• 제목/요약/키워드: Mixed Mode Crack

검색결과 207건 처리시간 0.021초

Brittle fracture analysis of the offset-crack DCDC specimen

  • Ayatollahi, M.R.;Bagherifard, S.
    • Structural Engineering and Mechanics
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    • 제29권3호
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    • pp.301-310
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    • 2008
  • Applications of fracture mechanics in the strength analysis of ceramic materials have been lately studied by many researchers. Various test specimens have been proposed in order to investigate the fracture resistance of cracked bodies under mixed mode conditions. Double Cleavage Drilled Compression (DCDC) specimen, with a hole offset from the centerline is a configuration that is frequently used in subcritical crack growth studies of ceramics and glasses. This specimen exhibits a strong crack path stability that is due to the strongly negative T-stress term. In this paper the maximum tensile stress (MTS) criterion is employed for investigating theoretically the initiation of brittle fracture in the DCDC specimen under mixed mode conditions. It is shown that the T-stress has a significant influence on the predicted fracture load and the crack initiation angle. The theoretical results suggest that brittle fracture in the DCDC specimen is controlled by a combination of the singular stresses (characterized by KI and KII) and the non-singular stress term, T-stress.

다단계 하중방향 변화에 의한 피로균열 전파거동에서의 모드II 영향 (Effect of Mode II in The Fatigue Crack Propagation Behavior by Variation of Multilevel Loading Direction)

  • 홍석표;송삼홍
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2004년도 추계학술대회 논문집
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    • pp.725-728
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    • 2004
  • In this study, the effect of mode II by variation of multilevel loading direction was experimentally investigated in the fatigue crack propagation behavior. To generate mixed-mode I+II loading state, the compact tension shear(CTS) specimen and loading device were used in this tests. The experimental method divided into three steps and three cases that were step I(0$^{\circ}$), step II(30$^{\circ}$, 60$^{\circ}$, 90$^{\circ}$),step III(0$^{\circ}$) and case I(0$^{\circ}$ ⇒ 30$^{\circ}$ ⇒ 0$^{\circ}$), case II(0$^{\circ}$ ⇒ 60$^{\circ}$ ⇒ 0$^{\circ}$), case III(0$^{\circ}$ ⇒ 90$^{\circ}$ ⇒ 0$^{\circ}$). The result of test, the step II affected to the step III in the all case. Specially, The fatigue crack propagation rate was faster and the fatigue life was smaller than of mixed mode I+II(30$^{\circ}$,60$^{\circ}$) due to the effect of mode II in the step III of the case III

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CFRP 복합재료의 혼합모드 I/II 층간파괴인성치에 관한 연구 (A Study on Mixed Mode I/II Interlaminar Fracture Toughness of Carbon Fiber Reinforced Plastic Composites)

  • 김형진;박명일;김재동;고성위
    • 동력기계공학회지
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    • 제4권3호
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    • pp.48-54
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    • 2000
  • This paper describes the effect of molding pressure, specimen geometries for Mixed Mode I/II interlaminar fracture toughness of carbon fiber reinforced plastic composites by using asymmetrical double cantilever beam(ADCB) specimen. The value of $G_{I/IIC}$ as a function of various molding pressure is almost same at 307, 431, 585 kPa. However it shows the highest value under 307 kPa molding pressure. The effect of $G_{I/IIC}$ due to the change of initial crack length of ADCB specimen was almost negligible in this study. It turns out that the condition for mix mode quasi-static crack growth in ADCB specimen is the ratio of the crack length to that of the specimen, i.e., ${\alpha}/L<0.4$.

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경계요소법에 의한 포물선형 인장과 비틀림을 받는 유한폭 판재의 혼합 Mode 표면균열에 대한 해석 (Analysis of Mixed Mode Surface Crack in Finite-Width Plate Subjected to Uniform Shearing by Boundary Element Method)

  • 박성완;홍재학
    • 한국정밀공학회지
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    • 제7권4호
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    • pp.103-116
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    • 1990
  • The mixed mode surface crack in finite-width plate subjected to uniform shearing has been analyzed in 3-D problem by using boundary element method. The calculations were carried out for the surface crack angles (${\alpha}$) of $0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}, 60^{\circ}, and 75^{\circ}, $ and for the aspect ratio(a/c) of 0.2, 0.4, 0.6 and 1.0 to get stress intensity factors at the boundary points of the surface crack. For the aspect ratio of 1.0 and the surface crack angles, finite element method was used to check the results in this in this study. Comparison of the results from both method showed good agreement.

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경계요소법에 의한 포물선형 인장과 비틀림을 받는 유한폭 판재의 혼합 Mode 표면균열에 대한 해석 (Analysis of Mixed Mode Surface Crack in Finite-Width Plate Subjected to Uniform Shearing by Boundary Element Method)

  • 박성완;홍재학
    • 한국정밀공학회지
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    • 제7권4호
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    • pp.117-129
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    • 1990
  • The mixed mode surface crack in finite-width plate subjected to uniform shearing has been analyzed in 3-D problem by using boundary element method. The calculations were carried out for the surface crack angles (${\alpha}$) of $0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}, 60^{\circ}, and 75^{\circ}, $ and for the aspect ratio(a/c) of 0.2, 0.4, 0.6 and 1.0 to get stress intensity factors at the boundary points of the surface crack. For the aspect ratio of 1.0 and the surface crack angles, finite element method was used to check the results in this in this study. Comparison of the results from both method showed good agreement.

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단일과대하중의 작용모드가 피로균열의 전파거동에 미치는 영향 (Effects by Applying Mode of Single Overload on Propagation Behavior of Fatigue Crack)

  • 송삼홍;이정무
    • 한국정밀공학회지
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    • 제21권6호
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    • pp.109-116
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    • 2004
  • In this study, when variable-amplitude load with various applying mode acts on the pre-crack tip, we examined how fatigue cracks behave. Hence aspects of the deformation caused by changing the applying mode of single overload and propagation behavior of fatigue crack were experimentally examined: What kinds of the deformation would be formed at pre-crack and its tip\ulcorner What aspects of the residual plastic deformation field would be formed in front of a crack\ulcorner How aspects of the plastic zone could be evaluated\ulcorner As applying mode of single overloading changes, the deformation caused by tensile and shear loading variously showed in each applying mode. The different aspects of deformation make influence on propagation behavior of cracks under constant-amplitude fatigue loading after overloading with various modes. We tried to examine the relationship between aspects of deformation and fatigue behavior by comparing the observed deformation at crack and crack propagation behavior obtained from fatigue tests.

초기 균열길이 및 섬유방향이 CFRP/GFRP 하이브리드 적층재의 층간 파괴에 미치는 영향 (The Effects of the Initial Crack Length and Fiber Orientation on the Interlaminar Delamination of the CFRP/GFRP Hybrid Laminate)

  • 권오헌;권우덕;강지웅
    • 한국안전학회지
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    • 제28권1호
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    • pp.12-17
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    • 2013
  • Considering the wind power system and the rotor blades which are composed of much technology, the wind power blade would be the most dangerous part because it revolves at high speed and weighs about dozens of tons, if the accident happens. Therefore, the light weight composite materials have been replacing as substitutional materials. The object of this study is to examine the delamination and damage for CFRP/GFRP hybrid composite that is used for strength improvement of a wind power blade. The influence of the initial crack length and fiber orientation for the interlaminar delamination was exposed for the blade safety. Plain woven CFRP instead of GFRP was inserted into the layer of the box spar for improving the strength and blade life. DCB(Double Cantilever Beam) specimen was used for evaluating fracture toughness and damage evaluation of interlaminar delamination. The material used in the experiment is a commercial material known as CF 3327 EPC in plain woven carbon prepreg(Hankuk Carbon Co.) and UD glass fiber prepreg(Hyundai Fiber Co.). From the results, crack growth rate is not so different according to the variation of the initial crack length. Mode I interlamainar fracture toughness of fiber direction $0^{\circ}$ is higher than that of $45^{\circ}$. Interlaminar fracture has an effect on fiber direction and K decreased with lower value according to increasing initial crack length. Also energy release rate fracture toughness was evaluated because CFRP/GFRP hybrid composite with a different thickness is under the mixed mode loading condition. The interlaminar fracture was almost governed by mode I fracture even though the mixed mode.

에너지 방출률에 의한 접착이음의 계면균열에 대한 파괴인성의 평가 (Evaluation of Fracture Toughness by Energy Release Rate for Interface Crack in Adhesively Bonded Joints)

  • 정남용;이명대;강삼근
    • 대한기계학회논문집A
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    • 제24권9호
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    • pp.2174-2183
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    • 2000
  • In this paper, the evaluation method of interfacial fracture toughness to apply the fracture toughness was investigated in adhesively bonded joints of AI/Ced./A1. Four types of adhesively bonded double-cantilever beam(DCB) joints with the interface crack were prepared for the test of interfacial fracture toughness. The experiments to measure the interfacial fracture toughness were performed under the various mixed-mode conditions. The critical energy release rate, Gc, was obtained by the experimental measurement of compliances. From the experimental results, the interfacial fracture toughness for the mixed-mode specimens is well characterized by the energy release rate, and the method of strength evaluation by the interfacial fracture toughness was discussed in adhesively bonded joints.

혼합모우드 변형하에 있는 복합재료 유한평판의 경사진 균열해석 (Analysis of an Inclined Crack in Finite Composite Plate Under Mixed Mode Deformation)

  • 염영진;홍창선
    • 대한기계학회논문집
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    • 제13권4호
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    • pp.625-635
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    • 1989
  • 본 논문에서는 이 방법을 사용하여 glass/epoxy와 graphite/epoxy 유한평판이 균일응력과 균일변위 경계조건을 받을 때 평판 종횡비 H/W를 1,2,3, 균열길이와 폭의 비 L/W를 0.1부터 0.7까지, 균열각도를 0, 30, 45, 60으로 변화 시키면서 응력강도수정계수를 구하려고 한다.

Al/Steel 이종재료의 접착이음에 대한 혼합모드의 파괴기준 (Fracture criterion of mixed mode in adhesively bonded joints of Al/Steel dissimilar materials)

  • 정남용;장진모
    • 대한기계학회논문집A
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    • 제21권8호
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    • pp.1322-1331
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    • 1997
  • A method of strength evaluation applying fracture mechanics in the adhesively bonded joints of Al/Steel dissimilar materials was investigated in this paper. Various shapes of adhesively bonded Al/Steel scarf joints focussing on fracture criterion of mixed mode crack were prepared for the static tests. Also, stress intensity factors of the interface cracks in adhesively bonded joints of Al/Steel dissimilar materials were analyzed with 2-dimensional elastic program of boundary element method(BEM), and the experiment of fracture toughness were carried out under various mixed mode conditions. From the results, the fracture criterion and method of strength evaluation by the fracture toughness in adhesively bonded joints of Al/Steel dissimilar materials were proposed.