Full-Scale Testing for Strain-Based Design Pipelines: Lessons Learned and Recommendations

2014 ◽  
Author(s):  
Doug P. Fairchild ◽  
Svetlana Shafrova ◽  
Huang Tang ◽  
Justin M. Crapps ◽  
Wentao Cheng
Keyword(s):  
Full Scale ◽  
Lessons Learned ◽  
Weld Strength ◽  
Material Strength ◽  
Pipe Material ◽  
Strain Capacity ◽  
Post Test ◽  
Full Scale Tests ◽  
Welded Pipe ◽  
Full Scale Testing

There are generally two reasons for conducting full-scale tests (FSTs) for the measurement of pipe or weld strain capacity, (1) to generate data useful in verifying the accuracy of a strain capacity prediction model, or (2) to test materials being considered for use. The former case involves exploring variables important to the scope of the model, while the latter involves project specific materials and girth weld procedures often combined with upper bound cases of weld misalignment. Because the challenge of strain-based design is relatively new, FSTs should be used for both reasons cited above. This paper provides observations, lessons learned, and recommendations regarding full-scale pipe strain capacity tests. This information has been developed through the conduct, witness, or review of 159 FSTs. One of the most important aspects of full-scale testing is the preparation of welded pipe test specimens. It is imperative that the specimens be fabricated with materials of known properties and that all possible measures be taken to limit variations from the intended specimen design. It has been observed that unexpected results are often due to irregularities in pipe material strength, weld strength, weld toughness, or the presence of unintended weld defects in a specimen designed to contain just man-made defects. Post-test fractography and metallurgical examination are very useful in explaining the performance of a FST; therefore, failure analysis is discussed.

Development of Fatigue Design Data for the Ormen Lange Offshore Project: An Overview

2006 ◽  
Author(s):  
Hans Olav Knagenhjelm ◽  
Oddvin O̸rjasæter ◽  
Per J. Haagensen
Keyword(s):  
Crack Growth ◽  
Full Scale ◽  
Small Scale ◽  
Formation Water ◽  
Worst Case ◽  
Vortex Induced Vibrations ◽  
Welding Defects ◽  
Condensed Water ◽  
Full Scale Tests ◽  
Full Scale Testing

The Ormen Lange offshore pipelines from shore to the field go through very difficult terrain creating freespans in the range 40–80m for the 30” lines. For the 6” lines long freespans will be present prior to burial and vortex induced vibrations (VIV) will give a contribution during laying due to strong currents. Using existing codes for fatigue calculation was giving too conservative results compared to the welding technology used and experience from SCR work showed that better S-N data should be expected. A dedicated program was started as part of the Ormen Lange (OL) technology verification program overseen by Norwegian Authorities. An overview of the results is presented here. A full evaluation of the data is not yet complete. Papers will be published later presenting the full technical details and dataprocessing. Fatigue test results from the OL pipeline fatigue verification are presented focusing on the following topics: • Defect sizes in pipeline production welds; • Contractor-A: 5G welding position; • Contractor-B: 2G welding position; • 6” pipe full scale testing; • 30” pipe full scale testing; • Residual stresses; • Crack growth tests and sector specimen fatigue tests in production environments. The following are a summary of the main test variables in the program: • Mapping of actual welding defects compared to AUT results. • Welds with varying misalignment (high/low) and lack of penetration (LOP) from installation contractors tested in air. • Welds with natural welding defects in internal environment (Condensed water and formation water). • Welds with notches made by electrical discharge machining (EDM) (2×65mm and 2×15mm) in internal environment (condensed water and formation water). • Crack growth tests using large compact tension (CT) specimens in air, seawater and internal product environments (condensed water and formation water). • Full scale tests including worst case high/low, LOPs, and tests with normal welds including repair welds. The following main conclusions can be drawn from the work: • Small scale testing with representative worst case defects predicts well large scale testing results with the same features when the small scale specimen stresses are corrected for bending moments etc. arising from the cutout of the pipe. • Full scale testing of 30”×35.5mm wall thickness 2G pipes welded continuously (without start/stop) with worst case defects and high/low exceeds the D curve. • Full-scale tests of 30”×35.5mm wall thickness 5G non continuous welds with worst case defects and high/low exceeds the E curve. • Pipe welds showed low or even compressive residual stresses in the root. For continuously welded pipes the stress levels were low but more varying, also on the cap side. This partly explains the good results. • It is verified that the fatigue loads during operation are below the threshold of crack growth, and thus fatigue will not be a probable failure mechanism. This is under the condition that the measurements of vortex induced vibrations (VIV) during operation confirm the engineering calculations.

scholarly journals Modeling Material Failure During Cab Car End Frame Impact

2009 ◽  
Author(s):  
Richard Stringfellow ◽  
Christopher Paetsch
Keyword(s):  
Static Loading ◽  
Full Scale ◽  
Test Material ◽  
Material Strength ◽  
Model Parameters ◽  
Material Failure ◽  
Failure Model ◽  
Shell Elements ◽  
Fea Model ◽  
Full Scale Tests

New standards have been proposed to increase the strength requirements for cab car end structures and impose further requirements on their ability to absorb energy during a grade-crossing collision [1, 2]. To aid in the development of these new standards, the Federal Railroad Administration (FRA) and the Volpe Center recently completed a set of full-scale tests aimed at assessing the quasi-static and dynamic crush behavior of these end structures. In support of this testing program, end frames designed to meet the new standards were fabricated and retrofitted onto the forward end of an existing cab car. A series of large-deformation quasi-static and explicit dynamic finite element analyses (FEAs) were performed to evaluate the performance of the design. Based on the results of a 2002 full-scale test in which a heavy steel coil impacted the corner post of an end frame built to these new standards, some fracture was expected in certain key end frame components during the tests. For this reason, a material failure model, based on the Bao-Wierzbicki fracture criterion [3], was implemented in the FEA model of the cab car end frame using ABAQUS/Explicit. The FEA model with material failure was used to assess the effect of fracture on the deformation behavior of cab car end structures during quasi-static loading and dynamic impact and, in particular, the ability of such structures to absorb energy. The failure model was implemented in ABAQUS/Explicit for use with shell elements. A series of preliminary calculations were first conducted to assess the effects of element type and mesh refinement on the deformation and fracture behavior of structures similar to those found on cab car end frames, and to demonstrate that the Bao-Wierzbicki failure model can be effectively applied using shell elements. Model parameters were validated through comparison to the results of the 2002 test. Material strength and failure parameters were derived from test data for A710 steel. The model was then used to simulate the three full-scale tests that were conducted during 2008 as part of the FRA program: a collision post impact, and quasi-static loading of both a collision post and a corner post. Analysis of the results of the two collision post tests revealed the need for revisions to both the design of some key end frame components and to key material failure parameters. Using the revised model, pre-test predictions for the outcome of the corner post test were found to be in very good agreement with test results.

Large Scale Tests of Strain Capacity of Pipe Sections With Circumferential Defects Subjected to Installation-Induced Plastic Strain History

2009 ◽  
Author(s):  
Ba˚rd Nyhus ◽  
Erling O̸stby ◽  
Zhiliang Zhang ◽  
Erlend Olso̸ ◽  
Per Arne Ro̸stadsand ◽  
...  
Keyword(s):  
Large Scale ◽  
Base Material ◽  
Bending Moment ◽  
Full Scale ◽  
Strain History ◽  
Strain Capacity ◽  
Four Point Bending ◽  
Full Scale Tests ◽  
Circumferential Defects ◽  
Large Scale Tests

Installation of offshore pipelines by reeling introduces plastic pre-straining. The pre-strain history is not homogenous and it will vary around the circumference of the pipe. The pre-strain history will modify the yield and flow properties. Also, the fracture toughness may be influenced by the pre-straining. The result is that the bending strain capacity of pipelines during operation will differ depending on how the bending moment coincides with pipe orientation during installation. Three full scale tests of 12″ x-60 pipes with wall thickness 19.3mm and a 3×100 mm outer surface defect were performed to investigate the effect of pre-strain history. Two pipes were pre-strained in bending to 2% strain in the outer fibre and then straightened to simulate the reeling. The final tests to establish the strain capacity during operation as a function of strain history were performed in four point bending with an internal pressure of 325 bar. The strain capacity for the side of the pipe that ends in tension and the side that ends in compression from pre-straining was 1.7% and 2.6% respectively. The strain capacity of the third test without pre-straining was 5.7%. The results show that pre-straining will modify the strain capacity and the effect must be taken into account in engineering critical assessment of pipes during operation. The effect of prestraining should be evaluated for all installation methods that involve plastic deformation during installation, and not only reeling. It is important to note that the notch size in the full scale tests was larger than what would normally be accepted for reeling. In addition the notch was positioned in base material and not in weld metal, which is a more realistic position for a notch. The welds are normally overmatched and this might reduce the effect of prestraining.

Strain Capacity Prediction of Strain-Based Pipelines

2014 ◽  
Author(s):  
Huang Tang ◽  
Doug Fairchild ◽  
Michele Panico ◽  
Justin Crapps ◽  
Wentao Cheng
Keyword(s):  
Damage Mechanics ◽  
Critical Role ◽  
Active Regions ◽  
Full Scale ◽  
Element Analysis ◽  
Strain Capacity ◽  
Fea Model ◽  
Full Scale Tests ◽  
Numerical Program ◽  
Allowable Stress Design

Strain-based design (SBD) is used to complement conventional allowable stress design for pipelines operated in environments with potentially large ground movements such as those found in permafrost and seismically active regions. Reliable and accurate prediction of tensile strain capacity (TSC) plays a critical role in strain-based design. As reported previously over the past 6+ years, a comprehensive experimental and numerical program was undertaken to characterize the TSC of welded pipelines, develop a finite element analysis (FEA) approach and equations capable of predicting TSC, and establish a strain-based engineering critical assessment (SBECA) methodology. The previous FEA model and TSC equations were validated against about 50 full-scale pipe strain capacity tests and are accurate within the validated variable ranges. In the current paper, enhancements of the previous model and equations are described. The enhancements include incorporation of advanced damage mechanics modeling into TSC prediction, development of a new TSC equation, expansion of variable ranges and functionality upgrades. The new model and equation are applicable over larger ranges of material properties and flaw sizes. The new FEA model is also used to establish surface flaw interaction rules for SBD. The new FEA model is validated against more than 40 full-scale non-pressurized and pressurized tests and underpins the development of the new TSC equation. The equation is validated against a total of 93 full-scale tests (FST). In addition to the enhancements, sample applications of the TSC model and equation are presented in the paper, for example, an investigation of the effects on strain capacity of Lüders strain and ductile tearing. Challenges in predicting TSC are also addressed.

Assessment of Dents Under High Longitudinal Strain

2018 ◽  
Author(s):  
Bo Wang ◽  
Yong-Yi Wang ◽  
Brent Ayton ◽  
Mark Stephens ◽  
Steve Nanney
Keyword(s):  
Longitudinal Strain ◽  
Scale Validation ◽  
Compressive Strain ◽  
Full Scale ◽  
Ground Movement ◽  
Strain Capacity ◽  
Parametric Analyses ◽  
Full Scale Tests ◽  
Assessment Procedures ◽  
The Impact

Pipeline construction activities and in-service interference events can frequently result in dents on the pipe. The pipelines can also experience high longitudinal strain in areas of ground movement and seismic activity. Current assessment procedures for dents were developed and validated under the assumption that the predominant loading is internal pressure and that the level of longitudinal strain is low. The behavior of dents under high longitudinal strain is not known. This paper discusses work funded by US DOT PHMSA on the assessment of dents under high longitudinal strain. Parametric numerical analyses were conducted to identify and examine key parameters and mechanisms controlling the compressive strain capacity (CSC) of pipes with dents. Selected full-scale tests were also conducted to experimentally examine the impact of dents on CSC. The focus of this work was on CSC because tensile strain capacity is known not to be significantly affected by the presence of dents. Through the parametric analyses and full-scale validation tests, guidelines on the CSC assessment of dented pipes under high longitudinal strain were developed.

Burst Pressure Prediction of Pipes With SCC Colonies: Evaluation of Intelligent Flaw Interaction Rules Using Full-Scale Burst Tests

2020 ◽  
Author(s):  
Bo Wang ◽  
Banglin Liu ◽  
Yong-Yi Wang ◽  
Alex Wang ◽  
Steve Rapp
Keyword(s):  
Crack Opening ◽  
Charpy Impact ◽  
Crack Size ◽  
Full Scale ◽  
Burst Pressure ◽  
Small Scale ◽  
Pipe Material ◽  
Video Cameras ◽  
Post Test ◽  
Material Tests

Abstract This is the second paper in a two-paper series which covers the PRCI-funded work aimed at the development of intelligent flaw interaction rules (termed PRCI-CRES SIA-1-5 rules). The first paper focused on the development of the rules using numerical analyses. This paper covers the evaluation of the rules through full-scale burst tests and accompanying small-scale material tests. Four full-scale burst tests were conducted on 20” and 18” OD pipe segments with SCC. The SCC colonies on the test sections were inspected using MPI, PAUT, ECA, and IWEX. The small-scale material tests were conducted to measure pipe tensile strength and Charpy impact energy. The four test sections were pressurized until burst. The burst tests were recorded using multiple video cameras to capture the global behavior and detailed crack opening process at the burst locations. With the videos and the post-test examination of the failure surfaces, the full-scale burst tests provide not only the burst pressure but also information for the validation of the fundamental principles of the new interaction rules. The modified Ln-sec method was used to predict the burst pressure using the equivalent crack size from different flaw interaction rules and the measured pipe material properties. The PRCI-CRES SIA-1-5 rules were found to provide the most accurate and precise burst pressure prediction when factors other than flaw interaction rules remain the same. The application of the PRCI-CRES SIA-1-5 rules can reduce unnecessary hydrotests and/or other remediation actions with accurate, not overly conservative, burst pressure prediction.

Protecting Fittings on Tank Cars: Preliminary Evaluation of Pressure Tank Cars

2014 ◽  
Author(s):  
Anand Prabhakaran ◽  
Francisco González
Keyword(s):  
Test Methods ◽  
Full Scale ◽  
Lessons Learned ◽  
Mitigation Strategies ◽  
Preliminary Evaluation ◽  
Damage And Failure ◽  
Pressure Tank ◽  
Test Methodology ◽  
Scale Test ◽  
Full Scale Tests

Railroad tank car top fittings are susceptible to damage and failure in rollover derailments, which might result in release of hazardous material lading. Prior research has focused on the susceptibility of fittings on non-pressure tank cars and potential mitigation strategies. This paper presents current work that extends the analysis/test methods and lessons learned to fittings on pressure tank cars. Pressure tank cars carry significantly more hazardous materials such as Chlorine and Anhydrous Ammonia, which are classified as Toxic Inhalation Hazards (TIH). In particular, this paper presents the results of analytical modeling and validation testing of top fittings on a base design Chlorine car. In addition, the paper compares and contrasts the test methodology employed in prior full scale tests of tank car fittings against the 9 mph evaluation scenario outlined in current Federal regulations governing the design of fittings on TIH tank cars, and further explores how full scale test results may be interpreted.

A Preliminary Strain-Based Design Criterion for Pipeline Girth Welds

2002 ◽  
Author(s):  
Yong-Yi Wang ◽  
David Rudland ◽  
Rudi Denys ◽  
David Horsley
Keyword(s):  
Strain Hardening ◽  
Design Criterion ◽  
Defect Size ◽  
Applied Strain ◽  
Full Scale ◽  
Weld Strength ◽  
Factors Affecting ◽  
Strain Capacity ◽  
Girth Welds ◽  
Strain Hardening Rate

The strain capacity of girth welds containing surface-breaking welding defects is examined through numerical analysis and experimental verification under a PRCI (Pipeline Research Council International) funded project. Some important insights on the various factors affecting the girth weld strain capacity are generated. The defect size is identified as one of the most important factors in determining strain capacity of a girth weld. Other factors, such as the strain hardening rate of the pipe and weld metals, weld strength mismatch, fracture toughness, and weld cap height, can play a significant role if the defect size is within certain limits. It is discovered that the girth weld response to the remotely applied strain may be characterized by a three-region diagram. For a given set of defect size and weld strength mismatch conditions, the crack driving force may be bounded, unbounded, or gradually changing, with respect to the remotely applied strain. A set of parametric equations is developed that allow the computation of allowable strains with the input of defect depth, defect length, CTOD toughness, and weld strength mismatch. The comparison of the developed strain criteria with full-scale bend tests and tensile-loaded CWPs (curved wide plates) shows the criteria are almost always conservative if lower bound CTOD toughness for a given set of welds is used. However, the criteria can significantly underpredict strain capacity of girth welds with short defects. Although defect length correction factors were added to the strain criteria based on the comparison of axisymmetric finite element (FE) results and full-scale bend test results, a more thorough investigation of the effects of defect length on strain capacity is needed. Future investigation that incorporates the finite length defects is expected to greatly reduce the underprediction. The influence of other factors, such as strain hardening rate, should be further quantified.

Finite Element Analysis of Composite Repairs With Full-Scale Validation Testing

2016 ◽  
Author(s):  
Colton Sheets ◽  
Robert Rettew ◽  
Chris Alexander ◽  
Ashwin Iyer
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Materials ◽  
Scale Validation ◽  
Full Scale ◽  
Element Analysis ◽  
Composite Repair ◽  
Full Scale Tests ◽  
Validation Testing ◽  
Full Scale Testing

Composite repair systems for pipelines are continuing to be used for increasingly difficult and complex applications which can have a high consequence of failure. In these instances, full-scale testing is typically pursued at a high-cost to the manufacturer or operator. Finite element analysis (FEA) modeling is a valuable tool that becomes especially attractive as a method to reduce the number of full-scale tests required. This is particularly true when considering the costs associated with recreating complex load and temperature conditions. In order for FEA to fill this role, it is necessary to validate the results through full-scale testing at the same loads and temperatures. By using these techniques, FEA and full-scale testing can be used in unison to efficiently produce accurate results and allow for the adjustment of critical parameters at a much lower cost than creating additional full-scale tests. For this program, a series of finite element analysis (FEA) models were developed to evaluate the performance of composite materials used to reinforce corroded steel pipe in critical applications at elevated temperatures up to 120 °C. Two composite repair manufacturers participated in the study which was conducted on 12-inch × 0.375-inch Gr. X60 pipes with machined simulated corrosion defects that represented 50% wall loss. Load conditions consisted of axial compressive loads or bending moments to generate compressive stresses in the machined defect. In the described evaluation program, FEA simulations were able to produce results which supported those found in full-scale validation testing. From the FEA models stresses and strains were extracted from the reinforced steel and composite materials. Good correlation was observed in comparing the results. Although limitations of the modeling included accurately capturing differential thermal strains introduced by the elevated test temperature, the results indicated that FEA models could be used as a cost-effective means for assessing composite repair systems in high-temperature applications.

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