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RISS 인기검색어
- 검색키워드
- 저자 : Jiwang Yan (검색결과 5 건)
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Response of Resin Coating Films Containing Fine Metal Particles to Ultrashort Laser Pulses
Ayumi Nakajima,Jiwang Yan 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.4
Resin coating films are extensively used for aesthetic improvement and preventing deterioration of metal surfaces. Some of the films contain fi ne metal particles for the purpose of coloring. For such films, surface waviness with millimeter-scale wavelength is a significant problem because it induces visible irregularities on the surface. Conventionally, man-powered polishing has been used to planarize the waviness. However, it is labor-intensive and leads to other problems such as waste slurry disposal and embedment of abrasive grains in the fi lm. Hence, a new method is required to eliminate the surface waviness. In this study, ultrashort pulsed laser irradiation on resin coating films is proposed. By controlling the focal position and/or scanning speed of the laser beam along the surface, protrusions are preferentially removed. Firstly, the effects of pulse width, laser fluence, and scanning speed on surface morphology were clarified. Next, the material removal mechanism was examined by elemental analysis of the surface and its cross section after irradiation. Finally, as a preliminary result of surface flattening, the arithmetic mean waviness in the wavelength range of 2.4–5.0 mm was reduced by 45.3%. This study demonstrated the feasibility of selectively removing and flattening of resin coating films by substituting laser processing for man-powered polishing.
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Improvement of Glass Formability in Ultrasonic Vibration Assisted Molding Process
Tianfeng Zhou,Jiaqing Xie,Jiwang Yan,Kuriyagawa Tsunemoto,Xibin Wang 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.1
Micro optical elements with complex shapes are needed increasingly in optical, optoelectronic and biomedical industries. Since glass molding process is an effective approach to fabricate microstructures, and its surface quality strongly depends on the filling capacity of glass at high temperature. To improve the formability and reduce adhesion between the glass and the mold at high temperature, ultrasonic vibration is applied to improve the formability in the molding process. Fundamental experiments are carried out to test the effectiveness of ultrasonic vibration on friction force decrease and a bonding model on the glass-mold interface at elevated temperature is proposed. Finite element method (FEM) simulation and glass molding experiments are conducted to evaluate the improvements of material formability brought about by ultrasonic vibration. The results show that the ultrasonic vibration can significantly lower the friction force and increase the glass formability.
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Microscale Surface Patterning of Zirconia by Femtosecond Pulsed Laser Irradiation
Yuka Yamamuro,Tomotaka Shimoyama,Jiwang Yan 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.2
Irradiation of yttria-stabilized zirconia (YSZ) was performed by a femtosecond pulsed laser to investigate the feasibility of V-shaped groove microstructure fabrication. Firstly, fundamental characteristics of microgroove fabrication was investigated by varying scanning speed of laser and number of scans. Higher scanning speed resulted in a smooth surface without any debris adhesion. By increasing number of scans, the cross-sectional profile of the microgroove became a well-defined V shape, and the taper angle of the V-shaped groove can be precisely controlled by laser scanning speed. Moreover, the laserinduced phase transformation of YSZ was characterized, and it was found that the monoclinic ratio after irradiation decreased in comparison with original YSZ surface, indicating improved strength and toughness. TEM cross-sectional observation of the microgrooves was performed and tetragonal phase was detected independent of locations. Finally, micro pyramid structures were created on the YSZ surface by perpendicularly crossing the laser scan directions. The resulting surface showed a drastic change in surface wettability. These findings demonstrated the possibility of generating precise complex microstructures on YSZ surface with high functionality and low subsurface damage, presenting great potential of wide applications in industry.
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Qian Yu,Tianfeng Zhou,Yupeng He,Peng Liu,Xibin Wang,Jiwang Yan 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7
Relative tool sharpness (RTS) is identified as the ratio of undeformed chip thickness to tool cutting edge radius. This paper studies the effects of RTS on the surface generation mechanism of precision turning of electroless nickel-phosphorus (Ni-P) coating. An Rshaped tungsten carbide (WC) tool was adopted for the face turning experiment. The cutting edge radius was 1.84 μm measured by a laser scanning confocal microscope (LSCM). The chip formation behavior, cutting forces and surface morphology were investigated under different RTS values. Results showed that the chip changes from continuous to discontinuous as RTS decreases from 0.54 to 0.27, indicating the transition of the material removal mechanism. The periodical fluctuations with small amplitudes on the machined surface are associated with the high-frequency tool-tip vibration. The low-frequency fluctuations of the cutting forces are related to the material swelling and recovery. The optimal machined surface roughness was obtained at the RTS of 0.38.
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Seyed Nader Ameli Kalkhoran,Mehrdad Vahdati,Zhiyu Zhang,Jiwang Yan 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.2
Lubrication can improve the tool-workpiece interface condition in ultraprecision machining, especially in microgrooving processes. The aim of this study was to compare the effects of dry, liquid (cutting oil), solid (wax) and hybrid (cutting oil and wax) lubrication conditions, on the creation of arc-sectioned microgrooves on single-crystal silicon wafers using a singlecrystal diamond tool. Micro cutting forces, chip morphology, and surface quality at different locations of the grooves were investigated. Rose-shaped continuous chips were observed in dry cutting, indicating stable ductile mode material removal. The entrance side of the groove was always smoother than the exit side with a higher degree of phase transformation. Chip adhesions on the tool edge were found in dry and oil lubricated cutting, whereas wax coating could prevent the adhesion. Wax coating played the dual roles of a chip breaker as well as a high-performance lubricant, thus improved the surface integrity. This study demonstrated the capability of using wax coating as an environmentally friendly solid lubricant for microgrooving of single-crystal silicon and possibly for other hard brittle materials.
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