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.     

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。     

Junction like behavior in polycrystalline diamond films

We have successfully fabricated polycrystalline diamond rectifying junction devices on n-type (1 0 0) silicon substrates by Hot Filament Chemical Vapor Deposition (HFCVD) using methane/hydrogen process gas and trimethyl borate and trimethyl phosphite dissolved in acetone as p- and n-type dopants, respectively. Impedance spectroscopy and current-voltage analysis indicates that the conduction is vertical down the grains and facets and not due to surface effects. Electrical characteristics were analyzed with In and Ti/Au top metal contacts with Al as the substrate contact. Current-voltage characteristics as a function of temperature showed barrier potentials of 1.1 eV and 0.77 eV for the In and Ti/Au contacts, respectively. Barrier heights of 4.8 eV (In) and 4.4 eV (Ti/Au) were obtained from capacitance-voltage measurements.     

铝基结合剂金刚石制品的组织观察

为研究Ti、Ni、Co对铝基结合剂性能的影响及结合剂对金刚石包裹情况,用热压烧结的方法制备了金刚石磨轮,采用扫描电镜研究了磨轮的断口形貌、结合剂与金刚石的界面结合以及元素的分布情况.研究表明:Al-Sn-Ti-Ni-Co是较好的结合剂体系,300℃烧结断口平坦,金刚石颗粒局部黏附有结合剂;Ti、Ni在结合剂中偏聚或形成独立相,可降低结合剂的塑性,改善结合剂的可磨削性;Co在结合剂中总体上分布均匀,有利于提高结合剂对金刚石的把持力.Al-Sn-Ti-Ni-Co结合剂对金刚石包裹较好,Ti、Ni、Co起到了改善结合剂性能的作用.     

Physical cutting model of Polyetheretherketone composites

This paper presents a study on the experimental physical model of the orthogonal cutting on the composite polyetheretherketone (PEEK) and PEEK CF30 (reinforced with 30% of carbon fiber). The objective of this study is evaluating the influence of the reinforcement on the chip thickness ratio (R), chip deformation (ε), friction angle (ρ), shear angle (), normal stress (σ) and shear stress (τ) under prefixed cutting parameters (cutting velocity and feed rate). The experimental physical model was compared with the Merchant equation.     

Ф25 mm PDC复合材料界面与复合机理研究

通过超高压高温烧结实验制备了典型界面结构的Ф25 mm PDC复合材料,通过扫描电镜观察分析了PDC样品纵断面上界面附近粘结元素Co的分布;通过剪切和淬火压溃实验测试了典型界面结构的Ф25 mm PDC界面结合强度和界面耐热性能;在实验观察分析的基础上进一步探讨了其界面的复合机理.研究结果表明随界面的钴含量增高,其结合强度从2.67 GPa增加到2.82 GPa,然后减小到1.47 GPa,但其耐热性能(即检测到样品分层开裂时淬火急冷次数)却分别从15次、11次降低至5次;粗晶粒(180#,80μm)界面结合强度和耐热性能分别为0.52GPa和7次,与细晶粒(W10,10μm)相比(2.67 GPa,15次)大幅度降低.这表明PDC材料界面性能不仅与界面钴含量及其存在状态有关,而且还与界面晶粒大小相关.     

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。     

MgO与Li2O摩尔比及烧结温度对结合剂及cBN磨具性能的影响

以ZnO-Na₂O-SiO₂-Al₂O₃-B₂O₃陶瓷体系为基础, 制备了添加不同摩尔比Li₂O和MgO的陶瓷结合剂及立方氮化硼(cBN)磨具。利用X衍射测试仪、线性热膨胀测试仪、扫描电镜等研究了MgO∶Li₂O摩尔比( M 值)和烧结温度对陶瓷结合剂及磨具性能的影响。结果表明: 随着 M 值增加, 结合剂的软化点温度增加, 耐火度及化学稳定性均增强, 线性热膨胀系数先增加后降低。当 M 值为0.67时, 随着烧结温度的升高, 石英晶相的析出被抑制, 诱导析出Mg(Zn)Al₂O₄晶相, 且含量逐渐增加, 尺寸先减小后增加; 当温度为870 ℃时, Mg(Zn)-Al₂O₄晶粒尺寸最小, 约为2 μm, 结合剂结构最为致密, 抗折强度达到最大值136.28 MPa。随着烧结温度的提高, cBN磨具气孔率和吸水率先降低后增加, 体积密度、硬度、抗折强度、磨耗比以及磨削效率先增加后降低; 当烧结温度为890 ℃, 磨耗比及磨削效率最高, 分别为98.72%和1.3675 g·min^-1。     

脱钴对聚晶金刚石热稳定性能的影响

本文介绍了一种在碱性电解液中电解聚晶金刚石内金属钴的方法。通过BSE观察到聚晶金刚石内金属钴的堆积方式有两种:大部分钴沿着金刚石颗粒边界延伸并包围金刚石颗粒,少量的钴团聚在一起,呈岛状堆积。EDS确定脱钴区域残余的钴含量为2.75%,而未脱钴区域的钴含量为13.45%,即79.5%钴在电解过程中溶解,且深度为170μm。模拟聚晶金刚石复合片在钻头胎体合金上面的焊接温度,对脱钴及未脱钴聚晶金刚石复合片进行热处理,用光学体式显微镜观察其表面的裂纹,采用XRD固定ψ法检测脱钴聚晶金刚石的残余热应力仅为241.46kg·mm-2,而未脱钴试样残余热应力值为2094.79kg·mm-2,即脱钴处理能有效降低聚晶金刚石复合片在下井使用前的热应力,使其残余热应力降低至原来的1/10。     

两段成长法改善微波电浆辅助化学气相沉积多晶金刚石之品质

以化学气相沉积法成长多晶金刚石薄膜时,薄膜的品质会受到成长时间、成长压力、反应气体比例、偏压与否及成核的机制等因素影响.研究采用微波电浆辅助化学气相沉积(MPECVD)法,以甲烷(CH4)和氢气(H2)作为反应气体原料,在P型(111)硅基板沉积多晶金刚石薄膜.典型沉积多晶金刚石薄膜的制程可分为四个阶段:抛蚀表面阶段、渗碳阶段、偏压增强成核(BEN)阶段及成长阶段.研究将成长阶段划分为两个阶段,第一阶段压力较低(成长Ⅰ阶段),第二阶段压力较高(成长Ⅱ阶段).结果表明:第一阶段可大大改善金刚石薄膜的品质,所获多晶金刚石薄膜的晶粒具有明确的颗粒边界、较低的碳化物或缺陷,电导率急剧降低,显现出本徵金刚石半绝缘的性质.可以认为金刚石薄膜品质的改善完全为低压成长所致.实验发现在成长Ⅰ阶段或成长Ⅱ阶段施加偏压时,只会降低多晶金刚石薄膜的品质.     

碳化钨粉末对聚晶金刚石复合片钻头胎体组织与力学性能的影响

以铸造碳化钨粉末混合镍粉作为骨架粉末,采用无压浸渍工艺制备了聚晶金刚石复合片（PDC）钻头胎体材料。研究了碳化钨的粉末粒形、粒度及质量分数对PDC钻头胎体的微观组织和力学性能的影响。结果表明,碳化钨的粉末粒形、粒度及质量分数是影响胎体微观组织和力学性能的重要因素。与破碎碳化钨相比,粉末粒度适中的球形碳化钨作为骨架制备的胎体组织更均匀、更致密,胎体的力学性能明显提高。采用150~180 μm的球形碳化钨混合13wt%的镍粉作为骨架粉末制备的胎体力学性能优于石油天然气行业标准SY/T 5217—2000,其硬度、冲击韧性和抗弯强度分别为HRC 34、6.7 J/cm2和820 MPa。      

GRINDING OF NICKEL-BASED SUPER-ALLOYS AND ADVANCED CERAMICS

This paper studies grinding of Inconel 718, Hastelloy, and some advanced ceramics. A newly developed ultra-high-speed grinding machine and a conventional grinding machine were used for the experiments. The ultra-high-speed grinding machine is equipped with a specially designed and built spindle unit that can run up to 200 m sec^-1 and deliver a maximum output of 12 kW. The surface roughness and residual stress values of the ground super-alloys and advanced ceramics were measured using a profilometer and a residual stress analyzer, respectively. The ground surfaces were also assessed using a scanning electron microscope. The effect of h_m (undeformed chip thickness) on surface topography of the difficult-to-machine materials was also investigated. A higher grinding wheel speed produces a smaller cutting depth and undeformed chip thickness, and thus smaller grinding force, decreased residual surface stress, and better surface finish. High productivity and good surfaces with ductile streaks could be obtained by employing ultra-high-speed grinding, even at very large wheel depths of cut such as 400 μm, without cross feed.     

Further investigations on the use of polycrystalline CVD diamond as a UV detector

Metal-semiconductor-metal planar structures were fabricated on free-standing diamond films. The devices were found to operate successfully as photodetectors for deep ultraviolet light with their response being dependent on the post-growth treatment. However, evidences of trapping were found both in the spectral photoresponse and temporal response to monochromatic light transients.     

Precision grinding of microarray lens molding die with 4-axes controlled microwheel

This paper deals with precision grinding of microarray lens (fly eye) molding die by using a resinoid bonded diamond wheel. An ultra-precision grinding system of microarray lens molding die and new truing method of resinoid bonded diamond wheel were developed. In this system, a grinding wheel was four-dimensionally controlled with 1 nm resolution by linear scale feedback system and scanned on the workpiece surface. New truing method by using a vanadium alloy tool was developed and its performance was obtained with high preciseness and low wheel wear. Finally, the microarray lens molding dies of fine grain tungsten carbide (WC) was tested with the resinoid bonded diamond wheel to evaluate grinding performance.     

基于VMD-PNN的砂轮钝化声发射检测

在磨削加工过程中,加工刀具即砂轮会发生钝化现象,砂轮表面磨损影响加工精度和工件质量,需要及时检测并修整.磨粒的塑性变形、破碎、断裂等会产生声发射信号,能够作为精确识别砂轮钝化状态的依据,且不易被噪声干扰,因此提出一种基于变分模态分解(Variational Mode Decomposition,VMD)和概率神经网络(...