基于双磁场磁性复合流体的抛光性能

目的 针对微结构抛光过程中形貌精度损伤的问题,开发一种环状MCF（Magnetic Compound Fluid,MCF）抛光工具,探究在双磁场作用下MCF工具的抛光性能。方法 采用工业相机观察不同条件下MCF抛光工具的成形特征,通过定量分析MCF抛光工具的成形参数,构建最优MCF抛光工具特征参数;通过分析双磁场作用下工件表面的磁场强度,建立磁场矢量模型,探究磁场分布与MCF宏观形貌的内在联系;观察磁簇微观形貌,分析MCF抛光工具的内部特征;试验研究MCF组分、磁铁转速nm、载液板转速nc和加工间隙Δ对工件表面粗糙度Ra的影响规律,探究最优的抛光参数。结果 当磁铁偏心距r=2 mm,MCF供应量V=1.5 mL时,MCF抛光工具的成形特征相对最优,得到了MCF抛光工具的参数,a=28.70 mm,b=26.90 mm,c1=1.58 mm,c2=1.30 mm,d0=48.60 mm,h=7.20 mm,di= 26.50 mm;磁簇分布方向与磁场矢量方向一致,铁粉沿着磁力线方向分布,磨粒分布在铁粉外部,α–纤维穿插于磁簇内部或磁簇与磁簇之间;通过抛光试验获得了较低表面粗糙度的最佳工艺参数,最佳MCF组分配比（均以质量分数计）为羰基铁粉40%、磨粒12%、α–纤维3%、水基磁流体45%,最佳载液板转速nc=300 r/min,最佳磁铁转速nm=400 r/min,最佳加工间隙Δ=1 mm。结论 在抛光20 min后,工件的表面粗糙度由0.578 μm降至0.009 μm,下降率约为98.44%,证明在双磁场作用下环状MCF抛光工具具有稳定且高效的抛光能力。     

十二烷基苯磺酸钠对磁性复合流体分散性及抛光质量的影响

目的 针对磁性复合流体(Magnetic Compound Fluid,MCF)中磨粒易团聚的问题,提出通过阴离子表面活性剂十二烷基苯磺酸钠(Sodium Dodecyl Benzene Sulfonate,SDBS)来提高MCF的分散性,进而提升抛光表面质量.方法 在MCF中添加不同质量分数的SDBS,采用激光粒度分...     

磁性复合流体对砷化镓晶片的超精密表面抛光

研究了磁性复合流体（MCF）浆料对砷化镓（GaAs）晶片表面纳米精密抛光的影响。通过混合CS羰基铁颗粒（CIPs）、Al₂O₃磨料颗粒、α-纤维素和磁性流体制备MCF浆料。首先,通过设计用于产生旋转磁场的MCF单元,建立了抛光装置。然后,对GaAs晶片表面进行了点抛光实验,以阐明MCF成分对不同抛光位置的表面粗糙度R_a和材料去除（MR）的影响。最后,使用含有不同直径颗粒的水基MCF浆料进行了扫描抛光实验。结果表明,在点抛光的情况下,水基和油基MCF处理后的初始表面粗糙度从954.07 nm分别降至1.02和20.06 nm。此外,MR的深度随着抛光时间的增加而线性增加。使用水基MCF的MR深度是使用油基MCF抛光的2.5倍。同时,抛光区的横截面轮廓显示出W型,这表明点抛光工件表面的MR不均匀。通过扫描抛光,抛光区的横截面轮廓显示出U型,这表明在给定的实验条件下,无论使用何种MCF,MR都是均匀的。使用含有直径为0.3 μm的磨粒的MCF能够获得R_a为0.82 nm的最光滑工作表面,同时MR速率为13.5 μm/h。     

磁性复合流体抛光氧化锆陶瓷的工艺优化

为提高氧化锆陶瓷工件的表面质量,采用磁性复合流体（由包含纳米级铁磁颗粒的磁流体与包含微米级羰基铁颗粒的磁流变液混合而成）对氧化锆陶瓷进行抛光,以达到降低材料表面粗糙度和减少表面与亚表面损伤的目的。利用田口方法设计3因素3水平正交试验,着重分析磁铁转速、加工间隙和抛光液磨粒粒径对表面粗糙度和材料去除率的影响规律,并采用方差分析法分析各因素对2个评价指标的影响权重。可达到最低表面粗糙度的工艺参数组合为：磁铁转速,300 r/min;加工间隙,0.5 mm;磨粒粒径,1.25μm。可达到最高材料去除率的工艺参数组合为：磁铁转速,400 r/min;加工间隙,0.5 mm;磨粒粒径,2.00μm。根据优化的工艺参数进行抛光,表面粗糙度最低可达4.5 nm,材料去除率最高可达0.117μm/min,优化效果显著。利用遗传算法优化BP神经网络建立抛光预测模型,预测误差为3.948 4%。     

直线型磁性流体行波泵仿真研究

磁性流体行波泵内填充磁性流体后,外加磁场对磁性流体在泵腔内的分布产生影响,同时由于磁性流体内磁性颗粒的存在对外加磁场也会产生影响,采用迭代解耦计算法分析直线型磁性流体行波泵中磁场和力场的耦合问题。在行波磁场的作用下,磁性流体会产生流动的现象,随着磁性流体饱和磁化强度的不断提高,磁性流体的流速也不断提高;随着磁场强度的增强,磁性流体的流量增大。泵腔中心线处的压强差最大,两侧处的压强差最小;泵腔中心线处的速度变化率最大,两侧处的速度变化率最小;相同的时间间隔内,泵腔中心线处的速度最快,向两侧处的速度逐渐降低,两侧处的速度最低。     

旋转型磁性流体行波泵仿真研究

以旋转型磁性流体行波泵为研究对象,理论分析了旋转磁场作用下磁性流体特性和压强的关系。通过磁场和力场解耦计算分析旋转磁场作用下磁性流体的运动特性、磁场特性以及与压强的关系。用实验验证分析计算的科学性和合理性。在旋转磁场的作用下,磁性流体行波泵内填充磁性流体后,外加磁场对磁性流体在泵腔内的分布产生影响,同时由于磁性流体内磁性颗粒的存在对外加磁场也会产生影响;磁性流体在泵腔内会产生流动的现象;随着磁场的不断增强,磁性流体的流量也不断增加。     

微小非球面碳化钨光学模具的磁流变抛光特性研究

超精密加工是光学模具获得高形状精度、表面精度和表面完整性的必要手段。通过实验比较抛光前后工件面形精度的PV值及RMS值来研究微小非球面碳化钨光学模具的磁流变抛光特性。结果表明:磁流变抛光技术对提高微小非球面碳化钨光学模具形状精度、表面精度等有较显著的作用。     

小口径非球面小球头接触式抛光及磁流变抛光组合加工

目的 为了提高非球面光学模具的表面质量和加工效率。方法 分析当前非球面超精密抛光方式及其特点,针对小口径非球面光学模具,提出一种小球头接触式抛光及磁流变抛光的组合加工方法,对小球头进行设计,并抛光碳化钨圆片,对比小球头接触式抛光及轴向、径向、水平方向磁极的永磁体球头的磁流变抛光的加工性能。分别对编号为1^#、2^#、3^#等3个相同轮廓形状的碳化钨非球面模具进行单一方式抛光试验和组合加工试验。结果 通过对小球头抛光碳化钨圆片的加工性能进行分析发现,接触式抛光小球头的去除率为926.5 nm/h,表面粗糙度达到4.396 1 nm;轴向、径向、水平方向磁极的永磁体小球头磁流变抛光的去除率分别为391.7、344.3、353.7 nm/h,表面粗糙度分别为1.425 2、1.877 6、1.887 5 nm。对采用组合加工方法抛光碳化钨非球面的有效性进行验证时发现,非球面1^#在单一接触式抛光60 min后表面粗糙度从8.786 6 nm降至3.693 2 nm;非球面2^#在单一磁流变抛光60 min后表面粗糙度从8.212 1 nm降至1.674 5 nm;非球面3^#在组合抛光方法下先进行15 min接触式抛光,再进行15 min磁流变抛光,表面粗糙度从8.597 2 nm降至1.269 4 nm,面形精度由175.2 nm提高到138.4 nm。结论 组合加工方法可以弥补单一抛光方法的缺陷,并能有效地提高工件的面形精度。与单一接触式抛光方法相比,组合加工方法获得的表面质量更好,抛光后表面粗糙度为1.269 4 nm,远小于单一接触式抛光下的3.693 2 nm;与单一磁流变抛光方法相比,组合加工方法更高效,将样件抛光到同等级别粗糙度所需时间从60 min减少至30 min。     

大问隙高转速条件下磁性流体密封性能的研究

通过实验研究了大间隙、高转速条件下磁性流体密封的规律，并对其进行了理论分析。另外还给出了改进大间隙条件下，提高密封性能的措施。     

扬声器用磁性流体

在FeCl3.6H2O、FeSO4.7H2O水溶液中加入强碱,通过调节pH值制备纳米粒径的Fe3O4磁粉,将磁粉均匀分散到有机溶剂中并加入表面活性剂,再分别均匀分散于聚a-烯烃和多元醇酯载液中,制备出聚a-烯烃和多元醇酯基两种扬声器用磁性流体。通过加入添加剂提高其化学和磁稳定性。用增粘剂调节其粘度、粘度指数和磁饱和强度,得到扬声器用磁性流体。通过在汽车高音扬声器中的应用,检测了该磁性流体在扬声器中的应用效果。     

磁流变液在磁场作用下基于铝的往复式摩擦特性(英文)

磁流变液被广泛地应用在汽车减震器、表面抛光和其他精加工处理中。讨论基于铝的磁流变液在磁场、不同的负载和振荡频率条件下的摩擦特性。在有、无磁场下对磁流变液基于铝的往返式摩擦特性进行评估。在不同荷载和振荡条件下分析实验条件与运动周期的关系。通过测量表面粗糙度和观察表面图像比较样品表面,并评估了磁流变液基于铝的往复摩擦特性。     

工件表面超声振动抛光方法发展概况

阐述了近几年来国内外对工件表面超声振动抛光加工和复合超声振动抛光加工研究的方法、原理及进展,并进行了对比分析。最后,指出了工件表面超声振动抛光的发展方向。      

Effects of pressure and shear stress on material removal rate in ultra-fine polishing of optical glass with magnetic compound fluid slurry

Optical glasses used in a range of industrially important optoelectronic devices must be polished to nano-level roughness for proper device operation. Polishing process with magnetic compound fluid slurry (MCF polishing) under a rotary magnetic field is an influential candidate for the method to precisely polish optical glass. MCF slurry has been successfully utilized to polish a variety of materials, ranging from soft optical polymers to hard optical glasses. MCF was developed by mixing a magnetic fluid and a magnetorheological fluid with the same base solvent, and hence includes not only μm-sized iron particles but also nm-sized magnetite particles. To elucidate the behaviour of material removal in MCF polishing, this study measured the normal and shear forces generated in the polishing zone during polishing. From these measurements, the distributions of pressure P and shear stress τ were obtained. The distribution of material removal rate (MRR) was investigated through spot polishing of borosilicate glass. The effects of three process parameters, namely magnet revolution speed, MCF carrier rotational speed and working gap, on pressure P, shear stress τ and the MRR were also investigated. The results revealed that P is higher near the centre of the interacting area (i.e. the polishing spot centre) and the point of maximum shear stress τ appears at about 5 mm from the polishing spot centre. All of P, τ and MRR are sensitive to MCF carrier rotational speed and working gap but insensitive to magnet revolution speed. Shear stress is more sensitive to these process parameters than the pressure. Cross-sectional profiles of the polishing spots exhibit a characteristic symmetric W-shape; material removals are minimal at the spot centre and maximal at approximately 8.2–10.2 mm from the spot centre depending on the process parameters. MRR is proportional to the MCF carrier rotational speed and is negatively correlated with working gap. An MRR model involving both the pressure and shear stress in MCF polishing is proposed. In the model, MRR is more dominated by shear stress than by pressure.     

纵向磁场作用下的旋转射流过渡的机理

介绍了纵向磁场作用下的旋转射流过渡的动态过程，分析了由于导电流体的旋转而引起的周向电流，以及由于周向电流与外加磁场的相互作用而产生的对熔滴过渡过程的影响。通过试验验证了外加磁场可以有效的控制高效MAG焊接的旋转射流过渡过程。在送丝速度45m／min，保护气体为80％，Ar 20%CO2，得到稳定性好、可控性好的旋转射流过渡，从而大大提高了焊接生产效率。实现了在连续大电流的区间获得稳定的无氦保护的低成本高效MAG焊接新工艺。     

金属液在旋转电磁搅拌器作用下的流动分析

对自行研制的电磁搅拌器中金属液的电磁场和流场进行数值模拟，并进行实验验证。结果表明：在旋转磁场搅拌器作用下，金属液中除存在横截面上的旋转离心流动外，还存在着纵向的大环流，但二者速度不同，前者比后者高出一个数量级：金属液表面的磁感应强度风与电流频率成反比，与输入的电压成正比：金属液所受电磁力的最大值与磁感应强度B0的平方成正比，与频率的n次方成反比，其中1／2≤n≤3／2：n与金属液的电阻率有关，电阻率越小则n越小：对于纯铝n为1／2，对于纯锡和纯铅n为1；金属液的转速与磁感应强度R0成正比，与金属液密度的平方根成反比。     

Modeling of contact behavior between polishing pad and workpiece surface

The polishing pad is one of the most significant components within a polishing system. It influences both the material removal rate and the surface finish. Furthermore, the wear behavior of the polishing pad is responsible for the shape accuracy. Nevertheless despite extensive research activity in recent years, there are still gaps of knowledge in terms of the working principle of a polishing pad. In this paper, the contact behavior of a polishing pad (polyurethane foam) with the workpiece surface is examined. For this, the polishing pad is modeled using a finite-element modeling (FEM) program and the deformation by pressing it against the rigid workpiece surface is investigated. Consequently, the local tensions are calculated, which are the basis for the penetration depth and therefore also for the material removal rate. The investigations presented in this paper were carried out within the research project SFB TR/4 funded by the German Research Association, Deutsche Forschungsgemeinschaft (DFG).     

Computation method of magnetic fluid in strong magnetic field

When the magnetic fluid lays in the magnetic field, interaction effects exist between them. Thus, the precise computation is considered as one of the precise methods of analyzing magnetic fluid in the magnetic field.Comparing with it, the linear computation will bring more error. The more error exists between the decoupled computation and the linear computation, the more saturation magnetization does on the border. Besides, the value of magnetic flux density is bigger when using the decoupled computation than that of linear computation. What's more,the equal magnetic flux density linear on the border varies slightly in the strong magnetic field when using the two computations. In a weaker magnetic field, the difference is bigger.     

Reliability of automatic eddy-current equipment with a rotating magnetic field

This paper presents a method for estimating the reliability of eddy-current nondestructive inspection by using the rotating magnetic field method. The results of the inspection are considered as memory-less stochastic processes, with the possibility of representation in a bi-dimensional space: ‘good product’ and ‘bad product’. The general formulae are calculated by using the master equation for the time behaviour of the probabilities, the numerical data used for results estimation being obtained by means of an automatic eddy current installation with rotating magnetic field. The samples used had 20 μm, 40 μm and 98 μm deep artificial faults, and the control speed ranged between 0.05 and 1 m s⁻¹.     

有限元法在旋转磁场磁粒研磨加工技术中的应用

磁场分布是影响磁粒研磨加工的重要因素之一，研究磁场分布的主要方法是数值计算法，本文介绍了旋转磁场磁粒研磨加工的基本原理，并用有限元法对旋转电磁场进行了计算，得到了一些重要结论。