• Title/Summary/Keyword: 연화역

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Study on Softening Characteristics of 9Cr-1Mo Steel Weldments for High Temperature and Pressure Vessels Application (고온고압장치 적용을 위한 9Cr-1Mo강 용접부의 연화특성에 관한 연구)

  • 이영호;이규천;윤의박;김기철
    • Journal of Welding and Joining
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    • v.10 no.3
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    • pp.40-53
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    • 1992
  • 고온고압장치(High Temperature and Pressure Vessels)의 적용을 위한 기초연구로서 9Cr-1Mo강 용접부의 연화특성에 대하여 검토하였다. 9Cr-1Mo 강재에 Bead-on-Plate용접을 실시한 후, 용접부의 기계적 성질과 그 현미경조직관찰 및 미세경도를 측정한 결과, As-Welded 및 용접 후열처리(PWHT)등의 조건에 관계없이 용접열향부의 변태역과 템퍼링역의 경계에서 모재의 경 도보다 낮은 경도값(연화역)을 나타내었으며 이러한 원인은 결정립계(Grain boundary)에 석출 되는 탄화물의 형성에 의한 뜨임 현상임이 판명되었다.

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The Effect of Fiber Volume Fraction on the Tension Softening Behavior of Steel Fiber-Reinforced Ultra High Strength Concrete (섬유혼입률이 강섬유보강 초고강도 콘크리트의 인장연화거동에 미치는 영향)

  • Kang, Su-Tae;Hong, Ki-Nam;Han, Sang-Hoon;Kim, Sung-Wook
    • Journal of the Korea Concrete Institute
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    • v.21 no.1
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    • pp.13-20
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    • 2009
  • The influence of steel fiber volume on the tension softening behavior in steel fiber-reinforced ultra high strength concrete was investigated. Three-point bending test (TPBT) with notched beams was performed and inverse analysis method by Uchida et al. was adopted to obtain the tension softening behaviors from the results of TPBT. It could be found that the intial stiffness was constant regardless of steel fiber volume, the increase of steel fiber volume fraction made the tensile strength higher, but all of the curves converged on an asymptote with a crack width. It was proposed the equation of softening curve expressed by combination of plastic behavior part and exponential descending behavior part considering the steel fiber volume fraction and $\omega_0$, which is corresponding to the maximum crack width of plastic area. Thereafter, the crack propagation analysis using finite element method with smeared crack model was also carried out and it was confirmed that the proposed equation had a good agreement with the experimental results.

Constitutive modeling for rock joints of tunnel (터널 암반절리에 대한 구성방정식 모델링)

  • Park, Inn-Joon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.101-111
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    • 2002
  • The purpose of this research is to develop improved model for joints of tunnel based on Disturbed State Concept (DSC) model. DSC model is verified with respect to comprehensive laboratory tests performed by Schneider and back prediction results. Based on results of this research, it can be stated that DSC model is capable of characterizing the strain softening and dilative behavior of rough granite joints under four different constant normal stresses.

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Moment-Curvature Analysis of Steel Fiber-Reinforced Ultra High Performance Concrete Beams with Tension Softening Behavior (인장연화거동을 고려한 강섬유 보강 초고성능 콘크리트 보의 모멘트-곡률 해석)

  • Yang, In-Hwan;Joh, Chang-Bin;Kim, Byung-Suk
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.3
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    • pp.237-248
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    • 2011
  • Tensile softening characteristics play an important role in the structural behavior of steel fiber-reinforced ultra high performance concrete. Tension softening modeling and numerical analysis method are necessary for the prediction of structural performance of steel fiber-reinforced concrete. The numerical method to predict the flexural behavior is proposed in this study. Tension softening modeling is carried out by using crack equation based on fictitious crack and inverse analysis in which load-crack opening displacement relationship is considered. Thereafter material modeling is performed considering tension softening. The comparison of moment-curvature curves of the numerical analysis results with the test results indicates a reasonable agreement. Therefore, the present numerical results prove that good prediction of flexural behavior of steel fiber-reinforced ultra high performance concrete beams can be achieved by employing the proposed method.

Effect of fiber volume fraction on the tensile softening behavior of Ultra High Strength Steel Fiber-Reinforced Concrete (섬유혼입률이 초고강도 강섬유 보강 콘크리트의 인장연화거동에 미치는 영향)

  • Kang, Su-Tae;Park, Jung-Jun;Lee, Si-Young;Park, Gun;Hong, Sung-Wook;Kim, Sung-Wook
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.421-424
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    • 2008
  • Ultra high strength steel fiber-reinforced concrete is characterized with high tensile strength and ductility. This paper revealed the influence of fiber volume fraction on the tensile softening behaviour of ultra high strength steel fiber-reinforced concrete and developed tensile softening model to predict the deformation capacity by finite element method analysis with experimental results. The initial stiffness of ultra high strength steel fiber-reinforced concrete was constant irrespective of fiber volume fraction. The increase of fiber volume fraction improved the flexural tensile strength and caused more brittle softening behaviour. Finite element method analysis proposed by Uchida et al. was introduced to obtain the tensile softening curve from three point notched beam test results and we proposed the tensile softening model as a function of fiber volume fraction and critical crack width.

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Numerical Analysis of Load Carrying Capacity of RC Structures Based on Concrete Damage Model (콘크리트 손상 모델을 적용한 콘크리트 구조물 구조내력 해석)

  • Woo, Sang Kyun;Lee, Yun;Yi, Seong Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.5
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    • pp.121-128
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    • 2012
  • In this paper, nonlinear analysis for reinforced concrete structure for power transmission line is performed by considering the characteristics of the failure, which are depend on loading conditions and concrete material models. On the numerical evaluation for the failure behavior, the finite element analysis is applied. For the concrete material model, microplane model based on concrete damage is introduced. However, to describe the crack bridging effect of long and short fiber of steel fiber reinforced concrete (SFRC), tensile softening model is suggested and applied for SFRC. An numerical results by finite element technique are compared with the experiment results for box culvert specimen. Comparing on the experimental and analytical results, validity and reliability of numerical analysis are investigated.

Pb Isotopic Composition of Yeonhwa and Janggun Pb-Zn Ore Deposits and Origin of Pb: Role of Precambrian Crustal Basement and Mesozoic Igneous Rocks (연화 및 장군 연-아연 광상의 Pb 동위원소 조성 및 Pb의 근원: 선캠브리아 기저 지각 및 중생대 화성암의 역할)

  • Park Kye-Hun;Chang Ho Wan
    • The Journal of the Petrological Society of Korea
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    • v.14 no.3 s.41
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    • pp.141-148
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    • 2005
  • Lead isotopic compositions are analyzed from the sulfide minerals of the Yeonhwa, Janggun and Uljin deposits and from host limestone, intrusives, and basement rocks to reveal the source of Pb in these deposits. In the $^{206}Pb/^{204}Pb$ vs $^{207}Pb/^{204}Pb$ plot, Galenas from the Yeonhwa mine display relatively well defined positive linear array, similar to the Precambrian basement rocks of the Korean peninsula. A galena sample from the Uljin mine, Janggun limestone and the basement rocks also follow the variation of Yeonhwa mine. However, ore minerals from the Janggun mine, having relatively low $^{206}Pb/^{204}Pb$ values, reveal offset from such trend toward lower $^{207}Pb/^{204}Pb$ values. Considering the fact that Mesozoic igneous rocks and ores within the Gyeongsang basin display considerably lower $^{207}Pb/^{204}Pb$ values than basement rocks of the Korean peninsula, the deviation of Janggun ore minerals can be interpreted as to reflect mixing between leads from old continental crustal materials and from Mesozoic igneous rocks with more mantle signature. The lead of the Yeonhwa and Uljin mine, following trend of Precambrian basement rather well, seems to have been originated mostly from such basement. However, regarding that they occupy low $^{207}Pb/^{204}Pb$ side of the variation trend of the basement, the possibility of having some leads derived from the Mesozoic igneous rocks cannot be excluded.