精细陶瓷材料的金刚石砂轮磨削性能

本文探讨了精细陶瓷材料的金刚石砂轮磨削性能的共同特点以及不同种类陶瓷和不同磨削方式的影响。研究结果表明：陶瓷材料磨削时，砂轮磨损大，磨削比小，磨削力大、磨削效率低，磨后陶瓷零件使用寿命大大降低；必须根据陶瓷种类的不同选择不同的磨削方式。     

聚晶金刚石复合片表面裂纹视觉检测技术研究

采用计算机视觉检测技术提取出表面缺陷特征量,完成聚晶金刚石复合片表面裂纹缺陷检测。首先,根据聚晶金刚石复合片表面特性,研究合适的光源照明系统。然后,提出一种基于直方图投影梯度极值的局部边界提取方法,将感兴趣区域进行提取。在此基础上,采用图像滤波、阈值分割的方法实现裂纹的准确提取。最后,通过计算裂纹连通域的圆形度和长宽比进行裂纹识别。实验结果表明,本方法可有效地对聚晶金刚石复合片表面裂纹缺陷进行检测。     

Performance of Diamond and CBN Single-Layered Grinding Wheels in Grinding Titanium

For their unique properties, titanium alloys have found wide application in high-tech engineering. But these alloys are difficult to machine and to grind for their high chemical reactivity and poor thermal properties, which aggravate the grinding zone temperature and its detrimental effects. The objective of this article is a comparison of the grindability of Ti-6Al-4V regarding cubic boron nitride (CBN) and diamond brazed type monolayered grinding wheels under the influence of different environments. In grinding this alloy, cryogenic cooling did not help visibly for both CBN and diamond, but the application of oil and also of alkaline coolant significantly gave the best results.     

Ni对金刚石磨具陶瓷结合剂性能的影响

采用粉末冶金法制备了不同Ni含量的金刚石磨具陶瓷结合剂。通过SEM、EDS、XRD、TG-DSC、三点弯曲等分析方法对含Ni陶瓷结合剂的微观结构、结合界面、氧化性能以及抗折强度等性能进行分析,同时研究了含Ni陶瓷结合剂对金刚石润湿性的影响。结果表明,在实验范围内,Ni的加入对陶瓷结合剂耐火度及流动性影响不大,但降低了结合剂的烧成收缩;750℃烧成时,Ni与陶瓷结合剂界面结合紧密,界面形成合金化结合,提高了结合强度,抗折强度随着Ni的加入量先升高后降低,当Ni含量为15%(质量分数,下同)时达到最大值62.8MPa,较基础陶瓷结合剂提高了19.41%;Ni的加入能够改善高温状态下陶瓷结合剂对金刚石的润湿性,当Ni添加量为15%时,陶瓷结合剂对金刚石的润湿角为64°,比未添加Ni时的润湿角(84.5°)减小了24.3%。     

热压烧结工艺对金刚石陶瓷磨边轮胎体性能的影响

本工作研究了分段式和抛物线式两种通用热压烧结工艺对金刚石陶瓷磨边轮胎体性能的影响。结果表明,分段式热压烧结工艺制备的胎体密度和硬度高于抛物线式热压烧结工艺制备的胎体,但采用后者工艺制备的胎体强度较前者工艺提高约12%。采用分段式工艺烧结过程中镍、锰、锡与铜形成固溶体,并与骨架相的铁元素互扩散,在胎体中生成枝状富铁相,提高了胎体的合金化程度和致密度,胎体断口较平整,存在解理断裂和沿晶断裂。抛物线式热压烧结工艺胎体中生成较多铜基固溶体,少量铜和镍、锰扩散进入片状富铁相中,通过固溶强化和弥散强化作用提高了胎体强度,胎体断口呈粗糙剥离态。     

基于模糊C均值聚类算法的金刚石砂轮磨粒边缘检测

基于模糊C均值(FCM)聚类算法将金刚石砂轮表面检测数据划分成金刚石和结合剂两个类别,以数据的质心初始化聚类中心,用迭代的方法分别求出相应的最优聚类中心和隶属度矩阵,通过选取合适的隶属度阈值以及两个聚类中心的欧氏距离阈值来区分金刚石和结合剂,确定磨粒边缘。为验证方法的可行性,对多组数据进行检测,并用模拟的砂轮表面形貌对此方法进行了评定,评定结果与设定值误差不超过2.0%。     

Grain-Scale Modeling of CVD of Polycrystalline Diamond Films

The evolution of grain size, grain-size distribution, morphological and crystallographic texture, surface roughness, and the contribution of various surface facets to the growth of polycrystalline diamond films is performed by carrying out a series of two-dimensional computer simulations. The films are assumed to grow from a set of randomly oriented, {100}- and {111}-faceted nuclei by the motion of their vertices (the points where the adjoining facets of the same or neighboring grains meet). The vertex velocities are found to be a function of the orientation and the growth rate of the adjoining facets. To quantify the latter, a {100} to {111} growth-rate parameter is used. The results show that the evolution of the grain size and its distribution, surface roughness, morphological and crystallographic texture, and the portion of the film grown from different surface facets are all mutually linked and governed by the magnitude of the growth-rate parameter. The latter can be controlled by the CVD processing conditions, such as the substrate temperature, reactor pressure, mole fraction of carbon-source gas (e.g., CH₄, C₂H₂).     

Parametric Study of Temperature Distribution in Electrodischarge Diamond Grinding

Electrodischarge diamond grinding (EDDG) is a potential process for machining of advance engineering components, but there is no theory to support it. The work reported in this article makes an attempt in this direction. This article reports on determination of temperature distribution in the workpiece due to EDDG using the finite element method. The temperature distribution in the workpiece domain due to EDDG is obtained by superposition of the two temperature distributions for grinding and electrical discharge mechining (EDM) (i.e., 2D for grinding and axisymmetric for EDM). The effects of duty cycle, on-time, current, energy partition, time of machining, and feed velocity while machining are computationally investigated.     

评价金刚石刀具各向异性的周期键链模型

金刚石刀具机械研磨时会表现出很强的各向异性,因此寻找合适的模型来定量地描述该各向异性成为亟待解决的问题.通过深入分析金刚石刀具机械研磨的材料去除机理,使用周期键链(PBC)理论建立了定量描述金刚石刀具机械研磨各向异性的PBC模型.然后使用该模型对金刚石晶体的典型单形进行了晶面及其"好磨"和"难磨"方向的判定.在圆弧刃金刚石刀具研磨机上对{100}和{110}晶面进行了研磨实验,{110}晶面沿<100>方向研磨时最大塑性沟槽深度为19.8 nm,<110>方向为5.1 nm;{100}晶面<100>方向为9.8 nm,<110>方向为3.5 nm,与PBC模型的结论完全一致.最后,根据该模型和金刚石刀具使用中的磨损情况得到了优选的刀具晶面组合:前刀面和后刀面均选用{110}晶面.该PBC模型将为金刚石刀具的机械研磨提供有力的技术支持.     

砂轮机隔振与办公楼的降噪

针对砂轮机运转所带来的办公楼噪声严重的问题，应用振动测试分析方法，找到了砂轮机未正确采取隔振措施是引起办公楼内严重噪声的主要原因。根据隔振理论和实际情况，选择了合适的隔振垫并进行了合理的安装。测试和实际感受表明，取得了良好的减振降噪效果，成为工程降噪的一个成功实例。     

Grinding of Single-Crystal Silicon Using a Microvibration Device

This paper presents experimental results of grinding of single-crystal silicon using a microvibration device and a diamond grindingwheel. Samples were cut from (100) silicon. The grinding direction was parallel to the [110] direction of (100) silicon. These samples were ground under the same grinding conditions but with different vibration directions, frequencies, and/or amplitudes. The surface roughness and the surface texture of all samples were analyzed for comparison. The R_a, R_q, and R_t values and the microphotographs of the ground silicon surfaces showed the dependency of surface finish on the grinding with vibrations. Samples ground with vibrations had better surface finish compared with the silicon surfaces ground without vibrations. Out of the 12 experiments, the best surface finish was achieved when (100) silicon was ground with horizontal vibrations at a 70-Hz frequency and 6-μm amplitude perpendicular to the grinding direction.     

聚晶金刚石在硝盐浴中的溶解机理的研究

根据金刚石可溶于熔融的钾硝石、钠硝石和磷酸钠这一特性，提出用溶融的硝盐浴对聚晶金刚石进行溶解腐蚀加工，以解决ＰＣＤ表面加工困难的问题，通过对盐浴溶解前后聚晶金刚石薄片试样的表面成份和形态的分析，初步探索出聚晶金刚石在熔融硝盐溶中的溶解机理，是一个电化学腐蚀所控制的碳的氧化过程，从而为聚晶金刚石在熔融硝盐浴中的溶解建立了理论模型。     

Coefficients of the crack tip asymptotic field for a standard compact tension specimen

The coefficients of the crack tip asymptotic field of a standard compact tension (CT) specimen are computed using a hybrid crack element (HCE). It allows the direct calculation (without post-processing) of not only the stress intensity factor (SIF) but also the coefficients of higher order terms of the crack tip asymptotic field. Approximate closed-form expressions for the first five terms for the CT specimen that are accurate for shallow to very deep cracks are obtained by fitting the computed data. The SIF formula proposed by Brown and Srawley (1966) is shown to be accurate when the crack length to depth ratio () ranges from 0.35 to 0.75. The formula proposed by Newman (1974) and Srawley (1976) is accurate for 0.15. However, the accuracy of available formulas for the second T-term in the literature is quite disappointing. Numerical results also show that, unlike the notched three-point bend beam and the wedge splitting specimen, the second T-term of the CT specimen is always positive.     

New Trends in the Use of Transition Metal–Ligand Complexes for Applications in Electroluminescent Devices

The advantage of using phosphorescent transition metal–ligand complexes in optoelectronic applications such as organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs) are described and evaluated. Additionally, different device constructions utilizing phosphorescent transition‐metal complexes like iridium(III ) mixed‐ligand complexes and ruthenium(II ) systems are reviewed and specified. Diverse host materials in which the phosphorescent emitters can be placed are discussed, such as small organic molecules and a few polymeric systems, and alternative processing technologies are briefly compared. Recent developments in the synthesis of iridium(III ) triplet emitters are discussed. Different device architectures require different kinds of metal–ligand complexes. The different synthetic routes leading to charged and non‐charged complexes are briefly discussed.     

On the Accuracy of a New Displacement Instrumentation for Rotary Tablet Presses

The Portable Press Analyzer? (PPA; Puuman Oy, Finland), a commercially available instrumentation for rotary tablet presses, was tested for accuracy of determination of force and displacement. The calibration of the force transducers (strain gauges) was tested under a static condition. The calibration of the displacement transducers (plastic film potentiometer) was compared for static and dynamic recordings. Force measurement was found precise (deviation < 1.1%) after alterations in the calibration procedure. Displacement measurement was affected by punch tilting and the application of the transducers. If tilting of punches was not considered, the deviation of displacement measurement from the true value (using steel tablets as a reference) was found up to 110 μm. By modifying the original PPA system by supplementing additional displacement transducers in the adjacent turret positions of the punches and adding a custom electronic device (Tilting Compensation Device), the accuracy of distance measurement was improved to 18.1 μm (±3.64). Furthermore, machine and tooling deformation were recorded and found different under static and dynamic conditions. Correction of punch displacement for elastic deformation therefore should preferably be made from dynamic recordings.