• Title/Summary/Keyword: curved crack

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Path Stability of a Crack with an Eigenstrain

  • Beom, Hyeon-Gyu;Kim, Yu-Hwan;Cho, Chong-Du;Kim, Chang-Boo
    • Journal of Mechanical Science and Technology
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    • v.20 no.9
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    • pp.1428-1435
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    • 2006
  • A slightly curved crack with an eigenstrain is considered. Solutions for a slightly curved crack in a linear isotropic material under asymptotic loading as well as for a slightly curved crack in a linear isotropic material with a concentrated force are obtained from perturbation analyses, which are accurate to the first order of the parameter representing the non-straightness. Stress intensity factors for a slightly curved crack with an eigenstrain are obtained from the perturbation solutions by using a body force analogy. Particular attention is given to the crack path stability under mode I loading. A new parameter of crack path stability is proposed for a crack with an eigenstrain. The path stability of a crack with steady state growth in a transforming material and a ferroelectric material is examined.

A Study on the Safety Assessment of Curved Hollow RC Slab Bridge Structures (곡선형 RC 중공 슬래브교의 안전성 평가 사례 연구)

  • Chai, Won-Kyu;Jo, Byung-Wan;Kim, Kwang-Il
    • Journal of the Korean Society of Safety
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    • v.21 no.6 s.78
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    • pp.96-100
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    • 2006
  • In this thesis, the crack investigation, the damage investigation, the drawing check, and the structural analysis were performed on a curved hollow RC(reinforced concrete) slab bridge structure to assess the structural safety of that. From the crack investigation result, main reason of crack occurrence is guessed with travelling of the large truck. Therefore reinforcement of slab structure is necessary by using the steel plate. When structural analysis, the straight beam model, the curved beam model, and the curved plate model is used. From the results of structural analysis for curved hollow RC slab bridge, the maximum bending moment and the maximum shear force was not a difference in each models. But the vertical displacement of mid span using the curved beam model was greater than that using the other models.

A Study on Accuracy of J-Resistance Curves Measured with Curved Compact Tension Specimen of Zr-2.5Nb Pressure Tube (Zr-2.5Nb 압력관의 휘어진 CT시편으로 측정한 J 저항곡선의 정확도에 관한 연구)

  • Yoon, Kee-Bong;Park, Tae-Gyu;Kim, Young-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.11
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    • pp.1986-1996
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    • 2003
  • Methodology based on the elastic-plastic fracture mechanics has been widely accepted in predicting the critical crack length(CCL) of pressure tubes of CANDU nuclear plants. A conservative estimate of CCL is obtained by employing the J-resistance curves measured with the specimens satisfying plane strain condition as suggested in the ASTM standard. Due to limited thickness of the pressure tubes the curved compact tension(CT) specimens taken out from tile pressure tube have been used in obtaining J-resistance curves. The curved CT specimen inevitably introduce slant fatigue crack during precracking. Hence, effect of specimen geometry and slant crack on J-resistance curve should be explored. In this study, the difference of J integral values between the standard CT specimens satisfying plane strain condition and the nonstandard curved CT with limited thickness (4.2mm) is estimated using finite element analysis. The fracture resistance curves of Zr-2.5Nb obtained previously by other authors are critically discussed. Various finite element analysis were conducted such as 2D analysis under plane stress and plane strain conditions and 3D analysis for flat CT, curved CT with straight crack and curved CT with slant crack front. J-integral values were determined by local contour integration near the crack tip, which was considered as accurate J-values. J value was also determined from the load versus load line displacement curve and the J estimation equation in the ASTM standard. Discrepancies between the two values were shown and suggestion was made for obtaining accurate J values from the load line displacement curves obtained by the curved CT specimens.

Repair and Retrofit of Fatigue crack for Curved Girder Bridge (곡선 강교량 피로균열 보수.보강방안)

  • Park, Jin-Eun;Kyung, Kab-Soo;Kwon, Soon-Cheol;Lee, Hee-Hyun
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.50-55
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    • 2008
  • In order to investigate and estimate the cause of fatigue crack occurred to curved girder bridge that is used during 20 years, in this study, filed tests to obtain the characteristic of stress hysteresis were performed under the real traffic flows. From these test results, we analyzed the cause of fatigue crack for various fatigue crack patterns. Also, the characteristic of structural behavior for the curved girder bridge were examined from the FE analysis. In addition, to retrofit various fatigue cracks occurred in the bridge, FE analyses considering the characteristics of crack patterns were performed and retrofitting methods were suggested.

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THE INDIRECT BOUNDARY INTEGRAL METHOD FOR CURVED CRACKS IN PLANE ELASTICITY

  • Yun, Beong-In
    • Journal of the Korean Mathematical Society
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    • v.39 no.6
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    • pp.913-930
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    • 2002
  • For curved crack problems in plane elasticity, subjected to the traction conditions on the crack faces, we present a system of boundary integral equations. The procedure is based on the indirect boundary integral method in terms of real variables. For efficient mathematical analysis, we decompose the singular kernel into the Cauchy singular part and the regular one. As a result, solvability of the presented system is proved and availability of the present approach is shown by the numerical example of a circular arc crack.

The Curved Interfacial Crack Analysis between Foam and Composite Materials under Anti-plane Shear Force (반평면 전단하중력을 받는 곡면형상을 가지는 폼과 복합재료 접합부의 계면크랙에 관한 연구)

  • 박상현;신재윤;전흥재
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2000.04a
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    • pp.101-104
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    • 2000
  • The general solution of the anti-plane shear problem for the curved interfacial crack between viscoelastic foam and composites was investigated with the complex variable displacement function and Kelvin-Maxwell model. The Laplace transform was applied to treat the viscoelastic characteristics of foam in the analysis. The stress intensity factor near the interfacial crack tip was predicted by considering both anisotropic and viscoelastic properties of two different materials. The results showed that the stress intensity factor increased with increasing the curvature of the curved interfacial crack and it also increased and eventually converged to a specific value with increasing time.

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In-plane vibrations of cracked slightly curved beams

  • Oz, H. Ridvan
    • Structural Engineering and Mechanics
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    • v.36 no.6
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    • pp.679-695
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    • 2010
  • In-plane vibrations of slightly curved beams having cracks are investigated numerically and experimentally. The curvature of the beam is circular and stays in the plane of vibration. Specimens made of steel with different lengths but with the same radius of curvature are used in the experiments. Cracks are opened using a hand saw having 0.4 mm thickness. Natural frequencies depending on location and depth of the cracks are determined using a Bruel & Kjaer 4366 type accelerometer. Then the beam is assumed as a Rayleigh type slightly curved beam in finite element method (FEM) including bending, extension and rotary inertia. A flexural rigidity equation given in literature for straight beams having a crack is used in the analysis. Frequencies are obtained numerically for different crack locations and depths. Experimental results are presented and compared with the numerical solutions. The natural frequencies are affected too much due to larger moments when the crack is around nodes. The effect can be neglected when it is at the location of maximum displacements. When the crack is close to the clamped end, the decrease in the frequencies in all modes is very high. The consistency of the results and validity of the equations are discussed.

Evaluation of the Crack Initiation of Curved Compact Tension Specimens of a Zr-2.5Nb Pressure Tube Using the Unloading Compliance and Direct Current Potential Drop Methods (제하 컴플라이언스법 및 직류전위차법을 이용한 Zr-2.5Nb 압력관 휘어진 CT 시편의 균열시작 평가)

  • Jeong, Hyeon-Cheol;Ahn, Sang-Bok;Kim, Young-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.8 s.239
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    • pp.1118-1122
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    • 2005
  • The direct current potential drop (DCPD) method and the unloading compliance (UC) method with a crack opening displacement gauge were applied simultaneously to the Zr-2.5Nb curved compact tension (CCT) specimens to determine which of the two methods can precisely determine the crack initiation point and hence the crack length for evaluation of their fracture toughness. The DCPD method detected the crack initiation at a smaller load-line displacement compared to the UC method. As a verification, a direct observation of the fracture surfaces on the curved compact tension specimens was made on the CCT specimens experiencing either 0.8 to 1.0 mm load line displacement or various loads from $50\%\;to\;80\%$ of the maximum peak load, or $P_{max}$. The DCPD method is concluded to be more precise in determining the crack initiation and fracture toughness, J in Zr-2.5Nb CCT specimens than the UC method.

Validation of 3D crack propagation in plain concrete -Part I: Experimental investigation - the PCT3D test

  • Feist, C.;Hofstetter, G.
    • Computers and Concrete
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    • v.4 no.1
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    • pp.49-66
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    • 2007
  • The objective of this paper is to provide experimental data on the propagation of curved crack-surfaces and the respective load-displacement diagrams for the validation of numerical models for cracking of concrete, subjected to three-dimensional stress states. To this end beam-shaped specimens are subjected to combined bending and torsional loading, leading to the formation of a spatially curved crack-surface. The experimental data contain the evolution of the load and of the strains at selected points in terms of the crack mouth opening displacement and the propagation of the crack surface.

Prediction of Failure Behavior for Nuclear Piping Using Curved Wide-Plate Test (흰 광폭평판 시험을 이용한 원자력 배관의 파괴거동예측)

  • Huh, Nam-Su;Kim, Yun-Jae;Choi, Jae-Boong;Kim, Young-Jin;Lim, Hyuk-Soon;Chung, Dae-Yul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.4
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    • pp.352-361
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    • 2004
  • One important element of the Leak-Before-Break analysis of nuclear piping is how to determine relevant fracture toughness (or the J-resistance curve) for nonlinear fracture mechanics analysis. The practice to use fracture toughness from a standard C(T) specimen is known to often give conservative estimates of toughness. To improve the accuracy, this paper proposes a new method to determine fracture toughness using a nonstandard testing specimen, curved wide-plate in tension. To show validity of the proposed curved wide-plate test, the J-resistance curve from the full-scale pipe test is compared with that from the curved wide-plate test and that from the C(T) specimen. It is shown that the J-resistance curve form the curved wide-plate tension test is similar to, but that from the C(T) specimen is lower than, the J-resistance curve from the full-scale pipe test. Further validation is performed by investigating crack-tip constraint conditions via detailed 3-D FE analyses, which shows that the crack-tip constraint condition in the curved wide-plate tension specimen is indeed similar to that in the full-scale pipe under bending.