Assessment of Local Wall Thinned Pipeline Under Combined Bending and Pressure

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1870-1876 ◽  
Author(s):  
D. J. Shim ◽  
J. B. Choi ◽  
Y. J. Kim ◽  
J. W. Kim ◽  
C. Y. Park
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Bending Moment ◽  
Combined Loading ◽  
Assessment Procedure ◽  
Dead Weight ◽  
Maximum Moment

Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G are still useful for assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element (FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on true ultimate stress (σu,t) were obtain from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.

Assessment of Local Wall Thinned Pipeline Under Combined Bending and Pressure

2002 ◽  
Author(s):  
D. J. Shim ◽  
J. B. Choi ◽  
Y. J. Kim ◽  
J. W. Kim ◽  
C. Y. Park
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Bending Moment ◽  
Combined Loading ◽  
Assessment Procedure ◽  
Dead Weight ◽  
Maximum Moment

Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G are still useful for assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element (FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on ultimate stress (σu) were obtained from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect oll the maximum moment.

Failure Strength Assessment of Pipes With Local Wall Thinning Under Combined Loading Based on Finite Element Analyses

2004 ◽  
Vol 126 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Do-Jun Shim ◽  
Jae-Boong Choi ◽  
Young-Jin Kim
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Nuclear Power ◽  
Bending Moment ◽  
Combined Loading ◽  
Assessment Procedure ◽  
Finite Element Analyses ◽  
Maximum Moment ◽  
Wall Thinning ◽  
Local Wall Thinning

Failure assessment of a pipe with local wall thinning draws increasing attention in the nuclear power plant industry. Although many guidelines have been developed and are used for assessing the integrity of a wall-thinned pipeline, most of these guidelines consider only pressure loading and thus neglect bending loading. As most pipelines in nuclear power plants are subjected to internal pressure and bending moment, an assessment procedure for locally wall-thinned pipeline subjected to combined loading is urgently needed. In this paper, three-dimensional finite element (FE) analyses are carried out to simulate full-scale pipe tests conducted for various shapes of wall-thinned area under internal pressure and bending moment. Maximum moments based on ultimate tensile stress were obtained from FE results to predict the failure of the pipe. These results are compared with test results, showing good agreement. Additional finite element analyses are then performed to investigate the effect of key parameters, such as wall-thinned depth, wall-thinned angle and wall-thinned length, on maximum moment. Moreover, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.

Three Dimensional Finite Element Analyses of Welding Residual Stresses of a Repaired Weld

2018 ◽  
Author(s):  
Mingya Chen ◽  
Weiwei Yu ◽  
Fei Xue ◽  
Francis Ku ◽  
Zhilin Chen ◽  
...  
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Fe Model ◽  
Dimensional Finite Element ◽  
Surge Line ◽  
Line Slope ◽  
Three Dimensional Finite Element

The objective of this study is to correct installation non-conformance of a surge line using the excavation and re-weld method which is widely used in nuclear power plants. The surge line with a backslope was not at the required design level after initial installation. In order to solve the problem, a repairing technology is shown as follows: the weld was successively excavated and welded again while the surge line slope was corrected with the help of jacks. Because many of the degradation mechanisms relevant to power plant components can be accelerated by the presence of welding residual stresses (WRS), the WRS caused by the repairing process need to be studied. In this paper, the WRS simulation technique employed in this project is sophisticated. It utilizes a 3-D finite element (FE) model, and simulates the weld sequencing and excavation. Moreover, the WRS simulation performed in this project not only uses the un-axisymmetric model, but also considers the deformation caused by the external jacking loads. The results show that the repairing process is effective, and strain damage induced by the welding repair is also acceptable.

On the Effectiveness of Composites for Repair of Pipelines Under Various Combined Loading Conditions: A Computational Approach Using the Cohesive Zone Method

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Shahin Shadlou ◽  
Farid Taheri
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Cohesive Zone ◽  
Loading Condition ◽  
Bending Moment ◽  
Combined Loading ◽  
Loading Conditions ◽  
Original Design ◽  
Zone Method ◽  
Noticeable Effect

ASTM PCC-2 standard provides a series of equations for establishing the composite repair's thickness required for bringing the capacity of dented/damaged pipes, to their original design state. However, the accuracy of the equations' predictions for pipes subjected to various combined loadings has not been fully explored. Moreover, the influence of the state of a pipe/composite wrap (CW) interface (i.e., whether perfectly intact or not intact), in reference to the predictions of the ASTM equations, has not been studied either. In consideration of the above-mentioned issues, a comprehensive finite-element (FE) study is conducted, using the cohesive zone methodology (CZM) to simulate the response of pipes repaired with composite wraps, under single and various combined loading conditions. Moreover, the influence of perfect (or tied) and imperfect (unintact) pipe/CW interface on the load-bearing capacity of repaired pipes is systematically investigated. Finally, the effects of composite repairs' thickness and length on their efficacy are also investigated. The results show that, although the pipe/CW interface state does not have any noticeable effect when the pipe is subjected to a combined loading state of bending moment and internal pressure, it plays a crucial role when the pipe is under a combined internal pressure and uniaxial loading condition. Furthermore, the predicted values calculated according to the ASME standard are compared with the finite-element results, demonstrating that ASTM-based predictions do not provide accurate results when a repaired pipe is subjected to an axial loading condition.

Experimental Investigation on Buckling of Steel Nuclear Containment With Elliptical Head

2016 ◽  
Author(s):  
Keming Li ◽  
Jinyang Zheng ◽  
Zekun Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Internal Pressure ◽  
Nuclear Power ◽  
Power Plants ◽  
Nonlinear Finite Element ◽  
Nonlinear Finite Element Method ◽  
Initial Shape ◽  
Nuclear Containment ◽  
Element Method

Thanks to relative ease of fabrication and erection, steel containments with a torispherical or elliptical head are common in large nuclear power plants with relatively high internal pressure. Buckling failure mode is critical in the design of a steel containment with elliptical head under internal pressure. An experiment on buckling of elliptical head under internal pressure is presented in this paper. A test vessel was designed to provide a substantial margin of safety which permitted testing the head to rupture. The head has a diameter of 4797 mm, radius-to-height ratio of 1.728 and nominal thickness of 5.5 mm. Initial shape and shell displacement measurements of the head were carried out by using 3D laser scanners. The details of the buckling behavior are given. Initial buckling pressure was predicted by nonlinear finite element method considering the measured initial shape of the head. The agreement between the initial experimental buckling pressure and that predicted by the nonlinear finite element method is good. It is very useful in the buckling evaluation and the development of design rules for steel nuclear containment with elliptical head.

PWR Nuclear Power Plants Reactor Vessel and Coolant System Cast Duplex Stainless Steel Elbows: New Results in Integrity Analysis

2003 ◽  
Author(s):  
G. Bezdikian ◽  
C. Faidy ◽  
P. Cambefort ◽  
D. Moinereau
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Reactor Vessel ◽  
Integrity Assessment ◽  
Reactor Coolant

The Reactor Pressure Vessel and Reactor coolant materials (hot and cold CAST elbows) are major components for integrity evaluation of nuclear plant units. The French Utility (Electricite de France) has engaged a few years ago an important program regarding the integrity assessment of RPV and cast duplex stainless steel elbows based on large real database. This paper deals with the verification of the integrity of the Reactor Vessel component by finite element mechanical studies, in all conditions of loading in relation with RTNDT (Reference Nil Ductility Transition Temperature), and considering all parameters. An overall review of actions will be presented describing the French approach regarding the assessment of nuclear RPV. The latest results obtained are based on generic integrity analyses for all categories of situations (normal upset emergency and faulted conditions), particularly in case of PTS, until the end of lifetime, postulating longitudinal shallow subclad flaws. For the Reactor Coolant Elbows, the results of structural integrity analyses, beginning with elastic computations and completed with three-dimensional finite element elastic-plastic computations for envelope cases, are compared with in-service inspection real flaw characterisation and the results are compared to the margin on loading condition with the criteria included in the code.

Sensitivity Analyses of Finite Element Method for Computing Residual Stress of Dissimilar Metal Multi-Pass Weld

2010 ◽  
Author(s):  
YaoLong Tsai ◽  
ChaoJen Li ◽  
TaiPing Tsai ◽  
Li-Hua Wang ◽  
TeWei Fan ◽  
...  
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Sensitivity Analyses ◽  
Dissimilar Metal ◽  
Welding Sequence ◽  
Dimensional Finite Element ◽  
Stress Computation

Recently the stress corrosion cracking cases of dissimilar metal welds are found in many nuclear power plants. Weld-induced residual stress is main factor for crack growth. Therefore exact estimation of residual stress is important for reliable operation. This paper presents residual stress computation performed by EU mock-up Nozzle. Based on ANSYS software, uncoupled thermal-mechanical three-dimensional (3D) and two-dimensional ax symmetric finite element models are developed. Based on 2 dimensional and 3 dimensional finite element analyses, effect of the welding sequence approaches for multi-pass weld such as lump, layer and ring etc. on residual stress variation is estimated for sensitivity analysis.

Effect of Torsion on Collapse Bending Moment for 24-Inch Diameter Schedule 80 Pipes With Wall Thinning

2012 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong Hoang
Keyword(s):  
Power Plants ◽  
Bending Moment ◽  
Combined Loading ◽  
Bending Moments ◽  
Compressive Stresses ◽  
Wall Thinning ◽  
Nominal Thickness ◽  
Calculation Results ◽  
Loading Modes ◽  
Local Wall Thinning

Piping items in power plants may experience combined bending and torsion moments during operation. Currently, there is a lack of guidance in the ASME B&PV Code Section XI for combined loading modes including pressure, torsion and bending. Finite element analyses were conducted for 24-inch diameter Schedule 80 pipes with local wall thinning subjected to tensile and compressive stresses. Plastic collapse bending moments were calculated under constant torsion moments. From the calculation results, it can be seen that collapse bending moment for pipes with local thinning subjected to tensile stress is smaller than that subjected to compressive stress. In addition, equivalent moment is defined as the root the sum of the squares of the torsion and bending moments. It is found that the equivalent moments can be approximated with the pure bending moments, when the wall thinning length is equal or less than 7.73R·t for the wall thinning depth of 75% of the nominal thickness, where R is the mean radius and t is the wall thickness of the pipe.

Elastic-plastic bending of the pipeline under combined loading

2021 ◽  
pp. 372-377
Author(s):  
Виктор Миронович Варшицкий ◽  
Евгений Павлович Студёнов ◽  
Олег Александрович Козырев ◽  
Эльдар Намикович Фигаров
Keyword(s):  
Internal Pressure ◽  
Limit State ◽  
Bending Moment ◽  
Axial Direction ◽  
Longitudinal Force ◽  
Combined Loading ◽  
Dimensional Problem ◽  
Elastic Plastic ◽  
Pipeline Section ◽  
Thin Walled Pipe

Рассмотрена задача упругопластического деформирования тонкостенной трубы при комбинированном нагружении изгибающим моментом, осевой силой и внутренним давлением. Решение задачи осуществлено по разработанной методике с помощью математического пакета Matcad численным методом, основанным на деформационной теории пластичности и безмоментной теории оболочек. Для упрощения решения предложено сведение двумерной задачи к одномерной задаче о деформировании балки, материал которой имеет различные диаграммы деформирования при сжатии и растяжении в осевом направлении. Проведено сравнение с результатами численного решения двумерной задачи методом конечных элементов в упругопластической постановке. Результаты расчета по инженерной методике совпадают с точным решением с точностью, необходимой для практического применения. Полученные результаты упругопластического решения для изгибающего момента в сечении трубопровода при комбинированном нагружении позволяют уточнить известное критериальное соотношение прочности сечения трубопровода с кольцевым дефектом в сторону снижения перебраковки. Применение разработанной методики позволяет ранжировать участки трубопровода с непроектным изгибом по степени близости к предельному состоянию при комбинированном нагружении изгибающим моментом, продольным усилием и внутренним давлением. The problem of elastic plastic deformation of a thin-walled pipe under co-binned loading by bending moment, axial force and internal pressure is considered. The problem is solved by the developed method using the Matcad mathematical package by a numerical method based on the deformation theory of plasticity and the momentless theory of shells. To simplify the solution of the problem, it is proposed to reduce a twodimensional problem to a one-dimensional problem about beam deformation, the material of which has different deformation diagrams under compression and tension in the axial direction. Comparison with the results of numerical solution of the two-dimensional problem with the finite element method in the elastic plastic formulation is carried out. The obtained results of the elastic-plastic solution for the bending moment in the pipeline section under combined loading make it possible to clarify criterion ratio of the strength of the pipeline section with an annular defect in the direction of reducing the rejection. Application of the developed approach allows to rank pipeline sections with non-design bending in the steppe close to the limit state under combined loading of the pipeline with bending moment, longitudinal force and internal pressure.

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