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허세곤(Segon Heo),김웅(Woong Kim),민병권(Byung-Kwon Min) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
Thermal analysis of electrical discharge machining (EDM) of polycrystal diamond (PCD) materials using finite element method is proposed. Material structure model for PCD were developed. Heat transfer and temperature of PCD material caused by a single discharge were simulated. The simulation results demonstrate that diamond particles are detached because of melting of the cobalt layer.
Voxel Based Fast Cutting Force Simulation in NC Milling Process
허세곤(Segon Heo),김창주(Chang-Ju Kim),오정석(Jeong Seok Oh) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.12
With the advent of the 4th industrial revolution, advanced digital manufacturing technologies are actively developed to strengthen manufacturing competitiveness. Smart factories require a real-time digital twin including a Cyber-Physical System (CPS) of machines and processes and intelligent technologies based on the CPS. To predict machining quality and optimize machines and processes, it is necessary to analyze the cutting force during machining. Therefore, for real-time digital twin, a fast cutting force simulation model that receives information such as the positions of the feed axes in short time intervals from the CNC and calculates the cutting force until the next information is input is required. This paper proposes a voxel-based fast cutting force simulation in NC milling for real-time digital twin. The proposed simulation model quickly calculates the cutting force by using only information of voxel elements removed by each tool edge without complicated Cutter-Workpiece Engagement (CWE) and chip thickness calculations in previous studies. To verify the performance of the developed simulation, experimental machining was performed and the measured cutting force and simulated cutting force were compared. It was demonstrated that the proposed model can successfully predict the cutting force 3.5 times faster than the actual process.
물 분자막의 두께와 윤활특성의 상관관계에 대한 분자시뮬레이션 연구
김현준,허세곤,Kim, Hyun-Joon,Heo, Segon 한국트라이볼로지학회 2022 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.38 No.5
This paper presents a numerical investigation of the influence of water molecule thickness on frictional behavior at the nanoscale using molecular dynamics simulation. Three different models, comprising water thin films of various thicknesses, were built, and indentation and sliding simulations were performed using the models. Various normal loads were applied by indenting the Si tip on the water film for the sliding simulation to evaluate the interplay between the water thin film thickness and the normal load. The results of the simulations showed that the friction force generally increased with respect to the normal load and thickness of the water thin film. The friction coefficient varied with respect to the normal load and the water film thickness. The friction coefficient was the smallest under a moderate normal force and increased with decreasing or increasing normal loads. As the water film became thicker, the contact area between the tip and water film became larger. Under well-lubricated conditions, the friction force was proportional to the contact area regardless of the water film thickness. As the normal force increased above a critical condition, the water molecules beneath the Si tip spread out; thus, the film could not provide lubrication. Consequently, the substrate was permanently deformed by direct contact with the Si tip, while the friction force and friction coefficient significantly increased. The results suggest that a thin water film can effectively reduce friction under relatively low normal load and contact pressure conditions. In addition, the contact area between the contacting surfaces dominates the friction force.
한민섭(Min-Seop Han),허세곤(Segon Heo),김웅(Woong Kim),민병권(Byung-Kwon Min) 한국생산제조학회 2010 한국공작기계학회 추계학술대회논문집 Vol.2010 No.-
Recently demands for precision micro-machining of hard and brittle material has dramatically increased in various industrial applications. In case of mechanical machining low surface integrity is produced due to the surface fractures and cracks. In this study thermal assisted mechanical micromachining of glass is proposed to improve the geometric accuracy and surface integrity by utilizing electrochemical discharge phenomena. Experimental investigation demonstrates improved machining performance for the fabrication of micro-features such as micro-holes and micro-channels of glass material.
DED Additive Manufacturing Using Auto-Surface Tracking Technology
하태호(Taeho Ha),허세곤(Segon Heo),이창우(Changwoo Lee),정민교(Min-Kyo Jung),최장욱(Jang-Wook Choi) Korean Society for Precision Engineering 2023 한국정밀공학회지 Vol.40 No.3
Directed energy deposition (DED) additive manufacturing technology enhances the functionality of existing or damaged parts by adding metallic materials to the surfaces. Blown-powder DED technology utilizes a focused, high-energy source to fuse the part’s surface with the supplied metal powder. Maintaining a constant stand-off distance (SOD), the distance between the deposition head and the workpiece, is a key factor in ensuring deposition quality, as variations in SOD will change the powder focus position and the laser spot size on the surface. Therefore, traditional additive manufacturing systems require CAD or pre-scanned surface data. In this study, we proposed auto-surface tracking technology. No workpiece CAD data or pre-scanned surface data are required, and in-situ measurement and feedback control can automatically consider the deposition height differences that cause a change in SOD when depositing the next layer. The accuracy of the SOD measurements and feedback control error was verified using a step height sample. The mean SOD measurement error was 4.7 ㎛ with a standard deviation of 42 ㎛ (reference SOD, 14 ㎜). The feasibility of the autosurface tracking technology was confirmed through the additive manufacturing processes of the gear and an actual blanking mold applied in the defense and industrial fields.