Bending Deformation Capacity of Large-Diameter Spiral-Welded Tubes

2014 ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos ◽  
Sjors H. J. van Es ◽  
Arnold M. Gresnigt
Keyword(s):  
Residual Stresses ◽  
Material Properties ◽  
Large Diameter ◽  
Local Buckling ◽  
Bending Moment ◽  
Deformation Capacity ◽  
Bending Deformation ◽  
Cold Bending ◽  
Bending Process ◽  
Actual Material

Numerical simulations are conducted to define the bending deformation capacity of large-diameter spiral-welded tubes, towards efficient strain-based design. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall. Bending moment, curvature and ovalization are monitored through the numerical analysis, and comparison is conducted with available test data on two 42-inch-diameter tubes, with D/t ratio of 67 and 119, described in detail elsewhere. The analysis accounts for the actual material properties. Initial geometric imperfections (profile, thickness, ovalization) are obtained from the tested specimens. Furthermore, residual stresses are also considered in the analysis, as computed by a numerical simulation of the cold bending process. A parametric analysis is also conducted on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes. Finally, a comparison with design equations for tube bending deformation capacity is conducted.

Strength and Deformation Capacity of Corroded Pipes: The Joint Industry Project

2013 ◽  
Author(s):  
Erik Levold ◽  
Andrea Restelli ◽  
Lorenzo Marchionni ◽  
Caterina Molinari ◽  
Luigino Vitali
Keyword(s):  
Failure Modes ◽  
State Of The Art ◽  
Local Buckling ◽  
Bending Moment ◽  
External Pressure ◽  
Fe Model ◽  
Deformation Capacity ◽  
Offshore Pipelines ◽  
Strength And Deformation ◽  
Bending Loading

Considering the future development for offshore pipelines, moving towards difficult operating condition and deep/ultra-deep water applications, there is the need to understand the failure mechanisms and better quantify the strength and deformation capacity of corroded pipelines considering the relevant failure modes (collapse, local buckling under internal and external pressure, fracture / plastic collapse etc.). A Joint Industry Project sponsored by ENI E&P and Statoil has been launched with the objective to quantify and assess the strength and deformation capacity of corroded pipes in presence of internal overpressure and axial/bending loading. In this paper: • The State-of-the-Art on strength and deformation capacity of corroded pipes is presented; • The full-scale laboratory tests on corroded pipes under bending moment dominated load conditions, performed at C-FER facilities, are shown together with the calibrated ABAQUS FE Model; • The results of the ABAQUS FEM parametric study are presented.

Finite Element Analysis of Cold Bend Pipes Under Bending Loads

2010 ◽  
Author(s):  
Millan Sen ◽  
Roger Cheng
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
Vertical Direction ◽  
Element Model ◽  
Element Analysis ◽  
Cold Bending ◽  
Bending Process ◽  
Cold Bends ◽  
Full Scale Tests ◽  
The Right

Cold bends are required in pipelines at locations of changes in horizontal or vertical direction in the right of way. Due to this change of direction, pipeline deformations caused by geotechnical or operational loading conditions tend to accumulate at the site of cold bends. These deformations may become sufficient to cause local buckling at the bend. For pipeline design, it is important to understand the level of deformation that a cold bend can accumulate prior to local buckling so that the strain capacity can be compared to the expected pipeline deformations. Evaluating the buckling strain of cold bends is extremely complex due to the residual stresses, ripples, and material transformations cause by the cold bending process. Accordingly a finite element model was developed herein. This model accounted for the cold bend geometry, initial imperfections, and the material transformations caused by the cold bending process. This model was validated against 7 full scale tests of cold bend pipes that were subjected to bend loading and internal pressure. The global and local behavior of this model exhibited reasonable correlation against the tests.

Effect of UOE Forming Process on the Buckling Strains of Steel Pipes

2018 ◽  
Author(s):  
Majid Tanbakuei Kashani ◽  
Magdi Mohareb ◽  
Mahyar Asadi ◽  
Mathew Smith
Keyword(s):  
Residual Stresses ◽  
Oil And Gas ◽  
Numerical Technique ◽  
Local Buckling ◽  
Forming Process ◽  
Bending Deformation ◽  
Steel Pipes ◽  
Plate Models ◽  
3D Fea ◽  
Flat Steel

Oil and gas pipelines are commonly made of steel pipes manufactured through the UOE process. This process starts with a flat steel plate, bends it into a U shape, then bends it further to form an O shape, welds the seam, and then radially expands (E) the pipe. The process induces significant residual stresses in the pipe wall. Such stresses have conventionally been ignored in past finite element analyses aimed at quantifying buckling strain thresholds. The present study develops a numerical technique to investigate the effect of the residual stresses induced in the UOE process on the local buckling strains of pipes. Two types of nonlinear 3D FEA models are developed to quantify the buckling strains of pipes under imposed bending deformation. The first model starts with a flat plate, models the UOE process to capture the residual stresses, and then subjects the pipes to imposed bending deformation, the second model assumes the pipe is free from residual stresses. Comparisons are then performed between the buckling strains predicted by both models.

Predictions of Residual Stresses and Deformations in Pipe Bends Produced Using Cold, Warm and Induction Bending Processes

2014 ◽  
Author(s):  
Y. Ding ◽  
M. Yetisir ◽  
S. Khajehpour
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Numerical Models ◽  
Local Heating ◽  
Safety Evaluation ◽  
Stress Distributions ◽  
Advantages And Disadvantages ◽  
Cold Bending ◽  
Bending Process ◽  
Thickness Variations

Cold bending, warm bending (bending with local heating) and induction bending are three manufacturing processes widely used to produce pipe bends. The cold and warm bending processes have been used for the fabrication of carbon steel feeder bends for CANDU® reactors, and the induction bending process was considered for the fabrication of stainless steel feeder pipes for an advanced CANDU reactor. Bending processes result in plastic deformation, and inevitably, introduce residual stresses in the deformed pipes. Residual stresses in feeder bends are believed to be a very important contributing factor in feeder cracking. Different bending processes result in widely different residual stress patterns and magnitudes in pipe bends. Hence, it is important to understand the effect of bending processes and the process parameters used on the residual stress distribution in the bent pipes. Numerical models have been successfully developed to predict the residual stresses and the deformed shapes induced by cold, warm and induction bending processes. This paper provides a comprehensive review of the predicted residual stress distributions, ovality and wall-thickness variations of the cold, warm and induction bends. The predicted results were compared to earlier measurements of spare CANDU feeder bends and test bends. Advantages and disadvantages of the three bending processes are summarized. Numerical approaches for the modeling of residual stresses could be of benefit to engineering estimates of residual stresses in feeder pipes for safety evaluation of nuclear reactors.

scholarly journals Cross-Section Deformation and Bending Moment of a Steel Square Tubular Section

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5170
Author(s):  
Stanisław Kut ◽  
Feliks Stachowicz
Keyword(s):  
Numerical Modeling ◽  
Cross Section ◽  
Circular Cross Section ◽  
Bending Moment ◽  
Experimental Tests ◽  
Cross Sectional ◽  
Cold Bending ◽  
Bending Process ◽  
The Cross ◽  
Sectional Shape

When bending thin-walled profiles, significant distortion of the cross-section occurs, which has a significant impact on the course of the bending moment characteristics and on the value of allowable bending curvatures. This paper presents the results of experimental and numerical modeling of the box profile bending process, which was carried out in order to determine the dependence of the cross-sectional shape and bending moment of bending curvature. Extensive numerical calculations were used to model the process of shaping a square pipe from a circular tube and to model the bending process, especially when taking into account the effects of such a deformation path. The pure bending moment characteristics and the deformation of the cross-section were performed for a 25 × 25 × 2 mm square tube made of S235JR structural steel. The innovative approach for determining the parameters of cold bending square tubes pertained to considering the stress state in the preserved material in individual areas of their cross-section. The results of numerical modeling—after considering the history of deformation (i.e., the process of forming a square pipe from a pipe with a circular cross-section)—gave a satisfactory agreement with the results of experimental tests, both in terms of the degree of pipe wall deflection and the characteristics of the bending moment.

An Evaluation Method for Plastic Buckling of Cantilever Type Pipes Controlled by Displacement Loads: Part 1—Proposal of the Estimation Method and the Criterion

2011 ◽  
Author(s):  
Masanori Ando ◽  
Taiji Tezuka ◽  
Toshio Nakamura ◽  
Tomohiro Okawa ◽  
Yasuhiro Enuma ◽  
...  
Keyword(s):  
Strain Hardening ◽  
Material Properties ◽  
Evaluation Method ◽  
Local Buckling ◽  
Bending Moment ◽  
Design Rule ◽  
Piping System ◽  
Hardening Behavior ◽  
Bending Strain ◽  
Strain Hardening Behavior

In Fast Breeder Reactor, dominant stresses in the piping system are secondary, which are induced by constraint of the thermal expansion of components and pipes. Therefore, the structural design rule should essentially prevent the buckling caused by displacement controlled loads. In this study, the evaluation method of the buckling criterion of cantilever type pipes subjected to lateral displacements is proposed. We define the criterion of the deformation controlled buckling based on bending strain at local buckling portion. Then finite element analysis (FEA) is performed for estimating the displacement and bending strain at local buckling portion during the displacement controlled buckling. Those defined criterion and results of FEA are availed to investigate the evaluation method of the displacement controlled buckling criterion. In those FEA, material properties of Mod.9Cr-1Mo steel are applied, because the material is a candidate for primary and secondary heat transport system components of JSFR (Japan Sodium cooled Fast Reactor), and those of 316FR (type 316 stainless steel modified for FR) are also used to compare the FEA results of Mod.9Cr-1Mo steel. Results of FEA suggest that buckling behaviors strongly depend on the distribution of bending moment and strain hardening behavior of the material. Therefore, those features must be considered in construction of the evaluation method of displacement controlled buckling. To consider the distribution of bending moment, two indexes are defined. One indicates nonlinear bending displacement of a straight pipe. The other indicates the configuration of the pipe and material properties. Relationship between those indexes, which including criterion of displacement controlled buckling, is formulated by the enveloped line considering the effect of the strain hardening behavior of the material. As a result, an equation which represents the criterion for displacement controlled buckling of cantilever type pipes was proposed. This equation consists of two indexes as mentioned above, and can estimate criterion of displacement controlled buckling by material properties and pipe configuration. The proposed equation can be applied to the pipes made of Mod.9Cr-1Mo steel and 316FR.

The Influence of Loads Superposition, Deterioration Due to Cracks and Residual Stresses on the Strength of Tubular Junction

2017 ◽  
Vol 68 (6) ◽  
pp. 1267-1273
Author(s):  
Valeriu V. Jinescu ◽  
Angela Chelu ◽  
Gheorghe Zecheru ◽  
Alexandru Pupazescu ◽  
Teodor Sima ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Residual Stresses ◽  
Bending Moment ◽  
Combined Loading ◽  
Torsional Moment ◽  
Calculation Methods ◽  
State Of Stress ◽  
Cracked Structures ◽  
Total Participation ◽  
Theoretical Results

In the paper the interaction of several loads like pressure, axial force, bending moment and torsional moment are analyzed, taking into account the deterioration due to cracks and the influence of residual stresses. A nonlinear, power law, of structure material is considered. General relationships for total participation of specific energies introduced in the structure by the loads, as well as for the critical participation have been proposed. On these bases: - a new strength calculation methods was developed; � strength of tubular cracked structures and of cracked tubular junction subjected to combined loading and strength were analyzed. Relationships for critical state have been proposed, based on dimensionless variables. These theoretical results fit with experimental date reported in literature. On the other side stress concentration coefficients were defined. Our one experiments onto a model of a pipe with two opposite nozzles have been achieved. Near one of the nozzles is a crack on the run pipe. Trough the experiments the state of stress have been obtained near the tubular junction, near the tip of the crack and far from the stress concentration points. On this basis the stress concentration coefficients were calculated.

scholarly journals The influence of freeform bending process parameters on residual stresses for steel tubes

2021 ◽  
pp. 100047
Author(s):  
Daniel Maier ◽  
Sophie Stebner ◽  
Ahmed Ismail ◽  
Michael Dölz ◽  
Boris Lohmann ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Process Parameters ◽  
Steel Tubes ◽  
Bending Process

scholarly journals Optimal Design of the Shape of a Non-Ball Mandrel for Thin-Walled Tube Small Radius Cold Bending

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1221
Author(s):  
Lu Bai ◽  
Jun Liu ◽  
Ziang Wang ◽  
Shuanggui Zou
Keyword(s):  
Ideal Point ◽  
Small Radius ◽  
Grey Wolf Optimizer ◽  
Forming Quality ◽  
Hollow Section ◽  
Cold Bending ◽  
Bending Process ◽  
Before And After ◽  
Thin Walled Tube ◽  
Thin Walled

In the field of cold bending, it is necessary to use ball mandrels, especially to bend thin-walled tubes with a small radius. However, the bending process with a ball mandrel is complex and expensive, and it is easy to jam the core ball inside the tube. To solve these issues, we designed two kinds of hollow non-ball mandrel schemes with low stiffness that were suitable for the small radius bending of thin-walled tubes. We evaluated the forming quality of cold bending numerically and the influence of the hollow section length and thickness on the forming indices. Our results showed that the thickness of the hollow section has a greater influence on forming quality than the length. As the hollow section’s thickness increased, the wrinkling rate first declined by approximately 40% and then increased by above 50%. When the thickness was 11 mm in scheme 1 and 13 mm in scheme 2, the wrinkling rate reached minimum values of 1.32% and 1.50%, respectively. As the hollow section’s thickness increased, the flattening rate decreased by more than 60% and the thinning rate increased by about 40%. A multi-objective optimization of forming indices was carried out by ideal point method and grey wolf optimizer. By comparing the forming results before and after optimization, the feasibility of using the proposed hollow mandrel was proved, and the hollow mandrel scheme of standard cylinder is therefore recommended.

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