Ductile Fracture Propagation and Arrest in Offshore Pipelines

1988 ◽  
Vol 41 (2) ◽  
pp. 85-95 ◽  
Author(s):  
G. Demofonti ◽  
A. Maresca ◽  
G. Buzzichelli
Keyword(s):  
Ductile Fracture ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Correct Choice ◽  
Buried Pipelines ◽  
Offshore Pipelines ◽  
The Past ◽  
Research Institutes ◽  
Full Scale Tests ◽  
Main Effects

The problem of ductile fracture propagation in pipelines, already extensively studied in the past in the case of buried pipelines, has been receiving the close attentions of research institutes and companies in the last decade or so for offshore pipelines too; the aim is to allow a correct choice of toughness levels of the steels employed for such applications. The first studies in the field consisted essentially in model tests; more recently full-scale tests were performed, while at the same time the first attempts were made to interpret and model marine backfill. As a result the main effects of marine backfill on ductile propagation were put into evidence and quantified. In particular, because of the overpressure field generated around the pipe subsequently to fracture initiation, the marine backfill comes out to be more effective than soil in arresting a running fracture, and consequently very low toughness levels are required for offshore pipelines.

Next Generation Ductile Fracture Arrest Analyses for High Energy Pipelines Based on Detail Coupling of CFD and FEA Approach

2018 ◽  
Author(s):  
K. K. Botros ◽  
E. J. Clavelle ◽  
M. Uddin ◽  
G. Wilkowski ◽  
C. Guan
Keyword(s):  
Ductile Fracture ◽  
Test Data ◽  
Fracture Propagation ◽  
Crack Tip ◽  
Propagation Speed ◽  
High Energy ◽  
Computational Effort ◽  
Pipe Material ◽  
The Past ◽  
Toughness Parameter

Axial ductile fracture propagation and arrest in high energy pipelines has been studied since the early 1970’s with the development of the empirical Battelle Two-Curve (BTC) model. Numerous empirical corrections on the backfill, gas decompression models, and fracture toughness have been proposed over the past decades. While this approach has worked in most cases, the dynamic interaction between the decompression of the fluid in the vicinity of the crack tip and the behaviour of the pipe material as it opens to form flaps behind the crack has been very difficult to solve from a more fundamental approach. The effects of the pressure distribution on the flap inner surface making up the crack-driving force which drives the crack propagation speed has been suggested in the past, but due to intensive computational effort required, it was never realized. The present paper attempts to tackle this problem by employing an iterative solution procedure where the gas pressure field in the vicinity of the crack tip is accurately solved for by computational fluid dynamics (CFD) for a given flap geometry determined from a dynamic FEA model to render a new flap geometry. In this model a cohesive-zone element at the crack tip is employed as a representation of the material toughness parameter. The final outcome is the determination of the cohesive energy in the FEA (as a representation of the material toughness parameter) to match the measured fracture propagation speed for the specific case. A case study was taken from full-scale rupture test data from one of the pipe joints from the Japanese Gas Association (JGA) unbackfilled pipe burst test data conducted in 2004 on the 762 mm O.D., 17.5 mm wall thickness, Gr. 555 MPa (API 5L X80) pipe.

Review of Fracture Control Technology for Gas Transmission Pipelines

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Ductile Fracture ◽  
Fracture Propagation ◽  
High Strength ◽  
Fracture Initiation ◽  
Alternative Methods ◽  
Opening Angle ◽  
Pipeline Steels ◽  
Control Plan ◽  
Fracture Control ◽  
Arrest Toughness

A fracture control plan is often required for a gas transmission pipeline in the structural design and safe operation. Fracture control involves technologies to control brittle and ductile fracture initiation, as well as brittle and ductile fracture propagation for gas pipelines, as reviewed in this paper. The approaches developed forty years ago for the fracture initiation controls remain in use today, with limited improvements. In contrast, the approaches developed for the ductile fracture propagation control has not worked for today’s pipeline steels. Extensive efforts have been made to this topic, but new technology still needs to be developed for modern high-strength pipeline steels. Thus, this is the central to be reviewed. In order to control ductile fracture propagation, Battelle in the 1970s developed a two-curve model (BTCM) to determine arrest toughness for gas pipeline steels in terms of Charpy vee-notched (CVN) impact energy. Practice showed that the BTCM is viable for pipeline grades X65 and below, but issues emerged for higher grades. Thus, different corrections to improve the BTCM and alternative methods have been proposed over the years. This includes the CVN energy-based corrections, the drop-weight tear test (DWTT) energy-based correlations, the crack-tip opening angle (CTOA) criteria, and finite element methods. These approaches are reviewed and discussed in this paper, as well as the newest technology developed to determine fracture arrest toughness for high-strength pipeline steels.

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.

scholarly journals Prediction of Ductile Fracture in Metal Blanking

1999 ◽  
Vol 122 (3) ◽  
pp. 476-483 ◽  
Author(s):  
A. M. Goijaerts ◽  
L. E. Govaert ◽  
F. P. T. Baaijens
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Ductile Fracture ◽  
Experimental Error ◽  
Fracture Initiation ◽  
Fracture Model ◽  
Ductile Fracture Model ◽  
Blanking Process ◽  
Ductile Fracture Initiation

This study is focused on the description of ductile fracture initiation, which is needed to predict product shapes in the blanking process. Two approaches are elaborated using a local ductile fracture model. According to literature, characterization of such a model should take place under loading conditions, comparable to the application. Therefore, the first approach incorporates the characterization of a ductile fracture model in a blanking experiment. The second approach is more favorable for industry. In this approach a tensile test is used to characterize the fracture model, instead of a complex and elaborate blanking experiment. Finite element simulations and blanking experiments are performed for five different clearances to validate both approaches. In conclusion it can be stated that for the investigated material, the first approach gives very good results within the experimental error. The second approach, the more favorable one for industry, yields results within 6 percent of the experiments over a wide, industrial range of clearances, when a newly proposed criterion is used. [S1087-1357(00)02202-4]

The Research Liaison Committee

1967 ◽  
Vol 10 (02) ◽  
pp. 19
Keyword(s):  
Field Research ◽  
Actual Cost ◽  
Institutional Affiliation ◽  
Academic Advisor ◽  
Liaison Committee ◽  
The Past ◽  
Research Institutes ◽  
Home Institution ◽  
Other Information ◽  
Oriented Research

The Research Liaison Committee of the African Studies Association has compiled A Directory of Studies Centers and Research Institutes Abroad engaged in Africa-oriented research. The Directory is available by individual countries or in its entirety by writing to the RLC office. Professors Igor Kopytoff, Vernon McKay, and Benjamin Rivlin are the 1967 liaison representatives of the Association. Each has visited African universities, research institutes, and government offices during the past few months to collect information on research in progress and on the perspectives and problems of field research in the countries of Africa. The 1968 liaison representatives have been appointed by the Association's president, William A. Hance. Professors Robert A. Lystad and Robert L. West have joined the RLC and will be traveling to Africa during the summer, 1968. A request to scholars recently returned or going to Africa. The RLC would welcome the following information: 1. Data on research project, including title of project, discipline or disciplines reflected, financial sponsorship, home institution, academic advisor, institutional affiliation in Africa, date of departure and expected duration of stay in Africa; 2. A brief report on living conditions, actual cost in relation to anticipated cost, field problems, and any other information with would be of assistance to those planning fieldwork in Africa.

Think Tanks in East Asia in Need of More Cooperation and More Networking: NEAT after its Ten Years

2012 ◽  
Vol 04 (03) ◽  
pp. 91-96
Author(s):  
John WONG
Keyword(s):  
East Asia ◽  
Working Group ◽  
Regional Cooperation ◽  
Process Research ◽  
Think Tanks ◽  
Relevant Research ◽  
The Past ◽  
Research Institutes ◽  
Working Groups ◽  
Important Progress

NEAT is a loosely constituted regional scheme under the ASEAN plus Three (APT) framework. Its main objectives are to promote exchange among APT scholars and research institutes in the region, and to promote relevant research that can facilitate the APT regional cooperation process. Research is done through organising Working Groups. NEAT has made important progress in the past 10 years. To grow and expand in future, it will have to improve on its networking function and strengthen its Working Group mechanism.

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