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RISS 인기검색어
- 검색키워드
- 저자 : Tianfeng Zhou (검색결과 4 건)
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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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Micro Convexity Elimination of Tungsten Carbide in Electrical Discharge Milling for Lens Moulds
Tianfeng Zhou,Si-Bo Wang,Xin Liu,Zhi-Qiang Liang,Xibin Wang 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.12
Electrical discharge milling (ED milling) using spherical electrode is considered to fabricate tungsten carbide (WC) lens moulds for high volume and cost efficient mass production comparing with hemispherical electrode whose wear is noticeably larger. However, micro convexity with dome shape generating in the center of the mould leads to poor surface quality of moulds when using spherical electrode. Therefore, based on boundary layer theory, the forming mechanism of the micro convexity is analyzed in detail by measuring its height and profile by virtue of 3D laser scanning microscope and scanning electron microscope (SEM). The relationship between the boundary layer thickness and the discharge gap is subsequently established, which can be utilized to reduce the convexity to improve the surface quality of lens mould. Then a method to eliminate the micro convexity is proposed. In addition, experiments of different discharge gaps were carried out to confirm the boundary layer theory. Results show that the height of micro convexity can be reduced to 4 μm when the discharge gap was specified to the boundary layer thickness at certain rotational speed.
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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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Effects of intermittent chemical dosing on volatile sulfur compounds in sewer headspace
Guijiao Zhang,Tianfeng Gu,Yongchao Zhou,David Z. Zhu,Yiping Zhang 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.3
Volatile sulfur compounds (VSCs), including hydrogen sulfide (H₂S) and volatile organic sulfide compounds (VOSCs), can be produced in sewer systems causing sewer odor problems. In this study, the effects of intermittently dosing ferric iron, hydrogen peroxide, and nitrate on H₂S and VOSCs in sewer headspace were investigated. In order to characterize the composition of VSCs, an HC-3 trace sulfur analyzer and gas chromatograph (GC) equipped with a triple quadrupole-type mass spectrometry (MS) apparatus were used to determine the VSCs. The results indicated that the effect of intermittent addition of 40 mg/L ferric iron or 40 mg/L hydrogen peroxide is limited for VSCs inhibition. The H₂S and VOSCs concentrations increased significantly in the late-stage experiments, even around 20% and 30% respectively higher than the initial average concentrations. However, the intermittent addition of 40 mg N/L nitrate has a relatively stable control effect of H₂S and VOSCs which maintaining 60% removal rate. Moreover, methyl mercaptan (MeSH) was the most abundant compound of the total VOSCs released and the results of the theoretical odor concentration study also indicate MeSH is the main VOSC causing the significant odor problem. Therefore, more attention should be focused on the VOSCs which have extremely low odor threshold.
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