基于双盘直槽研磨的圆柱滚子自转运动研究

为了解决双盘直槽研磨方法实施过程中的关键技术问题,针对圆柱滚子在研磨状态下的自转运动展开相关研究.首先,对圆柱滚子在研磨状态下的自转运动进行理论分析,得到了其稳定自转的条件.然后,基于ADAMS(automatic dynamic analysis of mechanical systems,机械系统动力学自动分析)软...     

固结磨料研磨SiC单晶基片(0001)C面研究

碳化硅(SiC)单晶基片已广泛应用于微电子、光电子等领域.本文针对传统游离磨料研磨加工的缺点,提出了固结磨料研磨SiC单晶基片技术,以前期研究的SiC单晶基片研磨膏配方,试制了一系列固结磨料研磨盘,研究了固结磨料研磨SiC单晶基片(0001)C面时的材料去除率、表面粗糙度及平面度,并与游离磨料研磨进行了对比.结果表明,固结磨料研磨后样品表面有深度较浅的划痕,游离磨料研磨后表面没有划痕,但表面呈凹坑状;游离磨料研磨后工件表面粗糙度轮廓最大高度Rz远大于固结磨料研磨;固结磨料研磨的材料去除率高于游离磨料,固结磨料研磨后的表面粗糙度Ra远低于游离磨料研磨,固结磨料研磨可提高平面度;研究结果可为进一步研究固结磨料化学机械研磨盘、固结磨料研磨工艺参数及机理提供参考依据.     

纳米蒙脱石填充PTFE和UHMWPE的摩擦磨损性能

用纳米蒙脱石(nano-MMT)对聚四氟乙烯(PTFE)和超高分子量聚乙烯(UHWMPE)进行填充改性,在往复式滑动摩擦试验机上进行摩擦磨损实验,用扫描电镜观察了材料摩擦表面形貌.结果表明:nano-MMT可以提高PTFE和UHWMPE材料的耐磨性,而PTFE基和UHWMPE基复合材料的摩擦系数无明显增大.与UHMWPE相比,nano-MMT更能提高PTFE基材料的耐磨性;nano-MMT/PTFE复合材料比nano-MMT/UHMWPE复合材料具有更低的摩擦系数和更好的导热性;纯PTFE、纯UHWMPE和10%nano-MMT/PTFE复合材料磨损机理主要为粘着和犁沟效应,而10%nano-MMT/UHWMPE复合材料表现为犁沟和疲劳机制.     

基于双平面轨迹均匀法的高精度圆柱滚子加工方法研究

针对目前超精密圆柱滚子加工精度和一致性很难保证的问题,提出了利用行星式双平面研磨方式进行圆柱滚子的加工方法。同时对该方法的加工原理进行分析以及对保持架进行了模态仿真。在研究了圆柱滚子双平面加工运动轨迹基础上,发现靠近研磨盘中心以及研磨盘边缘的轨迹线分布比较集中,而靠近研磨盘中间环带部分的轨迹线分布较为均匀。据此设计并加工了实验装置,采用基于双平面轨迹均匀方法进行超精研磨和抛光。实验研究表明,工件的圆度误差达到了0.295μm,批直径变动量达到了1μm,表面粗糙度Ra达到了0.054μm,圆柱滚子的表面质量可以达到镜面级别,微观加工纹路具有多向性。公差等级达到了国家标准0级要求。     

研磨手机屏幕玻璃用新型树脂研磨垫的磨料选择

选用两种不同粒度的RVD金刚石原生料和破碎料,分别与树脂结合剂混合制成新型研磨垫用来加工手机屏幕玻璃。考察了金刚石磨料的种类和粒度对研磨切削力、研磨盘耐磨性及研磨后的玻璃表面粗糙度的影响,并分析了不同研磨表面的微观形貌。结果表明:随金刚石粒度的减小,金刚石研磨盘的切削力降低,耐磨性也有所下降,但玻璃产品表面平均粗糙度降低,表面质量较好;相同粒度下两种金刚石相比较,金刚石原生料研磨手机屏幕玻璃可获得较好的磨削效果。     

石墨和铜粉分别填充聚四氟乙烯摩擦学性能比较

将石墨和铜粉分别填充聚四氟乙烯制备两种复合材料,并对材料的结构进行分析,在干摩擦条件下通过M-2000A型磨损试验机对其摩擦磨损性能进行测试。结果表明:两种填充物改变了聚四氟乙烯结构,均提高了聚四氟乙烯的硬度和耐磨性能。石墨与聚四氟乙烯摩擦过程协同作用使得石墨填充聚四氟乙烯复合材料比纯聚四氟乙烯表现出更低的摩擦系数,聚四氟乙烯材料的耐磨性不仅与硬度有关,还与填充物的润滑性能有关。     

碳纤维改性聚四氟乙烯的摩擦及振动性能

文中研究了20%的碳纤维(体积分数)改性聚四氟乙烯在干摩擦和水润滑摩擦条件下的摩擦系数、磨损性能和摩擦振动性能。结果表明:(1)在干摩擦下,随着线速度增加,摩擦界面生成大量的热,黏着磨损和磨粒磨损严重,表面越来越粗糙,摩擦系数明显变大,摩擦振动加速度增加。而在水润滑条件下,随着线速度增加,摩擦界面间形成了一层水润滑膜,使摩擦系数降低,另外由于转速增加,使流噪声增加,从而使振动增加。(2)在干摩擦下,随着比压增加,摩擦系数和摩擦振动变化较大,而在水润滑条件下,随着比压增加,摩擦系数和摩擦振动变化较小。(3)干摩擦时,碳纤维增强聚四氟乙烯复合材料在不同比压下的磨损机理主要是磨粒磨损和黏着磨损;水润滑条件下,碳纤维增强聚四氟乙烯复合材料在高比压下的磨损机理主要是黏着磨损。因此,碳纤维改性聚四氟乙烯复合材料应该在水润滑条件下应用有利于提高耐磨性,降低摩擦系数和摩擦振动。     

三维网络结构Al2O3陶瓷/高铬铸铁复合材料干摩擦磨损性能

采用往复式滑动摩擦磨损（SRV）试验机研究了高铬铸铁及三维网络结构Al₂O₃陶瓷增强高铬铸铁复合材料的干摩擦磨损性能,测量了高铬铸铁和Al₂O₃陶瓷/高铬铸铁复合材料在不同摩擦频率及载荷下的摩擦系数和磨损率;用扫描电镜观察磨损表面形貌,并分析了三维网络Al₂O₃陶瓷对复合材料磨损机制的影响。结果表明：陶瓷Al₂O₃与高铬铸铁基体之间具有良好的界面结合,复合材料的摩擦系数随摩擦频率和载荷的变化保持稳定,耐磨性远优于高铬铸铁,而且随着摩擦频率和载荷的增加,Al₂O₃陶瓷/高铬铸铁复合材料的抗磨损性能明显提高,这是由于复合材料中Al₂O₃与高铬铸铁相之间三维空间结构和良好的界面结合有利于摩擦载荷的传递;三维Al₂O₃陶瓷骨架在磨损表面形成硬的网络突体并起承载作用,能有效保护金属基体;磨损机制为氧化磨损及磨粒磨损共同作用。     

温度对混杂纤维制动材料摩擦学性能的影响

利用JF150D-Ⅱ型摩擦试验机分析了所研制的轿车用混杂纤维盘式制动材料与灰铸铁在不同温度下滑动摩擦的摩擦磨损性能,并借助SEM观察材料形貌.研究结果表明以硅酸铝纤维、叶蜡石粉等无机材料为主要组元的新型混杂纤维制动复合材料,摩擦系数稳定,各温度下的磨损率也较低.各组元的磨损形式不同,硅酸铝纤维主要表现为脆断和磨料磨损;而钢纤维则表现为塑性流动和粘着磨损;树脂主要表现为热磨损.     

Fe3Al基摩擦材料的结构与摩擦磨损性能

采用热压烧结方法制备了一种适用于重载高速工况下的新型Fe3Al金属间化合物基摩擦材料,并对其微观结构、力学性能以及干滑动摩擦磨损性能进行了试验研究.结果表明,Fe3Al金属间化合物基摩擦材料密度低,强度高,摩擦系数高而稳定,高温耐磨性好.不同条件下摩擦磨损机制不同,轻载荷下主要是磨粒磨损和疲劳磨损,表现为微犁沟和凹坑;重载荷下摩擦初中期表现为严重塑性变形、裂纹扩展和疲劳断裂,摩擦后期以氧化磨损为主.     

含Nb高碳钢的组织及耐磨性能

采用金相显微镜、扫描电镜表征了含Nb高碳钢的显微组织,并采用MFT-3000型摩擦磨损试验机,在室温下研究了摩擦载荷、滑动速度及滑动时间对铸态高碳钢的摩擦性能的影响。结果表明,铸钢组织由莱氏体和珠光体组成,洛氏硬度为37.3HRC。随施加载荷、滑动速度的增加,磨损失重量增加;摩擦系数随载荷增加而降低,随滑动速度增加而增加,随滑动时间的延长先增加后趋于稳定。磨损机制是以粘着磨损为主的粘着与磨粒磨损的混合磨损,高速、长时间滑动时,还存在明显的氧化磨损。     

Loose abrasive lapping hardness of optical glasses and its interpretation

We present an interpretation of the lapping hardness of commercially available optical glasses in terms of a micromechanics model of material removal by subsurface lateral cracking. We analyze data on loose abrasive microgrinding, or lapping at fixed nominal pressure, for many commercially available optical glasses in terms of this model. The Schott and Hoya data on lapping hardness are correlated with the results of such a model. Lapping hardness is a function of the mechanical properties of the glass: The volume removal rate increases approximately linearly with Young's modulus, and it decreases with fracture toughness and (approximately) the square of the Knoop hardness. The microroughness induced by lapping depends on the plastic and elastic properties of the glass, depending on abrasive shape. This is in contrast to deterministic microgrinding (fixed infeed rate), where it is determined from the plastic and fracture properties of the glass. We also show that Preston's coefficient has a similar dependence as lapping hardness on glass mechanical properties, as well as a linear dependence on abrasive size for the case of brittle material removal. These observations lead to the definition of an augmented Preston coefficient during brittle material removal. The augmented Preston coefficient does not depend on glass material properties or abrasive size and thus describes the interaction of the glass surface with the coolant-immersed abrasive grain and the backing plate. Numerical simulations of indentation are used to locate the origin of subsurface cracks and the distribution of residual surface and subsurface stresses, known to cause surface (radial) and subsurface (median, lateral) cracks.     

Effect of load on tribofilms at the contact interface under dry sliding conditions at 500 °C

This paper presents a study of the effect of load on the retention of the tribofilms formed at the interface of a dry sliding contact between exhaust valve material, Nimonic alloy (N 80A) and valve‐seat material, ductile cast iron (GGG‐40), at a temperature of 500 °C. The role of tribofilms in influencing friction and wear behaviour at elevated temperature is highlighted. Reciprocating pin‐on‐disc experiments were conducted using a hemispherical shaped pin sliding against a flat disc at 20 Hz oscillating frequency, 2 mm stroke at loads of 20 N to 50 N. Low coefficient of friction, in the range of 0.13 to 0.15, was observed at loads up to 40 N whereas at a load of 50 N, the average coefficient of friction increased to 0.29. Optical and scanning electron micrographs with energy dispersive spectroscopy analysis indicate evidence of formation and retention of well compacted and strongly adhering tribofilms at loads up to 40 N. At 50 N, even though more abrasive wear is seen, initial deterioration and subsequent reforming of the tribofilms with increasing sliding time is observed. Overall, more wear was observed for the valve‐seat material as compared to the valve material. Raman spectroscopy primarily indicates the presence of hematite on the worn surfaces at loads of 20 N to 40 N, whereas magnetite presence is strongest at the highest load of 50 N. Increase in tribofilm hardness was observed with increase in contact load whereas the thickness of the tribofilm was not significantly affected by the contact load.     

聚丙烯腈填充聚四氟乙烯复合材料摩擦磨损性能研究EI

用机械共混、冷压成型和空气中烧结的方法制备了不同质量分数的聚丙烯腈填充聚四氟乙烯制品。用MM-200摩擦磨损试验机测试不同样品在干摩擦下的摩擦学行为;用扫描电子显微镜和光学显微镜对几种样品的磨损面、磨屑和转移膜进行观察和分析。结果表明,聚丙烯腈的加入,不但使聚四氟乙烯的磨损量大幅降低,而且还使其摩擦系数有所降低。通过扫描电子显微镜观察发现填充聚丙烯腈的聚四氟乙烯样品的对磨面有完整而且不易脱落的转移膜,这是其具有良好耐磨性的主要原因。     

Tribological investigations of polyetherimide composite

Polyetherimide (PEI), commercially known as ULTEM and manufactured by GEC (USA), is one of the newest high-performance thermoplastics. Its graphite and short-glass-fibre (GF) filled composition was evaluated for friction and wear properties. Tribological studies of the material sliding against mild steel, under different loads, counterface roughnesses and sliding distances were performed on a pin and disc configuration. It was observed that this composite displayed very good wear resistance due to glass-fibre reinforcement and low friction due to the solid lubricant graphite. The wear mechanism was studied with scanning electron microscopy by observing the worn pin and disc surfaces. Fatigue was observed to be the main factor in wear, along with adhesive and abrasive modes.     

Grinding process for beveling and lapping operations in lens manufacturing

A grinding process that uses loose abrasives for the beveling of lenses is presented. Determination of the parameters of grinding tools with loose abrasives for beveling applications with various optical elements is discussed. The process of grinding with loose abrasives for a lapping operation is analyzed by examination of the influence of optical glass material parameters on material removal and surface roughness for lens manufacturing conditions. The model established for this analysis uses the concept of lateral fracture, which is based on removal of optical glass material by rolling abrasive particles. The particles remove material by lateral cracking. The abrasive mineral Barton Garnet was used in the lapping experiments. Under specific large-diameter lens manufacturing conditions, lapping time values at the conventional removal depth have been obtained for various optical glasses.     

金属填充PTFE复合材料的摩擦磨损性能研究

利用ＭＨＫ－５００型环块磨损实验机,对金属Ｃｕ、ｐｂ及Ｎｉ填充改性的ＰＴＥＦＥ复合材料在干摩擦条件下与ＧＣｒ１５轴承钢对摩时的摩擦磨损性能进行了系统研究,并利用ＪＥＭ－１２００ＥＸ／Ｓ分析电子显微镜和光学显微镜对ＰＴＥＥ复合材料的磨屑及摩擦磨损表面进行了考察。摩擦磨损实验的结果表明,金属填料Ｃｕ、Ｐｂ及Ｎｉ大大改善了ＰＴＦＥ复合材料的耐磨性,ＰＴＦＥ复合材料的磨损量比纯ＰＴＦＥ降低了１－２个数量级     

改性聚酰亚胺摩擦磨损性能的研究

论述了不同含量的聚四氟乙烯对聚酰亚胺(P I)/聚四氟乙烯(PTFE) 复合材料摩擦磨损性能的影响。研究结果表明, PTFE 的加入可有效地改善P I 的摩擦磨损特性, 当PTFE 含量在10～20% 的范围内时, 可明显降低P I 的摩擦系数, 其磨损特性主要表现为磨料摩擦和粘着磨损。在P I中添加不同含量的PTFE 的比较结果为: 当PTFE 含量为20% 时, 复合材料的综合性能最佳。      

硅线石填充双马来酰亚胺摩擦学性能的研究

用Ｍ－２００型试验机在干摩擦条件下考察了硅线石单独填充双马来酰亚胺（ＢＭＩ）和硅线石与聚四氟乙烯（ＰＴＦＥ）共同填充ＢＭＩ两类复合材料的摩擦学特性。结果表明，适量的Ｓａ能降低ＢＭＩ的摩擦系数和磨损量，但会在对偶件上造成划伤，ＰＴＦＥ与Ｓａ共同填充ＢＭＩ，不仅能进一步降低复合材料的μ和磨损量，而且能有效地抑制对偶件上的划伤，经过分析，Ｓａ填充ＢＭＩ的复合材料，对磨时其表面较高的粗糙度和Ｓａ硬粒子友承