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최한신(H.S. Choi),김한성(H. S. Kim),최용제(Y.J. Choi) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
This paper presents the signal analysis of an acoustic roughness measurement device for rail. In order to reduce rail noise, the device development and measurement process are essential. Based on the design of the hand-operated CAT3(1), the device prototype including sensor and actuation modules has been developed. Before the signal processing, acoustic roughness signals from the accelerometer attached at the end of cantilever beam are analyzed with different beam thicknesses and actuation speeds.
플라즈마 전해산화공정을 이용한 Mg<sub>95</sub>Zn<sub>4.3</sub>Y<sub>0.7</sub> 합금분말 성형체의 표면특성제어
김재호,최한신,김도향,황덕영,김형섭,김택수,Kim, J.H.,Choi, H.S.,Kim, D.H.,Hwang, D.Y.,Kim, H.S.,Kim, T.S. 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.2
The investigation is to modify the mechanical and chemical properties of Mg alloys using a combination of rapid solidification and surface treatment. As the first approach, $Mg_{95}Zn_{4.3}Y_{0.7}$ was gas atomized and pressure sintered by spark plasma sintering process (SPS), showing much finer microstructure and higher strength than the alloys as cast. Further modification was performed by treating the surface of PM Mg specimen using Plasma electrolytic oxidation (PEO) process. During the PEO processing, MgO layer was initiated to form on the surface of Mg powder compacts, and the thickness and the density of MgO layer were varied with the reaction time. The thickening rate became low with the reaction time due to the limited diffusion rate of Mg ions. The surface morphology, corrosion behavior and wear resistance were also discussed.
초고속 화염용사 공정변수에 따른 나노 WC-Co의 코팅특성 평가
김병문,황순영,최한신,이창희 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10
High velocity oxy-fuel thermally sprayed coating of the WC-Co cermet material is a well-established process for modifying the surface properties of the structural components exposed to the corrosive and wear attacks. The hard WC phase in the coating resists to the wear while the soft metallic Co increases the adhesive and cohesive bonding properties. The coating properties deposited by the HVOF process are greatly dependent on the feedstock materials and processing parameters. The effects of the feedstock material and process parameters including the inflight particle parameters and resultant coating microstructures were observed in this study. Both the NW10Co powder containing nano-sized WC particle and the micro-sized WC embedded MW12Co powder were thermally sprayed by the table of orthogonal array of the processing parameters. The in-flight particle parameters such as the particle temperature and velocity were directly measured along the hot gas downstream using the DPV-2000 system. In-flight particle parameters were affected by the properties of the feedstock materials. Especially, the particle temperature of the NW10Co was higher than that of the MW12Co from the barrel exit point to the deposition point, irrespective of the condition of the processing parameters. Porosity in the as-sprayed HVOF coating was measured using an image analyzer. And the Vickers microhardness was measured under applied load of 300 g for 15 seconds. Phase compositions of the as-sprayed HVOF WC-Co coatings were measured and analyzed using the X-ray diffraction. The effects of the feedstock materials and process parameters on the coating properties of the as-sprayed HVOF coatings were discussed in terms of the in-flight particle properties during processing.