On the Gasdynamics of Running Ductile Fracture in a Pressurized Line Pipe

1978 ◽  
Vol 100 (1) ◽  
pp. 13-17 ◽  
Author(s):  
D. M. Parks ◽  
L. B. Freund
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Driving Force ◽  
Crack Opening ◽  
Two Dimensional ◽  
Line Pipe ◽  
New Model ◽  
Large Crack ◽  
Two Dimensional Flow ◽  
Axial Crack

Developments in the modeling of the gasdynamics associated with running ductile fracture in pressurised line pipe are reviewed and critically examined. It is argued that existing models of gas escape through a flaring axial crack in a pipe may not be generally applicable. A new model of gas escape, based on two-dimensional flow and directed toward large crack opening situations, is presented, and results obtained with this model compare favorably with experiments. Implications of the present results concerning the driving force for crack propagation are discussed.

Ductile Fracture Analysis Under Large Amplitude Cycles

2014 ◽  
Author(s):  
B. Tranchand ◽  
S. Chapuliot ◽  
V. Aubin ◽  
S. Marie ◽  
M. Bourgeois
Keyword(s):  
Crack Propagation ◽  
Fracture Energy ◽  
Ductile Fracture ◽  
Crack Closure ◽  
Large Amplitude ◽  
Crack Opening ◽  
Image Correlation ◽  
Potential Measurement ◽  
Loading Ratio

Demonstration of large components integrity under seismic loading is based up to now on monotonic tearing resistance curves. However, it is well known that cycles decrease the fracture resistance of the material, mainly according to the loading ratio. Most studies use monotonic methods to analyze reversible cyclic loading and the associated increase of crack propagation: Delta J-R curves are largely used. For monotonic loadings, Turner [1] proposed a decomposition of the rate of dissipated fracture energy. This decomposition led on the determination of an energetic criterion for ductile fracture [2]. This intrinsic criterion allows the fracture prediction on large components. This paper aims to propose an analysis of cyclic ductile fracture which should allow the determination of an energetic criterion under large amplitude cycles. For that purpose, compact tension specimens are taken from a carbon steel pipe (Tu42C) used in the secondary circuit of French PWR. A series of cyclic tearing tests are carried out under quasi-static loadings. The effects of loading ratio and incremental plastic displacement are quickly studied. Here, we present an energetic analysis which take into account the crack closure and crack opening. Indeed, displacement fields around the crack tips are measured with digital image correlation and linked with electric potential measurement. That allows an accurate determination of crack closure and crack opening and let a precise calculation of fracture energy possible. The energetic fracture criterion will be confirmed with crack propagation prediction on different geometry like CT specimen and a through-wall-cracked pipe under cyclic reversed loadings.

Effect of Separation on Ductile Crack Propagation Behavior During Drop Weight Tear Test

2010 ◽  
Author(s):  
Takuya Hara ◽  
Taishi Fujishiro
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Fracture Resistance ◽  
High Strength ◽  
Opening Angle ◽  
Ductile Crack ◽  
Line Pipe ◽  
Propagation Behavior ◽  
Drop Weight ◽  
Drop Weight Tear Test

The demand for natural gas using LNG and pipelines to supply the world gas markets is increasing. The use of high-strength line pipe provides a reduction in the cost of gas transmission pipelines by enabling high-pressure transmission of large volumes of gas. Under the large demand of high-strength line pipe, crack arrestability of running ductile fracture behavior is one of the most important properties. The CVN (Charpy V-notched) test and the DWTT (Drop Weight Tear Test) are major test methods to evaluate the crack arrestability of running ductile fractures. Separation, which is defined as a fracture parallel to the rolling plane, can be characteristic of the fracture in both full-scale burst tests and DWTTs. It is reported that separations deteriorate the crack arrestability of running ductile fracture, and also that small amounts of separation do not affect the running ductile fracture resistance. This paper describes the effect of separation on ductile propagation behavior. We utilized a high-speed camera to investigate the CTOA (Crack Tip Opening Angle) during the DWTT. We show that some separations deteriorate ductile crack propagation resistance and that some separations do not affect the running ductile fracture resistance.

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.

Two-Dimensional Flow of Polymer Solutions Through Porous Media

1999 ◽  
Vol 2 (3) ◽  
pp. 251-262
Author(s):  
P. Gestoso ◽  
A. J. Muller ◽  
A. E. Saez
Keyword(s):  
Porous Media ◽  
Polymer Solutions ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow

STUDY OF NON-ISOTHERMAL TWO-DIMENSIONAL FLOW OVER A SQUARE CYLINDER IMMERSED IN A CHANNEL

2019 ◽  
Author(s):  
Gabriel Machado dos Santos ◽  
Ítalo Augusto Magalhães de Ávila ◽  
Hélio Ribeiro Neto ◽  
João Marcelo Vedovoto
Keyword(s):  
Two Dimensional ◽  
Square Cylinder ◽  
Dimensional Flow ◽  
Two Dimensional Flow

Influence of Partial Blocking of the Electrode Surface on the Transfer Coefficients

1993 ◽  
Vol 58 (3) ◽  
pp. 496-505
Author(s):  
Ondřej Wein
Keyword(s):  
Surface Activity ◽  
Elliptic Problem ◽  
Electrode Surface ◽  
Driving Force ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Constant Potential ◽  
Numeric Solution ◽  
Active Zones ◽  
Partial Blocking

Partial blocking of the transport surface under the stagnant (nerst) layer is simulated by periodically alternating bands of perfectly insulating zones and active zones with a constant potential of driving force. The numeric solution of the corresponding two-dimensional elliptic problem is represented by a simple empirical correlation for the transfer coefficients. The result is interpreted in terms of a simple electrochemical problem about limiting diffusion currents at electrodes with non-uniform surface activity.

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