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RISS 인기검색어
- 검색키워드
- 저자 : Chunhui Chung (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Generation of Diamond Wire Sliced Wafer Surface based on the Distribution of Diamond Grits
Chunhui Chung,Le Van Nhat 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
Diamond wire sawing is one of the abrasive machining processes. The cutting tool is a tiny steel wire coated with a large numberof diamond grits. Although wire saw is widely used for slicing hard and brittle materials, it is still very complicated to be analyzedand understood because of the unique characteristics of the wire. This study takes the advantage of modern computer technology tosimulate the wire sawing process kinematically. The wire parameters with random features including the sizes and positions of theabrasive grits have been considered in the wire model. Based on process parameters, the cutting process was simulated by mappingthe cutting profile into the array representing the workpiece. The sliced surface topography was then generated depended oninteraction between the active abrasive grits and the workpiece. Experiment was conducted to verify the simulation results. The effectsof process parameters including wire speed, feed rate, the size and distribution of the diamond grits to the sliced wafer surface qualityare also investigated. The approach proposed in this study makes it possible to investigate the effect of process parameters anddiamond grits to improve the practical wire sawing process.
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Estimation of Process Damping Coefficient Using Dynamic Cutting Force Model
Chunhui Chung,Minh-Quang Tran,Meng-Kun Liu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.4
A model of process damping in milling was developed in this study. The process damping is a critical parameter to increasethe stable cutting region at low cutting speed to avoid chatter. The previous studies conducted experiments to estimate theprocess damping. Nevertheless, it is time and cost consuming. A model of dynamic cutting force was employed in this study. The plowing force generated by the fl ank-wave contact is considered as the main source of process damping to dissipatevibratory energy during cutting. In addition to the material properties and plowing force, the eff ects of chatter amplitudeand wavelength, which result in the various indentation conditions and aff ect the coeffi cient of process damping, were alsoconsidered. The consideration of wavy contact surface and indentation area in this model allows quick determination of cuttingstability conditions with high accuracy. The process damping coeffi cient estimated by the proposed model successfullyrepresented the eff ect of the tool wear on chatter because of the change of tool geometry. Experiments were conducted toverify the new model.
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Fabrication of PDMS Passive Micromixer by Lost-Wax Casting
Chunhui Chung,Yann-Jiun Chen,Pin-Chaun Chen,Chia-Yuan Chen 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
Microfluidic devices have attracted considerable attention for their applicability in disease detection, health care, and environmental monitoring. However, manufacturing at the microscale can be exceedingly difficult, particularly when dealing with devices with an intricate geometry. Most of the manufacturing methods used for microfluidic devices are unable to produce anything more complex than a simple 2.5D structure, which necessitates the bonding of multiple layers to produce a complete 3D structure. This study employs the lost-wax casting method, which is commonly used for the precision casting of metals, in the fabrication of a passive micromixer with two-layer structure using polydimethylsiloxane (PDMS) in a single-step process. The wax pattern was obtained by injection molding, whereupon PDMS was cast in the mold to produce a micromixer after dewaxing. Our results demonstrate the high fidelity of the replication process from the wax pattern to the PDMS micromixer. Furthermore, with the exception of the glass cover, no bonding is required to join multiple layers in the formation of the structure. Compared to other microfabrication methods, such as molding injection and hot embossing, the lost-wax casting method in this study is able to produce microdevices with more complex geometry without the problem of misalignment between bonding layers.
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Chunliang Kuo,Tingyu Chang,Jhihjie Liu,Chunhui Chung 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6
This paper presents a novel additive manufacturing process, namely the laser melting of polymer-metal colloids (LMC), which is advantageous for repairing features and reducing contamination sources. The developed polymer-metal colloids are conveyed via the designed spindle-driven dispensing system to demonstrate consolidations of the metallic phase onto heterogeneous substrate materials via laser melting. Modelling of the flow rate, velocity and pressure fields is linked to the geometric design of the mechanical devices in the spindle-driven process. The equilibriums of the heat transfer equations in the colloid element were initiated and presented for the estimations of input laser energy. When the input heat was absorbed by the colloid element, the average energy density could be obtained by the ratio of the overall energy density and the engaged laser scanning volume. In the experimental work of the validation tests, the polymer-metal colloid was consolidated on the substrate material with three different results: unconsolidated, partially consolidated and consolidated. The consolidation and bonding of metallic fractions on the heterogeneous substrate materials in the laser melting actions were evaluated and reported.
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Hybrid model- and signal-based chatter detection in the milling process
Meng-Kun Liu,Minh-Quang Tran,Chunhui Chung,Yi-Wen Qui 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1
Chatter causes machining instability and reduces productivity in the metal cutting process. It has negative effects on the surface finish, dimensional accuracy, tool life and machine life. Chatter identification is therefore necessary to control, prevent, or eliminate chatter and to determine the stable machining condition. Previous studies of chatter detection used either model-based or signal-based methods, and each of them has its drawback. Model-based methods use cutting dynamics to develop stability lobe diagram to predict the occurrence of chatter, but the off-line stability estimation couldn’t detect chatter in real time. Signal-based methods apply mostly Fourier analysis to the cutting or vibration signals to identify chatter, but they are heuristic methods and do not consider the cutting dynamics. In this study, the modelbased and signal-based chatter detection methods were thoroughly investigated. As a result, a hybrid model- and signal-based chatter detection method was proposed. By analyzing the residual between the force measurement and the output of the cutting force model, milling chatter could be detected and identified efficiently during the milling process.
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