Fracture Response of Girth-Welded Pipeline With Canoe Shape Embedded Crack Subjected to Large Plastic Deformation

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Lie Seng Tjhen ◽  
Zhang Yao ◽  
Zhao Hai Sheng
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Internal Pressure ◽  
Structural Integrity ◽  
Biaxial Loading ◽  
Finite Element Simulations ◽  
Critical Parameters ◽  
Large Plastic Deformation ◽  
Long Distance ◽  
Fracture Assessment

Long-distance offshore pipelines always suffer large plastic deformation during installation and operation. Accompanied by high internal pressure, potential flaws are found to initiate from the girth welds, and this brings a significant challenge to the structural integrity of the pipelines. The currently used procedures for fracture assessment of pipelines are usually stress based, which are unsuitable for application to cracked pipeline subjected to large plastic deformation. Therefore, the aim of this paper is to investigate the fracture assessment of pipeline subjected to large plastic deformation and identify and understand the critical parameters influencing the fracture responses under actual loading conditions. The evolution of crack tip opening displacement (CTOD) of a pipeline segment with an embedded canoe shape crack located in the middle of the girth weld is investigated under pure bending and biaxial loading through 3D elastic–plastic finite-element simulations. The effects of crack width, crack length, pipeline thickness, material hardening, and internal pressure on fracture response are discussed. Finally, a strain-based failure assessment diagram (FAD) is developed, and comparison between fracture assessment by BS7910:2013 and finite-element simulations concludes that the former produces conservative predictions for deep crack.

J and CTOD Based Tensile Strain Capacity Prediction for Pipelines with a Surface Crack in Girth Weld

2021 ◽  
Author(s):  
Youn-Young Jang ◽  
Nam-Su Huh ◽  
Ik-Joong Kim ◽  
Young-Pyo Kim
Keyword(s):  
Crack Initiation ◽  
Internal Pressure ◽  
Surface Crack ◽  
Driving Force ◽  
Tensile Strain ◽  
Structural Integrity ◽  
Accurate Estimation ◽  
Long Distance ◽  
Crack Driving Force ◽  
Girth Welding

Abstract Long-distance pipelines for the transport of oil and natural gas to onshore facilities are mainly fabricated by girth welding, which has been considered as a weak location for cracking. Pipeline rupture due to crack initiation and propagation in girth welding is one of the main issues of structural integrity for a stable supply of energy resources. The crack assessment should be performed by comparing the crack driving force with fracture toughness to determine the critical point of fracture. For this reason, accurate estimation of the crack driving force for pipelines with a crack in girth weld is highly required. This paper gives the newly developed J-integral and crack-tip opening displacement (CTOD) estimation in a strain-based scheme for pipelines with an internal surface crack in girth weld under axial displacement and internal pressure. For this purpose, parametric finite element analyses have been systematically carried out for a set of pipe thicknesses, crack sizes, strain hardening, overmatch and internal pressure conditions. Using the proposed solutions, tensile strain capacities (TSCs) were quantified by performing crack assessment based on crack initiation and ductile instability and compared with TSCs from curved wide plate tests to confirm their validity.

Failure of Locally Buckled Pipelines

2006 ◽  
Author(s):  
E. Dama ◽  
S. A. Karamanos ◽  
A. M. Gresnigt
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Fatigue Failure ◽  
Structural Integrity ◽  
Mechanical Damage ◽  
Strain Range ◽  
Structural Condition ◽  
Repeated Loading ◽  
Maximum Strain ◽  
Pipe Burst

Mechanical damage in steel pipelines in the form of local buckles due to excessive bending deformation, may severely threaten their structural integrity. The present paper describes experimental and numerical research conducted to assess the structural condition of buckled pipes, subjected to both bending and internal pressure. Fatigue failure under repeated loading is mainly investigated, whereas pipe burst due to internal pressure is also examined. Three full-scale buckled pipe specimens are tested under pressure and bending loads to determine their structural capacity. In addition, using nonlinear finite element tools, an extensive parametric study is conducted, to determine the critical locations at the buckled area, at which maximum strain variation occurs, as well as to investigate the influence of several geometrical and mechanical parameters. Using the maximum strain range from the finite element computations, and a simple S-N approach, reasonable predictions are obtained for the number of cycles to failure observed in the tests. The results of the present study demonstrate that under repeated loading, fatigue failure occurs in the buckled area at the location of maximum strain range. It is also found that the burst pressure may not be affected by the presence of buckles.

3-D Non-Linear Finite Element Analysis of a Non-Gasketed Flange Joint Under Combined Internal Pressure and Axial Loading

2007 ◽  
Author(s):  
Muhammad Abid ◽  
Abdul W. Awan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Structural Integrity ◽  
Experimental Studies ◽  
Axial Loading ◽  
External Loading ◽  
Flange Joint ◽  
Element Analysis ◽  
Bolted Flange

A number of analytical and experimental studies have been conducted to study ‘strength’ and ‘sealing capability’ of bolted flange joint only under internal pressure loading. Due to the ignorance of the external i.e. axial loading, the optimized performance of the bolted flange joint can not be achieved. A very limited work is found in literature under combined internal pressure and axial loading. In addition, the present design codes do not address the effects of axial loading on the structural integrity and sealing ability of the flange joints. From previous studies, non-gasketed joint is claimed to have better performance as compared to conventional gasketed joint. To investigate non-gasketed joint’s performance i.e. joint strength and sealing capability under combined internal pressure and any applied external loading, an extensive 3D nonlinear finite element analysis is carried out and overall joint performance and behavior is discussed.

Analysis of the Large Plastic Deformation Involved in Wear Processes Using the Finite Element Method With an Updated Lagrangian Formulation

1987 ◽  
Vol 109 (2) ◽  
pp. 330-337 ◽  
Author(s):  
Nobuo Ohmae
Keyword(s):  
Finite Element Method ◽  
Plastic Deformation ◽  
Finite Element ◽  
Equivalent Stress ◽  
Lagrangian Formulation ◽  
The Finite Element Method ◽  
Large Plastic Deformation ◽  
Updated Lagrangian Formulation ◽  
Updated Lagrangian ◽  
Element Method

Large plastic deformation caused by friction for high purity copper was investigated using the finite element method with an updated Lagrangian formulation. The phenomenological background of this large plastic deformation was studied with a scanning electron microscope, and the nucleation of voids similar to those obtained for copper rolled to over 50 percent reduction was observed. Void nucleation was found to correlate with the agglomeration of over-saturated vacancies formed under high plastic strains. The computer-simulation analyzed such heavy deformation with an equivalent stress greater than the tensile strength and with an equivalent plastic strain of 0.44. Crack propagation was discussed by computing the J-integrals.

scholarly journals Experimental and Numerical Analysis of Expanded Pipe using Rigid Conical Shape

2018 ◽  
Vol 24 (8) ◽  
pp. 106
Author(s):  
Ahmed Ibrahim Razooqi
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Numerical Analysis ◽  
Expansion Ratio ◽  
Large Plastic Deformation ◽  
Expansion Process ◽  
Finite Element Software ◽  
Conical Shape ◽  
Expansion Force ◽  
Good Agreement

The experimental and numerical analysis was performed on pipes suffering large plastic deformation through expanding them using rigid conical shaped mandrels, with three different cone angles (15◦, 25◦, 35◦) and diameters (15, 17, 20) mm. The experimental test for the strain results investigated the expanded areas. A numerical solution of the pipes expansion process was also investigated using the commercial finite element software ANSYS. The strains were measured for each case experimentally by stamping the mesh on the pipe after expanding, then compared with Ansys results. No cracks were generated during the process with the selected angles. It can be concluded that the strain decreased with greater angles of conical shape and an increase in expansion ratio results in an increase of expansion force and a decrease in the pipe thickness and length resulting in pipe thinning and shortening. Good agreement is evident between experimental and ANSYS results within discrepancy (16.90017%) in the X direction and (27.68698%) in the Y direction. Also, the stress distribution is investigated and it can be concluded that the case of Diameter (Do cone) = 35mm and (A) = α = 15° is the optimum.  

J and CTOD Estimation Procedure for Circumferentially Cracked Pipes Under Combined Bending and Internal Pressure

2011 ◽  
Author(s):  
Lui´s F. S. Parise ◽  
Claudio Ruggieri
Keyword(s):  
Internal Pressure ◽  
Structural Integrity ◽  
Biaxial Loading ◽  
Numerical Solutions ◽  
Driving Forces ◽  
Crack Depth ◽  
Bending Moment ◽  
Estimation Procedure ◽  
Wide Range ◽  
Bending Load

This work provides an estimation procedure to determine the J-integral and CTOD for pipes with circumferential surface cracks subjected to combined bending load and internal pressure for a wide range of crack geometries and material (hardening) based upon fully-plastic solutions. The present investigation broadens the applicability of current evaluation procedures for J and CTOD which enter directly into structural integrity analyses and flaw tolerance criteria. Extensive 3-D nonlinear analyses of circumferentially cracked pipes with surface flaws having different crack depth (a) over pipe wall thickness (t) ratios and varying crack length for different strain hardening properties provide the dimensionless parameters relating the elastic-plastic crack-tip driving forces with the applied (remote) bending moment and internal pressure. The investigation provides a fairly comprehensive body of numerical solutions for J and CTOD in circumferentially cracked pipes subjected to biaxial loading.

Plastic deformation behaviour of Fe–Cu composites predicted by 3D finite element simulations

2010 ◽  
Vol 48 (3) ◽  
pp. 456-465 ◽  
Author(s):  
Yanling Schneider ◽  
Albrecht Bertram ◽  
Thomas Böhlke ◽  
Christian Hartig
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Deformation Behaviour ◽  
Finite Element Simulations ◽  
3D Finite Element
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