• Title, Summary, Keyword: 연성파괴

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構造材料의 破壞 및 機能과 設計 (V) -정성파양과 기구-

  • 송삼홍
    • Journal of the KSME
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    • v.19 no.5
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    • pp.380-384
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    • 1979
  • 본 강좌(V)에서는 특히 연성파괴의 개요와 그 기구에 대하여 기술하여 보겠다. 기술하는 내용은 연성파괴의 형식, 연석파괴에 대한 역학적인 금속조직학적 인자와의 관계 및 연성파괴에 대한 이론적인 취급의 일예등이며, 이들에 대한 개요를 가능한 범위내에서 서술식으로 기술하겠다. 본 강좌는 학회지 내용을 보다 쉽게 하자는 편집 방법에 따라 매우 기초적인 것만을 다루었다.

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破面解析과 그 應용(II)

  • 김정규
    • Journal of the KSME
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    • v.24 no.2
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    • pp.106-114
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    • 1984
  • 이글에서는 파면해석과 그 응용에 관하여 알아보았다. 1. 정량 파면해석과 파괴역학 1.1 연성파괴 1.2 취성파괴 1.3 파괴인성

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파괴역학 연구의 고찰

  • 구인회
    • Journal of the KSME
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    • v.23 no.3
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    • pp.186-190
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    • 1983
  • 파괴역학 연구를 대상재료에 의해 구분하면 선형파괴와 탄소성재료의 파괴로 나눌 수 있다. 취 성파괴(brittle fracture)를 다루는 선형타성 파괴역학연구는 주로 여러가지 크랙의 모양, 시편모양, 부하형태에 따른 탄성응력분포 혹은 은력확대계수를 구하거나 에너지방법에 의해 안정비안정 크랙전파를 연구한다. 대개의 경우 취성파괴는 전체 구조물에 치명적이 되기 쉽다. 따라서 구조물 설계시에 취성파괴의 가능성을 배제하기 위해 재료의 적절한 선택과 같은 대책을 강구하는 것이 바람직하다. 다시 말해, 구조물 재료는 강도와 연성의 상황에 따른 적절한 조합을 필요로 한다. 오늘날 특수합금과 같은 고강도 금속에서의 취성화 경향이 증가하나 합금설계시 강도와 아울러 연성을 증가시키기 위한 여러 대책이 파괴역학 연구의 중요한 부분을 차지한다.

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Earthquake Resistance Design for a Typical Bridge Substructure (일반교량 하부구조의 내진설계)

  • Kook, Seung-Kyu
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.3
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    • pp.283-288
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    • 2011
  • For the earthquake resistance design designer should provide that structural yielding process is principally designed with the ductile failure mechanism. In order to get the ductile failure mechanism for typical bridges, pier columns yielding should occur before that of connections. However domestic bridge design with unnecessary stiff substructure leads to unnecessary seismic loads and makes it difficult to get the ductile failure mechanism. Such a problem arises from the situation that earthquake resistant design is not carried out in the preliminary design step. In this study a typical bridge is selected as an analysis bridge and design strengths for connections and pier columns are determined in the preliminary design step by carrying out earthquake resistant design. It is shown through this procedure that it is possible to get the ductile failure mechanism with structural members determined by other design.

No Collapse Design for Typical Bridges (일반교량의 붕괴방지설계)

  • Kook, Seung-Kyu
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.27 no.3
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    • pp.163-172
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    • 2014
  • The purpose of earthquake resistant design for typical bridges is the No Collapse Design and the Earthquake Resistant Design Part of Roadway Bridge Design Code provides a design process to construct the Ductile Failure Mechanism for the bridge structure. However, if it is not practical to provide the Ductile Failure Mechanism due to structure types or site conditions, the Brittle Failure Mechanism is an alternative way to get the No Collapse Design. As well as the existing design process constructing the Ductile Failure Mechanism, the Earthquake Resistant Design Part provides a ductility-based design process as an appendix, which is prepared for bridges with reinforced concrete piers. According to the new design process, designer determines a required response modification factor for substructure and transverse reinforcement for confinement therefrom. In this study, a typical bridge with steel bearing connections and reinforced concrete piers is selected for which the existing as well as the ductility-based design processes are applied and different results from the two design processes are identified. Based on the results, an earthquake resistant design procedure is proposed in which designers should consider the two design processes.

Fracture Prediction in Drawing Processes of AZ31 alloy Sheet by the FEM combined with a Ductile Fracture Criterion considering Strain Rate Effect (변형률 의존성 연성파괴이론과 유한요소법에 의한 AZ31합금 판재의 드로잉 성형공정시 파단발생 예측)

  • Kim, Sang-Woo;Lee, Young-Seon;Kim, Dae-Yong
    • Proceedings of the KAIS Fall Conference
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    • pp.614-616
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    • 2011
  • 본 연구에서는 유한요소법과 변형률 의존성 연성파괴이론을 이용하여 드로잉 공정에서의 AZ31 마그네슘 합금 판재의 파단 발생을 예측 하였다. 다양한 온도에서의 사각컵 드로잉 실험을 수행하여, 각 온도조건에서의 파단깊이를 측정하였으며, 고온 인장시험을 통해 연성파괴상수를 온도 및 변형률 속도에 의존적인 값으로 표현하고, 실험과 동일하게 모사된 유한요소해석을 수행하였다. 해석결과 얻어진 각 요소의 온도 및 변형률 속도에 따른 연성파괴상수를 이용하여 파단발생을 예측하였으며, 실험결과와 검증하였다.

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Analysis on Dynamic Ductile Fracture of Transportation Pipeline for Carbon Dioxide Capture and Storage System (CO2 배관의 연속연성파괴 분석)

  • Jeong, Hyo-Tae;Choe, Byung-Hak;Kim, Woo-Sik;Baek, Jong-Hyeon
    • Journal of the Korean Institute of Gas
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    • v.18 no.3
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    • pp.13-19
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    • 2014
  • Dynamic ductile fracture (DDF) has been studied in the transportation pipeline for the carbon dioxide capture and storage(CCS) system. DDF behavior of CCS transportation pipeline has been analyzed using Battelle Two Curve Method (BTCM) and compared with the DDF behavior of natural gas pipeline. The operating safety criteria against the DDF has been investigated based on the sensitivity analyses of the pipe thickness and the operating temperature for the $CO_2$ pipeline. The DDF criteria can be applied to confirm the operating safety of the $CO_2$ pipeline. If the commercial natural gas pipeline were used at room temperature as a $CO_2$ pipeline, the thickness of pipe should be at least 7mm and the pressure should be less than 54bar for the $CO_2$ pipeline system.

Estimation of fracture toughness of X65 and X70 steels by DWTT (X65 및 X70강 가스배관의 DWTT 및 파괴인성평가)

  • Cho, Ye-Won;Song, Young-Ho;Kim, Jeong-Min;Kim, Woo-Sik;Park, Joon-Sik
    • Journal of the Korean Institute of Gas
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    • v.16 no.3
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    • pp.54-64
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    • 2012
  • DWTT (Drop Weigh Tearing Test) is one critical method that can exhibit the fracture properties of line pipe steel, since it estimates the properties with real pipe steel. In this study, the ductile portion, inverse fracture ratio and absorbed energy of API X65 and X70 line pipe steels were estimated with temperature variation. Both steels showed that the ratio of ductile area and absorbed energy were decreased with respect to decreasing the test temperature. However, while the ductile fracture behavior exhibited until $-40^{\circ}C$ for the X70 steel, but it showed until $-30^{\circ}C$ for the X65 steel. The fracture properties were discussed with respect to test temperatures.

A Numerical Ductile Failure Simulation Technique Based on Phenomenological Damage Concept (수치해석을 이용한 현상학적 연성파괴 모사 기법)

  • Kim, Nak-Kyun;Oh, Chang-sik;Min, Sung-hwan;Kim, Yun-Jae
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.5 no.2
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    • pp.27-34
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    • 2009
  • This paper proposes a simple numerical method to simulate ductile failure behaviors. The method is based on finite element analysis with a simple damage theory. To validate the proposed method, simulated results are compared with experimental data. Despite its simplicity, the proposed method well predicts experimental results systematic analyses are also performed to investigate the effect of the element size.

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Microscopic fracture criterion of crack growth initiation (연성 균열성장 개시의 미시적 파괴조건)

  • 구인회
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.5
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    • pp.740-745
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    • 1987
  • For the prediction of the crack growth initiation from a blunt notch or a precrack in a prestrained material under plane strain tension and small-scale yielding conditions, a microscopic fracture criterion is proposed in terms of the crack tip opening displacement(COD) needed for the attainment of fracture strain at a microstructural distance. Smooth blunting of a crack tip with an initial root radius is assumed, and strain distributions on the crack-line axis are calculated at each deformation stage until the distributions against an original distance normalized to the COD are insensitive to an initial root radius. This case of no initial-root-radius effect is taken as for a sharp crack tip, on which the criterion is applied to determine the characteristic length of material from a critical COD for a fatigue-precracked specimen. The predicted COD at the fracture initiation from a crack with an initial root radius or a prestraining shows reasonable agreement with experimental values.