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。     

硬盘巨磁电阻磁头的超精密抛光工艺

硬盘巨磁电阻磁头的抛光可分为自由磨粒抛光和纳米研磨,在自由磨粒抛光中,精确控制载荷和金刚石磨粒的粒径,可以避免脆性去除实现延性去除。通过控制抛光过程中的抛光盘表面粗糙度、金刚石粒径大小及粒径分布和载荷等进行滚动磨粒和滑动磨粒比例的调控,获得较好的磁头表面质量和较高的材料去除率。在自由磨粒抛光阶段,先采用铅磨盘抛光,然后用锡磨盘抛光,以纳米研磨作为最后一道抛光工序对磁头表面进行研磨,获得了亚纳米级粗糙度的磁头表面。用两种工艺制作的纳米研磨盘进行加工,分别获得了0.37nm和0.8nm的磁头表面粗糙度,去除率分别为5.3 nm/min和3.9nm/min。     

石英玻璃超精密磨削加工的表面完整性研究

为了实现石英玻璃的高效低损伤超精密磨削加工,研究不同粒度金刚石砂轮磨削石英玻璃的表面和亚表面质量,建立表面粗糙度与亚表面损伤深度之间的关系模型。通过石英玻璃磨削试验研究400#、1 500#、2 000#和5 000#金刚石砂轮磨削石英玻璃的表面微观形貌、表面粗糙度及其亚表面损伤深度,分析相应的材料去除方式;基于压痕断裂力学理论分析脆性域磨削石英玻璃时工件表面微观形貌和亚表面微裂纹的形成机理,建立表面粗糙度PV值和亚表面损伤深度SSD之间的定量关系。研究结果表明:随着砂轮粒度的减小,石英玻璃磨削表面的凹坑、微裂纹、深划痕等缺陷逐渐减少,表面粗糙度Ra和PV以及亚表面损伤深度SSD均随之明显减小,从400#砂轮磨削表面的R_a 274.0 nm、PV 5.35μm和SSD 5.73μm降低至5 000#砂轮磨削表面的Ra 1.4 nm、PV 0.02μm和SSD 0.004μm。500#和1 500#砂轮磨削表面的材料去除方式为脆性断裂去除,2 000#砂轮磨削表面的材料去除方式同时包括脆性断裂去除和塑性流动去除,但以塑性流动去除为主,5 000#砂轮磨削表面的材料去除方式为塑性流动去除;脆性域磨削石英玻璃的表面粗糙度PV与亚表面损伤深度SSD之间满足SSD=(0.627～1.356) PV~(4/3)的数学关系。     

集群磁流变平面抛光加工技术

基于磁流变效应和集群原理提出集群磁流变效应平面抛光技术,对磁极排布方式、端面形状及其尺寸的磁场特性进行静磁场有限元分析优化,结果表明,选取圆柱平底磁极进行同向规律排布时容易形成由多个独立"微磨头"组成的柔性抛光膜,能实现加工表面与"微磨头"的实际接触面积最大化。通过设置"微磨头"尺寸及数量与工件的接触状态,对K9玻璃、单晶硅和单晶6H-SiC三种硬脆材料基片加工出弧形抛光带,试验验证集群磁流变效应抛光膜的集群特性。对加工表面与抛光盘表面之间的间隙、加工时间、磁感应强度和转速等集群磁流变平面抛光工艺参数进行试验优化,并采取优化工艺对三种硬脆材料进行30 min抛光,K9玻璃表面粗糙度从Ra0.34μm下降到Ra1.4 nm,单晶硅从Ra57.2 nm下降到Ra4 nm,单晶SiC从Ra72.89 nm下降到Ra1.92 nm,均能获得纳米级粗糙度表面。     

钇铝石榴石(YAG)和钆镓石榴石(GGG)外延衬底的超精密制备技术

根据YAG和GGG晶体的性质，研究制订出从晶体外圆滚磨、定向、切割到研磨、抛光及检验的一套工艺方法，其中抛光工序是最关键的工序。为了保证抛光表面精度、质量及抛光效率，将抛光工序分成三步，首先用W0．5金刚石在锡盘上初抛，然后在无纺抛光布上细抛，最后用胶体软磨料抛光液在无纺抛光布上精抛。被抛光表面粗糙度Ra≤8nm，经腐蚀法及外延生长检验表面无缺陷和损伤。     

氧化铝陶瓷基片高效减薄和超光滑抛光加工研究

对氧化铝陶瓷基片进行了系统的单面研磨抛光和双面研磨抛光试验,结果表明,单面研磨抛光相对双面研磨抛光具有明显的效率优势,获得单面研磨的优化条件为:研磨压力15.19 kPa,研磨转速40 r/min,研磨液流量10 ml/min,研磨液浓度8wt%;以粒度W40、W20和W5的金刚石磨料在优化工艺条件下进行粗研磨、半精研磨和精研磨,减薄加工获得表面粗糙度Ra0.12μm的研磨片,进而采用W0.5的SiC磨料进行单面抛光可以获得平均表面粗糙度Ra10 nm的光滑表面。     

化学气相沉积碳化硅平面反射镜的高精度超光滑加工

针对化学气相沉积碳化硅平面反射镜的材料特性与技术要求,制定了"传统研抛 离子束抛光"的工艺方法,并在一块口径为100mm的试件上进行了验证。首先基于加工效率和亚表面损伤选择合理的工艺参数,并采用磁流变抛光斑点法测量各道工序的亚表面损伤,并以此为依据规划下一道工序的材料去除量;然后分析抛光表面粗糙度的影响因素,在此基础上对抛光工艺参数进行优化,获得表面粗糙度均方根方差值为0.584nm的超光滑表面,并控制工件的面形误差;最后采用离子束抛光进行精度提升,使工件的低频和中频误差均大幅下降,最终工件的面形精度均方根方差值达到0.007λ(λ=632.8nm),表面粗糙度均方根方差值为0.659nm。     

单晶SiC基片的集群磁流变平面抛光加工

基于集群磁流变效应超光滑平面抛光理论及研制的试验装置,对单晶SiC基片进行了平面抛光试验研究。研究结果表明,金刚石磨料对单晶SiC基片具有较好的抛光效果;加工间隙在1.4mm以内抛光效果较好,30min抛光能使表面粗糙度值减小87%以上;随着加工时间的延长,表面粗糙度越来越小,加工30min时粗糙度减小率达到86.54%,继续延长加工时间,加工表面粗糙度趋向稳定。通过优化工艺参数对直径为50.8mm(2英寸)6H单晶SiC进行了集群磁流变平面抛光,并用原子力显微镜观察了试件加工前后的三维形貌和表面粗糙度,发现经过30min加工,表面粗糙度Ra从72.89nm减小至1.9nm,说明集群磁流变效应超光滑平面抛光用于抛光单晶SiC基片可行有效且效果显著。     

蓝宝石晶体双面研磨加工的实验研究

为了实现对蓝宝石晶体的高效低损伤研磨加工,对蓝宝石晶体的双面研磨加工表面粗糙度、研磨均匀性和亚表面损伤层的深度进行试验研究。采用280#碳化硼磨粒双面研磨(0001)面蓝宝石晶体,首先考察了研磨时间对材料去除速率、表面粗糙度的作用规律,根据蓝宝石晶体切割表面状态确定了双面研磨的加工余量,接着,通过WYKO粗糙度仪从微观上分析了蓝宝石晶体表面的研磨均匀性,最后应用纳米压入测试分析了亚表面损伤层的深度。实验结果表明：蓝宝石晶体经过120分钟的双面研磨加工后可以获得Ra0.523μm,Rt<6.0μm的表面,亚表面损伤层小于1μm。     

光学材料磨削的亚表面损伤预测

基于压痕断裂力学理论,建立了工件表面粗糙度与亚表层损伤深度的理论关系模型,用于预测磨削加工脆性光学材料引起的亚表层损伤深度.利用磁流变角度抛光技术检测了不同磨削加工工艺条件下亚表层的损伤深度,验证了理论模型的正确性.分析了加工工艺参数对工件表面粗糙度及亚表层损伤深度的影响规律,提出了提高材料去除率的磨削加工工艺方案.分析结果表明:脆性材料工件的亚表层损伤深度与工件的表面粗糙度呈非线性单调递增关系.工件亚表层损伤深度及工件表面粗糙度均随着切削深度和进给速度的增加而增加,随着主轴转速的增加而减小.对比实验结果与理论模型预测结果表明,提出的模型可以准确、无损伤地的预测磨削加工引起的工件亚表层损伤深度.     

Grinding damage of BK7 using copper-resin bond coarse-grained diamond wheel

Coarse-grained wheels can realize high efficient grinding of optical glass. However, the serious surface and subsurface damage will be inevitably introduced by the coarse-grained wheels. In this paper, the grinding damage of a copper-resin bond coarse-grained diamond wheel with grain size of 150μm was investigated on optical glass BK7. The wheel was first properly trued with a metal bond diamond wheel, then pre-dressing for the wheel and grinding experiments are carried out on a precision grinder assisted with electrolytic in process dressing (ELID) method. The surface roughness (Ra) of ground surface was measured using an atomic force microscope (AFM) and the surface topography were imaged by a white light interferometer (WLI) and the AFM. The subsurface damage level of ground surface was evaluated by means of both MRF spot method and taper polishing-etching method, in term of the biggest depth of subsurface damage, distribution of micro defects beneath the ground surface, the cluster depth of subsurface damage, relationship between subsurface damage (SSD) and PV surface roughness (SR), propagating distance and pattern of cracks beneath the ground surface. Experimental results indicate that a well conditioned copper-resin bond coarse-grained diamond wheel on a precision grinder can generate good surface quality of Ra less than 50nm and good subsurface integrity with SSD depth less than 3.5ε for optical glass BK7.     

细粒度金刚石砂轮超精密磨削硅片的表面质量

为实现硅片高质量表面的超精密磨削，研究了5000目、8000目和30 000目金刚石砂轮磨削硅片的表面质量。利用数学模型预测了硅片磨削表面的粗糙度Ra并对预测结果进行了试验验证，分析了硅片磨削表面的形貌特征；通过磨床主轴电机的电流变化对比分析了5000目、8000目和30 000目砂轮磨削过程中的磨削力变化趋势。研究结果表明：8000目砂轮磨削后的单晶硅表面粗糙度Ra小于10 nm,亚表面损伤深度小于150 nm,磨削过程中的磨削力稳定，磨削质量优于5000目砂轮，磨削过程的稳定性优于30 000目砂轮。     

电镀金刚石砂轮高效精密修整及熔融石英磨削试验研究

大尺寸光学玻璃元件主要采用细磨粒金刚石砂轮进行精密/超精密磨削加工,但存在砂轮修整频繁、工件表面面形精度难以保证、加工效率低等缺点。采用大磨粒金刚石砂轮进行加工则具有磨削比大、工件面形精度高等优点,然而高效精密的修整是其实现精密磨削的关键技术。采用Cr12钢对电镀金刚石砂轮(磨粒粒径151 μm)进行粗修整,借助修整区域聚集的热量加快金刚石的磨损,可使砂轮的回转误差快速降至10 μm以内。结合在线电解修锐技术,采用杯形金刚石修整滚轮对粗修整后的电镀砂轮进行精修整,砂轮的回转误差可达6 μm以内,轴向梯度误差由6 μm降至2.5 μm。通过对修整前后的金刚石砂轮表面磨损形貌成像及其拉曼光谱曲线分析了修整的机理。对应于不同的砂轮修整阶段进行熔融石英光学玻璃磨削试验,结果表明,砂轮回转误差较大时,工件材料表面以脆性断裂去除为主;随着砂轮回转误差和轴向梯度误差的减小,工件表面材料以塑性去除为主,磨削表面粗糙度为Ra19.6 nm,亚表层损伤深度低至2 μm。可见,经过精密修整的大磨粒电镀金刚石砂轮可以实现对光学玻璃的精密磨削。     

新型反应烧结碳化硅陶瓷的超精密磨削

介绍了一种可用作光学反射镜材料的新型反应烧结碳化硅。采用超精密磨床结合在线电解修整的磨削方法对新型反应烧结碳化硅进行磨削，研究了不同磨粒尺寸、不同结合剂以及不同形状砂轮对磨削面性状的影响，分析了磨削面微段差的形成机理。获得了表面粗糙度Ra=0．57nm的超平滑镜面。     

基于准布儒斯特角法研究抛光过程中光学材料的表面质量

光学硬脆材料在机械加工过程中不可避免地形成表面/亚表面损伤,对器件性能、使用寿命等具有至关重要的影响。相较于磨削、研磨两种前道工艺,抛光阶段材料的损伤逐渐减少至极其微量的程度,而最终残留的损伤将伴随材料的使用全周期,研究抛光阶段表面质量的变化过程对掌握抛光的工艺质量十分必要,但测量难度高。针对这一问题,本文在总结抛光阶段损伤形式的基础上,首先仿真分析了准布儒斯特角法检测表面质量的原理和优势,随后以Nd∶GGG激光晶体为研究对象,利用椭偏仪对不同抛光工艺下样品表面质量的变化进行了实验研究。通过与白光干涉法测量的表面形貌进行对比,准布儒斯特角偏移量和相位角变化曲线斜率准确地反映了抛光过程中表面质量的变化,展现了该方法的无损伤和高灵敏度特性,以及辅助研究抛光工艺的可行性。最后,对准布儒斯特角法在表面质量检测方面面临的问题进行了分析和展望。     

An association rule mining and maintaining approach in dynamic database for aiding product–service system conceptual design

Many previous researches on high-speed machining have been conducted to pursue high machining efficiency and accuracy. In the present study, the characteristics of cutting forces, surface roughness, and chip formation obtained in high and ultra high-speed face milling of AISI H13 steel (46–47 HRC) are experimentally investigated. It is found that the ultra high cutting speed of 1,400?m/min can be considered as a critical value, at which relatively low mechanical load, good surface finish, and high machining efficiency are expected to arise at the same time. When the cutting speed adopted is below 1,400?m/min, the contribution order of the cutting parameters for surface roughness Ra is axial depth of cut, cutting speed, and feed rate. As the cutting speed surpasses 1,400?m/min, the order is cutting speed, feed rate, and axial depth of cut. The developing trend of the surface roughness obtained at different cutting speeds can be estimated by means of observing the variation of the chip shape and chip color. It is concluded that when low feed rate, low axial depth of cut, and cutting speed below 1,400?m/min are adopted, surface roughness Ra of the whole machined surface remains below 0.3?μm, while cutting speed above 1,400?m/min should be avoided even if the feed rate and axial depth of cut are low.     

Subsurface crystal lattice deformation machined by ultraprecision grinding of soft-brittle CdZnTe crystals

Cd_0.96Zn_0.04Te (111) single crystals were ultraprecisely ground by #1500, #3000, and #5000 diamond grinding wheels, and the corresponding surface roughness Ra is 49.132, 18.746, and 5.762 nm. High-resolution field emission scanning electron microscope and transmission electron microscope were employed to investigate the surface and subsurface damage. After ultraprecision grinding by three kinds of diamond wheels, the subsurface can achieve ultra-low damage layer with thickness of 1–2 nm made of amorphous state material and lattice distortion layer. For the #1500 precision grinding, the subsurface damage is mainly multi-nanocrystal with diameter in the range of 5–20 nm. While for the #3000 precision grinding, the subsurface damage is made of amorphous state material containing nanocrystals with diameter mainly in the range of 2–5 nm, and the bending deformation is mainly conducted through dislocation pleat formation. For #5000 ultraprecision grinding, the subsurface damage is mainly amorphous state material, and nanocrystals with diameter in the range of 2–5 nm enrich adjacent to the ground surface. Moreover, the size of nanocrystal ground by #5000 diamond grinding wheel is mainly 2 nm. Fracture mechanism ground by #5000 diamond grinding wheel firstly turns onto thin amorphous state film, then fracture.     

Ultraprecision grinding of TiC-based cermet hemisphere couples

In aerospace industry, TiC-based cermet hemisphere couples are widely used as dry sliding bearing and gyro due to its high resistance to wear and heat. To enhance the grinding precision, this paper presents an ultraprecision grinding technique for machining TiC-based cermet hemisphere couples. The factors affecting the form and dimension accuracy of the hemisphere couples in ultraprecision grinding were analyzed theoretically. The optimization of grinding conditions and ground surface morphology of TiC-based cermets were investigated. In addition, the subsurface damage of ground TiC-based cermet hemisphere couples was observed by focused ion beam FIB. The research results show that position errors have more significant impact on concave in grinding of hemisphere couples. The TiC-based cermet ground surface revealed a smooth surface covered by micropits, traces, and reliefs because of the special material properties, and the surface roughness could be improved by the decrease of feed rate, while the different feed rates did not influence form accuracy. Finally, TiC-based cermet hemisphere couples with 16 nm surface roughness, 0.3 μm PV form accuracy, radius deviation of less than 3 μm, and subsurface damage depth of less than 2.5 μm were obtained.     

高速铣合金铸铁实验结果的稳健设计优化分析

针对高速切削新型合金铸铁类难加工材料时,因刀具磨损严重而导致刀具成本高的问题,采用成本较低的硬质合金刀具对Cr15Mo工件进行了铣削实验,研究了切削参数对切削力和表面粗糙度的影响,获得了可达到磨削加工效果（Ra=0.4 μm）的最佳参数组合,即切削速度vc=800 m/min,轴向切削深度ap=0.4 mm和进给量f=0.6 mm/r。基于稳健设计优化原理对实验结果进行了理论分析,研究结果表明：理论分析结果与实验结果具有很好的一致性,为同时实现高速、高质量和低成本加工的多目标参数优化方法提供了一种有效的途径。     

Theoretical model of brittle material removal fraction related to surface roughness and subsurface damage depth of optical glass during precision grinding

Brittle material removal fraction (BRF) is defined as the area fraction of brittle material removed on machined surface. In the present study, a novel theoretical model of BRF was proposed based on indentation profile caused by intersecting of lateral cracks. The proposed model is related to surface roughness and the subsurface damage (SSD) depth of optical glass during precision grinding. To investigate the indentation profile, indentation tests of K9 optical glass were conducted using single random-shape diamond grains. The experimental results indicate that the indentation profile is an exponent function. To verify the proposed BRF model, BRF, surface roughness and SSD depth of K9 optical glasses were investigated by a series of grinding experiments with different cutting depths. The experimental results show that BRF is dependent on surface roughness and SSD depth. The relationship between BRF, surface roughness and SSD depth is in good accordance with the proposed theoretical model. The proposed BRF model is a reasonable approach for estimating surface roughness and SSD depth during precision grinding of optical glass.