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.

Tensile Strain Capacity Equations for Strain-Based Design of Welded Pipelines

2010 ◽  
Author(s):  
Sandeep Kibey ◽  
Xiangyu Wang ◽  
Karel Minnaar ◽  
Mario L. Macia ◽  
Doug P. Fairchild ◽  
...  
Keyword(s):  
Tensile Strain ◽  
Large Scale ◽  
Active Regions ◽  
Full Scale ◽  
Dimensional Parameter ◽  
Strain Capacity ◽  
Design Qualification ◽  
Full Scale Tests ◽  
Pipe Geometry ◽  
Tensile Strain Capacity

Various industry efforts are underway to improve or develop new methods to address the design of pipelines in harsh arctic or seismically active regions. Reliable characterization of tensile strain capacity of welded pipelines is a key issue in development of strain-based design methodologies. Recently, improved FEA-based approaches for prediction of tensile strain capacity have been developed. However, these FEA-based approaches require complex, computationally intensive modeling and analyses. Parametric studies can provide an approach towards developing practical, efficient methods for strain capacity prediction. This paper presents closed-form, simplified strain capacity equations developed through a large-scale 3D FEA-based parametric study for welded pipelines. A non-dimensional parameter is presented to relate the influence of flaw and pipe geometry parameters to tensile strain capacity. The required input parameters, their limits of applicability and simplified equations for tensile strain capacity are presented. The equations are validated through a comprehensive full-scale test program to measure the strain capacity of pressurized pipelines spanning a range of pipe grades, thickness, weld overmatch and misalignment levels. It is shown that the current simplified equations can be used for appropriate specification of weld and pipe materials properties, design concept selection and the design of full-scale tests for strain-based design qualification. The equations can also provide the basis for codified strain-based design engineering critical assessment procedures for welded pipelines.

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.

scholarly journals A New Method for Seismically Safe Managing of Seismotectonic Deformations in Fault Zones

2020 ◽  
pp. 45-66
Author(s):  
Valery V. Ruzhich ◽  
Evgeny V. Shilko
Keyword(s):  
Large Scale ◽  
Scale Validation ◽  
Fault Zones ◽  
Full Scale ◽  
Coseismic Slip ◽  
Stick Slip ◽  
Slip Regime ◽  
Deep Wells ◽  
Seismic Vibrations ◽  
Large Scale Tests

AbstractThe authors outline the results of long-term interdisciplinary research aimed at identifying the possibility and the methods of controlling tangential displacements in seismically dangerous faults to reduce the seismic risk of potential earthquakes. The studies include full-scale physical and numerical modeling of P-T conditions in the earth’s crust contributing to the initiation of displacement in the stick-slip regime and associated seismic radiation. A cooperation of specialists in physical mesomechanics, seismogeology, geomechanics, and tribology made it possible to combine and generalize data on the mechanisms for the formation of the sources of dangerous earthquakes in the highly stressed segments of faults. We consider the prospect of man-caused actions on the deep horizons of fault zones using powerful shocks or vibrations in combination with injecting aqueous solutions through deep wells to manage the slip mode. We show that such actions contribute to a decrease in the coseismic slip velocity in the fault zone, and, therefore, cause a decrease in the amplitude and energy of seismic vibrations. In conclusion, we substantiate the efficiency of the use of combined impacts on potentially seismically hazardous segments of fault zones identified in the medium-term seismic prognosis. Finally, we discuss the importance of the full-scale validation of the proposed approach to managing the displacement regime in highly-stressed segments of fault zones. Validation should be based on large-scale tests involving advanced technologies for drilling deep multidirectional wells, injection of complex fluids, and localized vibrational or pulse impacts on deep horizons.

Large-Scale Tests Performed in Support of LBB Projects Applied to WWER Type NPPs in the Czech Republic in Years 1992–1994

2009 ◽  
Author(s):  
Dana Lauerova ◽  
Jiri Palyza ◽  
Jiri Zdarek
Keyword(s):  
Czech Republic ◽  
Large Scale ◽  
Bending Moment ◽  
Limit Load ◽  
Computational Results ◽  
The Czech Republic ◽  
Normal Operating ◽  
Two Stages ◽  
Large Scale Tests ◽  
Stable Tearing

In the paper, an overview of large-scale experiments performed on components of WWER primary circuits within several LBB projects conducted in the Czech Republic in years 1992 – 1994 is presented. The tested components were replicas of the real ones; they contained a through-wall crack and were loaded by pressure and bending moment in two stages, as appropriate according to the LBB methodology. All tested components exhibited stable behaviour under normal operating loading superposed with safe shutdown earthquake loading (NOC + SSE) applied during 1st stage of experiment. During 2nd stage of experiment, under loading by bending moment only, the models usually exhibited stable tearing of the crack, in some cases limit load (maximum force at loading controlled by displacement) was reached. In the paper, the experiments are briefly described, with presenting the main experimental and (in some cases) FE computational results.

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.

The FEBEX Project. General Overview

1997 ◽  
Vol 506 ◽  
Author(s):  
F. Huertas ◽  
J.L. Santiago
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Near Field ◽  
Thermal Response ◽  
Crystalline Rock ◽  
Full Scale ◽  
Deep Geological Disposal ◽  
Heating Test ◽  
Large Scale Tests ◽  
Term Performance

ABSTRACTUnderstanding the near-field evolution of a deep geological disposal system for HLW is crucial for assessing its long term performance and, therefore, safety. For that reason ENRESA devised the FEBEX Project, a Full Scale Engineered Barriers Experiment in crystalline rock. The project consists of a full-scale “in-situ” heating test, a large-scale laboratory mock-up and supporting materials tests, and modelling.Even though the object of the project is to contribute to the search for methods of behaviour and of safety analyses for a repository, other subinvestigations have been/are being included. The stated objectives are to demonstrate the procedures of constructing an engineered barrier system (EBS), especially the fabrication, handling, and installation of bentonite blocks (buffer) at an almost industrial scale, to improve and validate the numerical models for thermo-hydro-mechanical behaviour, and to investigate the geochemical processes that are produced in the buffer including canister corrosion, as well as the generation and transport of gas. Since early 1997, with the commencement of the heating phase, both large-scale tests have been fully operative. At this point it can be said that the demonstration objective of constructing the EBS has been successfully achieved. The measured thermal response of the buffer follows the pattern predicted in the preliminary modelling. The saturation rate of the buffer and associated mechanical processes are being continuously monitored.

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.

Comparison of Probabilistic Fracture Mechanics Evaluations for a Through-Wall Cracked Pipe Under the STYLE Project

2014 ◽  
Author(s):  
John Sharples ◽  
Colin Madew ◽  
Vasile Radu ◽  
Peter Budden
Keyword(s):  
Fracture Mechanics ◽  
Large Scale ◽  
Bending Moment ◽  
Sensitivity Analyses ◽  
Probabilistic Fracture Mechanics ◽  
Benchmark Study ◽  
Four Point Bending ◽  
Growth Initiation ◽  
Log Normal ◽  
Parameter Values

One of the large scale mock-up experiments (Mock-Up 2) of the recent STYLE European project was a ductile fracture test carried out on a pipe containing a circumferential through-wall crack located in a repair weld and loaded under four-point bending. This experiment has been used as a basis for undertaking a comparative probabilistic fracture mechanics benchmark study by a number of the organisations participating in STYLE. In launching the benchmark study, the pipe and crack dimensions were specified as fixed values, applied bending stress (moment) was considered as a deterministic variable and three values were taken for weld residual stress (assuming constant membrane values). Tensile and fracture toughness material properties were considered to be random variables and these were specified by log-normal distribution parameter values. In undertaking their evaluations, the participants were asked to evaluate J-integral versus applied bending moment, probability of crack growth initiation versus applied bending moment, probability of net-section collapse versus applied bending moment and carry out various sensitivity analyses. This paper focuses mainly on the contribution to the benchmark study primarily based on the R6 methodology and includes examples of contributions provided using other methods.

Calibration of Flaw Extension Model Under Ratcheting Fatigue

2009 ◽  
Author(s):  
Paulo Gioielli ◽  
Jaime Buitrago ◽  
Wan Kan ◽  
Michael Weir ◽  
Graham Chell ◽  
...  
Keyword(s):  
Large Scale ◽  
Fatigue Behavior ◽  
High Growth ◽  
Fatigue Loading ◽  
Small Scale ◽  
Extension Model ◽  
Full Scale Tests ◽  
Welded Pipe ◽  
Large Scale Tests ◽  
Tearing Resistance

Ratcheting fatigue loading arises from the superposition of elastic cyclic loads and monotonically increasing mean strains well into the plastic domain, resulting in simultaneous tearing and fatigue of initial welding flaws. The ratcheting loads may be due to thermal gradients set by startups and shutdowns or by soil uplifts and settlements. Under these conditions, fatigue and fracture phenomena could interact, accelerating the extension of initial fabrication flaws above that predicted to occur by either mechanism acting alone. Evaluation of ratcheting fatigue behavior will impact the weld inspection criteria that ensure pipeline integrity. A previous paper [Gioielli, et al ’08] described a model that evaluates 1) tearing based on applied elastic-plastic driving force (J) versus tearing resistance obtained from standard J-R curve tests and 2) tearing-fatigue based on an extension of Paris law re-expressed in terms of an effective ΔJ instead of ΔK enabling it to be extrapolated to the very high growth rates encountered in the elasto-plastic regime. The model was successfully calibrated to small-scale tests. This paper extends the model calibration to large-scale welded pipe tests subjected to cyclic tensile loads while internally pressurized. To that end, 1) new J solutions were developed for pressurized pipes under load-controlled conditions, and 2) comparisons were made of predicted flaw extensions to those obtained experimentally from full-scale tests. The model predictions using average tensile properties and SENT-based tearing resistance of flaw extensions compared favorably to those measured in the large-scale tests, but additional tests are needed before the model can be used in design.

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