http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
가스분무주조 Cu-Sn-Ni-Si 합금의 미세조직 및 상온 인장성질
강희수,이언식,이규창,백경호,Kang, Hee-Soo,Lee, Eon-Sik,Lee, Gyu-Chang,Baik, Kyeong-Ho 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.6
In this study, Cu-10Sn and Cu-10Sn-2Ni-0.2Si alloys have been manufactured by spray casting in order to achieve a fine scale microstructure and high tensile strength, and investigated in terms of microstructural evolution, aging characteristics and tensile properties. Spray cast alloys had a much lower microhardness than continuous cast billet because of an improved homogenization and an extended Sn solid solubility. Spray cast Cu-Sn-Ni-Si alloy was characterized by an equiaxed grain microstructure with a small-sized (Ni, Si)-rich precipitates. Cold rolling of Cu-Sn-Ni-Si alloy increased a tensile strength to 1220 MPa, but subsequent ageing treatment reduced a ultimate tensile strength to 780 MPa with an elongation of 18%.
장동훈,강신일,이언식,Jang, Dong-Hun,Gang, Sin-Il,Lee, Eon-Sik 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.6
A numerical method is presented to predict and analyze the shape of a growing billet produced from the "spray forming process" which is a fairly new near-net shape manufacturing process. It is important to understand the mechanism of billet growing because one can obtain a billet with the desired final shape without secondary operations by accurate control of the billet shape, and it can also serve as a base for heat transfer and deformation analysis. The shape of a growing billet is determined by the flow rate of the alloy melt, the mode of nozzle scanning which is due to cam profile, the initial positio of the spray nozzle, scanning angle, and the withdrawal speed of the substrate. In the present study, a theoretical model is first established to predict the shape of the billet and next the effects of the most dominent processing conditions, such as withdrawal speed of the substrate and the cam profile, on the shape of the growing billet are studied. Process conditions are obtained to produce a billet with uniform diameter and flat top surface, and an ASP30 high speed steel billet is manufactured using the same process conditions established from the simulation.imulation.
Ni/Mo 합금분말(FLC-4608)의 소결경화 공정에서 유한요소법을 이용한 마르텐사이트 분율의 예측
박효욱,주수현,이언식,권기혁,김형섭,Park, Hyo Wook,Joo, Soo-Hyun,Lee, Eon Sik,Kwon, Ki Hyuk,Kim, Hyong Seop 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.1
In recent years, industrial demands for superior mechanical properties of powder metallurgy steel components with low cost are rapidly growing. Sinter hardening that combines sintering and heat treatment in continuous one step is cost-effective. The cooling rate during the sinter hardening process dominates material microstructures, which finally determine the mechanical properties of the parts. This research establishes a numerical model of the relation between various cooling rates and microstructures in a sinter hardenable material. The evolution of a martensitic phase in the treated microstructure during end quench tests using various cooling media of water, oil, and air is predicted from the cooling rate, which is influenced by cooling conditions, using the finite element method simulations. The effects of the cooling condition on the microstructure of the sinter hardening material are found. The obtained limiting size of the sinter hardening part is helpful to design complicate shaped components.
나노인덴테이션과 유한요소법을 결합한 철 분말의 기계적 물성 취득
정혁재,이동준,윤은유,이언식,김낙준,김형섭,Jeong, Hyeok Jae,Lee, Dong Jun,Yoon, Eun Yoo,Lee, Eon Sik,Kim, Nack Joon,Kim, Hyeong Seop 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.4
Stress-strain curves are fundamental properties to study characteristics of materials. Flow stress curves of the powder materials are obtained by indirect testing methods, such as tensile test with the bulk materials and powder compaction test, because it is hard to measure the stress-strain curves of the powder materials using conventional uniaxial tensile test due to the limitation of the size and shape of the specimen. Instrumented nanoindentation can measure mechanical properties of very small region from several nanometers to several micrometers, so nanoindentation technique is suitable to obtain the stress-strain curve of the powder materials. In this study, a novel technique to obtain the stress-strain curves using the combination of instrumented nanoindentation and finite element method was introduced and the flow stress curves of Fe powder were measured. Then obtained stress-strain curves were verified by the comparison of the experimental results and the FEA results for powder compaction test.
분말 표면 조도의 3차원 레이저 분석기를 이용한 정량화와 압분성형체 강도에 미치는 영향 분석
이동준,윤은유,김하늘,강희수,이언식,김형섭,Lee, Dong-Jun,Yoon, Eun-Yoo,Kim, Ha-Neul,Kang, Hee-Soo,Lee, Eon-Sik,Kim, Hyoung-Seop 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.5
Green strength is an important property of powders since high green strength guarantees easy and safe handling before sintering. The green strength of a powder compact is related to mainly mechanical and surface characters, governed by interlocking of the particles. In this study, the effect of powder surface roughness on the green strength of iron powders was investigated using a transverse rupture test. Three-dimensional laser profiler was employed for quantitative analyses of the surface roughness. Two different surface conditions, i.e. surface roughness, of powders were compared. The powders having rough surfaces show higher green strength than the round surface powders since higher roughness leads increasing interlocked area between the contacting powders.
Core-shell 구조를 지니는 하모닉 분말의 성형거동 분석
주수현,박효욱,강수영,이언식,강희수,김형섭,Joo, Soo-Hyun,Park, Hyo Wook,Kang, Soo Young,Lee, Eon Sik,Kang, Hee-Soo,Kim, Hyong Seop 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.2
In this study, effect of core-shell structure on compaction behavior of harmonic powder is investigated. Harmonic powders are made by electroless plating method on Fe powders. Softer Cu shell encloses harder Fe core, and the average size of Fe core and thickness of Cu shell are $34.3{\mu}m$ and $3.2{\mu}m$, respectively. The powder compaction procedure is processed with pressure of 600 MPa in a cylindrical die. Due to the low strength of Cu shell regions, the harmonic powders show better densification behavior compared with pure Fe powders. Finite element method (FEM) is performed to understand the roll of core-shell structure. Based on stress and strain distributions of FEM results, it is concluded that the early stage of powder compaction of harmonic powders mainly occurs at the shell region. FEM results also well predict porosity of compacted materials.
수분사법으로 제조된 순철 분말의 고압비틀림 성형 공정에 의한 치밀화 및 나노결정화
윤은유,이동준,김하늘,강희수,이언식,김형섭,Yoon, Eun-Yoo,Lee, Dong-Jun,Kim, Ha-Neul,Kang, Hee-Soo,Lee, Eon-Sik,Kim, Hyoung-Seop 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.5
In this study, powder metallurgy and severe plastic deformation by high-pressure torsion (HPT) approaches were combined to achieve both full density and grain refinement at the same time. Water-atomized pure iron powders were consolidated to disc-shaped samples at room temperature using HPT of 10 GPa up to 3 turns. The resulting microstructural size decreases with increasing strain and reaches a steady-state with nanocrystalline (down to ~250 nm in average grain size) structure. The water-atomized iron powders were deformed plastically as well as fully densified, as high as 99% of relative density by high pressure, resulting in effective grain size refinements and enhanced microhardness values.