研究了抛光后的工件表面粗糙度和下表面破坏层的情况。阐述了今后如何根据磁流变抛光规律来控制被加工工件的面形。更多还原

【Abstract】 Magnetorheological finishing (MIRE) is an advanced optical manufacturing technology, which has evolved over the past decade. It fits for rapid polishing of medium or small size optical elements. In magnetorheological finishing, magnetically stiffened magnetorheological (MR) abrasive fluid flows through a preset converging gap that is formed by a workpiece surface and a moving rigid wall, to create precise material removal and polishing. A fundamental advantage of MRF over traditional polishing is that the polishing tool does not wear, since the recirculated fluid is continuously monitored and maintained. Therefore, during polishing, the material removal function is not changed, that is useful for us to control the polishing process. There are two preconditions before MIRE: One is presenting a suitable gradient magnetic field, the other is preparing magnetorheological polishing fluids (MRP fluids) with good rheology. In this thesis we first study on these two preconditions. On the one hand, we design a magnetic circuit, which is similar to that of Ferrograph. According to the analysis of the forces acting on magnetic particles in this magnetic field, we find that MRP fluids can form a ribbon that is regarded as 損olishing tool? It is true that MRP fluids really form a ribbon in our MIRE experiment. On the other hand, on the basis of studying on compositions, properties and rheology of MR.P fluids, we prepare several kinds of MRP fluids with good properties. By using them in our MIRE experiment, we get a good polishing result. Secondly, the mechanism of MIRE is studied. When MIRP fluidsis delivered to the vicinity of the gap formed by convex part and moving wall, it is pressed by the magnetic field gradient against the wall, so it stiffens, and becomes a plastic Bingham medium before it enters the gap. When plastic Bin~ham medium enters the gap, a core attaching to the moving wall is formed in 損olishing spot? So, a very small gap is formed between the upper surface of the core and the part surface. Thereafter, a shear flow occurs in this very small gap, resulting in the development of high pressure or high stress on surface of the part and thus, material removal a portion of the part surface. According to Preston equation, mathematics model of MIRE is established in this thesis. The III reliability of the mathematics model is verified by MRF experiment. At the end of the thesis, based on MIRE experiment, the curves and the laws of the effect on MRF by several parameters are given. These parameters include polishing time, velocity of moving wall, magnetic field intensity, size of the gap between the part and moving wall, hardness of the part and concentration of MIRP fluids. After polished, t microroughness and subsurface damage of the part are studied. Also, we explain how to correct figure of the workpiece.更多还原