Tensile Strain Capacity of Pipelines for Strain-Based Design

2008 ◽  
Author(s):  
Bing Liu ◽  
X. J. Liu ◽  
Hong Zhang
Keyword(s):  
Finite Element ◽  
Quantitative Determination ◽  
Internal Pressure ◽  
Tensile Strain ◽  
Surface Defects ◽  
Axial Strain ◽  
Finite Element Analyses ◽  
Axial Tensile ◽  
Strain Limit

Traditional pipeline design methods presented in various codes are usually based on limit stress criteria. However, these methods may be inapposite to modern steels, especially for displacement controlled loads such as ground displacement load. The design of pipelines for plastic strain should account for both tension strain limit and compression strain limit along the axial direction of the pipe. In tension, the issues relate to the failure modes of plastic collapse or fracture. Tensile axial strain of the pipe often results in rupturing. The capacity of tensile axial strain of the pipe is affected by a large number of factors: D/t ratio, Y/T ratio, internal pressure, girth weld effect, and defect size and location. Consequently, full solutions for tensile strain limits related to above-mentioned factors do not yet exist in codes and standards. In recent years, a number of projects have been funded to develop a quantitative determination of tensile strain limits in China. This paper covers the technical basis of the procedures. The development of the quantitative approach to tensile strain limits involves both experimental tests and finite element analyses, and the process is as follows. Firstly, a series of curved wide plate tests under the axial tensile strain have been done, especially including more than 60 girth weld specimens with not only buried or surface defects but also various defect-sizes and defect-locations. Based on these test data and other available experiment data of full scale tests under the axial tensile strain and internal pressure loading, a valid finite element model has been found. Then a total of 110 finite element analyses produced a lot of data for a wide range of material, D/T ratios, various defect sizes or locations, buried or surface defects, and various internal pressures. So some parametric equations can be developed from finite element analyses. The safety factors and appropriate limits for the parametric equations have been identified against much more experimental data. It is believed that the approach to axial tensile strain limit presented in this paper may lay the initial basis for the quantitative determination of tensile strain limits to pipelines.

scholarly journals A Quantitative Determination of Minimum Film Thickness in Elastohydrodynamic Circular Contacts

2021 ◽  
Author(s):  
Wassim Habchi ◽  
Philippe Vergne
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Model ◽  
Film Thickness ◽  
Quantitative Determination ◽  
Excellent Agreement ◽  
Operating Conditions ◽  
Pure Rolling ◽  
Minimum Film Thickness

Abstract The current work presents a quantitative approach for the prediction of minimum film thickness in elastohydrodynamic lubricated (EHL) circular contacts. In contrast to central film thickness, minimum film thickness can be hard to accurately measure, and it is usually poorly estimated by classical analytical film thickness formulae. For this, an advanced finite-element-based numerical model is used to quantify variations of the central-to-minimum film thickness ratio with operating conditions, under isothermal Newtonian pure-rolling conditions. An ensuing analytical expression is then derived and compared to classical film thickness formulae and to more recent similar expressions. The comparisons confirmed the inability of the former to predict the minimum film thickness, and the limitations of the latter, which tend to overestimate the ratio of central-to-minimum film thickness. The proposed approach is validated against numerical results as well as experimental data from the literature, revealing an excellent agreement with both. This framework can be used to predict minimum film thickness in circular elastohydrodynamic contacts from knowledge of central film thickness, which can be either accurately measured or rather well estimated using classical film thickness formulae.

Design of the Full Scale Experiments for the Testing of the Tensile Strain Capacity of X52 Pipes With Girth Weld Flaws Under Internal Pressure and Tensile Displacement

2014 ◽  
Author(s):  
Celal Cakiroglu ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Millan Sen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Tensile Strain ◽  
Oil And Gas ◽  
Full Scale ◽  
Element Analysis ◽  
Simultaneous Application ◽  
Strain Capacity ◽  
Tensile Strain Capacity

Pipelines can be subjected to significant amounts of tensile forces due to geotechnical movements like slope instabilities and seismic activities as well as due to frost heave and thaw cycles in arctic regions. The tensile strain capacity εtcrit of pipelines is crucial in the prediction of rupture and loss of containment capability in these load cases. Currently the Oil and Gas Pipeline Systems code CSA Z662-11 0 contains equations for the prediction of εtcrit as a function of geometry and material properties of the pipeline. These equations resulted from extensive experimental and numerical studies carried out by Wang et al [2]–[6] using curved wide plate tests on pipes having grades X65 and higher. Verstraete et al 0 conducted curved wide plate tests at the University of Ghent which also resulted in tensile strain capacity prediction methods and girth weld flaw acceptability criteria. These criteria are included in the European Pipeline Research Group (EPRG) Tier 2 guidelines. Furthermore Verstrate et al 0 introduced a pressure correction factor of 0.5 in order to include the effect of internal pressure in the tensile strain capacity predictions in a conservative way. Further research by Wang et al with full scale pipes having an internal pressure factor of 0.72 also showed that εtcrit decreases in the presence of internal pressure [10]–[15]. In their work, Wang et al presented a clear methodology for the design of full scale experiments and numerical simulations to study the effect of internal pressure on the tensile strain capacity of pipes with girth weld flaws [10]–[15]. However, there has been limited testing to enable a precise understanding of the tensile strain capacity of pipes with grades less than X65 as a function of girth weld flaw sizes and the internal pressure. In this paper the experimental setup for the testing of grade X52 full scale specimens with 12″ diameter and ¼″ wall thickness is demonstrated. In the scope of this research 8 full scale specimens will be tested and the results will be used to formulate the tensile strain capacity of X52 pipes under internal pressure. The specimens are designed for the simultaneous application of displacement controlled tensile loading and the internal pressure. Finite element analysis is applied in the optimization process for the sizes of end plates and connection elements. Also the lengths of the full scale specimens are determined based on the results from finite element analysis. The appropriate lengths are chosen in such a way that between the location of the girth weld flaw and the end plates uniform strain zones could be obtained. The internal pressure in these experiments is ranging between pressure values causing 80% SMYS and 30% SMYS hoop stress. The end plates and connection elements of the specimens are designed in such a way that the tensile displacement load is applied with an eccentricity of 10% of the pipe diameter with the purpose of increasing the magnitude of tensile strains at the girth weld flaw location. The results of two full scale experiments of this research program are presented. The structural response from the experiments is compared to the finite element simulation. The remote strain values of the experiment are found to be higher than the εtcrit values predicted by the equations in 0.

A Study of the Conservatism in ASME BPVC Section VIII Division 2 Opening Design for External Pressure

2019 ◽  
Author(s):  
Barry Millet ◽  
Kaveh Ebrahimi ◽  
James Lu ◽  
Kenneth Kirkpatrick ◽  
Bryan Mosher
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
External Pressure ◽  
The Other ◽  
Finite Element Analyses ◽  
Division 1 ◽  
Section Viii ◽  
Allowable Compressive Stress ◽  
Division 2

Abstract In the ASME Boiler and Pressure Vessel Code, nozzle reinforcement rules for nozzles attached to shells under external pressure differ from the rules for internal pressure. ASME BPVC Section I, Section VIII Division 1 and Section VIII Division 2 (Pre-2007 Edition) reinforcement rules for external pressure are less stringent than those for internal pressure. The reinforcement rules for external pressure published since the 2007 Edition of ASME BPVC Section VIII Division 2 are more stringent than those for internal pressure. The previous rule only required reinforcement for external pressure to be one-half of the reinforcement required for internal pressure. In the current BPVC Code the required reinforcement is inversely proportional to the allowable compressive stress for the shell under external pressure. Therefore as the allowable drops, the required reinforcement increases. Understandably, the rules for external pressure differ in these two Divisions, but the amount of required reinforcement can be significantly larger. This paper will examine the possible conservatism in the current Division 2 rules as compared to the other Divisions of the BPVC Code and the EN 13445-3. The paper will review the background of each method and provide finite element analyses of several selected nozzles and geometries.

Evaluation of the Effect of Internal Pressure and Flaw Size on the Tensile Strain Capacity of X42 Vintage Pipeline Using Damage Plasticity Model in Extended Finite Element Method (XFEM)

2019 ◽  
Author(s):  
Sylvester Agbo ◽  
Meng Lin ◽  
Iman Ameli ◽  
Ali Imanpour ◽  
Da-Ming Duan ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Internal Pressure ◽  
Tensile Strain ◽  
Extended Finite Element Method ◽  
Full Scale ◽  
Flaw Size ◽  
Test Results ◽  
Extended Finite Element ◽  
Tensile Strain Capacity

Abstract Pipelines subjected to displacement-controlled loading such as ground movement may experience significant longitudinal strain. This can potentially impact pipeline structural capacity and their leak-tight integrity. Reliable calibration of the tensile strain capacity (TSC) of pipelines plays a critical role in strain-based design (SBD) methods. Recent studies were focused mostly on high toughness modern pipelines, while limited research was performed on lower-grade vintage pipelines. However, a significant percentage of energy resources in North America is still being transported in vintage pipelines. Eight full-scale pressurized four-point bending tests were previously conducted on X42, NPS 22 vintage pipes with 12.7 mm wall thickness to investigate the effect of internal pressure and flaw size on TSC. The pipes were subjected to 80% and 30% specified minimum yield strength (SMYS) internal pressures with different girth weld flaw sizes machined at the girth weld center line. This paper evaluates the TSC of X42 vintage pipeline by utilizing ductile fracture mechanics models using damage plasticity models in ABAQUS extended finite element method (XFEM). The damage parameters required for simulating crack initiation and propagation in X42 vintage pipeline are calibrated numerically by comparing the numerical models with the full-scale test results. With the appropriate damage parameters, the numerical model can reasonably reproduce the full-scale experimental test results and can be used to carry out parametric analysis to characterize the effect of internal pressure and flaw size on TSC of X42 vintage pipes.

Non-Contacting Bi-Axial Strain Measurement Method on Steel Pipeline

2008 ◽  
Author(s):  
Stephen Westwood ◽  
Michael Martens ◽  
Richard Kania ◽  
David Topp ◽  
Raymond Kare´ ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Strain Measurement ◽  
Measurement Method ◽  
Axial Strain ◽  
Compressive Load ◽  
Ferromagnetic Materials ◽  
Strain Gauges ◽  
Steel Pipeline ◽  
Strain Measurements ◽  
Axial Tensile

The StressProbe is a non-contacting electromagnetic tool that responds to material strain in ferromagnetic materials. Previous studies have concentrated on uni-axial strain measurements; in this study, we extend the scope of work by measuring bi-axial strains on a pipe specimen subject to internal pressure and to a displacement-controlled, axial tensile/compressive load. Specified pressure and load combinations were obtained, and measurements from the StressProbe were compared to those from tri-axial strain gauges installed on the pipe specimen. In this paper, we present the theory behind this measurement method and the results from this study. Also discussed are measurement applications both inside and outside the pipe specimen.

Determination of critical angle of circumferential throughwall crack for structurally distorted 90° pipe bends under bending moment with and without internal pressure

2017 ◽  
Vol 233 (5) ◽  
pp. 817-830 ◽  
Author(s):  
S Sumesh ◽  
AR Veerappan ◽  
S Shanmugam
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Closed Form ◽  
Bending Moment ◽  
External Loading ◽  
Element Analysis ◽  
Critical Crack ◽  
Structural Distortions ◽  
Internal Pressures

Throughwall circumferential cracks (TWC) in elbows can considerably minimize its collapse load when subjected to in-plane bending moment. The existing closed-form collapse moment equations do not adequately quantify critical crack angles for structurally distorted cracked pipe bends subjected to external loading. Therefore, the present study has been conducted to examine utilizing elastic-plastic finite element analysis, the influence of structural distortions on the variation of critical TWC of 90° pipe bends under in-plane closing bending moment without and with internal pressure. With a mean radius ( r) of 50 mm, cracked pipe bends were modeled for three different wall thickness, t (for pipe ratios of r/ t = 5,10,20), each with two different bend radius, R (for bend ratios of R/r = 2,3) and with varying degrees of ovality and thinning (0 to 20% with increments of 5%). Finite element analyses were performed for two loading cases namely pure in-plane closing moment and in-plane closing bending with internal pressure. Normalized internal pressures of 0.2, 0.4, and 0.6 were applied. Results indicate the modification in the critical crack angle due to the pronounced effect of ovality compared to thinning on the plastic loads of pipe bends. From the finite element results, improved closed-form equations are proposed to evaluate plastic collapse moment of throughwall circumferential cracked pipe bends under the two loading conditions.

Analytical Investigations of Compact Reinforcement for Radial Nozzles in Spherical Shells

1971 ◽  
Vol 93 (4) ◽  
pp. 905-912 ◽  
Author(s):  
R. C. Gwaltney ◽  
J. M. Corum
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Experimental Results ◽  
Finite Element Analyses ◽  
Spherical Shells ◽  
Theoretical Predictions

Compact reinforcement for a series of models having single nozzles radially attached to spherical shells was examined by means of finite element analyses. Parameters studied were diameter-to-thickness ratios of the nozzles, diameter-to-thickness ratios of the spherical shells, percentage of reinforcement, outside reinforcement, inside reinforcement, and “balanced” reinforcement (reinforcement on both the inside and outside surfaces). The loading was internal pressure. Comparisons of theoretical predictions with experimental results are presented for one reinforced model. Twelve models were analyzed to examine the effect of compact reinforcement.

Tensile Strain Capacity of X80 Pipeline Under Tensile Loading With Internal Pressure

2010 ◽  
Author(s):  
Satoshi Igi ◽  
Takahiro Sakimoto ◽  
Nobuhisa Suzuki ◽  
Ryuji Muraoka ◽  
Takekazu Arakawa
Keyword(s):  
Internal Pressure ◽  
Driving Force ◽  
Tensile Strain ◽  
Surface Defects ◽  
Axial Loading ◽  
Element Analysis ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
High Internal Pressure ◽  
Tensile Strain Capacity

This paper presents the results of experimental and finite element analysis (FEA) studies focused on the tensile strain capacity of X80 pipelines under large axial loading with high internal pressure. Full-pipe tensile test of girth welded joint was performed using high-strain X80 linepipes. Curved wide plate (CWP) tests were also conducted to verify the strain capacity under a condition of no internal pressure. The influence of internal pressure was clearly observed in the strain capacity. Critical tensile strain is reduced drastically due to the increased crack driving force under high internal pressure. In addition, SENT tests with shallow notch specimens were conducted in order to obtain a tearing resistance curve for the simulated HAZ of X80 material. Crack driving force curves were obtained by a series of FEA, and the critical global strain of pressurized pipes was predicted to verify the strain capacity of X80 welded linepipes with surface defects. Predicted strain showed good agreement with the experimental results.

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