• 제목/요약/키워드: mixed-mode crack

검색결과 205건 처리시간 0.026초

Crack tip plastic zone under Mode I, Mode II and mixed mode (I+II) conditions

  • Ayatollahi, M.R.;Sedighiani, Karo
    • Structural Engineering and Mechanics
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    • 제36권5호
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    • pp.575-598
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    • 2010
  • The shape and size of the plastic zone around the crack tip are analyzed under pure mode I, pure mode II and mixed mode (I+II) loading for small scale yielding and for both plane stress and plane strain conditions. A new analytical formulation is presented to determine the radius of the plastic zone in a non-dimensional form. In particular, the effect of T-stress on the plastic zone around the crack tip is studied. The results of this investigation indicate that the stress field with a T-stress always yields a larger plastic zone than the field without a T-stress. It is found that under predominantly mode I loading, the effect of a negative T-stress on the size of the plastic zone is more dramatic than a positive T-stress. However, when mode II portion of loading is dominating the effect of both positive and negative T-stresses on the size of the plastic zone is almost equal. For validating the analytical results, several finite element analyses were performed. It is shown that the results obtained by the proposed analytical formulation are in very good agreements with those obtained from the finite element analyses.

2축 하중주파수가 피로균열진전거동에 미치는 영향 (The Effect of Behavior Fatigue Crack Propagation on 2-Axle Load Frequency)

  • 김상희;;최성대
    • 한국기계가공학회지
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    • 제14권1호
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    • pp.78-84
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    • 2015
  • The stress state acting on mechanical parts and structures is generally mixed stress. This complex stress state, which is subject to changes in the environment, will produce many. Cars running on roads with different road conditions will subject the automotive parts to combined stress state. In the x direction and the y direction, a different amplitude and frequency of the fatigue load can be present. However, the load amplitude for Mode I and Mode II in a 2-axis fatigue test is limited to a constant ratio; the load frequency is always the same for any mode. In this paper, it is verified how the variation of the load frequency for mode II affects the behavior of fatigue crack propagation under mixed mode.

흑연/에폭시 복합재료의 혼합모우드 층간분리 해석 (Analysis of Mixed Mode Delamination in Graphite/Epoxy Composite)

  • 염영진;유희
    • 한국자동차공학회논문집
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    • 제4권4호
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    • pp.171-178
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    • 1996
  • DCB(pure mode I) and CLS(mixed mode) tests were performed to investigate the effect of fracture mode on the interlaminar fracture of composite laminate. Mode I critical strain energy release rate was found to be $133J/m^2$ from the DCB test and total strain energy release rate decreased from $1, 270J/m^2$ as thickness ratio(tl/t) varied from 0.333 to 0.667 from the crease from the CLS test. Crack length had no effect on the total strain energy release rate and load was almost constant during the crack growth of the specimen which had the specific thickness ratio. Crack initiated when the stress of the strap ply reached constant stress $42kgf/mm^2$ which was found to be independent of the thickness ratio.

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이종 접합체의 원공에서 파생하는 균열에 대한 혼합모드 파괴기준의 설정 (Establishment of Fracture Criteria for Mixed Mode in Bonded Dissimilar Materials with an Crack Emanating from an Edge Semicircular Hole)

  • 정남용;송춘호
    • 대한기계학회논문집A
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    • 제25권6호
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    • pp.907-915
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    • 2001
  • Application of bonded dissimilar materials in many industries are increasing. When these materials are to be used in structures, it needs to evaluate the failure strength applying fracture mechanics. Al/Epoxy bonded dissimilar materials with an interface crack and an interface crack emanating from an edge semicircular hole were prepared, experiment of fracture toughness were carried out. Stress intensity factors of interface cracks in bonded dissimilar materials were computed with boundary element method(BEM) and the fracture criteria of mixed mode crack were analyzed. From the results, the fracture criteria and the method of strength evaluation by the fracture toughness in Al/Epoxy bonded dissimilar materials were proposed.

2축하중을 받는 직교이방성체내 경사균열진전의 해석 (Analysis of Inclined Crack Extension in Orthotropic Solids Under Biaxial Loading)

  • 임원균;최승룡
    • 대한기계학회논문집A
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    • 제26권6호
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    • pp.993-1000
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    • 2002
  • The objective of this work is to develop the capability to analyze accurately the mixed-mode propagation of a crack in composite structures with elastic orthotropic material stiffness properties and anisotropic material strength characteristics. In order to develop the capability to fully analyze fracture growth and failure in anisotropic structures, we examined the fundamental problem of mixed mode fracture by carrying out the analysis on orthotropic materials with an inclined crack subject to biaxial loading. Our goal here is to include an additional term in the asymptotic expansion of the crack tip stress field and to show that the direction of crack initiation can be significantly affected by that term. We employ the normal stress ratio theory to predict the direction of crack extension. It is shown that the angle of crack extension can be altered by horizontal loads and the use of second order term in the series expansion is important f3r the accurate determination of crack growth direction.

혼합형 하중항에 있는 판재로 보강된 균열판의 응력세기계수 (Stress intensity factor in cracked plate reinforced with a plate under mixed mode loading)

  • 이강용;김옥환
    • 대한기계학회논문집A
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    • 제22권3호
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    • pp.569-578
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    • 1998
  • The mode I and II stress intensity factors have been calculated theoretically for the cracked plate reinforced with a plate by symmetric spot welding under remote mixed mode loading. This is the extension of authors' previous work for the reinforced cracked plate under remote normal stress. Regardless of loading types, the reinforcement effect gets better as one joining spot is closer to the crack tip and the others are closer to the crack surface, and optimum number of the joining spots can be existed. For the present model, the remote loading parallel to crack surface produces the mode I stress intensity factor.

균열에너지밀도에 의한 이종재 계면균열의 기초적 검토 (A Fundamental Analysis of an Interface Crack by Crack Energy Density)

  • 권오헌;도변승언;서창민;김영호
    • 대한기계학회논문집
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    • 제16권8호
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    • pp.1458-1467
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    • 1992
  • 본 연구에서는 균질재에서의 결과를 토대로 이종재에서도 그 성질이 보존될 것으로 기대되기 때문에 계면균열에서의 CED의 기본적 성질을 검토한후, 각 모드 인자 의 분리법과 평가법을 CED를 통해 제시한다. 또 제시한 수법을 이용하여 우선 탄성 균열 모델에서 유한요소해석을 통해 CED 및 각 모드 인자의 평가 및 기초적 검토를 실시하여 그 유효성을 확인한다.

Computation of mixed-mode stress intensity factors in functionally graded materials by natural element method

  • Cho, J.R.
    • Steel and Composite Structures
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    • 제31권1호
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    • pp.43-51
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    • 2019
  • This paper is concerned with the numerical calculation of mixed-mode stress intensity factors (SIFs) of 2-D isotropic functionally graded materials (FGMs) by the natural element method (more exactly, Petrov-Galerkin NEM). The spatial variation of elastic modulus in non-homogeneous FGMs is reflected into the modified interaction integral ${\tilde{M}}^{(1,2)}$. The local NEM grid near the crack tip is refined, and the directly approximated strain and stress fields by PG-NEM are enhanced and smoothened by the patch recovery technique. Two numerical examples with the exponentially varying elastic modulus are taken to illustrate the proposed method. The mixed-mode SIFs are parametrically computed with respect to the exponent index in the elastic modulus and external loading and the crack angle and compared with the other reported results. It has been justified from the numerical results that the present method successfully and accurately calculates the mixed-mode stress intensity factors of 2-D non-homogeneous functionally graded materials.

탄소섬유직물/에폭시 복합재의 혼합모우드 층간파괴 거동 (Mixed Mode Interlaminar Fracture Behaviors of Carbon Fabric/Epoxy Composites)

  • 윤성호;허광수;오진오
    • 한국항공우주학회지
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    • 제35권1호
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    • pp.58-65
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    • 2007
  • MMF 시험을 적용하여 혼합모우드 비율을 20%~90%의 범위 내에서 변화시키면서 탄소섬유직물/에폭시 복합재의 혼합모우드 층간파괴 거동을 조사하였다. 혼합모우드 층간파괴 거동을 예측하기 위해 NL점과 5% offset점에 근거한 혼합모우드 층간파괴 결정식을 제시하였다. 파단면 양상과 균열진전 거동은 이동식 현미경과 전자현미경을 통해 조사하였다. 연구결과에 따르면 혼합모우드 층간파괴 거동은 NL점에 근거한 경우 매개변수 m=1.5와 n=0.5, 5% offset점에 근거한 경우 매개변수 m=2와 n=3인 혼합모우드 층간파괴 결정식에 의해 잘 예측되어진다. 파단면 양상과 균열진전 거동은 혼합모우드 비율에 매우 민감하게 변하며 MMF 시험은 혼합모우드 층간파괴인성의 평가에 성공적으로 적용됨을 알 수 있었다.

이종 접합체에 대한 혼합모드 파기기준의 설정 (Establishment of fracture Criterion for Mixed Mode in Bonded Dissimilar Materials)

  • 정남용
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 1998년도 추계학술대회 논문집
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    • pp.254-260
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    • 1998
  • Application of bonded dissimilar materials in various industries are increasing. When these materials are used in structures, it needs to investigate strength evolution applying fracture mechanics. Al/Epoxy bonded dissimilar materials with an interface crack and an interface crack emanating from an edge semicircular hole were prepared for the static tests so that experiment of fracture toughness were carried out. Stress intensity factors of interface cracks in bonded dissimilar materials were computed with boundary element method(BEM) and the fracture criterion of mixed mode crack were analyzed. From the results, the fracture criterion and the method of strength evolution by the fracture toughness in Al/Epoxy bonded dissimilar materials were proposed.

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