Post-Buckling Failure Modes of X65 Steel Pipe: An Experimental and Numerical Study

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Nima Mohajer Rahbari ◽  
Mengying Xia ◽  
Xiaoben Liu ◽  
J. J. Roger Cheng ◽  
Millan Sen ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Failure Modes ◽  
Bending Test ◽  
Bending Load ◽  
Post Buckling ◽  
X65 Steel ◽  
Bending Loads ◽  
Buckling Failure ◽  
Longitudinal Strains

In service pipelines exhibit bending loads in a variety of in-field situation. These bending loads can induce large longitudinal strains, which may trigger local buckling on the pipe's compressive side and/or lead to rupture of the pipe's tensile side. In this article, the post-buckling failure modes of pressurized X65 steel pipelines under monotonic bending loading conditions are studied via both experimental and numerical investigations. Through the performed full-scale bending test, it is shown that the post-buckling rupture is only plausible to occur in the pipe wall on the tensile side of the wrinkled cross section under the increased bending. Based on the experimental results, a finite element (FE)-based numerical model with a calibrated cumulative fracture criterion was proposed to conduct a parametric analysis on the effects of the internal pressure on the pipe's failure modes. The results show that the internal pressure is the most crucial variable that controls the ultimate failure mode of a wrinkled pipeline under monotonic bending load. And the post-buckling rupture of the tensile wall can only be reached in highly pressurized pipes (hoop stress no less than 70% SMYS for the investigated X65 pipe). That is, no postwrinkling rupture is likely to happen below a certain critical internal pressure even after an abrupt distortion of the wrinkled wall on the compressive side of the cross section.

A Theoretical and Experimental Analysis of the Bending Behavior of Unbonded Flexible Pipes

2014 ◽  
Author(s):  
Tatiana Vargas-Londoño ◽  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Internal Pressure ◽  
Cross Section ◽  
Structural Response ◽  
Experimental Tests ◽  
Theoretical Models ◽  
External Pressure ◽  
Local Behavior ◽  
Flexible Pipes ◽  
Floating System ◽  
Bending Loads

Due to its compound cross-section, the prediction of the structural response of flexible pipes to loads such as their self-weight, internal and external pressure, movements imposed by the floating system and environmental loads such as currents, waves and wind is quite complex. All these loads generate stresses and strains in the cross section of the pipe that have to be properly evaluated in order to ensure integrity of the line. Research has been done on the local behavior of flexible pipes under combined axisymmetric loads as well as under bending loads. However, there is a lack of research combining both axisymmetric and bending loads, as also in the study of the strains in the tensile amour layers of the pipes, aspects which are important for the calibration of theoretical models to predict such behavior. Based on that, this study aims to evaluate the local behavior of flexible pipes under combinations of axisymmetric (tension, and internal pressure) and bending loads via a series of experimental tests in a 9.13″ I.D pipe. In the experimental tests, the behavior of the pipe was studied for three load combinations: i) bending combined with tension; ii) bending combined with internal pressure; and iii) bending combined with tension and internal pressure. Based on these tests, the authors obtained the strains in the tensile armor layer, axial elongation due to tension, axial reaction forces due to internal pressure, and deflection due to bending. These measurements were used to calibrate a theoretical model devoted to simulate the pipe’s response, getting accurate results for stiffness and stresses of the pipe in each scenario.

Numerical Analysis of High Pressure Cold Bend Pipe to Investigate the Behaviour of Tension Side Fracture

2012 ◽  
Author(s):  
Celal Cakiroglu ◽  
Amin Komeili ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Millan Sen
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Internal Pressure ◽  
Experimental Studies ◽  
Element Model ◽  
Combined Loading ◽  
Element Analysis ◽  
Bend Pipe ◽  
Bending Load ◽  
Bending Loads

The cold bend pipelines may be affected by the geotechnical movements due to unstable slopes, soil type and seismic activities. An extensive experimental study was conducted by Sen et al. in 2006 to understand the buckling behaviour of cold bend pipes. In their experiments, it was noted that one high pressure X65 pipe specimen failed under axial and bending loads due to pipe body tensile side fracture which occurred after the development of a wrinkle. The behaviour of this cold bend pipe specimen under bending load has been investigated numerically to understand the conditions leading to pipe body tension side fracture following the compression side buckling. Bending load has been applied on a finite element model of the cold bend by increasing the curvature of it according to the experimental studies conducted by Sen [1]. The bending loads have been applied on the model with and without internal pressure. The distribution of the plastic strains and von Mises stresses as well as the load–displacement response of the pipe have been compared for both load cases. In this way the experimental results obtained by Sen [1] have been verified. The visualization of the finite element analysis results showed that pipe body failure at the tension side of the cold bend takes place under equal bending loads only in case of combined loading with internal pressure.

Combined Loading Tests of Large Diameter Corroded Pipelines

2000 ◽  
Author(s):  
Marina Q. Smith ◽  
Christopher J. Waldhart
Keyword(s):  
Internal Pressure ◽  
Thermal Stresses ◽  
Failure Modes ◽  
Prediction Models ◽  
Large Diameter ◽  
Bending Moment ◽  
Combined Loading ◽  
Analytical Models ◽  
Bending Load ◽  
Full Scale Tests

Current methods for estimating the remaining strength of aging, corroded pipelines have been restricted to the capabilities of pressure based engineering models that rely on the definition of hoop stress in the pipe wall. Because in practice, pipelines are subjected to a variety of loading conditions (e.g.; axial bending from settlement and thermal stresses) that act in concert with those derived by internal pressure, a multi-year combined testing and analysis program was initiated by the Alyeska Pipeline Service Company aimed at developing computer tools for the prediction of rupture and wrinkling in corroded pipes. During the program, seventeen full-scale tests of mechanically corroded 48-inch diameter (1219-mm), X65 pipes subjected to internal pressure, axial bending, and axial compression were performed to provide data necessary for the verification of analytical models and failure prediction models. While all of the tests were designed to produce rupture, wrinkling, as defined by the occurrence of a limit moment during the application of bending loads, was produced in eleven of the tests either prior to or instead of rupture. Loading of the pipe was intended to simulate that which would be observed by a pipe in-service and included both load control and displacement control of the applied bending load, and in some tests, intended to define the amount of additional pressure required to cause burst after wrinkling was produced. Results of the tests showed that two different failure modes are produced depending on whether the bending moment is transmitted to the pipe as a fixed load or a fixed displacement, and consequently, the burst capacity of the corroded pipe may not be compromised by the presence of axial loads. This paper discusses the tests performed, including a description of the load schedule and corrosion geometries, and key results of the tests that were used in the development of a new strain-based burst prediction procedure for corroded pipes subjected to combined loads.

Effect of Internal Pressure and Dent Depth on Strain Distribution of Pressurized Pipe Subjected to Indentation

2013 ◽  
Vol 376 ◽  
pp. 135-139 ◽  
Author(s):  
Maziar Ramezani ◽  
Thomas Rainer Neitzert
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Cross Section ◽  
Strain Distribution ◽  
Fe Simulation ◽  
Circular Cross Section ◽  
Numerical Results ◽  
Rectangular Shape ◽  
Longitudinal Strains ◽  
Dent Depth

A dent in a pipeline is a permanent plastic deformation of the circular cross section of the pipe. This paper discusses numerical results obtained from finite element (FE) simulation of pressurized pipe subjected to radial denting by a rigid indenter. Dent produced by rectangular shape indenter is assessed and the strain distribution of the pipe is investigated. The effect of internal pressure and dent depth on the distribution of strain is also studied. The results show that the circumferential and longitudinal strains increase with increasing the internal pressure and the depth of the dent. Numerical results are compared with an empirical theoretical model in order to demonstrate the accuracy of the analysis.

Stress Analysis of Non-Conventional Composite Pipes: An Experimental and Numerical Approach

2009 ◽  
Author(s):  
Muhammad A. Wahab ◽  
Prashanth Ramachandran ◽  
Su-Seng Pang ◽  
Randy A. Jones
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Failure Modes ◽  
Bending Strength ◽  
Numerical Study ◽  
Numerical Approach ◽  
Failure Behavior ◽  
Finite Element Software ◽  
Bending Load ◽  
Composite Pipes

This paper discusses an experimental and numerical study to investigate the failure behavior of non-conventional cross-sectioned fiber reinforced composite pipes filled with glass beads subjected to internal pressure and bending loads. An adaptive filament winder for non-conventional pipes was exclusively designed to fabricate the samples used in the experiments. Experiments were conducted on triangular and rectangular cross-sectioned samples as per ASTM standards to find the internal burst pressure, bending strength, and failure modes of the pipes. Numerical analysis for the pipe loading process has been developed based on the finite element method for a linear orthotropic problem for composite pipes. The finite element software ANSYS was used to build the model and predict the stresses imposed on the pipes. The relationships between the applied internal pressure and peak hoop stress, bending load, and bending strength with reference to the fillet radius were determined; and generally a good correlation was found between the experimental and numerical results.

Failure Analysis of Plastic Pipe Reinforced by Cross Helically Wound Steel Wire Subjected to Internal Pressure and Bending Load

2016 ◽  
Author(s):  
Jie Zhang ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Internal Pressure ◽  
Steel Wire ◽  
Operating Conditions ◽  
Combined Loading ◽  
Design Parameters ◽  
Fe Model ◽  
Plastic Pipe ◽  
Bending Load ◽  
Calculation Results ◽  
Bending Loads

Plastic pipe reinforced by cross helically wound steel wire (PSP) has been widely used in the transportation of petroleum, natural gas, municipal water, etc. In some serious occasions, PSP suffers from bending load caused by operating conditions such as ocean wave, pipeline laying and geological sedimentation, besides internal pressure. Thus, to understand the strength of PSP under the complex loads is crucial for ensuring safety. In this study, a finite element (FE) model of PSP was proposed by taking both internal pressure and bending load into consideration. By gradually increasing the bending load, the strength of PSP was obtained by taking the break of steel wires as the failure criterion. Then, combined loading tests were conducted to verify the proposed model. The results show that the applied bending loads bear a nonlinear relationship with the increasing deformation. By comparing experimental results and FE model calculation results, good agreement was obtained. Based on the verified FE model, the limit bending load and the effects of design parameters and internal pressure on the strength of PSP were discussed.

scholarly journals Retrofitting of Reinforced Concrete Beams Using a Fiberglass Jacketing System

2021 ◽  
Vol 4 (1) ◽  
pp. 44
Author(s):  
Titik P. Artiningsih ◽  
Lirawati L. ◽  
Navi Helmi
Keyword(s):  
Experimental Testing ◽  
Load Capacity ◽  
Reinforced Concrete Beams ◽  
Bending Test ◽  
Building Collapse ◽  
Load Factors ◽  
Bending Load ◽  
Loading System ◽  
Earthquake Load ◽  
Bending Loads

Building collapse that occurred mostly caused by structure failure in containment earthquake load. Factors that lead to the failure of the beam, among others is beam planning that does not calculate ductility or restraint, resulting decline of beams performance. One way to improve beam strength and ductility are to retrofit the beam by wrapping beams using fiberglass. Research aims to discover the increase amount of bending load capacity from concrete beam that has been retrofitted using jacketing fiberglass. Experimental testing was carried out on beam specimens with a cross section size of 150x200 mm and a length of 1400 mm. Three beam specimens were subjected to bending loads with a three point loading system, with different levels of damage, namely BL1 with collapse at level-1, BL2 at level-2, and BL0 at level-5 as a comparison. Then the BL1 and BL2 were retrofitted by being coated with 2 layers of fiberglass which were glued using epoxy resin. Beams BL-1 and BL-2 are then subjected to a bending test again until they reach level-5 collapse. The test results showed that retrofitted beams were able to increase flexural strength, BL-1 increased 115.15% from the original load and BL-2 increased 52.27% from the original load.

Variations in the Postbuckling Behavior of Straight Pipes Due to Steel Grade and Internal Pressure

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ngoan T. Do ◽  
Celal Cakiroglu ◽  
Mustafa Gul ◽  
Roger Cheng ◽  
Millan Sen ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Failure Mode ◽  
Material Properties ◽  
Failure Modes ◽  
Experimental Studies ◽  
Equivalent Plastic Strain ◽  
Slope Instability ◽  
Structural Behavior ◽  
Discontinuous Permafrost ◽  
Bending Loads

Pipelines can be subjected to bending loads due to a variety of factors such as seismic activity, slope instability, or discontinuous permafrost. Experimental studies of Sen et al. [1–3] showed that pipelines can fail under bending loads due to pipe body tension side fracture which is a mostly overlooked failure mode in pipelines. Recent numerical studies on the structural behavior of cold bent pipes [4–6] also confirmed the likelihood of the pipe body tension side fracture. Furthermore, it was shown that both the material properties and the level of internal pressure can have a considerable effect on the failure mode of the pipe. In this current work, the parametric studies of internal pressure and material properties are extended to straight pipes using finite-element analysis. The differences in the structural behavior due to using stress–strain curves from test specimens in longitudinal and circumferential direction of the pipe are demonstrated. Using failure criteria based on the equivalent plastic strain, different failure modes corresponding to different levels of internal pressure and yield strength are shown on straight pipes.

scholarly journals Design Improvement of Y-TZP Three Unit Bridges by Predicted Stress Concentration Using FEA and Experimental Failure Modes after Three Point Bending Test

2019 ◽  
Vol 70 (1) ◽  
pp. 336-342
Author(s):  
Adrian Almasi ◽  
Iulian Antoniac ◽  
Sergiu Focsaneanu ◽  
Marius Manole ◽  
Robert Ciocoiu ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Failure Modes ◽  
Bending Test ◽  
Design Improvement ◽  
Cross Section Area ◽  
Section Area ◽  
Starting Point ◽  
Cad Cam ◽  
Experimental Trials

In this study an attempt to improve a three unit partial denture design is presented by performing experimental trials to find the failure load of a Y-TZP dental infrastructure. The experimental results are linked with FEA predictions to explain failure and find the optimum design. The test samples used were three unit fixed partial dentures obtained by CAD/CAM using as starting point a clinical case. Design improvement attempt was to increase connector cross-section size and modify its shape. Four samples with circular and elliptical connector cross-sections and 5mm2 and 9mm2 area were tested in flexure. The models created for CAM were used to perform FEA and find the stress distribution, pinpoint the stress concentrators and link the results to experimental failure modes. The results showed that connector design plays an important role in restoration success and increasing connector cross-section area the stress is distributed in a uniform manner. It was concluded that increasing connector cross-section area and using a wider shape (ellipse) strongly decreases failure probability.

Deformation and Ductile Cracking Behavior of X80 Grade Induction Bends

2002 ◽  
Author(s):  
Ryuji Muraoka ◽  
Nobuyuki Ishikawa ◽  
Shigeru Endo ◽  
Masaki Yoshikawa ◽  
Nobuhisa Suzuki ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Maximum Load ◽  
Ground Movement ◽  
Bending Test ◽  
Pipe Bend ◽  
Cracking Behavior ◽  
Initiation Point ◽  
Load Point ◽  
Bending Load ◽  
Maximum Load Point

Permanent ground movement is expected in seismic areas and in permafrost regions, and pipelines buried in those areas need to be designed to have sufficient deformability. Especially, bends need to have superior deformability, because it was pointed out in the recent earthquake event that deformation tends to concentrate in the connection region of pipelines. Severe deformation can lead to a fracture of the pipe wall and this may cause explosion of the pipeline or leakage of the gas, which need to be prevented in the areas with high population density. In spite of the importance of deformability for pipe bends, there are only a few reports on this issue. Furthermore, those investigations are limited for up to X65 grade induction pipe bends. In this study, two types of API X80 grade induction pipe bends, 610mmOD × 11.0mmWT and 610mmOD × 16.6mmWT, bending radius of three times the pipe diameter and bending angle of 90 degree for both, were manufactured using longitudinally submerged arc welded pipes as mother pipes. And large scale bending test using X80 grade pipe bend was conducted by applying closing displacement on the tangents under the internal pressure of 12MPa by water. Bending load was continuously applied up to the maximum load point, and then prescribed displacement was applied until twice the maximum load point. Local deformation was shown in the middle of the bend portion, however, no cracking was observed. Furthermore, EF analysis of bending test was performed for precise estimation of stress/strain response of pipe bend, and analytical results were compared with experimental data. These bending tests proved that large deformability could be expected on the X80 grade pipe bends even under the high internal pressure. In order to investigate ductile cracking behavior of the X80 grade induction pipe bend, notched round bar tensile tests were also conducted, and the criterion for ductile cracking was compared with X65 grade bend material. Relation between equivalent plastic strain and stress triaxiality at a ductile crack initiation point was determined by FE analysis, and this analysis proved that X80 grade bend material has enough resistance to ductile cracking compared to X65 grade bend. This result also corresponds to the results of the bend test, which is showing enough deformability of the X80 grade induction bends.

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