• 제목/요약/키워드: mixed-mode crack

검색결과 205건 처리시간 0.024초

Mode Decomposition in Three Dimensional Cracks using Mutual Integrals

  • Kim, Young-Jong
    • International Journal of Precision Engineering and Manufacturing
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    • 제1권2호
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    • pp.14-23
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    • 2000
  • A numerical scheme is proposed to obtain the individual stress intensity factors in an axisymmetric crack and in a three dimensional mixed mode crack. The method is based on the path independence of J and M integral and mutual or two-state conservation integral , which involves two elastic fields. Some numerical example are presented to investigate the effectiveness and applicability of the method for and axisymmetric crack and a three dimensional penny shaped crack problem under mixed mode.

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Al 5083-O재에 있어서 $K_{III}$ 모드 4점 전단 하에서의 피로파단면 무늬와 피로균열진전거동의 관계 (Relationship between Pattern of Fatigue Crack Surface and Fatigue Crack Growth Behavior under $K_{III}$ Mode-Four Point Shear in Al 5083-O)

  • 김건호;원영준;케이코 사카쿠라;타케히로 후지모토;토시히사 니시오카
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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    • pp.43-44
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    • 2006
  • Generally almost all fatigue crack growth is affected by model. For this reason a study on model has concentrated in the field of fracture mechanics. However the fatigue crack initiation and growth in machines and structures usually occur in mixed mode loading. If there is any relationship between the cause of fracture in mixed mode loading and fracture surface, fracture surface pattern will be the main mean explaining reasons of fatigue fracture and obtaining further information about fracture process. In this paper four point shear-fatigue test with Aluminum alloy Al 5083-O is carried out from this prospect and then the mixed mode distribution of fracture surface is examined from the result after identifying the generation of fatigue crack surface pattern. It was found from the experimental results that the fatigue crack surface pattern and the fatigue crack shear direction are remarkably consistent. Furthermore It is possible that the analysis of distribution of mixed mode through the fatigue crack surface pattern.

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Effect of the thickness on the mixed mode crack front fields

  • Khan, Shafique M.A.
    • Structural Engineering and Mechanics
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    • 제42권5호
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    • pp.701-713
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    • 2012
  • Results pertaining to 3D investigations on the effect of the thickness on the stress fields at the crack front are presented. A 3D finite element analysis is performed using a modified single edge-notched tension specimen configuration, with an inclined crack to include mixed mode I-II. A technique to mesh the crack front (3D) with singular finite elements in ANSYS without using third party software is introduced and used in this study. The effect of the specimen thickness is explicitly investigated for six thicknesses ranging from 1 to 32 mm. In addition, three crack inclination angles, including pure Mode-I, are used to study the effect of mixed-mode I-II fracture. An attempt is made to correlate the extent of a particular stress state along the crack front to thickness. In addition, ${\sigma}_{zz}/{\nu}({\sigma}_{xx}+{\sigma}_{yy})$ contours at the crack front are presented as a useful means to analyze the stress state.

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

  • 홍석표;박세민;김주희
    • 대한기계학회논문집A
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    • 제41권9호
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    • pp.853-860
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    • 2017
  • 본 연구는 균열 발생 및 전파단계에서 하중모드 II의 영향을 평가하기 위해 피로균열 하한계 영역의 혼합모드 I+II 하중을 통해 실험적으로 평가하였다. 균열 발생단계(Stage I)에서는 혼합모드상태에서 하중작용 각도(${\theta}$)가 증가할수록 모드 II 영향으로 인하여 낮은 하중에서 균열이 발생하고, 균열 전파단계 (Stage II)에서는 균열전파 속도는 감소하였다. 다단계 하중작용 각도변화에 따른 하중모드 II영향은 균열전파단계 실험을 통해 평가하였다. 혼합모드 I+II 하중 작용 시 작용각도 ($0^{\circ}{\rightarrow}{\theta}{\rightarrow}60^{\circ}$) 증가에 따라 피로균열전파속도는 감소하였으며 늦게 발생한 균열에서도 마찬가지로 감소하였다. 작용각도가 ${\theta}{\geq}75^{\circ}$ 범위에서는 하중작용각도 증가에 따라 피로균열전파속도가 증가하고 피로수명이 감소하는 것을 확인하였다.

혼합모드하중을 받는 매석배관강의 피로균열전파 거동 (Fatigue crack propagation of buried pipe steel under mixed model loading)

  • 이억섭;최용길
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2000년도 추계학술대회 논문집
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    • pp.473-476
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    • 2000
  • Recently, many studies focus on mixed-mode fatigue-fracture characteristics of characteristics of materials. In order to reveal crack initiation and propagation mechanisms in combined -mode fatigue. This paper investigates the initiation and propagation behavior of the fatigue crack of the STS304 specimens under mixed mode loading conditions. moreover crack arrest and branch phenomena were analyzed with respect to the change do the angle of inclined loading. The relationship between the angle of inclined loading and the angle of branched crack was studied. A greate number of cycles are necessary to initiate a new crack from the initial crack. The direction of the new crack propagation is determined by MTS theory.

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혼합모드 단일과대하중 하에서 피로균열 전파거동의 예측 (Prediction of Fatigue Crack Propagation Behavior Under Mixed-Mode Single Overload)

  • 이정무;송삼홍
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.359-364
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    • 2004
  • In this study, experiments were tried on the mixed-mode I+II single overloading model which changes the loading mode of overload and fatigue load. Aspects of deformation field in front of the crack which is formed by mixed-mode I+II single overloading were experimentally studied. Then the shape and size of mixed-mode plastic zone were approximately calculated. The propagation behavior of fatigue crack was examined under the test conditions combined by changing the loading mode. The behavior of fatigue cracks were greatly affected by shapes of plastic deformation field and applying mode of fatigue load. Accuracy of prediction and evaluation for fatigue life may be improved by considering all aspects of deformation and behavior of fatigue cracks.

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기계적 체결부 균열의 피로균열성장에 관한 연구 (A Study on the Fatigue Crack Growth of Cracks in Mechanical Joints)

  • 허성필;양원호;정기현
    • 한국자동차공학회논문집
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    • 제10권1호
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    • pp.187-194
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    • 2002
  • It has been reported that cracks in mechanical joints is generally under mixed-mode and there is critical inclined angle at which mode I stress intensity factor becomes maximum. The crack propagates in arbitrary direction and thus the prediction of crack growth path is needed to provide against crack propagation or examine safety. In order to evaluate the fatigue life of cracks in mechanical joints, horizontal crack normal to the applied load and located on minimum cross section is major concern but critical inclined crack must also be considered. In this paper mixed-mode fatigue crack growth test is performed far horizontal crack and critical inclined crack in mechanical joints. Fatigue crack growth path is predicted by maximum tangential stress criterion using stress intensity factor obtained from weight function method, and fatigue crack growth rates of horizontal and inclined crack are compared.

단일 및 혼합모드 하중하에서의 레일강의 파괴조건 및 피로균열진전거동 (Fracture Criterion and Fatigue Crack Growth Behavior of Rail Steel Under Mode I & Mixed Mode Loading)

  • 김정규;이종선;김철수
    • 대한기계학회논문집A
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    • 제23권6호
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    • pp.1039-1047
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    • 1999
  • It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

접착이음의 계면균열에 대한 파괴인성 및 평가방법 (Mehods of Fracture Toughness and Evaluation for Interface Crack in Adhesively Bonded Joints)

  • 정남용
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 1998년도 춘계학술대회 논문집
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    • pp.220-226
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    • 1998
  • In this pater, a method of strength evaluation applying fracture mechanics in adhesively bonded joints of A1/A1 materials was investigated. Various adhesively bonded joints of double-cantilever beam with a interfacial crack in its adhesive layer were prepared for the fracture toughness test of comprehensive mixed mode conditions from nearly pure mode I to mode II. The experiment of fracture toughness was carried out under various mixed mode conditions with an interfacial crack and critical energy release rate, Gc by the experimental measurements of compliances was determined. From the results, fracture toughness on mixed mode with an interfacial crack is well characterized by strain energy release rate and a method of strength evaluation by the fracture toughness in adhesively bonded joints of A1/A1 materials was discussed.

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응력비 변화에 따른 혼합모드 피로균열 전파거동 (The Mixed Mode fatigue Crack Propagation Behavior with the Variation of Stress Ratio)

  • 송삼홍;최지훈;이정무
    • 대한기계학회논문집A
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    • 제26권11호
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    • pp.2287-2296
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    • 2002
  • Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So, it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper, the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0$^{\circ}$, 30$^{\circ}$, 60$^{\circ}$ to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress ratio and loading mode condition, we have concluded the dominant factors of the crack propagation rate at each case.