永磁流变抛光中磁流变液的性能研究

利用永磁流变抛光技术制造超光滑光学元件是一项极具前景的超精密制造技术.本文在明确磁流变抛光机理的基础上,主要对一种新颖的油基磁流变抛光液进行了配制,并对其主要性能如流变性、稳定性进行了试验研究,所获得的油基磁流变液的初始粘度达到0.5 Pa·s,流变性具有较大范围内的稳定性.对油基磁流变液抛光性能的试验研究证明其具有良好的抛光特性,抛光23min后工件表面粗糙度降低到0.6739nm.     

水基磁流变液的制备及其性能研究

以经过表面处理的微米级羰基铁粉、亚微米级四氧化三铁粉末为悬浮相,去离子水为悬浮介质,加入适当的添加剂,通过一定的工艺制备出综合性能良好的水基磁流变液.研究了几种含有不同悬浮相粒子和不同添加剂的磁流变液的剪切性能和沉降稳定性能,分析了悬浮相的组成对磁流变液磁流变性能的影响以及添加剂对改善磁流变液抗沉降团聚稳定性的作用.     

磁流变液的研发与应用

本文简介和评价了国内外近年磁流变液的研发概况，包括磁流变减振（震）液、磁流变抛光液、磁流变密封液的研究和应用情况。     

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。     

油基磁流变液的开发及抛光性能研究

磁流变抛光技术可用于具有超光滑要求光学元件的超精密制造。在明确磁流变抛光机理的基础上,开发了油基磁流变抛光液,其体积比配方是:33.84%的羰基铁,57.34%的硅油,6%的氧化铈,2.82%的稳定剂。抛光液初始粘度达到0.5Pas,流变性具有较大范围的稳定性能。实验中,利用磁流变液在外磁场作用下形成的强剪切应力对一平面K9玻璃进行了可控抛光,结果证明其具有良好的抛光特性,抛光23分钟后工件表面粗糙度降低到0.6739nm。     

磁流变抛光中的磁场与磁流变液缎带成型分析

利用标量磁位对磁流变抛光中的磁场进行了分析计算,并根据磁偶极子在磁场空间受力的模型,对磁流变液中的磁性微粉颗粒的受力进行理论推导,进一步分析磁流变液形成单一稳定缎带凸起的条件。理论分析经过试验验证,证明分析是正确的。     

磁流变液及其应用

介绍了磁流变液的发展历史、组成、特点;综述了磁流变液的应用情况,其中包括减振器、抛光装置、密封装置、制动器、离合器等;展望了磁流变液在自动武器、疾病治疗等方面的应用前景;指出了磁流变液目前存在的主要问题及发展方向.     

磁流变液的特性研究

对以金属铁颗粒为主体的磁流变液的一般特性进行了研究。详细研究了材料的颗粒大小、形状、比例以及温度等对磁流变液特性的影响。研究了流体的屈服应力与磁场关系,剪切应力与磁场以及剪切速率的关系。实验发现,磁流变液出现磁饱和现象不仅与材料特性有关,而且与配比比例有关;剪切应力不仅与材料的颗粒大小有关,还与材料的制备工艺有关。     

磁流变液动密封实验研究

磁流变液是一种由铁磁性悬浮相、悬浮介质和添加剂组成的分散体材料,具有高的饱和磁化强度,在外磁场作用下能产生高的屈服应力,可用于旋转轴的较高压差密封.设计了一种旋转轴密封装置,该装置包括高性能的永磁体、导磁良好的极靴和旋转轴,注入自制的磁流变液,在轴转速8000r/min时能够密封的氢气压差达到0.3MPa.     

Development of magnetorheological finishing process for external cylindrical surfaces

The recent increase in demand for functional and technological requirements of the component results in the development of complex geometrical shapes and that too with close tolerances and fine surface quality. To fulfill the needs for finishing the external cylindrical surfaces such as groove, taper, step surfaces, and threads, an advanced finishing process based on magnetorheological (MR) fluid has been developed. The developed process can finish the external cylindrical surfaces with controlled magnetic field as likely similar to turning operation. Fine finishing of external cylindrical surfaces is a significant requirement in many functional applications. The wide applications of this present process can be valuable in automotive, machine tool production, valves manufacturing, and aerospace. A modified new MR finishing tool with flat and curved tip surface has been made to perform finishing on external cylindrical surfaces. The present cylindrical finished workpiece is useful in macaroni manufacturing machine. The surface roughness values Ra, Rq, and Rz are reduced to 54.41%, 51.65%, and 40% with flat tool tip surface and 80.88%, 81.32%, and 82.5% with curved tool tip surface in 90 min of finishing time. The overall results reported that the present process with curved tool tip surface is comparatively more useful in finishing the external cylindrical surfaces.     

磁流变液的流体动力学理论

在外加磁场作用下,磁流变液从牛顿流体变成了Bingham体,超过屈服应力开始流动,其的流变性(弹性、塑性、粘性)、磁化性、导电性、传热性以及其它的机械性质和物理学性质皆发生显著的改变.研究磁流变液在外加磁场作用下,流场分布规律随磁场强度变化的动态特性,建立磁流变液的流体动力学理论,对开发和设计磁流变器械至关重要.本文运用物理学和流体力学的基本理论,结合本构方程,考虑磁场对磁流变液的流动的影响,建立了磁流变液力磁耦合的流体动力学模型,给出了描述磁流变液流动的基本方程组.     

实用型磁流变体材料研究

研究了基液和添加剂对磁流变体的温度稳定性、润滑减磨性及磁流变性能的影响规律。实验结果表明采用合理的基液和添加刑复合工艺制备的磁流变体材料,最低使用温度达-40℃。0．5T磁场下剪切应力值达56kPa,且具有良好的润滑性能和抗沉降团聚稳定性能。     

A new magnetorheological finishing process for ferromagnetic cylindrical honed surfaces

In today’s industries, the internal surface finishing of cylindrical objects is highly demanded to improve their functional performance in various engineering applications. During the traditional honing operation, the finishing forces produced by abrasives on the workpiece surface are not easily controllable and also produce various surface defects. Therefore, to further improve the surface integrity of the traditionally cylindrical honed surface made of ferromagnetic or non-ferromagnetic materials, a new magnetorheological (MR) finishing process has been used with a controlled magnetic field. The experimentation is performed on the honed surface made of gray cast iron, which is generally used as a cylinder liner. The percentage change in surface roughness values, i.e., Ra, Rq and Rz, reduced by 77.44%, 70.16% and 72.16%, respectively, with better improvement in surface after 90 minutes of finishing. The experimental results demonstrated the effectiveness of present process for improving the functional applications of ferromagnetic cylindrical honed surface after removing the various surface defects such as deeper grooves, honing grooves with shaper edges, torn and folded metals, and cavities or holes. The applications of new MR finishing process can also be useful in the internal finishing of injection barrel of a molding machine, cylindrical molds and dies, hydraulic cylinder, etc.     

磁流变抛光液的研制

磁流变抛光是近十年来新兴的一种先进光学制造技术。首先简要介绍了磁流变抛光的抛光机理，然后对在磁流变抛光中起重要作用的磁流变抛光液的组成，流变性和稳定性进行了研究。在外加磁场强度高于318kA/m时，磁流变抛光液的剪切应力大于20kPa，该应力足以完成磁流变抛光，最后给出一个磁流变抛光的实例，证明了磁流变抛光液的实用性，实验中磁流变抛光的最大材料去除率约为0.2μm/s.     

Analysis of particles in magnetorheological polishing fluid for finishing of ferromagnetic cylindrical workpiece

Magnetorheological honing process is developed for nanofinishing of internal surfaces of ferromagnetic and non-ferromagnetic cylindrical objects. The process makes use of smart fluid called magnetorheological (MR) polishing fluid for finishing which has a property to become stiff in the existence of magnetic field. The smart MR polishing fluid is made with the ingredients of carbonyl iron (CI) particles, abrasive particles, and base fluid. Direct current given to the electromagnet coil engenders magnetic field on finishing tool surface. Magnetic force acts on magnetic CI particles which further exert the repulsive force on nonmagnetic silicon carbide (SiC) abrasive particles and performs finishing when tool rotates as well as reciprocates inside the cylindrical workpiece. The CI and SiC particles present in MR polishing fluid are magnetically simulated and analyzed using finite element (FE) analysis. The distribution of magnetic flux density and magnitude of magnetic force acting on CI particles are analyzed through FE analysis. It is found that the CI particles which are available adjacent to the active abrasives are major responsible for indenting the active abrasive particles into workpiece surface. Also, the effect of finishing tool surface areas and particles size on the strength of chains of CI particles in MR polishing fluid have been analyzed.     

Synthesis of polishing fluid and novel approach for nanofinishing of copper using ball-end magnetorheological finishing process

Ball-end magnetorheological (MR) finishing process utilizes the magnetically controlled stiffened ball of an MR fluid for finishing purposes. Copper is a mechanically soft and chemically reactive material, so it is difficult to finish up to the nanometer-order level by traditional and most of the advanced finishing processes. In this research work, the problems associated with ball-end MR finishing of copper have been explored and a fluid composition suitable for the finishing of copper has been developed. A novel approach using two opposite magnetic poles has been used to enhance the magnetic flux density distribution between the tool tip and the copper workpiece surface. The same has been magnetically simulated and verified experimentally. The effect of fluid composition parameters has been analyzed by the statistical model developed by response surface. After 30 minutes of finishing time, a nano-finished surface with very few shallow scratches was achieved.     

磁流变阻尼器管道流动特性研究

磁流变阻尼器是一种应用广泛的磁流变器件,其利用磁流变液独特的磁流变效应的工作.然而,磁流变体阻尼器设计中,一般地将磁流变液作为粘性流体建立流动的力学模型,进行流动分析以及参数设计,这样设计的结果与实测出现了较大的误差.本文将磁流变体作为一种粘塑性流体,建立了描述磁流变液流动的力学场和电磁场耦合的流体动力学基本方程组,分析研究了磁流变阻尼器沿狭长管道流动的特征,为磁流变阻尼器的设计提供了可靠的理论基础.     

软性沉降磁流变液的研制及性能实验研究

首先从磁性颗粒的沉降状态出发,提出了磁流变液软性沉降的概念及形成途径;而后在此基础上,研制成功了两种以OP乳化剂和有机粘土为触变剂的、具有软性沉降特征的磁流变液;最后探讨了两种添加剂的作用机理。