• 제목/요약/키워드: J-Intergral

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J-적분을 이용한 저탄소강의 파괴탄성치 결정 (Fracture toughness of Low-carbon steel using J-intergral Principle)

  • 안득만;곽병만
    • 대한기계학회논문집
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    • 제3권4호
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    • pp.133-142
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    • 1979
  • The fracture toughness of a hot rolled 100 mm thick SS41 steel plate was investigated for various crack ratios and thichnesses using the method of J-integral. The experiments were performed on an MTS machine and the crack initiation point was detected by using an electricl impedance method. The J-integral computed at the initiation point of the slow stable crack growth was almost constant within the range of crack ratios tested. The fracture toughness thus obtained was $J_{1c}/=27.0kgf/mm$ for specimens having fracture plane parallel to the rolling direction and 35.5kgf/mm for those perpendicular to the rolling direction. The J- integral computed at maximum load point was found to be unsuitable for fracture toughness determination, becaese of large variation depending on the crack ratio and thickness. It was also found that the slow stable crack growth increases as the thickness and/or crack ration of the specimen decrease.

점용접시편의 과부하해석 및 유효 J-적분에 의한 피로수명예측 (Overload Analysis and Fatigue Life Prediction Using an Effective J-Integral of Spot Welded Specimens)

  • 이형일;최진용
    • 대한기계학회논문집A
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    • 제24권3호
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    • pp.567-580
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    • 2000
  • This paper proposes an integrated approach, which is independent of specimen geometry and loading type, for predicting the fatigue life of spot welded specimens. We first establish finite element models reflecting the actual specimen behaviors observed on the experimental load-deflection curves of 4 types of single spot welded specimens. Using finite element models elaborately established, we then evaluate fracture parameter J-integral to describe the effects of specimen geometry and loading type on the fatigue life in a comprehensive manner. It is confirmed, however, that J-integral concept alone is insufficient to clearly explain the generalized relationship between load and fatigue life of spot welded specimens. On this ground, we introduce another effective parameter $J_e$ composed of $J_I$, $J_{II}$, $J_{III}$, which has been demonstrated here to more sharply define the relationship between load and fatigue life of 4 types of spot welded specimens. The crack surface displacement method is adopted for decomposition of J, and the mechanism of the mixed mode fracture is also discussed in detail as a motivation of using $J_e$.

해양구조물의 균열불안정성 해석에 대한 파괴역학의 응용 (Application of Fracture Mechanics Method to Ottshore Structural Crack Instability Analysis)

  • ;이희종
    • 한국해양공학회지
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    • 제1권1호
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    • pp.94-103
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    • 1987
  • 균열불안정 해석법인 COD설계곡선법과 R6파괴 평가도법에 있어서 그 응용 한계의 확립과 타당성 수준의 정량화를 위해 포괄적인 비교 연구가 수행되었다. 참고로서 J-적분 균열불안정성 해석법이 이용되었다. 본 연구의 결과로서, 균열확장의 유무에 대한 R6 파괴 평가도법이 매우 우수한 방법임을 보여준다. COD 설계곡선법에 대한 영국 표준국 순서에 따른 결과로서는, 큰 스캐터 밴드를 가진 상당량의 부당성 해를 보여준다. 이러한 COD설계곡선법의 해를 개선하기 위한 새로운 접근법이 개발되었고, 그 타당성이 입증되었다.

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안정피로성장 중인 표면균열 형상변화의 해석 (Analysis of Shape Change of a Surface Crack during Stable Fatigue Growth)

  • 주석재
    • 대한기계학회논문집A
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    • 제20권9호
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    • pp.2843-2853
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    • 1996
  • The multi-point procedure is developed to predict the shape change of a semi-elliptical surface crack during stable fatigue crack growth. 3-D stress intensity factors along a crack front are calculated using the simplified 3-D J-intergral. Crack growth rate coefficient in the Paris law is assumed to be constant along the crack growth. Crack growth rate is set to be the distance between the two parallel tangent lines on the two semi-elliptic crack fronts before and after crack growth.

${\alpha}$-셀룰로오즈의 열분해에 관한 연구(I) - 산촉매 NaCl의 영향 - (Kinetics of Pyrolysis Degradation of on ${\alpha}-Cellulose$. - Effect of Acid Catalysts NaCl-)

  • 나상도;황준호;최경선;설수덕;손진언
    • Elastomers and Composites
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    • 제31권2호
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    • pp.122-129
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    • 1996
  • The Thermal decomposition of the ${\alpha}-Cellulose$ and NaCl was studied using a thermal analysis technique in the steam of nitrogen gas with 30ml/min at various heating ranges from 4 to $20^{\circ}C/min$. The Derivative and Integral method used to be obtained values of activation energy of decomposition reaction. 1. The values of activation energy evaluated by Derivative and Intergral method were consistent with each other very well. 2. The maximum value of heat of decomposition evalated by DSC method was ${\alpha}-Cellulose/NaCl= 90/10$. 3. The thermogravimetric trace curve agreed with the theoretical equation.

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탄소성 파괴역학적 건전성 평가 시스템의 개발 I (A Development of Integrity Evaluation System Based on Elastic Plastic Fracture Mechanics(I) - Specimen Cases -)

  • 김영진;최재붕;손상환;이주진;허용학
    • 대한기계학회논문집
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    • 제14권3호
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    • pp.646-655
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    • 1990
  • 본 연구에서는 EPIES 프로그램의 상세한 내용과 이를 이용한 5가지 파괴역학 시편에 대한 사례 연구에 대하여 보고하고자 한다.

SUS 304鋼 의 크리이프 溫度領域 에 관한 時間依存型 및 사이클依存型 疲勞크랙 傳播 의 遷移 (Transition from Cycle-Dependent to Time-Dependent Fatigue Crack Propagation at Creep Temperature of SUS 304 Steel)

  • 유헌일;주원식
    • 대한기계학회논문집
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    • 제9권5호
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    • pp.539-547
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    • 1985
  • 본 논문에서는 이상과 같은 연구현상을 배경으로 응력비 R.geq.0인 사인응력파 에서도 사이클의존형 크랙전파가 공존하는가, 공존한다면 그 전이를 결정짓는 조건을 구하기 위해, 대표적인 고온용 재료인 SUS 304강을 이용하여 온도 650.deg. C, 대기중에서 반복속도 .nu., 응력비 R, 응력레벨 .sigma.$_{maxo}$등의 실험조건을 바꾸어 고온저사이클 피로실험을 하였다. 또 이 현상의 기초과정을 이해하는데 도움을 주기 위하여 파면 관찰을 행하였다.

하중감소효과를 고려한 원자력 주증기 배관의 균열 안정성 평가 (Crack Stability Evaluation of Nuclear Main Stream Pipe Considering Load Reduction Effect)

  • 고봉환;김영진;석창성
    • 대한기계학회논문집A
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    • 제20권6호
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    • pp.1843-1853
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    • 1996
  • The objective of this paper is to evaluate the crack stability of the nuclear main stresm pipes, considering the load reduction effect due to the presence of circumferential throuth-wall crack. Also, the optimization techniques are adoped tosimulate the crack effect on the elbow component of the piuping system. By using a general beam elemetn which contains a discontinuous cross-section, the piping analysis is accomplished to acquire the reduced load. Considering this reduced load, it is feasible for the LBB application in nuclear main stresm pipe. Also, by combining an optimization program and a genaral finite element analysis program, the appropriate dimensions of the simplified beam elemtn which represents the effect of crack in elbow could be successfully determined.