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유인동 ( In Dong You ),이만석 ( Man Suk Lee ),김호경 ( Ho Kyung Kim ) 한국안전학회(구-한국산업안전학회) 2012 한국안전학회지 Vol.27 No.3
The fatigue behavior of AM60 magnesium alloy produced by equal channel angular pressing(ECAP) process was investigated through fatigue lifetime and fatigue crack propagation rate tests. The grain structure of the material was refined from 19.2 μm to 2.3 μm after 6 passes of ECAP at 493 K. The yield strength(YS) and ultimate tensile strength (UTS) increase after two passes but decrease with further pressing, although the grain size becomes finer with increasing pass number. The softening effect due to texture anisotropy overwhelmed the strengthening effect due to grain refinement after 2 passes. A large enhancement in fatigue strength was achieved after two ECAP passes. The current finding suggests that two passed material is better than the multi-passed material in view of the static strength and fatigue performance
마그네틱 파우더 브레이크를 이용한 소형 진자형 충격시험기 개발
유인동(You In-Dong),이만석(Lee Man-Suk),김호경(Kim Ho-Kyung) 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.3
A miniature pendular type impact testing machine was designed and developed, adopting a magnetic powder brake in order to investigate tensile and shear behavior of a small solder ball at high speed. In this testing system, the potential energy of the pendulum is transferred into the impact energy during its drop. Then, the impact energy is transmitted through the striker which is connected to the push rods to push the specimen for tensile loading. The tensile behavior of lead-free solder ball in diameter of 760 ㎛ was successfully investigated in a speed range of 0.15 m/s~1.25 m/s using this designed device. The maximum tensile strength of the solder joint decreases with the loading speed in the testing condition. The maximum tensile strength of the joint was 56 ㎫ in the low speed region.
안종곤 ( Jong Gon Ahn ),유인동 ( In Dong You ),권석진 ( Seok Jin Kwon ),김호경 ( Ho Kyung Kim ) 한국안전학회(구-한국산업안전학회) 2012 한국안전학회지 Vol.27 No.2
Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7MPa and 626MPa, respectively. The uniaxial fatigue limit was 422.5MPa, corresponding 67% of the ultimate tensile strength. The ratio of Te/Oe was 0.63. Fatigue strength coefficient and exponent were 1319.5MPa and 0.339, respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal fatigue condition.
안종곤(Ahn, Jong Gon),유인동(You, In Dong),권석진(Kwon, Suk Jin),김호경(Kim, Ho Kyung) 한국도시철도학회 2013 한국도시철도학회논문집 Vol.1 No.1
본 연구는 도시철도에서 운영하고 있는 차량의 차륜재에서 일축 시험편과 이축 비틀림 시험편을 피로 및 인장 시험을 수행하였다. 이를 통하여 다축응력상태에서의 피로수명을 평가하는데 필요한 재료 물성치를 평가하였다. 인장실험 결과 최대 인장강도 및 항복강도는 각각 1027.7 MPa , 626.7 MPa이며 연실율은 40.4%로 나타나 인장 및 항복강도 측면에서 고속 차륜재와 유사하며 연신율은 약 2.5배 우수한 것으로 나타났다. 일축 피로 한도는 422.5 MPa로 인장강도 대비 67%로 나타났으며 이축 비틀림 피로한도 대비 일축 피로한도의 비 τe /σe는 0.63으로 통상적인 연성재에 해당하는 값인 0.6에 근접한다. Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7 MPa and 626 MPa. respectively. The uniaxial fatigue limit was 422.5 MPa, corresponding 67% of the ultimate tensile strength. The ratio of was 0.63. Fatigue strength coefficient and exponent were 1319.5 MPa and 0.339, respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal condition.
안종곤(Ahn jong-gon),유인동(you in-dong),권석진(kwon suk-jin),손영진(son young-jin),김호경(kim ho-kyung) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.10
Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7 MPa and 626 MPa respectively. The uniaxial fatigue limit was 422.5 MPa corresponding 67% of the ultimate tensile strength. The ratio of was 0.63. Fatigue strength coefficient and exponent were 1319.5 MPa and 0.339 respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal fatigue condition.
안종곤(Jong-Gon Ahn),권석진(Seok-Jin Kwon),김호경(Ho-Kyung Kim),유인동(IN-Dong You) 한국트라이볼로지학회 2012 한국윤활학회지(윤활학회지) Vol.28 No.1
Rolling contact fatigue of an urban railway wheel was analysed during its rolling. A FEM analysis was performed using a 3D modelling of rail and wheel, considering the slope of the rail and nonlinear isotropic and kinematic hardening behavior of the rail and the wheel. The maximum von-Mises stress and contact pressure between the rail and wheel were 656.9 MPa and 1111.4 MPa, respectively, under axial load of 85 kN with friction coefficient of 0. The fatigue initiation life prediction relationships by strain-lifetime (ε-N) and Smith-Watson-Topper method were drawn for the wheel steel as follows: N1 = 7.35 × 10<SUP>6</SUP>×SWT<SUP>3.56</SUP>(ε-N) and and N, = 5.41 × 10-9×(Δε/2)-5.77. The fatigue lifetimes of the wheel due to rolling contact were determined to be infinite by ε-N and SWT methods.
혼합모드 하중조건에서의 철도 차륜재의 피로균열 실험에 관한 연구
김택영 ( Taek Young Kim ),이만석 ( Man Suk Lee ),유인동 ( In Dong You ),김호경 ( Ho Kyung Kim ) 한국안전학회(구 한국산업안전학회) 2013 한국안전학회지 Vol.28 No.4
Fatigue crack growth tests were conducted on urban railway wheel steel under mode I and mixed-mode conditions. Fatigue crack growth rates were evaluated in terms of equivalent stress intensity factor ranges, using both the extended and projected crack lengths. The equivalent stress intensity factor range with the growth rate results obtained under mode I loading conditions can be used to predict the crack growth rate under mixed-mode loading conditions. Extended crack length rather than projected crack length is appropriate for the prediction of the crack growth rate under the mixed-mode loading conditions.