• Title, Summary, Keyword: 한계하중

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Evaluation of Limit Loads for Circumferentially Cracked Pipes Under Combined Loadings (원주방향 표면 결함이 존재하는 배관에 가해지는 비틀림을 포함한 복합하중에 대한 한계하중식 제시)

  • Ryu, Ho-Wan;Han, Jae-Jun;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.5
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    • pp.453-460
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    • 2015
  • Since the Fukushima nuclear accident, several researchers are extensively studying the effect of torsion on the piping systems In nuclear power plants. Piping installations in power plants with a circumferential crack can be operated under combined loading conditions such as bending and torsion. ASME Code provides flaw evaluations for fully plastic fractures using limit load criteria for the structural integrity of the cracked pipes. According to the recent version of Code, combined loadings are provided only for the membrane and bending. Even though actual operating conditions have torsion loading, the methodology for evaluating torsion load is not established. This paper provides the results of limit load analyses by using finite element models for circumferentially cracked pipes under pure bending, pure torsion, and combined bending and torsion with tension. Theoretical limit load solutions based on net-section fully plastic criteria are suggested and verified with the results of finite element analyses.

Plastic Loads of Mitred Bends under Internal Pressure and Bending Moment (굽힘 하중과 내압이 가해지는 미터밴드의 소성하중)

  • Min, Sung-Hwan;Kim, Yun-Jae;Jeon, Jun-Young;Lee, Kuk-Hee
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.6
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    • pp.549-555
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    • 2009
  • Based on three-dimensional(3-D) finite element limit analyses, this paper provides limit and TES (Twice-Plastic Load) loads for mitred pipe bends under bending and pressure. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly-plastic materials using the small and large geometry change option. A wide range of parameters related to the mitred bend geometry is considered. Based on the finite element results, closed-form approximations of plastic limit and TES plastic load solutions for mitred pipe bends under bending are proposed.

Mismatch Limit Load Analyses for V-groove Welded Pipe with Through-wall Circumferential Defect in Centre of Weld (원주방향 관통균열이 용접부 중앙에 존재하는 V-그루브 맞대기 용접배관의 한계하중 해석)

  • Kim, Sang-Hyun;Han, Jae-Jun;Chung, Jin-Taek;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.11
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    • pp.1379-1386
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    • 2013
  • The present work reports the mismatch limit loads for a V-groove welded pipe for a circumferential crack using finite element (FE) analyses. To integrate the effect of groove angles on mismatch limit loads, one geometry-related slenderness parameter was modified by relevant geometric parameters including the groove angle, crack depth, and root opening based on plastic deformation patterns in the theory of plasticity. Circumferential through-wall cracks are located at the centre of the weldments with two different groove angles ($45^{\circ}$, $90^{\circ}$). With regard to the loading conditions, axial (longitudinal) tension and bending are applied for all cases. For the parent and weld metal, elastic-perfectly plastic materials are considered to simulate and analyze under- and over-matching conditions in plasticity. The overall results from the proposed solutions are found to be similar to the FE results.

Applicability of the mα-tangent Method to Estimate Plastic Limit Loads of Elbows and Branch Junctions (선형탄성해석과 mα-tangent방법을 이용한 배관 한계하중 평가 적용성)

  • Gim, Jae-Min;Kim, Sang-Hyun;Bae, Kyung-Dong;Kim, Yun-Jae;Kim, Jong-Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.6
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    • pp.499-505
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    • 2017
  • In this study, the limit loads calculated by the $m_{\alpha}-tangent$ method based on the linear finite element analysis are compared with the closed form solutions that are proposed by various authors. The objects of the analysis is to select the elbow and the branch pipe which are representative structure of piping system. The applicability of the $m_{\alpha}-tangent$ method are investigated by applying it to cases with various geometries. The internal pressure and the in-plane bending moment are considered and the $m_{\alpha}-tangent$ method is in good agreement with the existing solutions in case of elbows. However, the limit loads calculated by the $m_{\alpha}-tangent$ method for branch junctions do not agree well with the existing solutions and do not show any tendency. The reason is a biased result due to the stress concentration of the discontinuous parts.

PWR 운전조건하에서 원주방향 균열을 가진 페라이틱 배관의 파괴 거동에 관한 실험적 연구

  • ;;;;;G. Wilkowski
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.296-301
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    • 1996
  • 이 연구의 목적은 원주방향 균열을 가진 페라이틱 배관의 파괴거동을 실험적으로 평가하는데 있다. 한계하중방법, SC.TNP 방법, R6방법, 그리고 ASME Code방법과 같은 여러 파괴거동 평가 방법의 타당성이 PWR 운전조건(압력:15.5MPa, 온도:228$^{\circ}C$)하에서의 직경 16인치의 대규모 배관파괴실험을 통해 조사된다. 모사지진하중, 단일주파수 사인함수하중, 정하중과 같은 여러 가지 형태의 하중이 배관의 하중지지능력에 미치는 영향이 조사된다. 또한 엘보우부위와 직관부의 영향과 표면균열 및 관통균일의 영향 등도 함께 조사된다. 결과는 다음과 같다. (1) 표면균열을 가진 배관의 파괴거동은 한계하중방법과 SC.TNP 방법에 의해 잘 예측할 수 있다. 반면 관통균열의 경우는 한계하중방법에 의해 잘 예측된다. (2) 모사지진하중하에서는 단일주파수 사인함수하중이나 정하중 하에서 보다 하중지지능력이 크게 예측된다. (3) 엘보우부위와 직관부, 관통균열과 표면균열 사이에 파괴거동에 대한 큰 차이는 없다.

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Limit Loads for Circular Wall-Thinned Feeder Pipes Considering Bend Angle (굽힘각도를 고려한 원형 감육이 발생한 중수로 피더관의 한계하중)

  • Bae, Kyung-Dong;Je, Jin-Ho;Kim, Jong-Sung;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.3
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    • pp.313-318
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    • 2012
  • In CANDU, feeder pipes supply heavy water to pressure tube and steam generator. Under service conditions, Flow-Accelerated Corrosion (FAC) produces local wall-thinning in the feeder pipes. The wall-thinning in these pipes affects the integrity of the piping system, as verified in previous research. This paper provides limit loads for wallthinned feeder pipes with $45^{\circ}$ and $60^{\circ}$ bend angles, and proposes an equation that predicts the limit loads for wallthinned feeder pipes with arbitrary bend angles. On the basis of finite element limit analyses, limit loads are obtained for wall-thinned feeder pipes under in-plane bending and internal pressure. There are two cases of in-plane bending: the in-plane closing direction and the in-plane opening direction. The material is considered the effect of the large deformation, so an elastic-perfectly-plastic material is assumed in the calculations.

혼합모드 I+II 피로 하한계 영역에서의 모드II 영향에 관한 고찰

  • 홍석표;송삼홍;이정무
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.113-113
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    • 2004
  • 실제 사용중인 기계나 기계구조물은 다양한 환경 및 복잡한 설계조건으로 인하여 변동하중과 다축에서 작용하는 혼합모드 하중 상태에 놓이는 경우가 대부분이다. 하지만, 순수 모드 I 하중상태 하에서의 연구는 활발히 이루어졌으나, 실제 구조물에서 대부분 발생하는 혼합모드 하중상태 하에서의 연구는 아직 부족한 실정이다. 또한 기계구조물내의 많은 성분요소에 존재하는 작용 하중 방향에 수직적이지 않게 되며, 초기균열의 균열선상에서 성장하지 않는다.(중략)

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Load & Resistance Factors Calibration for Limit State Design of Non-Perforated Caisson Breakwater (직립무공케이슨방파제 한계상태설계를 위한 하중저항계수 보정)

  • Kim, Dong Hyawn
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.31 no.6
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    • pp.351-355
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    • 2019
  • Load resistance factors for the limit state design of vertical caisson breakwaters are presented. Reliability analysis of 16 breakwaters in nationwide ports was conducted to calculate the partial safety factors and they were converted into load and resistance factors. The final load resistance factor was calibrated by applying the optimization technique to the individually calculated load resistance factors. Finally, the breakwater was redesigned using the optimal load resistance factor and verified whether the target level was met. The load resistance factor according to the change of the target reliability level is presented to facilitate the limit state design of breakwater.

Study on the Strength of Limit Axial Force and Accumulated Limit Axial Force of Concrete Filled Square Tube Columns (콘크리트 충전 각형강관 기둥부재의 한계축력 및 누적한계축력에 관한 연구)

  • Seo, Seong Yeon;Jung, Jin Ahn;Kim, Sung Yong
    • Journal of Korean Society of Steel Construction
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    • v.17 no.5
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    • pp.605-615
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    • 2005
  • Experimental and analytical work was conducted to investigate the relations of axial force and deformational capacity of concrete-filled square steel tube columns. The test series consisting of 36 columns were tested under the constant axial load and horizontal cyclic load. The axial force of the columns that resisted under the cyclic lateral load was defined as a certified strength of limit axial force. The analytical model was defined as a cantilever beam-column. The axial force of the beam-column that resisted under the cyclic lateral load was defined as an accumulated certified strength of limit axial force. The purpose of this study is to investigate the certified strength of limit axial force of concrete-filled steel tube beam-columns, which were subjected to both axial and lateral load condition corresponding to a given constant rotation angle. Another purpose of this study is to discuss the comparison of the certified strength of limit axial force of concrete and the accumulated certified strength of limit axial force of concrete-filled steel tube columns.

Plastic Limit Loads for Slanted Circumferential Through-Wall Cracked Pipes Using 3D Finite-Element Limit Analyses (3차원 유한요소 한계해석을 이용한 원주방향 경사관통균열 배관의 소성한계하중)

  • Jang, Hyun-Min;Cho, Doo-Ho;Kim, Young-Jin;Huh, Nam-Su;Shim, Do-Jun;Choi, Young-Hwan;Park, Jung-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1329-1335
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    • 2011
  • On the basis of detailed 3D finite-element (FE) limit analyses, the plastic limit load solutions for pipes with slanted circumferential through-wall cracks (TWCs) subjected to axial tension, global bending, and internal pressure are reported. The FE model and analysis procedure employed in the present numerical study were validated by comparing the present FE results with existing solutions for plastic limit loads of pipes with idealized TWCs. For the quantification of the effect of slanted crack on plastic limit load, slant correction factors for calculating the plastic limit loads of pipes with slanted TWCs from pipes with idealized TWCs are newly proposed from extensive 3D FE calculations. These slant-correction factors are presented in tabulated form for practical ranges of geometry and for each set of loading conditions.