• Title/Summary/Keyword: 혼합모드 하중

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혼합모드 I+II 피로 하한계 영역에서의 모드II 영향에 관한 고찰

  • 홍석표;송삼홍;이정무
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.05a
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    • pp.113-113
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    • 2004
  • 실제 사용중인 기계나 기계구조물은 다양한 환경 및 복잡한 설계조건으로 인하여 변동하중과 다축에서 작용하는 혼합모드 하중 상태에 놓이는 경우가 대부분이다. 하지만, 순수 모드 I 하중상태 하에서의 연구는 활발히 이루어졌으나, 실제 구조물에서 대부분 발생하는 혼합모드 하중상태 하에서의 연구는 아직 부족한 실정이다. 또한 기계구조물내의 많은 성분요소에 존재하는 작용 하중 방향에 수직적이지 않게 되며, 초기균열의 균열선상에서 성장하지 않는다.(중략)

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혼합모드 피로균열의 응력재분배 상태 하의 전파거동

  • 이정무;송삼홍
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.05a
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    • pp.103-103
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    • 2004
  • 실제 작용하는 하중상태는 요소의 형상과 작용하중의 복잡성 때문에 혼합모드 하중상태를 나타낸다. 또한 혼합모드 피로균열은 전파과정 동안 부재의 구속형상이나 외부 작용하중의 급격한 변화에 의해서도 영향 받게 된다. 이로 인하여 피로균열은 균열선단에서 지속적이면서 급격한 응력 재분배의 상태를 경험한다. 그러므로 다양한 응력 재분배 상태에서의 혼합모드 피로균열에 대한 고찰이 필요하다. 본 연구에서는 응력 재분배상태 하에서 나타나는 혼합모드 피로균열의 전파거동에 대한 특징이 실험적으로 고찰되었다.(중략)

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Effects of Failure Mode II on Crack Initiation and Crack propagation Steps Using Multilevel Fatigue Loading Test (다단계 피로하중 실험을 통한 균열 발생 및 전파단계에서 파괴모드 II 영향 분석)

  • Hong, Seok Pyo;Park, Sae Min;Kim, Ju Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.9
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    • pp.853-860
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    • 2017
  • To evaluate the effects of mode II on the crack initiation and propagation stages, the effects in the fatigue threshold region under a mixed-mode I+II loading state was experimentally investigated. In the case of mixed-mode I + II, during the crack initiation stage, as the loading application angle (${\theta}$) increased, cracks occurred in the lower load owing to the effects of mode II, while the crack propagation rate decreased. The effects of mode II were experimentally investigated in the crack propagation stage by means of multilevel loading direction variation. Following mixed-mode I+II ($0^{\circ}{\rightarrow}{\theta}{\rightarrow}60^{\circ}$), as the load application angle increased, the fatigue crack propagation rate decreased, as did the fatigue crack propagation rate, which occurred later. Following mixed-mode I + II in case of(${\theta}{\geq}75^{\circ}$), the fatigue crack propagation rate was found to increase, while the fatigue life decreased.

Fracture Behavior of Rail Steel under Mixed Mode Loading (혼합모드하에서의 레일강의 파괴거동)

  • Chang, Dong Il;Kim, Sung Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.4
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    • pp.761-769
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    • 1994
  • Actual load acting on rail surface in the track is the combined mode loading due to the contact rolling load of the wheels. To investigate the fracture behavior on rail steel under combined modes I and II, fracture tests were performed by using the test jigs and fracture specimen which were designed by Richard. The analysis results of experimental fracture data were compared with various fracture criteria that have been introduced for determination of the crack propagation direction and the critical stress of fracture of a crack submitted to a mixed mode loading. From the results, it was shown that the actual crack propagation direction of rail steel agree with the crack propagation directions predicted by maximum tangential stress criterion and strain energy density criterion, and that fracture criterion follows principal strain criterion.

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Mixed-mode fracture toughness measurement of a composite/metal interface (복합재료/금속 접착 계면의 혼합모드 파괴인성 측정)

  • Kim, Won-Seock;Jang, Chang-Jae;Lee, Jung-Ju
    • Composites Research
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    • v.24 no.2
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    • pp.1-8
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    • 2011
  • Interfacial fracture toughness under various mixed-mode loading is measured to provide a mixed-mode fracture criterion of a composite/metal bonded joint. Experimental fracture characterization tests were carried out using a SLB (single leg bending) specimen, which controls mode ratio with the specimen thickness. The experimental result of the SLB test conforms that interfacial fracture toughness increases as the mode II component increases. The effect of loading mode on interfacial crack growth is investigated on the basis of crack path observation using microscopic image acquisition technique. The influence of interfacial roughness on adhesion strength is also discussed.

Strain Energy Release Rate of Carbon/Epoxy Composite Material under Mixed Mode Delamination (혼합모우드 층간분리하에 있는 탄소/에폭시 복합재료의 변형에너지 방출율)

  • Yum, Y.J.;You, H.
    • Composites Research
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    • v.12 no.3
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    • pp.66-74
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    • 1999
  • A modified mixed mode bending test was performed to investigate the mixed mode delamination for carbon/epoxy composite material. Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. The modified mixed mode bending test was analyzed to obtain strain energy release rates using beam theory, compliance method and finite element method, This results were in good agreement with the experimental result, which confirmed the validity of this test.

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An Experimental Study on the Fatigue Crack Propagation Behavior Under Mixed-Mode Single Overload (혼합모드 단일과대하중 하의 피로균열 전파거동에 관한 실험적 연구)

  • Song, Sam-Hong;Lee, Jeong-Moo;Hong, Suck-Pyo
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.119-124
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    • 2003
  • In this study, retardation behavior of fatigue crack under single overloading of the mixed mode I+II state was experimentally investigated. To produce single overload in the mixed mode I+II state, the compact tension shear (CTS) specimen and loading device were used. The propagation tests for fatigue crack were performed under mode I loading overloading afterwards. We examined the observed deformation aspects, variation of fatigue life and crack propagation rate, and the aspects of retardation behavior from tests. The retardation effect of mixed-mode single overload on fatigue crack propagation behavior was smaller than that of mode I single overload. It has been confirmed that the retardation behavior did not immediately appear and the retardation length was short when the component of mixed-mode overload was changed.

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