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김길수(K. S. KIM),박세만(S. M. BAHK),박명균(M. K. PARK) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.11_1
This investigation determines dynamic crack initiation roughnesses(K_id, J_id) of metallic materials such as SM20C and STD 11. Dynamic fracture toughnesses were was evaluated by conducting instrumented charpy impact tests. Specially, in this study, signals obtained from the strain gage implanted in the impact tup is transformed to Load-Time data by digital signal processings. To obtain appropriate data, the data were critically reviewed and tested against three criteria; inertia effects, limited frequency responses and energy levels. Initiation energy was determined using the method of compliance changing rate and was corrected to take into account of energy which was absorbed by inertia force.<br/>
계장화 샤피충격시험기를 이용한 재료의 동적파괴특성에 관한 연구
김길수(K. S. KIM),김기동(K. D. KIM),박세만(S. M. BAHK),박명균(M. K. PARK) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
This investigation determines dynamic fracture characteristics of metals such as SM45C, SM20C and SS41. One of the dynamic' characteristics, dynamic fracture toughness, was evaluated by conducting instrumented charpy impact tests. Specially, in this study, signals obtained from the strain gage implanted in the impact tup is transformed to Load-Time data by digital signal processing. To obtain appropriate dynamic fracture toughness, the Load-Time data is critically reviewed and tested based on three criteria; inertia effect, limited frequency response and energy levels. This procedure ensures the reliability of the data. The data is, then, examined in view of topological aspects of fractured surfaces of the metals to reveal dynamic natures of materials failure.<br/> <br/>
3차원 탄소성 유한요소법을 이용한 SiC 휘스커강화 AI복합재와 ZrO₂접합체의 잔류응력해석
주재황(J.H.JOO),박명균(M.K.PARK),박세만(S.M.BAHK) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_1
Employing a three dimensional finite element method a thermal elasto-plastic stress analysis was conducted to investigate residual stress distributions on the joining area between a ceramic(ZrO₂) and a SiC whisker-reinforced aluminum (AI composite). For purposes of comparisons, residual stresses at the interfaces on the joining area were first analyzed for<br/> varying volume fractions of SiC whiskers utilizing two dimensional elasto-plastic models. The<br/> results from the 2-D models were compared with those from 3-D models to understand the practical nature of residual stresses produced during industrial joining procssses for ceramics and metal matrix composites. Additionally, the same procedures were applied to compute stress variations along a line passing through the joining area to obtain a physical insight and to offer a plausible explanations for fracture patterns occuring at the interfaces during bending.<br/>
Brazing 과 Metallizing에 의한 세라믹/금속 접합재 잔류응력의 유한요소 해석
최영택(Y.T.Choi),박명균(M.K.Park),박세만(S.M.Bahk),선동주(D.J.Sun) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
In this study finite element method(FEM) is utilized to determine residual stress distributions induced by heat generated during joining processes of ceramics and metals.<br/> The finite element analysis is focused on the joining area. That comprises the interfacial area between a metal and a insert-layer. The inser-tlayer itself and adjoining area between the insert-layer and a ceramic.<br/> The residual stress distributions on the joining area are analyzed as functions of thicknesses and yield stresses of the insert-layer(Brazing Filler Metal). And for different kinds of metals including SUS304 and SM45C.<br/> Two typical joining processes are considered in this investigation: Active Metal Brazing and Metallizing. Stress distributions on the joining areas are computed for both processes and are compared with one another. This comparison can lead to the better joining method in reducing the residual stresses and consequently provide improved joining technologies.<br/>
유한요소법을 이용한 단순인장 시험편의 탄소성파괴인성치 예측
선동주(D.J.Sun),박명균(M.K.Park),박세만(S.M.Bahk),최영택(Y.T.Choi) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
In oder to predict the elastic-plastic fracture toughness for metallic materials, Finite Element Method(FEM) was used for analysis of compact tension specimen. ASTM E399 test procedure was adopted for simulation of FEM. The Load-Crack Mouth Opening Displacement curve obtained from this analysis was used to detect the crack initiation point and determine the elastic-plastic fracture toughness J_IC. In order to prove the results, they were compared with the results from previous experiments and they agree with experimental results.
정재진(J.J.Jung),박명균(M.K.Park),박세만(S.M.Bahk.) 한국자동차공학회 1994 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A two dimensional finite element analysis was performed to study residual stress distributions in ceramic/metal joints with a copper interlayer between the ceramic and the metal. Residual stress distributions due to differences in material properties were investigated by varying material parameters. Specifically, stress distributions between the copper later and ceramics, and between the copper layer and metals were computationaly analyzed. A thermo-elastic-elastic-plastic finite element analysis was conducted to determine effects of interlayer properties on residual stress distributions. Based on the results of current analysis, recommendations were made to decrease the residual stresses in ceramic/metal joints.