International Journal of Abrasive Technology (13 papers in press)
An experimental study for evaluating speed parameters on surface roughness of LS-WEDT and its application in fabricating microelectrodes
by Yadong Gong, Yao Sun, Xiaoteng Ma
Abstract: The demand for microelectrodes has greatly increased with the micromaching techniques have become a hot issue in modern industry. The non-contact of EDM process makes it have the unique superiority in fabricating microelectrodes.Therefore,this paper proposed the low speed wire electrical discharge turning (LS-WEDT) method to fabricate microelectrodes. Firstly,the influence of speed parameters including the rotated speed (Vn), feeding speed (Vs) and wire speed (Vw) involved in LS-WEDT are discussed.More importantly,the microelectrode made of CuW70 material with diameter of 58μm is firstly and sucessfully fabricated by LS-WEDT. Futhermore,the scanning electron microscope observations disclosed that the microelectrode has good surface quality and high machining precision without ridges and bending.Besides, many small micro-voids with the diameter less than 1μm can be observed on the microelectrode surface. Finally,the energy dispersive spectrograph analysis suggested the presence of foreign elements including zinc and oxygen on the microelectrode surface machined by LS-WEDT.
Keywords: Low speed wire electrical discharge turnning; microelectrodes; speed parameters; CuW70; surface roughness.
Microcontact mechanism in silicon wafer self-rotating grinding based on force decomposition
by Qinglei Ren, Xin Wei
Abstract: Carrying out silicon wafer self-rotating grinding using a cup-type diamond grinding wheel is a typical ultra-precision machining technique of silicon wafers. Studying the mechanism of the self-rotating grinding is the basis of the processing. The research takes the microcontact between the micro-element in the grinding wheel and the silicon wafer extracted during the steady ductile-regime grinding as the object and builds a mechanical model. On this basis, the research investigates the microscopic mechanism of the self-rotating grinding using the force decomposition method. The force decomposition in the normal direction using the Hertz theory in contact mechanics and the cavity model obtained the distributions of the load and stress on the silicon wafer in the elastic and plastic phases, as well as the corresponding stress distribution on the micro-element in the grinding wheel. The force decomposition in the tangential direction based on the microscopic friction theory yields the sliding friction. The superposition of normal and tangential forces reveals the overall distribution of microcontact stress. The analysis results are validated by comparing with corresponding experimental and simulation results.
Keywords: Self-rotating grinding; silicon wafer; microcontact; micro-element in grinding wheel; diamond abrasive.
Characterization of microcrystalline diamonds deposited by HFCVD
by Tao Zhang, Feng Qin, Wanghuan Qian, Lijun Zhang, Fanghong Sun
Abstract: The performances of CVD microcrystalline diamond powders by the seeding and self-nucleation method, including the particle size composition, crystal morphology, and diamond purity, are evaluated by the China industry standard of conventional diamond powders (JB/T 7990-2012). The detection results show over 80 % particles grown on the seeds exhibit a cubo-octahedral with smooth surfaces and no obvious growth defects, while they can hardly meet the corresponding commercial requirements of particle size composition due to the existence of 10-23 % spontaneous particles (0.5~1.2 μm). For the powders deposited by self-nucleation method, the particle size composition agrees well with the model defined by the industry standard, and 70.5 % crystals exhibit the cubo-octahedral or icosahedron morphology, as well as their surface quality are little worse than the ones grown on the seeds due to unwanted secondary nucleation. Besides, the two types of CVD powders have a high purity detected by Micro-Raman Spectroscopy.
Keywords: microcrystalline diamond particles; morphology; particle size; hot filament CVD.
Simulation investigation into mechanics behavior in material removal process of ultrasonic assisted grinding of silicon carbide ceramics
by Jianguo Cao, Yueming Liu, Meng Nie, Qinjian Zhang
Abstract: Ultrasonic assisted grinding (UAG), due to its advantage in improving machining efficiency and work-surface quality, has been extensively employed in grinding of hard and brittle material. Grinding force and stress in the UAG process influence on the material removal behavior, however, they can not directly observed through the experiment, which finally hinder the understanding of the material removal mechanism of UAG. In this study, the simulation investigation of the material removal process, by ultrasonic-assisted scratching (UAS) of silicon carbide using a single abrasive grain in UAG process was conducted, to reveal the mechanics behavior. i.e., the grinding force and stress variation behavior. Conventional scratch (CS) without ultrasonic vibration was also carried out on the same condition for comparison. The results showed that (1) the UAS process the cutting forces undergo a periodic sinusoidal change, whereas those in the CS process are basically stabilized to a certain level after the tool cuts into the workpiece completely. (2) the investigations of the stress distribution on the cross and top surfaces along the cutting direction show that the stress fields on both surfaces become wider in the UAS process than in the CS process. (3) the kinetic energy of the grain consumed in UAS process is bigger than that in CS process, leading to the impact of the grain on the workpiece.
Keywords: SiC ceramics; ultrasonic vibration assisted internal grinding; grinding force; surface roughness; form accuracy; grinding efficiency.
High-speed high-efficient grinding of CMCs with structured grinding wheels
by Bahman Azarhoushang, Mohammadali Kadivar, Robert Bösinger, Sergey Shamray, Ali Zahedi, Amir Daneshi
Abstract: Ceramic Matrix Composites (CMCs) are counted as new materials which are widely applied in various engineering and technological fields owing to their superior properties. In spite of their remarkable properties, their implantation is limited due to their high machining costs as a result of high grinding forces and tool wear. To overcome mentioned problems, modified grinding wheels, one macro-structured by segmenting and another micro-structured (half lasered structured and half non-structured) were used in this study. The grinding tests were carried out at different material removal rates and cutting speeds. The grinding forces, generated surface roughness, and induced residual stress by means of grinding with the structured and non-structured wheels were compared. Reduction in the static cutting edges via wheel structuring resulted in a better performance of the grinding wheel through the reduction of rubbing and ploughing regimes. The grinding forces were respectively 30% and 20% lower in the case of segmented wheel and laser-structured wheel in comparison with the conventional grinding. In addition, the tensile residual stress can be reduced as a negative output of the grinding process via structuring. Moreover, a high-speed high-efficient grinding of CMCs without presence of surface damage was achieved by optimizing the process parameters. The material removal rate can be elevated without changing the grinding forces with application of the structured wheel.
Keywords: High speed high efficiency grinding; CMCs; Segmented wheel; laser-structure.
Experimental study on the characteristics of high speed cylindrical plunge grinding for annealed bearing steel 100Cr6
by Wei Liu, Zhaohui Deng, Zhouqiang Xiao
Abstract: The bearing steel such as 100Cr6 offers many desirable characteristics for industrial use in terms of its excellent qualities of high hardness, high wear resistance and high contact fatigue strength. For the usage in the bearing, cylindrical grinding should be adopted to machine 100Cr6. In order to ensure processing quality and processing efficiency, it is necessary to carry out high speed grinding. Therefore, the orthogonal experiments of high speed cylindrical plunge grinding (HSCPG) were carried out on the annealed 100Cr6 with a ceramic bonded cubic boron nitride (cBN) grinding wheel, to study the effects of grinding wheel speed, workpiece speed and grinding depth on the grinding force, grinding temperature, surface roughness, surface morphology, surface hardening and deteriorative layer. The study demonstrates that a larger material removal rate and a better surface integrity can be achieved simultaneously by a large grinding wheel speed, a moderate workpiece speed and grinding depth.
Keywords: Bearing steel; annealed 100Cr6; cylindrical plunge grinding; high speed; characteristics.
An experimental investigation on precision machining mechanism of carbon fiber reinforced polymer
by Xiaojiang Cai, Ruhao Zhou, Lifeng Shen, Hongliang Tang, Qinglong An
Abstract: With the rapid development of carbon fiber reinforced polymers (CFRP) as main aerospace structural materials, it is necessary to manufacture CFRP structural components for high dimensional accuracy by means of precision machining. In this paper, orthogonal cutting was used to investigate machining process and surface quality of CFRP materials for precision machining An intensive discussion was given about fiber orientation and cutting parameter range when machining CFRP for high accuracy application and optimized cutting method, including cutting speed, cutting depth, edge radius, fiber orientation, was obtained to reduce cutting force and surface roughness and get smooth surface topography. The cutting speed over 200m/min and small cutting depth slightly large than edge radius were advisable, the fiber direction 0~45
Keywords: carbon fiber reinforced polymers (CFRP); precision machining; cutting force; cutting speed; cutting depth; surface roughness; surface topography.
Effect of small quantity lubrication on grindability of hardened AISI 4340 steel
by Sirsendu Mahata, Joydip Roy, Ankesh Samanta, Bijoy Mandal, Santanu Das
Abstract: The process of grinding is normally associated with generation of considerable amount of heat. To reduce thermal damages, grinding zone is often flooded with liquid coolant, most of which is wasted and may cause severe environmental pollution. In the present work, grindability of hardened AISI 4340 steel is assessed at various infeeds, using an eco-friendly vegetable oil applied by small quantity lubrication (SQL) technique, so as to reduce the quantity of coolant. At the same infeed, grinding is also performed by applying a uniform layer of semi-solid lubricant (grease) on the work surface. Comparison is made between the two methods in terms of force, surface roughness, specific grinding energy and observed chip forms. Results prove that SQL technique using vegetable oil is better than grease as a lubricant in terms of force requirement, while surface quality shows improvement with grease layer lapped on the work surface than with SQL technique.
Keywords: grinding; grindability; cooling; lubrication; small quantity lubrication; SQL; roughness; force; eco-friendly manufacturing.
Development of cBN electroplated end-mill combined cutting and grinding for precision machining of CFRP
by Tatsuya Furuki, Yugo Kabaya, Toshiki Hirogaki, Eiichi Aoyama, Kiyofumi Inaba, Kazuna Fujiwara
Abstract: Carbon-fibre reinforced plastic (CFRP) has been applied to various fields because of its excellent mechanical properties. Generally, after fabrication with moulding, CFRP requires additional machining, such as cutting or grinding. As the cutting tool for CFRP, a diamond-coated end-mill with high wear resistance has been developed. However, burr or uncut fibre is easily formed. Meanwhile, in the case when a grinding wheel is used, the machining efficiency is low even though there are sharp edges with burr or uncut fibres. Therefore, there is a need for the development of a versatile tool that can achieve precision machining of CFRP with high efficiency. This study develops a cBN electroplated end-mill that is a combination of a cutting tool and a grinding wheel. This report shows that the developed tool is able to perform high-efficiency cutting like the diamond coated end-mill, and high-precision grinding like a diamond wheel.
Keywords: carbon-fibre reinforced plastic; CFRP; cubic boron nitride; cBN; electroplated end-milling; grinding; machining centre.
Study on the segmentation of abrasive grains in diamond tools
by Yanfen Lin, Congfu Fang
Abstract: Segmentation of abrasive images of diamond tools is the most important part of computer vision, which is the basis for detecting the state of diamond tools, such as the characteristics of diamond number, distribution, size and state. As diamond images have rich irregular background textures and reflective features, it is a major challenge to detect and segment these diamond images. The present work demonstrates an invalid edge elimination method for such images to segment and mat the diamond grains, which mainly consists of histogram, edge detection, and morphology. Based on the method, the part of diamond in the original images can be accurately and effectively segmented and matted. Then, the method is also used to segment and mat the diamond grains in other images of different diamond tools, and it also has a good segmenting and matting effect. Finally, the segmented and extracted diamond grains are used to analyse the diamond number, density and its wear state, the result indicates that the proposed method can be used in diamond tool detection.
Keywords: diamond tool; topography; abrasive grain; segmentation; matting.
Experimental study on abrasive water jet machining of AA5083 in a range of thicknesses
by Gurusamy Selvakumar, Shanmuga Sundaram Ram Prakash, Nagarajan Lenin
Abstract: The objective of this study is to present the optimal machining parameters for abrasive water jet machining (AWJM) of Aluminium alloy 5083 (AA5083) by employing artificial neural networks (ANN) modelling for various material thicknesses. Al 5083 alloy finds vast applications in ship building, rail cars, and vehicle bodies and exclusively for cryogenic applications. The experimental work was carried out by using Taguchi L18 orthogonal array to study the influence of the process parameters such as jet diameter, stand-off distance and abrasive flow rate for various ranges of thicknesses over the process yields namely material removal rate (mrr), surface roughness and taper error. Technological table for optimal machining of AA5083 alloy in AWJM was reported for ready to use in industry.
Keywords: abrasive water jet machining; AWJM; aluminium alloy; Taguchi method; artificial neural networks; ANN; Pareto optimisation; technology table.
Chemical catalysts of Fenton reaction for single-crystal SiC based on nanoindentation
by Huazhuo Liang, Jiabin Lu, Qiusheng Yan, Tao Song
Abstract: Aiming at production of single-crystal SiC for chemical mechanical polishing, Fenton reaction, and catalytic efficiency of FeSO4, Fe2(SO4)3, FeO, Fe3O4, and Fe2O3 were studied. The mechanical properties are obtained by nanoindentation experiments. Different catalysts can promote Fenton reaction, and all reaction layers formed with the same chemical composition, atomic structure, and hardness at 1.5 GPa. When Fe3O4 was used as catalyst in Fenton reaction, the effect was optimal because its hardness and modulus remained low. After 2 min, the thickness of reaction layer had reached 200 nm, which can fully meet requirements of CMP. Fenton reaction depends on ability of catalyst to ionise Fe2+. The higher concentration of Fe2+, the higher concentration of OH, and the faster reaction rate of SiC surface material.
Keywords: single-crystal SiC; Fenton reaction; catalyst; nanoindentation.
Experimental study on surface generation in optical glass with fluid jet polishing process
by Kumaresan Gladys Anbarasu, Lakshmanan Vijayaraghavan, Narayanaperumal Arunachalam
Abstract: Fluid jet polishing process is an inexpensive technique and capable to produce ultra-smooth surface. In fluid jet polishing process, the surface generation mainly depends upon the size and type of the abrasive particle, the jet pressure, the exposure time, the impact angle, etc. In this work, experimental investigation were carried out to study the influence of different slurry exposure time on surface roughness of optical glass with varying jet pressure, particle diameter and type of particle at 30° impact angle. The surface roughness measurement and surface morphology characterisation were done to understand the surface changes.
Keywords: abrasives; particle size; surface roughness; exposure time; jet pressure.