http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
액체금속로 Y-구조물의 비탄성 열응력 해석 및 손상평가에 관한 유한요소해석
곽대영,임용택,김종범,이형연,유봉,Kwak, D.Y.,Im, Y.T.,Kim, J.B.,Lee, H.Y.,Yoo, B. 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.7
LMFBR(Liquid Metal Fast Breeder Reactor) vessel is operated under the high temperatures of 500-550.deg. C. Thus, transient thermal loads were severe enough to cause inelastic deformation due to creep-fatigue and plasticity. For reduction of such inelastic deformations, Y-piece structure in the form of a thermal sleeve is used in LMFBR vessel under repeated start-up, service and shut-down conditions. Therefore, a systematic method for inelastic analysis is needed for design of the Y-piece structure subjected to such loading conditions. In the present investigation, finite element analysis of heat transfer and inelastic thermal stress were carried out for the Y-piece structure in LMFBR vessel under service conditions. For such analysis, ABAQUS program was employed based on the elasto-plastic and Chaboche viscoplastic constitutive equations. Based on numerical data obtained from the analysis, creep-fatigue damage estimation according to ASME Code Case N-47 was made and compared to each other. Finally, it was found out that the numerical predictio of damage level due to creep based on Chaboche unified viscoplastic constitutive equation was relatively better compared to elasto-plastic constitutive formulation.
임용택(Y. T. Im),정기호(K. H. Jung),강성훈(S. H. Kang),이현철(H. C. Lee),김동규(D. K. Kim) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Recently, tip test was proposed and applied for friction measurement for cold forging. In the present paper, earlier works are reviewed to investigate the effect of various experimental conditions with different surface condition of bottom dies, different order of deformation speeds, two different sizes of the specimen, and different types of lubricant such as grease, VG100, VG32, com oil, etc. For all experimental conditions, linear relationships among the shear friction factor, non-dimensionalized measured tip distance, and non-dimensionalized maximum load were confirmed. The slope in the load versus tip distance curves was changed from positive to negative depending on the friction level of the counter punch due to different surface roughness. A single non-dimensional equation for determining the friction factor by the non-dimensional tip distance can be derived based on the conventional (30 ㎜ in diameter) and downsized (10 ㎜ in diameter) tip test results. According to these studies, the tip test was found to be more sensitive and versatile in determining a representative friction factor characterizing the friction conditions for cold forging than other testing methods available so far.
연속적 강소성 가공을 위한 스프링 가압형 ECAP 설계
진영관(Y. G. Jin),전병철(B. C. Jeon),임용택(Y. T. Im) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Severe plastic deformation processing by equal channel angular pressing (ECAP) has attracted noticeable attention because it is an effective technique to produce the ultrafine-grained materials with enhanced mechanical properties. In the present study, split dies combined with the principle of spring-loaded preform process were newly proposed to provide a solution for the inefficiency of ECAP process. The designed and constructed spring-loaded ECAP set-up was used to make the continuous process feasible. Experiments for a single pass of ECAP were carried out to process aluminum alloy AA6061 by using the multi-stage former at room temperature. Vickers microhardness test was applied to investigate strength increase in the specimen deformed by ECAP. The spring-loaded ECAP proposed might be beneficial in commercializing a continuous application of ECAP to produce a high strength part in industry.
고탄소강 온간공형압연의 초기조직에 따른 기계적 성질 고찰
오영석(Y. S. Oh),손일헌(I. H. Son),정경환(K. H. Jung),김동규(D. K. Kim),이덕락(D. L. Lee),임용택(Y. T. Im) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
It is well known that the ultrafine-grained steels, which guarantee both high strength and toughness, were manufactured by warm caliber rolling (WCR) owing to the continuous severe plastic deformation (SPD) technique. In this study, the effect of initial microstructure on the strength and toughness was investigated after WCR of the high carbon steel. The experiments were carried out with two kinds of starting microstructures. For comparison, the reference microstructure of austenite phase was prepared and assumed to be the case of conventional hot rolling. The experiments were conducted at the temperature of 500℃ and the accumulative reduction in area was about 83%. Based on this study, it was found that the product of WCR showed better mechanical properties in terms of strength and toughness compared to the conventional hot rolling. The improvement of strength and toughness was attributed to the grain refinement and delamination of lamellar structure consisting of ferrite and cementite, respectively.
CHABOCHE 통합 점소성 구성방정식을 이용한 재료거동해석
곽대영,임용택,김종범,이형연,유봉,Kwak, D.Y.,Im, Y.T.,Kim, J.B.,Lee, H.Y.,Yu, B. 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.11
Service conditions for structures at elevated temperatures in nuclear power plant involve transient thermal and mechanical load levels that are severe enough to caeuse inelastic deformations due to creep and plasticity. Therefore, a systematic mehtod of inelastic analysis is needed for the design of structural components in nuclear poser plants subjected to such loading conditions. In the present investigation, the Chabodhe model, one of the unified viscoplastic constitutive equations, was selected for systematic inelastic analysis. The material response was integrated based on GMR ( generallized mid-point rule) time integral scheme and provided to ABAQUS as a material subroutine, UMAT program. By comparing results obtaned from uniaxial analysis using the developed UMAT program with those from Runge-Kutta solutions and experimentaiton, the validity of the adopted Chaboche model and the numerical stability and accuracy of the developed UMAT program were verified. In addition, the developed material subroutine was applied for uniaxial creep and tension analyses for the plate with a hole in the center. The application further demonstrates usefulness of the developed program.
한영원(Y.W.Hahn),곽대영(D.Y.Kwak),임용택(Y.T.Im) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.6_2
In order to substitute steel for new material in fabrication of automotive hood, proper stiffness according to the constructed geometry should be guaranted. For this purpose, numerical analyses of self-weight deflection, oil canning test, and torsional deflection were carried out using steel and SMC (Sheet Molding Compound). For optimization of manufacturing cost and structural benefit, several geometries were considered for the arbitrarily selected hood design type. The current approach will be beneficial in determining the proper design parameters for fabrication of hood with new material such as composites or aluminium alloys.<br/>