Papers by Author: Ji Wang Yan

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Authors: Ji Wang Yan, Jiu Lang Xiong
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Authors: Ji Wang Yan, Takeo Sasaki, Junichi Tamaki, Akihiko Kubo, T. Sugino
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Authors: Tian Feng Zhou, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: This paper presents a glass molding press (GMP) method to fabricate microgroove array and micropyramid array on the glass plate by replicating the shape of the mold to the glass surface. The differences between microgroove forming and micropyramid forming were investigated by experiments and finite element method (FEM) simulations. Microgroove arrays and micropyramid arrays were generated on the flat glass plate in the GMP process by using an electroless-plated Nickel Phosphorus (Ni-P) mold, on which the microstructures are fabricated by micro cutting. Furthermore, FEM simulations were used to trace the stress distribution and the strain distribution during the glass deformation, which illustrates the glass material flow in the microgrooves and the micropyramids on the mold during pressing. By comparing the processes between microgroove forming and micropyramid forming, the differences between them observed in the experiments were explained by the simulation results. Finally, some techniques to improve the forming accuracy were proposed.
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Authors: Ji Wang Yan, Tooru Asami, Tsunemoto Kuriyagawa
Abstract: Ultraprecision diamond-cut silicon wafers were irradiated by a nanosecond pulsed Nd:YAG laser, and the resulting specimens were characterized using transmission electron microscopy and micro-Raman spectroscopy. The results indicate that at specific laser energy density levels, machining-induced amorphous layers and dislocated layers were both reconstructed to a complete single-crystal structure identical to the bulk region. Similar effects were confirmed for diamond-ground silicon wafers. Effects of overlapping irradiation were investigated and perfect crystallographic uniformity was achieved in the boundary region. The recovery process involved rapid melting of the near-surface amorphous layer, followed by epitaxial regrowth from the damage-free crystalline bulk.
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Authors: Nobuhito Yoshihara, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: The use of aspherical optical parts has become common as optical instruments are becoming smaller with and are achieving higher resolution. Nano-order roughness and high-precision shapes are simultaneously required for the surface of aspherical optical parts. At present, form accuracy of the aspherical lens becomes less than 50 nm, and the maximum height roughness becomes less than 20 nm. These values of form accuracy and maximum height roughness satisfy the requirement for most precision optical parts. However, nano-topography, which causes grinding marks and deteriorates accuracy of optical parts, is generated on the ground surface. Conventional evaluation criteria such as form accuracy and surface roughness cannot estimate the nano-topography. In the present paper, the cross sectional profile of the axisymmetric ground surface is calculated in order to estimate the distribution of the nano-topography. As a result, the possibility of control of the nano-topography distribution is confirmed. In addition, controlling the amplitude of nano-topography is easier than controlling the distribution of nano-topography.
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Authors: T. Tateishi, K. Shimada, Nobuhito Yoshihara, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: . Micro ultrasonic machining (micro-USM) is an effective machining method for hard brittle materials. In the micro-USM process, the workpiece materials are machined through the accumulation of small brittle fractures generated by the impacts of abrasive grains. Therefore, it becomes difficult to obtain a smooth machined surface. In the proposed electrorheological fluid-assisted ultrasonic machining (ER fluid-assisted USM), the behavior of abrasive grains is controlled using the effect of dielectrophoretic force acting on the abrasive grains and the ER effect. The behavior of the abrasive grains can be controlled by changing the electric field distribution. In the present paper, the shape and position of the auxiliary electrode are arranged in order to control the abrasive grains to the side surface of the micro rectangular tool. By positioning the auxiliary electrode parallel to the micro rectangular tool, it becomes possible to concentrate abrasive grains to the side surface of the micro rectangular tool. Smoothing of the side surface of the workpiece by using the side surface of the micro rectangular tool is then investigated. As a result, the surface roughness of the side surface of the workpiece can be improved.
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Authors: Tsutomu Ohta, Ji Wang Yan, Sunao Kodera, Shuuma Yajima, Naoyuki Horikawa, Youichi Takahashi, Tsunemoto Kuriyagawa
Abstract: The service life of a diamond tool in cutting single-crystal silicon is normally very short because of severe tool wear. Therefore, it is important to use a proper coolant in order to restrain tool wear. In this paper, the performances of oil-based and water-based coolants were compared in silicon machining by investigating cutting forces and tool wear geometries. The water-based coolant was found to restrain flank wear more effectively than the oil-based one. The effective tool life using the water-based one was averagely three times longer than that using the oil-based one. The tool wear mechanism might be related to microplasma generated between silicon and diamond during cutting.
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Authors: A.Q. Biddut, Ji Wang Yan, Liang Chi Zhang, Tsutomu Ohta, Tsunemoto Kuriyagawa, B. Shaun
Abstract: This paper investigates the deformation in monocrystalline silicon subjected to single-point cutting with the cutting speed up to 46.78 m/s, the depth of cut of 2 μm, and the feed rate of 5 and 30 μm/rev. Raman spectroscopy and transmission electron microscopy were used to characterize the subsurface damages. It was found that the increase of either the feed rate or cutting speed increases the thickness of amorphous layer and penetration depth of dislocations. At the feed rate of 30 μm/rev and cutting speed of 12.48 m/s, a new dislocation system was initiated. An unknown peak was detected by Raman spectroscopy, which may indicate an unknown Si phase.
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Authors: Toshihiko Shibuya, Mohammad Saeed Sepasy, Koichi Mizutani, Nobuhito Yoshihara, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: Thick films are needed in micro-electro-mechanical systems (MEMS) as insulation, piezoelectric and ferroelectric materials. To form the thick film, powder jet deposition (PJD) method has been proposed. In the PJD process, microparticles are sprayed out from nozzle under the conditions of room temperature and atmospheric pressure, and make a film on the substrate. We have developed a new jet mechanism of double-nozzle type, and reported its results previously [1]. In this study, we optimized the shape of the nozzle through investigating the influence of different dimensions and shape of the nozzle on the particles blasting velocity. As a result, it is found that nozzle diameter has a large affect on particles velocity.
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Authors: Hiroshi Matsuura, Yasuhiro Kunieda, Nobuhito Yoshihara, Ji Wang Yan, Tsunemoto Kuriyagawa
Abstract: A completely new diamond wheel, named the 3R wheel, has been developed. The 3R wheel has three unprecedented functions, reconfiguration, restoration and recyclability, and is molded from a mixture of special thermoplastic resin filler and diamond powder. The concept of the 3R wheel is to control the quantity and the position of abrasive material by actively using heat. In this study, tungsten carbide (WC) was ground using a thermoplastic resin bonded diamond wheels (radius 1.4 mm) with three different concentrations of 1500 grain size abrasive. As a result, a grinding ratio of over 200 and 18 nmRa roughness was achieved without dressing. In addition, a large quantity of abrasives was confirmed on the wheel surface by observation.
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