• 제목/요약/키워드: Circumferential cracked pipe

검색결과 28건 처리시간 0.023초

참조응력 개념을 이용한 원주방향 관통균열 배관의 파괴역학 해석;실배관 실험 데이터와의 비교 (Reference Stress Based Fracture Mechanics Analysis for Circumferential Through-Wall Cracked Pipes;Comparison with Pipe Test Data)

  • 허남수;심도준;김윤재;김영진
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.389-396
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    • 2003
  • This paper presents experimental validation of the enhanced reference stress based J estimates for circumferential through-wall cracked pipes, recently proposed by authors. Using the pipe test data for circumferential through-wall cracked pipes, the predicted fracture initiation and maximum moments according to the proposed enhanced reference stress method are compared with experimental ones as well as predictions from the R6 method. The results show that both the R6 method and the proposed method give conservative estimates of initiation and maximum moments for circumferential through-wall cracked pipes, compared to experimental data. For longer cracks, the proposed method reduces conservatism embedded in estimated J according to the R6 method, and the resulting predictions are less conservative, compared to those from the R6 method. For shorter cracks, on the other hand, the proposed method reduces possible non-conservatism embedded in estimated J according to the R6 method, and the resulting predictions are slightly more conservative.

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참조응력 개념을 이용한 원주방향 관통균열 배관의 파괴 역학 해석 - 실배관 실험 데이터와의 비교 - (Reference Stress Based Fracture Mechanics Analysis for Circumferential Through-Wall Cracked Pipes - Comparison with Pipe Test Data -)

  • 허남수;심도준;김윤재;김영진
    • 대한기계학회논문집A
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    • 제27권4호
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    • pp.638-646
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    • 2003
  • This paper presents experimental validation of the enhanced reference stress based J estimates for circumferential through-wall cracked pipes. recently proposed by authors. Using the pipe test data for circumferential through-wall cracked pipes, the predicted fracture initiation and maximum moments according to the proposed enhanced reference stress method are compared with experimental ones as well as predictions from the R6 method. The results show that both the R6 method and the proposed method give conservative estimates of initiation and maximum moments for circumferential through-wall cracked pipes, compared to experimental data. For longer cracks, the proposed method reduces conservatism embedded in estimated J according to the R6 method, and the resulting predictions are less conservative, compared to those from the R6 method. For shorter cracks, on the other hand, the proposed method reduces possible non-conservatism embedded in estimated J according to the R6 method, and the resulting predictions are slightly more conservative.

3차원 유한요소해석을 통해 도출한 균열배관의 소성한계압력식 (Plastic Limit Pressure Solutions for Cracked Pipes Using 3-D Finite Element Method)

  • 심도준;허남수;김윤재;김영진
    • 대한기계학회논문집A
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    • 제27권1호
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    • pp.26-33
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    • 2003
  • Based on detailed FE limit analyses, the present paper provides tractable approximations fer plastic limit pressure solutions fur axially through-wall-cracked pipe; axially (inner) surface-cracked pipe; circumferentially through-wall-cracked pipe; and circumferentially (inner) surface-cracked pipe. In particular, for surface crack problems, the effect of the crack shape, the semi-elliptical shape or the rectangular shape, on the limit pressure is quantified. Comparisons with existing analytical and empirical solutions show a large discrepancy in circumferential short through-wall cracks and in surface cracks (both axial and circumferential). Being based on detailed 3-D FE limit analysis, the present solutions are believed to be the most accurate, and thus to be valuable information not only for plastic collapse analysis of pressurised piping but also for estimating non-linear fracture mechanics parameters based on the reference stress approach.

Application of cohesive zone model to large scale circumferential through-wall and 360° surface cracked pipes under static and dynamic loadings

  • Moon, Ji-Hee;Jang, Youn-Young;Huh, Nam-Su;Shim, Do-Jun;Park, Kyoungsoo
    • Nuclear Engineering and Technology
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    • 제53권3호
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    • pp.974-987
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    • 2021
  • This paper presents ductile fracture simulation of full-scale cracked pipe for nuclear piping materials using the cohesive zone model (CZM). The main objective of this study is to investigate the applicability of CZM to predict ductile fracture of cracked pipes with various crack shapes and under quasi-static/dynamic loadings. The transferability of the traction-separation (T-S) curve from a small-scale specimen to a full-scale pipe is demonstrated by simulating small- and full-scale tests. T-S curves are calibrated by comparing experimental data of compact tension specimens with finite element analysis results. The calibrated T-S curves are utilized to predict the fracture behavior of cracked pipes. Three types of full-scale pipe tests are considered: pipe with circumferential through-wall crack under quasistatic/dynamic loadings, and with 360° internal surface crack under quasi-static loading. Computational results using the calibrated T-S curves show a good agreement with experimental data, demonstrating the transferability of the T-S curves from small-scale specimen.

하중-균열열림변위를 이용한 굽힘하중이 작용하는 원주방향 관통균열 배관의 새로운 J 실험법 (New J Testing Method Using Load-COD Curve for Circumferential Through-Wall Cracked Pipes under Bending)

  • 허남수;김윤재;김영진
    • 대한기계학회논문집A
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    • 제30권1호
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    • pp.60-65
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    • 2006
  • The present paper provides experimental J estimation equation for the circumferential through-wall cracked pipe under four-point bending, based on the load-crack opening displacement (COD) record. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic ${\eta}$-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element (FE) analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks, whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.

Ramifications of Structural Deformations on Collapse Loads of Critically Cracked Pipe Bends Under In-Plane Bending and Internal Pressure

  • Sasidharan, Sumesh;Arunachalam, Veerappan;Subramaniam, Shanmugam
    • Nuclear Engineering and Technology
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    • 제49권1호
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    • pp.254-266
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    • 2017
  • Finite-element analysis based on elastic-perfectly plastic material was conducted to examine the influence of structural deformations on collapse loads of circumferential through-wall critically cracked $90^{\circ}$ pipe bends undergoing in-plane closing bending and internal pressure. The critical crack is defined for a through-wall circumferential crack at the extrados with a subtended angle below which there is no weakening effect on collapse moment of elbows subjected to in-plane closing bending. Elliptical and semioval cross sections were postulated at the bend regions and compared. Twice-elastic-slope method was utilized to obtain the collapse loads. Structural deformations, namely, ovality and thinning, were each varied from 0% to 20% in steps of 5% and the normalized internal pressure was varied from 0.2 to 0.6. Results indicate that elliptic cross sections were suitable for pipe ratios 5 and 10, whereas for pipe ratio 20, semioval cross sections gave satisfactory solutions. The effect of ovality on collapse loads is significant, although it cancelled out at a certain value of applied internal pressure. Thinning had a negligible effect on collapse loads of bends with crack geometries considered.

배관에 존재하는 원주방향 표면균열에 대한 파괴거동 해석 (I) -J-적분 예측식 - (Fracture Behavior Estimation for Circumferential Surface Cracked Pipes (I) - J-Integral Estimation Solution -)

  • 김진수;김윤재;김영진
    • 대한기계학회논문집A
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    • 제26권1호
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    • pp.131-138
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    • 2002
  • This paper provides the fully plastic J solutions for circumferential cracked pipes with inner, semi- elliptical surface cracks, subject to internal pressure and global bending. Solutions are given in the form of two different approaches, the GEF/EPRl approach and the reference stress approach. For the GE/EPRl approach, the plastic influence functions for fully plastic J are tabulated based on extensive 3-D FE calculations using the Ramberg-Osgood (R-O) materials, covering a wide range of pipe and crack geometries. The developed GEf/EPRl-type fully plastic J estimation equations are then re-formulated using the concept of the reference stress approach for wider applications. Based on the FE results, optimized reference load solutions for the definition of the reference stress are found for internal pressure and for global bending. Advantages of the reference stress based approach over the GE/EPRl-type approach are fully discussed. Validation of the proposed reference stress based J estimation equations will be given in Part II, based on 3-D elastic-plastic or elastic creep FE results using typical tensile properties of stainless steels and generalized creep- deformation behaviours.

원주방향 관통균열이 존재하는 배관의 새로운 J-적분 및 COD 계산식-인장하중과 굽힘모멘트가 동시에 작용하는 경우 (New Engineering J and COD Estimation Method for Circumferential Through-Wall Cracked Pipes-Combined Tension and Bending Load)

  • 허남수;김윤재;김영진
    • 한국정밀공학회지
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    • 제18권7호
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    • pp.85-90
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    • 2001
  • In order to apply the Leak-Before-Break(LBB)concept to nuclear piping, accurate estimation of J-integral and crack opening displacement(COD) is essential for complex loading, such as combined tension and bending. This paper proposes a new engineering method to estimate J-integral and the COD for circumferential through-wall cracked pipes subject to combined tension and bending loading. The proposed method to estimate the COD is validated against three published pipe test data, generated from a monotonically increasing bending load with a constant internal pressure, which shows excellent agreements.

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배관에 존재하는 원주방향 표면균열에 대한 파괴거동 해석 (ll) - 유한요소해석을 통한 검증 - (Fracture Behavior Estimation for Circumferential Surface Cracked Pipes (ll) - Finite Element Validation -)

  • 김진수;김윤재;김영진
    • 대한기계학회논문집A
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    • 제26권1호
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    • pp.139-146
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    • 2002
  • This paper provides validations of the reference stress based J and $C^{*}$ estimations, proposed in Part I, for inner, circumferential surface cracked pipes under internal pressure and global bending against detailed 3-D elastic-plastic and elastic-creep FE results. For this purpose, actual tensile properties of two typical stainless steels (TP304 and TP316) are used for elastic-plastic FE analyses and two realistic creep laws are used for elastic-creep FE analyses. For a total of twenty cases considered in this paper, agreements between the proposed reference stress based J and $C^{*}$ estimations and the FE results are excellent. More important aspect of the proposed estimations is that they can be used to estimate J and $C^{*}$ not only at the deepest point of the surface crack but also at an arbitrary point along the crack front.front.

배관 원주방향 표면균열에 대한 탄소성 파괴 파라미터의 예측 (II) (Engineering Estimation of Elastic-Plastic Fracture Parameter for Circumferential Surface Cracked Pipes: Part II)

  • 김윤재;김진수;김영진;박윤원
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.310-315
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    • 2001
  • This paper provides validations of the reference stress based J and $C^*$ estimations, proposed in Part I, for inner, circumferential surface cracked pipes under internal pressure and global bending against detailed 3-D elastic-plastic and elastic-creep FE results. For this purpose, actual tensile properties of two typical stainless steels (TP304 and TP316) are used for elastic-plastic FE analyses and two realistic creep laws are used for elastic-creep FE analyses. For a total of twenty cases considered in this paper, agreements between the proposed reference stress based J and $C^*$ estimations and the FE results are excellent. More important aspect of the proposed estimations is that they can be used to estimate J and $C^*$ not only at the deepest point of the surface crack but also at an arbitrary point along the crack front.

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