Elastoplastic response of a pipe bend using Prandtl operator approach in a finite element analysis

Abstract The present paper makes an attempt to depict the effect of ovality in the inlet pigtail pipe bend of a reformer under combined internal pressure and in-plane bending. Finite element analysis (FEA) and experiments have been used. An incoloy Ni-Fe-Cr B407 alloy material was considered for study and assumed to be elastic-perfectly plastic in behavior. The design of pipe bend is based on ASME B31.3 standard and during manufacturing process, it is challenging to avoid thickening on the inner radius and thinning on the outer radius of pipe bend. This geometrical shape imperfection is known as ovality and its effect needs investigation which is considered for the study. The finite element analysis (ANSYS-workbench) results showed that ovality affects the load carrying capacity of the pipe bend and it was varying with bend factor (h). By data fitting of finite element results, an empirical formula for the limit load of inlet pigtail pipe bend with ovality has been proposed, which is validated by experiments.

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Using Finite Element Analysis to Prioritize ILI Calls for Combined Features: Dents in Bends

Volume 1: Pipeline and Facilities Integrity ◽

10.1115/ipc2018-78636 ◽

2018 ◽

Author(s):

David Kemp ◽

Justin Gossard ◽

Shane Finneran ◽

Joseph Bratton

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Metal Loss ◽

Remaining Life ◽

Case Scenario ◽

Element Analysis ◽

Pipe Bend ◽

Worst Case ◽

Worst Case Scenario ◽

Combined Features

Pipeline in-line-inspections (ILI) are used to assess and track the integrity of pipelines, aiding in identifying a variety of features such as: metal loss, dents, out-of-roundness, cracks, etc. The presence of these features can negatively affect the operation, integrity, and remaining life of a pipeline. Proper interpretation of the impacts these features may have on a pipeline are crucial to maintaining the integrity of a pipeline. Several codes and publications exist to assess the severity of these features under known operating conditions, either through empirical formulations or more detailed analysis, in order to aid the operator in determining a corrective action plan. These empirical formulations are generally applicable to assess a singular defect but require a more detailed assessment to evaluate combined defects (i.e. dent in a bend). These detailed assessments typically require a higher level numerical simulation, such as Finite Element Analysis (FEA). This detailed FEA can be quite costly and time consuming to evaluate each set of combined features in a given ILI run. Thus, engineering judgement is critical in determining a worst-case scenario of a given feature set in order to prioritize assessment and corrective action. This study aims to assess dent features (many associated with metal loss) occurring in a pipe bend to determine a worst-case scenario for prioritization of a given feature listing. FEA was used to simulate a field bend of a given radius and angle in order to account for residual stresses in the pipe bend. A rigid indenter was used to form a dent of the approximate length, width, and depth from the ILI data. Separate models were evaluated considering the dent occurring in the intrados, extrados, and neutral axis of the pipe bend to evaluate the worst-case scenario for further assessment. The resulting stresses in the pipe bend-dent geometry, under proper loading were compared to the same dent scenario in a straight pipe segment to develop a stress concentration factor (SCF). This SCF was used in the API 579-1/ASME FFS-1 Fitness for Service (API 579) [1] methodology to determine the impact on the remaining life of the combined features.

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Comparison of Cyclic and Burst Test Result With FE Simulation of a Locally Thinned Pipe Bend

ASME 2011 Pressure Vessels and Piping Conference: Volume 2 ◽

10.1115/pvp2011-58005 ◽

2011 ◽

Author(s):

Wolf Reinhardt ◽

Ali Asadkarami

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Structural Integrity ◽

Degradation Mechanism ◽

Element Analysis ◽

Pipe Bend ◽

Elastic Plastic ◽

Piping Systems ◽

Cyclic Part ◽

Test Result

Thinning of Carbon steel pipe subjected to water flow has been observed in many piping systems. The feeder pipes in CANDU® reactors have been found susceptible to this degradation mechanism. In response, an industry program has been initiated to investigate the effect of local thinning on structural integrity. A CANDU® feeder pipe bend specimen was thinned locally to about 70% of pressure based thickness near the weld at the onset of the bend. The test specimen was subjected to severe pressurized cyclic bending for over 1600 cycles, and was subsequently pressurized to failure under a constant applied bending deformation. The failed specimen was subjected to metallurgical examination. The present paper reports the results of a finite element analysis of the cyclic part of the test and an elastic plastic analysis for failure under pressurization. The results are compared with the experimental outcomes. The conclusions address specifically the test, more generally the failure of thinned pipe and the use of elastic-plastic finite element analysis to predict failure due to pressurization.

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Flexural behaviour of a polyvinyl chloride-lined glass-reinforced plastic composite multi-mitred pipe bend subjected to combined loads: A comparative finite element analysis and experimental case study

The Journal of Strain Analysis for Engineering Design ◽

10.1243/030932404773123877 ◽

2004 ◽

Vol 39 (2) ◽

pp. 137-146 ◽

Cited By ~ 5

Author(s):

S B Kochekseraii ◽

M Robinson

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Polyvinyl Chloride ◽

Flexural Behaviour ◽

Element Analysis ◽

Pipe Bend ◽

Plastic Composite ◽

Combined Loads ◽

Reinforced Plastic

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Investigating the Effects of Cyclic Thermo-Mechanical Loading on Cyclic Plastic Behavior of a Ninety-Degree Back-to-Back Pipe Bend System

Journal of Pressure Vessel Technology ◽

10.1115/1.4043376 ◽

2019 ◽

Vol 142 (2) ◽

Author(s):

Nak-Kyun Cho ◽

Haofeng Chen ◽

Donald Mackenzie ◽

Dario Giugliano

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Mechanical Loading ◽

Plastic Behavior ◽

Confined Space ◽

Element Analysis ◽

Pipe Bend ◽

Space Applications ◽

Cyclic Plastic ◽

Incremental Step

Abstract Pipe bends are generally employed for routing piping systems by connecting to straight pipes but back-to-back pipe bends are often necessary for confined space applications. In order to achieve safe operation under complex loading, it requires a thorough pipeline integrity assessment to be commenced. This paper investigates the effects of cyclic thermo-mechanical loading on cyclic plastic behavior of a 90-deg back-to-back pipe bend system, including temperature-dependent yield stress effects. Structural response interaction boundaries are determined for various different combinations of cyclic and steady loading. Constructed structural responses are verified by full cyclic incremental, step-by-step, finite element analysis. The numerical studies provide a comprehensive description of the cyclic plastic behavior of the pipe bends, and semi-empirical equations for predicting the elastic shakedown limit boundary are developed to aid pipeline designers in the effective assessment of the integrity of the pipe bends without a requirement for complex finite element analysis.

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