• Title, Summary, Keyword: 응력확대계수

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비틀림하의 복합원통에 있는 원주 표면균열에 대한 응력 확대 계수

  • Kim, Yeong-Jong
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.9
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    • pp.151-157
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    • 2000
  • Stress intensity factors for the circumferential surface crack of a long composite cylinder under torsion is investigated. The problem is formulated as a singular integral equation of the first kind with a Cauchy type kernel using the integral transform technique. The mode III stress intensity factors at the crack tips are presented when (a) the inner crack tip is away from the interface and (b) the inner crack tip is at the interface.

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On Computation of the Stress Intensity Factors in the V-Notched Plates using a contour integral method (경로적분법 을 이용한 V-노치 평판 의 응력확대계수 계산)

  • 김진우;김선덕;홍창선
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.8 no.3
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    • pp.232-240
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    • 1984
  • The plane elastostatic boundary value problem with the sharp V-notched singularity is formulated by a contour integral method for determining numerically the stress intensity factors. The integral formula is based on Somigliana type of reciprocal work in terms of displacement and traction vectors on the plate boundary. The characteristic singular solutions can be identified on the basis of traction free boundary conditions of two radial notch edges. Two numerical example examples are treated in detail; a symmetric mode-I type of notched plate with various interior angles and a mixed mode type of cantilever subjected to end shear.

Stress Intensity Factor Calculation for the Semi-elliptical Surface Flaws on the Thin-Wall Cylinder using Influence Coefficients (영향계수를 이용한 원통용기 표면결함의 응력확대계수의 계산)

  • Jang, Chang-Heui;Moonn, Ho-Rim;Jeong, Ill-Seok
    • Proceedings of the KSME Conference
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    • pp.280-285
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    • 2001
  • As an integral part of the probabilistic fracture mechanics analysis, stress intensity factor calculation scheme for semi-elliptical surface flaws in thin-walled cylinder has been introduced. The approximation solution utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite element analysis for cooldown boundary condition. The analysis results confirmed that the simplified methods provided sufficiently accurate stress intensity factor values for axial semi-elliptcal flaws on the surface of the reactor pressure vessel.

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Analysis of Interfacial Surface Crack Perpendicular to the Surface (표면에 수직한 계면방향 표면균열의 해석)

  • 최성렬
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.2
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    • pp.277-284
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    • 1993
  • Interfacial surface crack perpendicular to the surface, which is imbedded into bonded quarter planes under single anti-plane shear load is analyzed. The problem is formulated using Mellin transform, form which single Wiener-Hopf equation is derived. By solving the equation stress intensity factor is obtained in closed form. This solution can be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

The development of mongrel singular element with J-integral and the toughness test for Al 7075-T6 wing spar (J적분을 첨가한 mongrel 특이요소 개발 및 Al 7075-T6 wing spar파괴인성 실험)

  • 강치행
    • Journal of the Korea Institute of Military Science and Technology
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    • v.1 no.1
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    • pp.154-165
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    • 1998
  • In this paper, the mongrel singular element with 6 node triangle and 8 node quadrilateral element with J-integral are developed and applied to the various plane crack problems for the isotropic material. The convergence nature is excellent for various crack size with even coarse mesh using the direct method. But the results of the mongrel element with J-integral are worse than the former's ones. Fracture tests were conducted on precracked CT specimens. Results show that, for 7075-T6 aluminum wing spar materials, the fracture toughness is 31.06 ksi.inch $\frac{1}{2}$ in the L-T direction.

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Numerical Analysis of a Crack in the Vicinity of an Inclusion (함유체에 인접한 크랙에 관한 수치해석)

  • 이정기;라원석
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.12 no.3
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    • pp.465-474
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    • 1999
  • A recently developed numerical method based on a volume integral formulation is applied to calculate the accurate stress intensity factors at the crack tips in unbounded isotropic solids in the presence of multiple anisotropic inclusions and cracks subject to external loads. In this paper, a detailed analysis of the stress intensity factors are carried out for an unbounded isotropic matrix containing an orthotropic cylindrical inclusion and a crack. The accuracy and effectiveness of the new method are examined through comparison with results obtained from analytical method and finite element method using ANSYS. It is demonstrated that this new method is very accurate and effective for solving plane elastostatic problems in unbounded solids containing anisotropic inclusions and cracks.

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Mixed Mode Fracture of the Crack Inclined to the Grain Direction in Wood (목재(木材)의 섬유방향(纖維方向)에 경사(傾斜)진 균열의 혼합모-드파괴(破壞)에 관한 연구)

  • Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.17 no.4
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    • pp.83-88
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    • 1989
  • 목재의 섬유방향에 경사진 균열의 모-드I과 모-드II의 혼합모-드파괴시의 파괴거동을 조사하기 위하여 라왕(Shorea Spp.)의 LA시스템에 있어서 서로 다른 경사각도를 가진 SEN시험편(Single edge notch specimen)에 대하여 휨 시험을 행하였다. 얻이진 결과는 혼합모-드파괴시, 모-드I응력확대계수$K_I$과 모-드II응력확대계수$K_II$간에 일정한 상호작용이 존재한다는 것을 나타내었다. 또한, 모-드I과 모-드II의 임계응력확대계수(Critical stress intensity factor) $K_{IC}$$K_{IIC}$ 이용하여 혼합모-드파괴시의 $K_I$$K_II$간의 상호관계를 규정할 수 있었으며, 이미 보고된 여러 실험식과 본 실험결과를 비교하여 가장 적합한 관계로서 아래와 같은 관계를 얻을 수 있었다.

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Study on the Fatigue Crack Behavior by the Stress Intensity Factor and AE Parameters (응력확대계수와 음향방출 변수를 이용한 피로균열 거동 연구)

  • Yoon, Dong-Jin;Jeong, Jung-Chae;Park, Phi-Lip;Kim, Ki-Bok;Lee, Seung-Seok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.5
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    • pp.412-423
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    • 2000
  • By using the relation between stress intensity factor and AE parameter, new approach method for assessing the crack length and detectability of crack was proposed. Laboratory experiment was carried out to identify AE characteristics of fatigue cracks for compact tension specimen. The relationship between a stress intensity factor and AE signals activity as well as conventional AE parameter analysis was discussed. As a result, the features of specific parameter such as the length of crack growth the AE energy, the AE peak amplitude, and the cumulative AE hits, showed the almost same trend in their increase as the number of fatigue cycle increased. From the comparisons of peak amplitude and AE energy with stress intensity factor, it was verified that the higher stress intensity factors generated AE signals with higher peak amplitude and a larger number of AE counts. If we can get more reliable database for the relation between AE parameters and stress intensity factor, this approach will provide a good information for evaluating both the existence of crack and the minimum detectable size of crack.

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An Effect of Uplift Pressure Applied to Concrete Gravity Dam on the Stress Intensity Factor (중력식 콘크리트 댐에 작용하는 양압력이 응력확대계수에 미치는 영향)

  • Lee Young-Ho;Jang Hee-Suk;Kim Tae-Wan;Jin Chi-Sub
    • Journal of the Korea Concrete Institute
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    • v.16 no.6
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    • pp.841-850
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    • 2004
  • The modeling of uplift pressure within dam, on the foundation on which it was constructed, and on the interface between the dam and foundation is a critical aspect in the analysis of concrete gravity dams, i.e. crack stability in concrete dam can correctly be predicted when uplift pressures are accurately modelled. Current models consider a uniform uplift distribution, but recent experimental results show that it varies along the crack faces and the procedures for modeling uplift pressures are well established for the traditional hand-calculation methods, but this is not the case for finite element (FE) analysis. In large structures, such as dams, because of smaller size of the fracture process zone with respect to the structure size, limited errors should occur under the assumptions of linear elastic fracture mechanics (LEFM). In this paper, the fracture behaviour of concrete gravity dams mainly subjected to uplift Pressure at the crack face was studied. Triangular type, trapezoidal type and parabolic type distribution of the uplift pressure including uniform type were considered in case of evaluating stress intensity factor by surface integral method. The effects of body forces, overtopping pressures are also considered and a parametric study of gravity dams under the assumption of LEFM is performed.