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MIM(금속분말사출성형)공법으로 제작된 Fe-2%Ni합금의 미세조직 및 기계적 특성
조규상(K. S. Cho),김민종(M. J. Kim),김관영(K. Y. Kim),정재옥(J. O. Jeong),박시우(S. W. Park),이기안(K. A. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Microstructure and mechanical properties of Fe-2%Ni alloy produced by MIM(Metal Injection Molding) were investigated. Microstructure analysis, tensile test, and high cycle fatigue test were conducted. In the microstructure observation results, non-regular grain and inhomogeneous ferrite and pearlite were appeared. Non-sintered C, Si, Mn including phases were also detected. As a result of tensile test, MIMed Fe-2%Ni alloy represented yield strength of 285,5 MPa, tensile strength 605.7 MPa, and elongation 6.02%. The tensile properties of MIMed Fe-2%Ni alloy showed higher elongation and similar strengths compared to those of conventional Fe-2%Ni alloy. High cycle fatigue limit was obtained as 440 MPa. Micro-mechanisms of tensile and fatigue deformation behaviors in MIMed Fe-2%Ni alloy were also discussed based on the fractography observation.
압출재 6061 알루미늄 합금의 피로특성에 미치는 열처리의 영향
김선호(S. H. Kim),김규식(K. S Kim),어광준(K. J. Euh),조규상(K. S. Cho),이기안(K. A. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The effect of heat treatment on the high-cycle fatigue behavior of 6061 extruded alloys was investigated in this study. Microstructure examination, tensile and high-cycle fatigue test were conducted on both AI-Si-Mg extruded (F) and heat treated (T6) conditions. From the tensile tests, yield and tensile strengths increased and elongation decreased by T6 heat treatment. The high-cycle fatigue results indicated that the fatigue strength of the 6061-T6 alloy was significantly higher than that of the 6061-F alloys. Fatigue cracks were initiated near the surface of specimens regardless of heat treatment. In the case of6061-T6 alloy, 2<SUP>nd</SUP> cracks easily appeared when the fatigue crack met Mg₂Si phase during fatigue propagation. Fine Mg₂Si phases could be formed and homogeneously distributed by T6 heat treatment. The Mg₂Si was believed to act an effective role of retardation of fatigue crack initiation and propagation. The fatigue deformation mechanism of extruded 6061 aluminum alloy was also discussed.
Modified Al-Si-Mg 계 조조용 합금의 ECO-Mg 함량 변화에 따른 인장 및 피로 변형 거동
함기수(G.S. Ham),백상우(S.W. Baek),김민종(M.J. Kim),김세광(S.K. Kim),윤영옥(Y.O. Yoon),조규상(K.S. Cho),이기안(K.A. Lee) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.5
The effect of ECO-Mg addition on the microstructure, tensile and fatigue deformation behaviors of modified Al-Si-Mg casting alloy was investigated. Four different alloys having various amounts of ECO-Mg (0.3, 0.4, 1.0 and 1.5 wt.%) were prepared though sand casting process. OM microscopy, Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X-ray Diffraction (XRD) analyses was examined as well as hardness, tensile, and fatigue tests. Modified aluminum alloy consisted of α-Aluminum (dendrite shape), eutectic Si, Mg₂Si and Fe-intermetallic phases. It was found that DAS(Dendrite Ann Spacing) gradually decreased and eutectic Si, Fe-intermetallic phases were more finely distributed in the matrix with increasing the amount of ECO-Mg. Tensile and fatigue properties were also improved with increasing ECO-Mg content. The micro-mechanisms of tensile and fatigue deformations of the alloy were also discussed based on the fractography observation results.
Modified 2024 알루미늄 합금의 인장 및 피로 연구
김관영(G. Y. Kim),김선호(S. H. Kim),윤영옥(Y. O. Yoon),김세광(S. K. Kim),조규상(K. S. Cho),이기안(K. A. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In this study, the microstructures and mechanical properties of the recently developed Eco-2024-T3 alloy were examined. Eco2024 is made using Eco-Mg(Mg-Al₂Ca)in place of element Mg during the manufacture of alloy 2024-T3. This is an alloy that has economic advantage and excellent properties. Alloy Eco2024 showed smaller crystal grains that were distributed more evenly compared to the existing alloy 2024-T3. It consisted of Al matrices containing minute amounts of Al₂CuMg, Al₂Cu and Ca phases and showed microstructures with reduced amounts of Fe phases or oxide. As a result of tensile test, this alloy exhibited yield strength of 413MPA, tensile strength 527㎫, and elongation of 15.4%. In other words, it showed higher strength than the existing alloy 2024 but was similar to the existing alloy 2024 in terms of elongation. In fatigue tests, alloy Eco2024-T3 recorded fatigue limit of 330 ㎫ around 80% of its yield strength this is a much more excellent property compared to the existing alloy 2024-T3, which has fatigue limit of 250㎫. Based on the aforementioned results, the correlation between the excellent mechanical properties of alloy Eco2024-T3 and its microstructure was examined.
Modified 7075-T73 알루미늄 합금의 고주기 피로 변형 거동
김관영(C. Y. Kim),김선호(S. H. Kim),김세광(S. K. Kim),조규상(K. S. Cho),이기안(K. A. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Fatigue behavior of new developed Modified 7075-T73 alloy was investigated. Microstructure analysis, tensile test, high cycle fatigue test were conducted in this study. In the microstructure observation, average grain size of 2.9 um was measured and reduced oxide content was detected. The alloy consisted of AI matrix, AlzCuMg, MgZnz, and additional Ca including phase. Tensile properties of Modified 7075-T73 alloy were higher than those of convention 7075 AI alloy. Fatigue properties were significantly improved compared to those of conventional alloy (Fatigue limit of 340MPa). The superior tensile and fatigue properties of Modified 7075-T73 alloy were mainly attributed to grain size refinement, homogeneous distribution of 2od phases, and reduced oxides.
Modified 7050-T7451 알루미늄 합금의 고주기 피로 변형 거동에 미치는 Ca첨가의 영향
김관영(G. Y. Kim),김규식(K. S. Kim),김세광(S. K. Kim),조규상(K. S. Cho),이기안(K. A. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
This study examined the microstructures and mechanical and fatigue properties of the recently developed Eco7050-T7451 alloy. Eco7050-T7451 is made using Eco-Mg(Mg-Al₂Ca) in place of the element Mg during the manufacture of alloy 7050-T7451, having economically advantageous and superior properties. In the microstructure observation, average grain size was measured to be 5.2㎛. It consisted of Al matrix containing minute amounts of Al₂CuMg, MgZn₂, And Ca phases and showed microstructure with reduced amounts of Fe phases or oxides. Tensile test exhibited that this alloy had yield strength of 509 MPa, Tensile strength of 559 MPa, elongation of 13.8 %, which showed greater strength than conventional alloy 7050 but the same elongation. Fatigue properties were significantly improved compared to those of conventional alloy (fatigue limit of 350MPa). The superior tensile and fatigue properties of Modified 7050-T7451 alloy were mainly attributed to grain size refinement, homogeneous distribution of 2<SUP>nd</SUP> phases, and reduced oxides.
김규남(K.N.Kim),조규상(G.S.Cho),양태진(T.J.Yang),김경기(K.G.Kim) 대한전자공학회 1992 대한전자공학회 학술대회 Vol.1992 No.10
Multi-layered neural networks are applied to the identification and control of nonlinear dynamical system. Traditional adaptive control techniques can only deal with linear systems or some special nonlinear systems. A scheme for combining multi-layered neural networks with model reference network techniques has the capability to learn the nonlinearity and shows the great potential for adaptive control. In many interesting cases the system can be described by a nonlinear model in which the control input appears linearly. In this paper the identification of linear and nonlinear part are performed simultaneously. The projection algorithm and the new estimation method which uses the delta rule of neural network are compared throughout the simulation. The simulation results show that the identification and adaptive control schemes suggested are practically feasible and effective.
주조용 A356 합금의 피로 변형 거동에 미치는 기공 및 열처리의 영향
이영재(Y. J. Lee),김선호(S. H. Kim),어광준(K. J. Euh),조규상(K. S. Cho),이기안(K. A. Lee) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
The effect of heat treatment on the high-cycle fatigue behavior of A356 casting aluminum alloys was investigated in this study. Microstructure examination, tensile and high-cycle fatigue test were conducted on both Al-Si-Mg casted (F) and heat-treated (T6) conditions. The high-cycle fatigue results indicated that the fatigue strength of the A356-T6 alloy was higher than that of the A356-F alloys. The SEM fractography results showed that porosity affected detrimental effect on the fatigue life: 79% of all tested samples fractured as a result of porosity which acted as the main crack initiation site. It was found that fatigue life decreased as the size of pore increased. The mechanisms of fatigue crack initiation and propagation of A356 alloy, which is correlated with pore and microstructure, was also discussed.