Probability of Brittle Fracture in Gas Pipelines

2014 ◽  
Author(s):  
R. Kurth ◽  
S. Kalyanam ◽  
E. Kurth ◽  
G. Wilkowski ◽  
F. Brust ◽  
...  
Keyword(s):  
Probability Distribution ◽  
Brittle Fracture ◽  
Crack Propagation ◽  
Probabilistic Analysis ◽  
Crack Arrest ◽  
Gas Pipelines ◽  
Drop Weight ◽  
Propagation Velocities

This is a report of the calculation of the probability of brittle fracture and crack arrest for a series of X42 A-series and B-series pipelines. This paper provides the probabilistic analysis to determine the probability distribution of crack propagation velocities using the material resistance developed from Charpy and Drop Weight Tear Tests (DWTT).

Effect of Notch Type in Drop-Weight Tear Test Specimen on Crack Propagation and Arrest Behavior

2018 ◽  
Author(s):  
Satoshi Igi ◽  
Toshihiko Amano ◽  
Takahiro Sakimoto ◽  
Yasuhiro Shinohara ◽  
Tetsuya Tagawa
Keyword(s):  
Crack Propagation ◽  
Large Scale ◽  
Crack Arrest ◽  
Brittle Crack ◽  
Chevron Notch ◽  
Drop Weight ◽  
Drop Weight Tear Test ◽  
Shear Area ◽  
The Impact ◽  
Crack Propagation And Arrest

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle fracture propagation. However, in the recent years there is an ambiguity in its evaluation if inverse fracture appears on the specimen fracture surfaces. Although cause of the inverse fracture is not fully understood, compressive pre-straining near the impact hammer and existing tiny split have been discussed as a possible cause. In this paper, machined notch in brittle weld DWTT for X65 was performed and compared with various notch types of DWTTs such as conventional DWTT specimen with a pressed notch (PN), a chevron notch (CN) and a static pre-cracked (SPC). The fracture appearances were compared with different strength X65 - X80 grades linepipes and with different initial notch types. The frequency of the inverse fracture appeared in these DWTTs were different in each material and each specimen types, but there were no cases where the inverse fracture did not occurs. The purpose of DWTT is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. A large scale brittle crack arrest test, so called West Jeferson test is generally used to reproduce crack propagation and arrest behavior in an actual pipeline material. A middle scale test so called Crack Arrest Temperature (CAT) test was also proposed to check the shear area fraction measured in DWTT with API rating with that the local shear lip thickness fraction in those tests. CAT test can well reproduce crack propagation and arrest behavior under the condition of brittle crack initiation from the initial notch.

Cleavage Planes of Icosahedral Quasicrystals: A Molecular Dynamics Study

2003 ◽  
Vol 805 ◽  
Author(s):  
Frohmut Rösch ◽  
Christoph Rudhart ◽  
Peter Gumbsch ◽  
Hans-Rainer Trebin
Keyword(s):  
Molecular Dynamics ◽  
Brittle Fracture ◽  
Crack Propagation ◽  
Three Dimensional ◽  
Propagation Direction ◽  
Mode I ◽  
Dynamic Crack ◽  
Fracture Surfaces ◽  
Icosahedral Quasicrystals ◽  
Crack Tip Plasticity

ABSTRACTThe propagation of mode I cracks in a three-dimensional icosahedral model quasicrystal has been studied by molecular dynamics techniques. In particular, the dependence on the plane structure and the influence of clusters have been investigated. Crack propagation was simulated in planes perpendicular to five-, two- and pseudo-twofold axes of the binary icosahedral model.Brittle fracture without any crack tip plasticity is observed. The fracture surfaces turn out to be rough on the scale of the clusters. These are not strictly circumvented, but to some extent cut by the dynamic crack. However, compared to the flat seed cracks the clusters are intersected less frequently. Thus the roughness of the crack surfaces can be attributed to the clusters, whereas the constant average heights of the fracture surfaces reflect the plane structure of the quasicrystal. Furthermore a distinct anisotropy with respect to the in-plane propagation direction is found.

Design of crack arrestors for ultra high grade gas transmission pipelines: simulation of crack initiation, propagation and arrest

2011 ◽  
Vol 2 (2) ◽  
pp. 307-319
Author(s):  
F. Van den Abeele ◽  
M. Di Biagio ◽  
L. Amlung
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Large Scale ◽  
Large Diameter ◽  
Pipe Material ◽  
High Grade ◽  
Gas Pipelines ◽  
Ductile Crack ◽  
Reinforced Plastics ◽  
Four Point Bending

One of the major challenges in the design of ultra high grade (X100) gas pipelines is the identification of areliable crack propagation strategy. Recent research results have shown that the newly developed highstrength and large diameter gas pipelines, when operated at severe conditions, may not be able to arrest arunning ductile crack through pipe material properties. Hence, the use of crack arrestors is required in thedesign of safe and reliable pipeline systems.A conventional crack arrestor can be a high toughness pipe insert, or a local joint with higher wall thickness.According to experimental results of full-scale burst tests, composite crack arrestors are one of the mostpromising technologies. Such crack arrestors are made of fibre reinforced plastics which provide the pipewith an additional hoop constraint. In this paper, numerical tools to simulate crack initiation, propagationand arrest in composite crack arrestors are introduced.First, the in-use behaviour of composite crack arrestors is evaluated by means of large scale tensile testsand four point bending experiments. The ability of different stress based orthotropic failure measures topredict the onset of material degradation is compared. Then, computational fracture mechanics is applied tosimulate ductile crack propagation in high pressure gas pipelines, and the corresponding crack growth inthe composite arrestor. The combination of numerical simulation and experimental research allows derivingdesign guidelines for composite crack arrestors.

Short Crack Propagation Model Applied to Shot Peened Aluminium Alloys

2009 ◽  
Vol 65 ◽  
pp. 53-61 ◽  
Author(s):  
J. Solis ◽  
J. Oseguera-Peña ◽  
I. Betancourt
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Aluminium Alloys ◽  
Micromechanical Model ◽  
High Strength ◽  
Crack Arrest ◽  
Propagation Model ◽  
Safe Load ◽  
Compressive Residual Stresses

The Navarro-Rios micromechanical model was used to assess the bounds of two different damage zones: crack arrest region and crack propagation region of controlled shot peening (CSP) of high strength aluminium alloys. Performance of CSP in terms of fatigue resistance was investigated. This comparison indicated that CSP in terms of fatigue depends on the competition between its beneficial and detrimental products, i.e. surface roughness and compressive residual stresses respectively. The gathered information can be used for safe load determinations in design.

scholarly journals Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

2020 ◽  
Author(s):  
Frank Liebold ◽  
Ali A. Heravi ◽  
Oliver Mosig ◽  
Manfred Curbach ◽  
Viktor Mechtcherine ◽  
...  
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Vector Fields ◽  
Displacement Vector ◽  
Image Sequence ◽  
High Speed Camera ◽  
Sequence Processing ◽  
Image Sequence Processing ◽  
Propagation Velocities

The determination of crack propagation velocities can provide valuable information for a better understanding of damage processes of concrete. The spatio-temporal analysis of crack patterns developing at a speed of several hundred meters per second is a rather challenging task. In the paper, a photogrammetric procedure for the determination of crack propagation velocities in concrete specimens using high-speed camera image sequences is presented. A cascaded image sequence processing which starts with the computation of displacement vector fields for a dense pattern of points on the specimen’s surface between consecutive time steps of the image sequence chain has been developed. These surface points are triangulated into a mesh, and as representations of cracks, discontinuities in the displacement vector fields are found by a deformation analysis applied to all triangles of the mesh. Connected components of the deformed triangles are computed using region-growing techniques. Then, the crack tips are determined using principal component analysis. The tips are tracked in the image sequence and the velocities between the time stamps of the images are derived. A major advantage of this method as compared to established techniques is in the fact of its allowing for spatio-temporally resolved, full-field measurements rather than point-wise measurements and that information on crack width can be obtained simultaneously. To validate the experimentation, the authors processed image sequences of tests on four compact-tension specimens performed on a split-Hopkinson tension bar. The images were taken by a high-speed camera at a frame rate of 160,000 images per second. By applying to these datasets the image sequence processing procedure as developed, crack propagation velocities of about 800 m/s were determined with a precision in the order of 50 m/s.

scholarly journals Automated Brittle Fracture Rate Estimator for Steel Property Evaluation Using Deep Learning After Drop-Weight Tear Test

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 145095-145103 ◽  
Author(s):  
Gyogwon Koo ◽  
Crino Shin ◽  
Hyeyeon Choi ◽  
Jong-Hak Lee ◽  
Sang Woo Kim ◽  
...  
Keyword(s):  
Deep Learning ◽  
Brittle Fracture ◽  
Fracture Rate ◽  
Drop Weight ◽  
Property Evaluation ◽  
Drop Weight Tear Test ◽  
Steel Property

KIa Crack Arrest Toughness Assessment Using Thermal Shock on Notched Disks

2004 ◽  
Author(s):  
Me´jido Hajjaj ◽  
Ste´phane Bugat ◽  
Clotilde Berdin ◽  
Philippe Bompard
Keyword(s):  
Crack Propagation ◽  
Thermal Shock ◽  
Static Analysis ◽  
Thermal Analyses ◽  
Crack Arrest ◽  
The Finite Element Method ◽  
Wave Interference ◽  
Shock Experiment ◽  
T Values ◽  
Arrest Toughness

The aim of the study is to validate the KIa-T curve on a thermal shock experiment performed on a notched disk (DTSE) taken from a A533-B type steel. Several experiments have been performed. Non linear thermal analyses were carried out using the finite element method in order to obtain the full thermal field within the specimen during crack propagation. The results obtained are in excellent agreement with the experimental results. The DTSE is also interpretated in static terms to compare the obtained KIa (T) values with the limit curve. Finally, dynamic F.E. simulations allow to estimate the influence of dynamic effects in the DTSE and thus validate the methodology. According to the computations, the crack arrested when dK/da>0 and dKd/da = 0. The comparison between stress intensity factor computed from elastic-static analysis (or dynamic) and RCC-M code demonstrated the conservatism of the approach. Then static analysis is sufficient to analyse the result, since no wave interference with the crack propagation was identified.

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