Papers by Keyword: Hard Material

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Authors: Kenichiro Imai
Abstract: Engineering ceramics have received significant attention in the recent years owing to their exceptional mechanical properties, which are expected to be beneficial for engineering applications. However, it has always been a great challenge to realize ductile-mode grinding in engineering ceramics, with one of the critical obstacles being the heat generation that limits the removal rate. As a result, thermal damages are often observed on the ground surfaces. This paper presents the ductile-mode grinding. In the process the grinding wheel is excited along the radial direction by applying an ultrasonic vibration of frequency is 38.5 kHz and amplitude of 0-2 μm. The wheel comes in contact with the Al2O3 ceramic at constant forces 18-24 N. Experimental results indicate that the ground surface is devoid of thermal damages, when removal rate of the vibration-assisted process is approximately 1.5 times higher than without vibration.Keywords: ductile-mode grinding, radial directional vibration, hard and brittle material, engineering ceramic, thermal damage
Authors: Xue Ming Zhu, Bin Lin, Li Ping Liu
Abstract: Rotary ultrasonic machining(RUM) as a precise and efficient processing method for hard and brittle materials can be used for significantly improving processing efficiency, reducing the cutting force and cutting heat, improving the surface quality. Development of high performance RUM machine tools and equipments has been caused on widespread attention from the worldwide scholars. In this paper, the development of the RUM machine tools has been reviewed about the accessory RUM head and load matching system.
Authors: Li Ping Liu, Bin Lin, Feng Zhou Fang
Abstract: A novel adaptive force control table for rotary ultrasonic machine tool was developed for processing micro holes. The adaptive force control table, a mechanical balancing device by which the load can be adaptively adjusted without numerical control was adopted as an attachment in an ultrasonic machine tool. To verify the performance, micro holes were drilled on SiC workpiece. The drilling force, tool wear and profiles of these machined micro holes were investigated. According to the experimental results, it is confirmed that the newly developed table attached on the ultrasonic machine tool is an economical and efficient approach for machining micro holes on hard and brittle materials.
Authors: Quan Cheng Li, Jian Yun Shen, Cong Fu Fang, Xipeng Xu
Abstract: In this study, two different arrangement lapping disks fixed with brazed diamond pellets were used to lap silicon wafer and alumina ceramic. The effects of the surface morphology, roughness, and removal rate of workpiece caused by lapping pressure, lapping time, workpiece velocity, and disc arrangement were operated with serials experiments. The results of the researches provided guidance for fixed abrasive lapping of hard and brittle materials with the brazed micro powder diamond disk.
Authors: H. Kasuga, Hitoshi Ohmori, Y. Watanabe, T. Mishima
Abstract: Progress of new dental materials such as biocompatible metal, ceramics is being accelerated because of aging society and sophistication of medical treatment. In addition, the demand for dental implant treatment is increasing. Currently, dental implant crowns (superstructures) are formed by cutting semi-sintered ceramics and then sintering the ceramics at a high temperature. So, there is some concern that to maintain the form accuracy of the workpiece is difficult. Meanwhile, it is usually difficult to machine sintered ceramics with high precision and high efficiency. In this paper, we tried to apply grinding with metal bonded superabrasive wheels, and investigated the grinding and surface characteristics of an alumina and zirconia ceramics for dental implant superstructure due to lack of such data. As a result of experiments, sintered dental ceramics can be ground with high precision and Fe, it has harmful effect to human body, was not detected in sintered dental ceramics.
Authors: Xin Rui Tang, Keiichi Nakamoto, Kazushi Obata, Yoshimi Takeuchi
Abstract: Recently, in accordance with the technical development and miniaturization of the information equipments, the demand of optic elements with high precision and miniaturization is increased. The mold is used in the manufacture of the optic elements. Thus, it is needed to machine the mold with high efficiency and high precision. As the material of mold, hard material including cemented carbide and ceramics is used. However, it is a problem of the occurrence of severe tool wear when hard material is machined. To solve this problem, the cutting point swivel machining by using the diamond tool with special chamfer was proposed, which has the ability to suppress tool wear and to realize ultraprecise machining. It is confirmed that the cutting point swivel machining has the ability to suppress tool wear by the microgrooving experiment of SiC. This study aims at investigating the effect of the cutting point swivel machining, and making clear the relationship between tool rotation speed and tool wear. As a result, it is known that the actual cutting direction can be changed by using the cutting point swivel machining, and that the chipping of tool becomes conspicuous with increasing tool rotation speed.
Authors: Duck Soo Kang, Kee Do Woo, Sang Hyuk Kim, In Jin Shon, Ji Young Kim, Sang Hoon Park
Abstract: High frequency induction heated sintering (HFIHS) method is one of the rapid sintering methods. The advantage of rapid sintering method is that grain growth can be prevented during sintering at high temperature. Refinement of grains was known to increase the yield and flow stresses of crystals. The relation between the yield stress and the grain size is known as Hall-Petch relation. NbC-10vol.%Co, Ni and Fe composites were fabricated by HFIHS at 1060°C for 0 and 3 min as holding times under a pressure of 80MPa.The relative density of NbC-10vol.%Co, Ni and Fe composites which were sintered at 1060°C for 0min as holding time under 80MPa were 91.90%, 91.26% and 91.26%, respectively. These composites are difficult to use industrial parts due to low relative density. The longer sintering time was conducted for increasing relative density in this study. Nano-sized specimens, which were calculated grain size by full-width at half maximum (FWHM), can be obtained by HFIHS. The value of hardness and fracture toughness was investigated using 20kgf load Vickers indenter.
Authors: M. Meshii
Abstract: The discipline of Materials Science is, we believe, in the midst of the second transformation. The research and education of most of the Materials Science and Engineering departments in the United States have traditionally emphasized hard materials. The recent surge in research of soft materials and our perceptions that the Materials Science Methodology (both experimental and numerical) holds the advantage in the research of the soft materials prompt us to expand the area of soft materials at the expense of hard materials. Clearly the struggle between the two types of materials will continue for some time to come. The current struggle in weighting will be described in an historical fashion comparing it to the struggle in the first transformation that took place in the 1950's and 1960's.
Authors: Kenichiro Imai, Hiroshi Hashimoto
Abstract: Under optimum grinding conditions, a constant grinding force is exerted on a workpiece during ductile-mode grinding of BK7 glass. Based on the results, the cutting force, specific grinding energy, and depth of cut for a single grain were calculated. It was found that a single grain was easily removed from the material. However, grinding is impossible because surface burning occurs on the workpiece. In order to avoid burning, a single-crystal silicon wafer (1,0,0) surface was ground with thrust force directional vibration-assisted grinding. The normal grinding force with vibration was comparatively low, but was quite stable. The removal rate was approximately three times greater than that without vibration. The results indicate that the successive abrasive grains of the grinding wheel remove the material intermittently.
Authors: Xin Rui Tang, Miki Yoshinaga, Keiichi Nakamoto, Tohru Ishida, Yoshimi Takeuchi
Abstract: Recently, in accordance with the technical development and miniaturization of the information equipments, the demand of optic elements with high precision and miniaturization is increased. The die is used for manufacturing the optic elements. Thus, it is needed to machine the die with high efficiency and high precision. As the material of die, hard material including cemented carbide and ceramics is used. However, when hard material is machined, there is a problem that severe tool wear occurs, and worn tool shape is transferred into the surface so that precision machining cannot be realized. In this study, a method, called cutting point swivel machining, is proposed to suppress tool wear by using the tool with special chamfer and all parts of tool tip. The effect of tool wear suppression is verified by the machining of SiC. Then, the relation between the suppression of tool wear and tool rotation period is verified.
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