Plastic Limit Loads for Slanted Circumferential Through-Wall Cracked Pipes Using 3D Finite-Element Limit Analyses

2011 ◽  
Vol 35 (10) ◽  
pp. 1329-1335
Author(s):  
Hyun-Min Jang ◽  
Doo-Ho Cho ◽  
Young-Jin Kim ◽  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
...  
Author(s):  
Shunjie Li ◽  
Changyu Zhou ◽  
Jian Li ◽  
Xinting Miao

The effect of bend angle on plastic limit loads of pipe bends (elbows) under in-plane opening and closing bending moment is presented using three-dimensional large strain nonlinear finite element analyses. The results show that the presence of ovality significantly leads to the stress concentration in the middle cross section, which is the critical section of pipe bends. Meanwhile the state of stress concentration is also associated with the loading modes including the in-plane opening bending moment and the closing bending moment. Then plastic limit loads of pipe bends are further studied. It is found that plastic limit loads are decreasing with the increase of bend angles. Especially the variation of plastic limit loads of small angle pipe bends (bend angle from the 0 degree to 90 degree) is larger than that of large angle pipe bends (bend angle greater than 90 degree). Based on the finite element results, the present plastic limit load solutions are not fit for the large angle pipe bends (bend angle greater than 90 degree).


2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Doo-Ho Cho ◽  
Young-Hwan Choi ◽  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Jae-Boong Choi

The plastic limit load solutions for cylinder and plate with slanted through-wall cracks (TWCs) are developed based on the systematic three-dimensional (3D) finite element (FE) limit analyses. As for loading conditions, axial tension, global bending, and internal pressure are considered for a cylinder with slanted circumferential TWC, whereas, axial tension and internal pressure are considered for a plate and a cylinder with slanted axial TWC. Then, the verification of FE model and analysis procedure employed in the present numerical work was confirmed by employing the existing solutions for both cylinder and plate with idealized TWC. Also, the geometric variables of slanted TWC which can affect plastic limit loads were considered. Based on the systematic FE limit analysis results, the slant correction factors which represent the effect of slanted TWC on plastic limit load were provided as tabulated solutions. By adopting these slant correction factors, the plastic limit loads of slanted TWC can be directly estimated from existing solutions for idealized TWC. Furthermore, the modified engineering estimations of plastic limit loads for slanted TWC are proposed based on equilibrium equation and von Mises yield criterion. The present results can be applied either to diverse structural integrity assessments or for accurate estimation of fracture mechanics parameters such as J-integral, plastic crack opening displacement (COD) and C*-integral for slanted TWC based on the reference stress concept (Kim, et al., 2002, “Plastic Limit Pressure for Cracked Pipes Using Finite Element Limit Analyse,” Int. J. Pressure Vessels Piping, 79, pp. 321–330; Kim, et al., 2001, “Enhanced Reference Stress-Based J and Crack Opening Displacement Estimation Method for Leak-Before-Break Analysis and Comparison With GE/EPRI Method,” Fatigue Fract. Eng. Mater. Struct., 24, pp. 243–254; Kim, et al., 2002, “Non-Linear Fracture Mechanics Analyses of Part Circumferential Surface Cracked Pipes,” Int. J. Fract., 116, pp. 347–375.)


2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Da-Som Jeon ◽  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Sang-Min Lee

Based on the detailed three-dimensional (3D) finite element (FE) limit analyses, the present study investigates the plastic limit loads of complex-cracked pipes with two-layered materials for determining maximum load-carrying capacity or critical crack length of pipes with two-layered materials. The complex cracks in pipes with two-layered materials consist of a partial through-wall crack and 360-deg circumferential surface crack in the inner side of pipe in the same plane in pipe, which could be developed in the preemptive weld overlay region on the dissimilar metal weld (DMW) of nuclear pipe. In terms of FE limit analyses for complex-cracked pipes with two-layered materials, total thickness of pipe, depth of 360-deg internal surface crack, length of partial through-wall crack and the effect of strength mismatch between two materials are systematically considered in the present study. As for loading conditions, axial tension, global bending moment, and internal pressure are employed in the present FE analyses, and then, the confidence of the present FE procedure is confirmed by comparing the FE results with the existing solutions for complex cracks in single material. The results of the present FE plastic limit loads are compared with the existing solutions for complex-cracked pipes with two-layered materials. Also, a simple approach using equivalent single material based on the weighted average concept instead of using the properties of two materials is suggested for predicting plastic limit loads of two-layered materials. The present results can be applied to leak-before-break (LBB) analyses of nuclear piping with weld overlay.


Author(s):  
Hyun-Min Jang ◽  
Doo-Ho Cho ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
Nam-Su Huh ◽  
...  

Based on detailed three-dimensional (3-D) 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. To quantify the effect of slanted crack on plastic limit load, the slant correction factors for calculating plastic limit loads of pipes with slanted TWCs from pipes with idealized TWCs were newly proposed via extensive 3-D FE calculations. These slant correction factors are presented in a tabulated form for practical ranges of geometry and each loading conditions. Moreover, the present FE plastic limit loads were also compared with the existing solutions of pipes with slanted TWCs. These FE plastic limit load solutions can be applied to estimate elastic-plastic fracture mechanics parameters and creep fracture mechanics parameters, such as elastic-plastic J–integral and crack opening displacement, creep C*-integral and creep crack opening displacement, based on the reference stress concept considering more realistic crack shape.


2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Se-Chang Kim ◽  
Jae-Boong Choi ◽  
Hyun-Su Kim ◽  
Nam-Su Huh ◽  
Kyunghoon Kim

Pipe-in-pipes (PIPs) are generally applied to the extreme environments such as deep-sea and next-generation reactors due to their functionality and robustness. Thus, it is important to estimate the fracture behaviors of PIPs for integrity assessment of this unique piping system. In this work, the plastic collapse behaviors of PIPs with circumferential through-wall cracks (TWCs) are investigated based on three-dimensional finite element (FE) limit analysis, where the crack is assumed to be located at the inner pipe of PIPs. As for loading conditions, internal pressure, axial tension, and global bending moment are considered. In particular, the bending restraint effect induced by interconnection between the inner and outer pipes of PIPs is quantified through the FE analyses considering a practical range of geometries of PIPs. Based on the FE analysis results, the tabular and closed-form solutions of the plastic limit loads of the circumferential through-wall cracked PIPs are proposed, and then, validated against numerical simulations.


2005 ◽  
Vol 128 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Z. F. Sang ◽  
H. F. Wang ◽  
L. P. Xue ◽  
G. E. O. Widera

The purpose of this work is to study the plastic limit load of pad reinforced cylindrical vessels with different d/D ratios under out-of-plane moment loading on a nozzle. Three full-scale test models were designed and fabricated. A 3-D nonlinear finite element numerical analysis was also performed. Data on plastic limit moment is obtained from load-displacement and load-strain responses. The results indicate that plastic limit loads determined by test (including displacement and strain measurements) and finite element analysis are in agreement.


Author(s):  
Da-Som Jeon ◽  
Nam-Su Huh

In the present study, the plastic limit loads of the complex-cracked pipes, which have 360° internal surface crack along the circumference of pipe together with partial through-wall crack, are investigated via detailed 3-dimensional (3-D) finite element (FE) limit analyses. In terms of geometry of the complex-cracked pipe, the Alloys 82/182 butt weld that has welds overlay using the Alloys 52/152 for mitigating primary water stress corrosion cracking (PWSCC) in the nuclear pipe is considered. In the present FE limit analyses on complex-cracked pipes with welds overlay, the effect of strength mismatch between Alloys 82/182 and Alloys 52/152, depth of 360° internal surface crack and length of partial through-wall crack on plastic limit loads of complex-cracked pipes is systematically evaluated. As for loading conditions, axial tension, global bending and internal pressure are employed. The resulting FE plastic limit loads of complex-cracked pipes with welds overlay are also compared with the existing solutions, and finally the applicability of simple engineering estimate using the single material property based on the weighted average concept instead of using the properties of Alloys 52/152 and Alloys 82/182 to the prediction of the plastic limit loads of complex-cracked pipes with welds overlay is pursued.


2003 ◽  
Vol 80 (7-8) ◽  
pp. 527-540 ◽  
Author(s):  
Yun-Jae Kim ◽  
Do-Jun Shim ◽  
Kamran Nikbin ◽  
Young-Jin Kim ◽  
Seong-Sik Hwang ◽  
...  

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