Comparison of BTC, RBTC and HLP Models in the Calculation of the Dynamic Ductile Fracture Propagation Velocities Based on the X80 Full-Scale Burst Test

ICPTT 2013 ◽  
2013 ◽  
Author(s):  
He Li ◽  
Weiwei Zhang ◽  
Yanhua Li ◽  
Chunyong huo ◽  
Yaorong Feng ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Propagation ◽  
Full Scale ◽  
Burst Test ◽  
Propagation Velocities ◽  
Dynamic Ductile Fracture

Mechanical and Metallurgical Aspects of the Resistance to Ductile Fracture Propagation in the New Generation of Gas Pipelines

2014 ◽  
Author(s):  
Igor Pyshmintsev ◽  
Alexey Gervasyev ◽  
Victor Carretero Olalla ◽  
Roumen Petrov ◽  
Andrey Arabey
Keyword(s):  
Ductile Fracture ◽  
Mechanical Test ◽  
Fracture Propagation ◽  
Rolling Plane ◽  
Full Scale ◽  
Charpy Test ◽  
Line Pipe ◽  
Surface Separation ◽  
Fracture Arrest ◽  
New Generation

The microstructure and fracture behavior of the base metal of different X80 steel line pipe lots from several pipeline projects were analyzed. The resistance of the pipes to ductile fracture propagation was determined by the full-scale burst tests. The high intensity of fracture surface separation (secondary brittle cracks parallel to the rolling plane of the plate) appeared to be the main factor reducing the specific fracture energy of ductile crack propagation. A method for quantitative analysis of microstructure allowing estimation of the steel’s tendency to form separations is proposed. The procedure is based on the EBSD data processing and results in Cleavage Morphology Clustering (CMC) parameter evaluation which correlates with full-scale and laboratory mechanical test results. Two special laboratory mechanical test types utilizing SENT and Charpy test concepts for prediction of ductile fracture arrest/propagation in a pipe were developed and included into Gazprom specifications.

scholarly journals On Longitudinal Propagation of a Ductile Fracture in a Buried Gas Pipeline: Numerical and Experimental Analysis

2000 ◽  
Author(s):  
G. Berardo ◽  
P. Salvini ◽  
G. Mannucci ◽  
G. Demofonti
Keyword(s):  
Finite Element ◽  
Ductile Fracture ◽  
Driving Force ◽  
Fracture Propagation ◽  
Full Scale ◽  
Finite Element Code ◽  
Line Pipe ◽  
Real Phenomenon ◽  
Buried Gas Pipeline ◽  
Soil Pipe

The work deals with the development of a finite element code, named PICPRO (PIpe Crack PROpagation), for the analysis of ductile fracture propagation in buried gas pipelines. Driving force estimate is given in terms of CTOA and computed during simulations; its value is then compared with the material parameter CTOAc, inferred by small specimen tests, to evaluate the toughness of a given line pipe. Some relevant aspects are considered in the modelling with the aim to simulate the real phenomenon, namely ductile fracture mechanism, gas decompression behaviour and soil backfill constraint. The gas decompression law is calculated outside the finite element code by means of experimental data from full-scale burst tests coupled with classical shock tube solution. The validation is performed on the basis of full-scale propagation experiments, carried out on typical pipeline layouts, and includes verification of global plastic displacements and strains, CTOA values and soil-pipe interaction pressures.

Fracture Propagation in Underwater Gas Pipelines

1986 ◽  
Vol 108 (1) ◽  
pp. 29-34 ◽  
Author(s):  
W. A. Maxey
Keyword(s):  
Ductile Fracture ◽  
Pipe Wall ◽  
Fracture Propagation ◽  
Full Scale ◽  
Gas Pipelines ◽  
Buried Pipelines ◽  
Nitrogen Gas ◽  
Line Pipe ◽  
Fracture Velocity

Two full-scale ductile fracture propagation experiments on segments of line pipe pressurized with nitrogen gas have been conducted underwater at a depth of 40 ft (12 m) to evaluate the ductile fracture phenomenon in underwater pipelines. The pipes were 22-in. (559-mm) diameter and 42-in. (1067-mm) diameter. Fracture velocities were measured and arrest conditions were observed. The overpressure in the water surrounding the pipe resulting from the release of the compressed nitrogen gas contained in the pipe was measured in both experiments. The overpressure in the water reduces the stress in the pipe wall and thus slows down the fracture. In addition, the water surrounding the pipe appears to be more effective than soil backfill in producing a slower fracture velocity. Both of these effects suggest a greater tendency toward arrest for a pipeline underwater than would be the case for the same pipeline buried in soil onshore. Further verification of this effect is planned and a modified version of the existing model for predicting ductile fracture in buried pipelines will be developed for underwater pipelines.

Verification of Applicability of Battelle Two-Curve Method to Ultrahigh-Pressure Rich-Gas Pipelines Based on a Full-Scale Burst Test

2018 ◽  
Author(s):  
Yasuhito Imai ◽  
Masaki Mitsuya ◽  
Masao Toyoda
Keyword(s):  
Ductile Fracture ◽  
Full Scale ◽  
Ultrahigh Pressure ◽  
Experimental Result ◽  
Outer Diameter ◽  
Ductile Crack ◽  
Absorbed Energy ◽  
Burst Test ◽  
Curve Method ◽  
Charpy Absorbed Energy

A full-scale gas burst test was conducted to confirm the behavior of unstable ductile crack propagation and arrest and to confirm the required toughness value to prevent unstable ductile fracture under an ultrahigh pressure of 18 MPa. A full-scale test was conducted at the Spadeadam test site in the UK for unburied pipes. The test pipes used in this test were of API 5L Grade L450 with outer diameter of 610 mm and thickness of 17.5 mm. The toughness of the test pipes increased away from the center, where an explosive charge was placed across the top of the girth weld for crack initiation. The gas used in the test consisted of ∼89% methane and other heavy hydrocarbon gas components, and the test temperature was 0 °C. A gas circulation loop was constructed to ensure that a homogeneous gas mixture and temperature were achieved throughout the test rig. In addition to dynamically measuring the ductile crack velocity and decompression behavior of the rich gas, as has often been done in previous burst tests, the circumferential distribution of the decompression behavior was measured using circumferentially placed pressure transducers. Furthermore, the fracture strain near the propagating crack was measured. The initiated unstable ductile crack was arrested in the third pipe. From the material properties of the test pipes in which the unstable ductile crack was arrested, the required Charpy absorbed energy and DWTT absorbed energy to prevent unstable ductile fracture in unburied pipes were obtained. In addition, the above data can be useful for validating numerical models that evaluate the propagation/arrest of unstable ductile fracture. The required Charpy and DWTT absorbed energy values obtained in this test were compared with those predicted by the Battelle Two-Curve Method (BTCM). As noted in previous studies, it was confirmed that the BTCM underestimates the required Charpy absorbed energy and requires a certain correction factor for precise evaluation, whereas the DWTT absorbed energy predicted by BTCM was consistent with the experimental result.

Applicability of Existing Models for Predicting Ductile Fracture Arrest in High Pressure Pipelines

2006 ◽  
Author(s):  
John Wolodko ◽  
Mark Stephens
Keyword(s):  
High Pressure ◽  
Ductile Fracture ◽  
High Pressures ◽  
Fracture Propagation ◽  
High Strength Steels ◽  
High Strength ◽  
Full Scale ◽  
Stage Of Development ◽  
Fracture Arrest ◽  
Arrest Toughness

The ductile fracture arrest capability of gas pipelines is seen as one of the most important factors in the future acceptance of new high strength pipeline steels for high pressure applications. It has been acknowledged for some time that the current methods for characterizing and predicting the arrest toughness for ductile fracture propagation in high strength steels are un-conservative. This observation is based on the inability of existing models to predict the required arrest toughness in full-scale ductile fracture propagation tests. While considerable effort is currently being applied to develop more accurate methods for predicting ductile facture arrest, the resulting models are still in a preliminary stage of development and are not immediately amenable for use by the general engineering community. As an interim solution, a number of authors have advocated the empirical adjustment or reformulation of the existing models for use with the newer, high strength pipe grades. While this approach does not address the fundamental issues surrounding the fracture arrest problem, it does provide methods that can be used in the near term for analysis and preliminary design. The desire to use these existing methods, however, is tempered by the uncertainty associated with their applicability in situations involving high pressures and/or high toughness materials. In an attempt to address some of these concerns, a statistical analysis was conducted to assess the accuracy of a number of available fracture arrest models by comparing predictions to actual values determined from full-scale fracture propagation experiments. From the results, correction factors were developed for determining the required toughness levels in high pressure applications that account for the uncertainty in the theoretical prediction methods.

CO2SAFE-ARREST: A Full-Scale Burst Test Research Program for Carbon Dioxide Pipelines — Part 2: Is the BTCM Out of Touch With Dense-Phase CO2?

2018 ◽  
Author(s):  
Guillaume Michal ◽  
Bradley Davis ◽  
Erling Østby ◽  
Cheng Lu ◽  
Sigbjørn Røneid
Keyword(s):  
Ductile Fracture ◽  
Wall Thickness ◽  
Companion Paper ◽  
Full Scale ◽  
Test Material ◽  
Transient Pressure ◽  
Dense Phase ◽  
Burst Test ◽  
Drop Weight ◽  
Fracture Velocity

The CO2SAFE-ARREST joint industry project (JIP) aims to (1) investigate the fracture propagation and arrest characteristics of steel pipelines carrying anthropogenic CO2, and (2) to investigate the dispersion of CO2 following its release into the atmosphere. The project is supported by two full-scale burst tests, each based on a layout of eight X65 grade 24″ line pipes filled with a dense-phase CO2-N2 mixture. The tests were conducted over the 2017–2018 period at the DNV GL testing site at Spadeadam, UK. An overview of both the CO2SAFE-ARREST JIP and the first full-scale burst test is provided in a companion paper (IPC2018-78517). The dispersion aspect is covered in another companion paper (IPC2018-78530). This paper presents the material properties, the design layout and the results of the first full-scale burst test. Material characterisation of the pipes available to the project and the motivation leading to the design of the layout are first presented. Six pipes had a nominal wall thickness of 13.5 mm and the remaining two pipes had a nominal wall thickness of 14.5 mm. Laboratory testing was conducted on the material at the end of each pipe section. The testing consisted of Charpy impact and Drop Weight Tear tests, capturing the upper shelf fracture energy, load-displacement curves and an assessment of the fracture surfaces. Charpy and Drop Weight Tear test energies as well as strength data are provided. The layout reflects the research focus of the project with both conventional and less conventional pipe arrangements. The test was primarily designed around 13.5 mm nominal wall thickness pipes with a 1m depth backfill and laid East-West. The design was telescopic and introduced an asymmetry with respect to the mid-point by arranging pipe sections with increasing Charpy toughness on one side and increasing yield strength on the opposite side. The fracture was initiated at half-length, across the girth weld between the ‘west’ and ‘east’ initiation pipes. A running ductile fracture ensued, followed by an arrest in the third pipe on either side of the test section. Experimental data relevant to fracture velocity, decompression wave speed of the CO2-N2 mixture and pressure at the crack tip are presented. The discussion is driven from the perspective of traditional running ductile fracture control technology applied to dense-phase CO2 carrying pipelines. Emphasis is put on the analysis of the fracture velocity and transient pressure data relative to the properties of the material and CO2 mixture. The limitations of the Battelle Two-Curve Method (BTCM) traditionally used in the analysis of running ductile fracture are discussed. The design of this test was different from that used in the three full-scale burst tests conducted as part of the COOLTRANS project. The conclusions drawn here support those from the COOLTRANS project and apply to larger D/t ratios. The first CO2SAFE-ARREST test provides additional evidence that the original Battelle Two-Curve Model is not applicable to dense-phase CO2 carrying pipelines. A shift in prediction tool technology is called for.

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