Ductile Fracture Resistance Modeling Approach in Two High Grade Steels

2006 ◽  
Author(s):  
L. N. Pussegoda ◽  
A. Fredj ◽  
A. Dinovitzer ◽  
D. Horsley ◽  
D. Carlson
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Ductile Fracture ◽  
Fracture Resistance ◽  
Fracture Propagation ◽  
Tension Test ◽  
Model Parameters ◽  
High Grade ◽  
Damage Mechanisms ◽  
Point Bend

Recent developments in ductile fracture resistance measures in high grade steels in the pipeline industry include the crack tip opening angle (CTOA) and “steady state” fracture propagation energy, using 3-point bend specimens. The CTOA has been found to be a function of specimen ligament size. Alternatives would be “steady state” fracture propagation energy, critical fracture strain and adoption of damage mechanisms. This paper focuses on modeling approaches for crack propagation using damage mechanisms. The tension test is used to “calibrate” the damage model parameters and applied to the crack propagation in a 3-point bend specimen in candidate high grade steels. The effects of using parameters developed from tension test and extending to a 3-point bend crack propagation scenario is discussed.

Ductile Fracture Resistance Measurements in High Grade Steels

2006 ◽  
Author(s):  
L. N. Pussegoda ◽  
A. Fredj ◽  
A. Fonzo ◽  
G. Demofonti ◽  
G. Mannucci ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Steady State ◽  
Ductile Fracture ◽  
Fracture Resistance ◽  
Process Zone ◽  
Fracture Propagation ◽  
Crack Tip ◽  
Opening Angle ◽  
Displacement Curve ◽  
High Grade

Recent developments in ductile fracture resistance measures in high grade steels in the pipeline industry include the crack tip opening angle (CTOA) and “steady state” fracture propagation energy, using 3-point bend specimens. The CTOA has been found to be a function of specimen ligament size. With the availability of instrumented hammers, it became possible to resolve propagation energy using the load-displacement curve using a single specimen. This paper focuses on refining the steady state fracture propagation energy, using back-slotted Drop Weight Tear Test (DWTT) specimens. The study included numerical simulation of the dynamic response of back-slotted specimens. The significance of the back-slot in altering the stress/strain field ahead of the propagation crack is discussed. The numerical simulation was also used to determine the strain rate in the “process zone” of the crack tip during steady state fracture propagation.

Development of a Reliable Model for Evaluating the Ductile Fracture Propagation Resistance for High Grade Steel Pipelines

2012 ◽  
Author(s):  
M. Di Biagio ◽  
G. Demofonti ◽  
G. Mannucci ◽  
F. Iob ◽  
C. M. Spinelli ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Damage Model ◽  
Fracture Propagation ◽  
Fracture Parameter ◽  
High Grade ◽  
Propagation Resistance ◽  
Very High ◽  
Grade Steel

The recent experience on ductile fracture propagation control on gas pipelines has shown that the applicability of the Battelle Two Curve Method (based on Charpy-V energy) to high grade steel pipes from API5L-X80 to X120 (ISO3183-L555M to L830M) operated at very high hoop stress values (≥500 MPa) is highly questionable. The reduced geometry of the specimen, the intrinsic low value of ductility of very high strength steels, as low work-hardening and low value of the strain at maximum load are pointed out as the main causes of the mismatch. Starting from these assumptions a new EPRG (European Pipeline Research Group) project has been launched with the aim to develop, with reference to the ductile fracture propagation resistance, a suitable fracture parameter(s) with an associated laboratory methodology based on a simple sample which would be able to take into account the role of the ductility of the material on this specific fracture event. The present paper shows the approach adopted in this EPRG Project: an innovative approach based on “plastic damage model” which allows to describe the stable ductile crack propagation by means of stress-state parameters (named triaxiality and deviatoric parameters). Moreover the proposed “damage model” has been implemented inside a commercial finite element code and used to predict the fracture crack propagation behaviour of Single Edge Notch Bend (SENB) tests in terms of load-displacement diagram and residual plastic deformation. One of the main topics of this project was the application of this method to six selected grade steels (with grades in the range of API X65 – X100) many of them coming from experimental full scale burst tests. The comparisons between experimental results and numerical simulations are substantially good; besides the results confirm that Charpy-V specimens, during the fracture propagation, work in different “constraint” conditions with respect to pipe and that DWTT specimen is in the middle between the two. Finally the “damage model approach” seems also able to discriminate between low and high grade steels in terms of failure deformation at rupture. So it resulted very promising to quantify the role of both ductile of the steel and geometrical constraint of the specimen in the ductile fracture propagation event.

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.

Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines

2018 ◽  
Author(s):  
Aida Nonn ◽  
Marcelo Paredes ◽  
Vincent Keim ◽  
Tomasz Wierzbicki
Keyword(s):  
Ductile Fracture ◽  
Fracture Resistance ◽  
Pipeline Steel ◽  
Ductile Failure ◽  
Fracture Propagation ◽  
Plastic Behavior ◽  
Wide Range ◽  
X100 Pipeline Steel ◽  
Fracture Models ◽  
Stress States

Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology. In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.

Effect of Fracture Speed on Ductile Fracture Resistance: Part 1—Experimental

2010 ◽  
Author(s):  
Do-Jun Shim ◽  
Gery Wilkowski ◽  
Da-Ming Duan ◽  
Joe Zhou
Keyword(s):  
Steady State ◽  
Ductile Fracture ◽  
Fracture Resistance ◽  
State Energy ◽  
Crack Arrest ◽  
Experimental Results ◽  
Displacement Curve ◽  
Charpy Test ◽  
Line Pipe ◽  
Drop Weight Tear Test

The effect of fracture speed on the ductile fracture resistance of line-pipe steels can have an important effect in the basic understanding of the toughness requirements for crack arrest. Over the last few decades, it has become recognized that the drop-weight tear test (DWTT) better represents the ductile fracture resistance than the Charpy test since it utilizes a specimen that has the full thickness of the pipe and has a fracture path long enough to reach steady-state fracture resistance. However, the fracture speed in the DWTT is typically 50 to 60 feet per second (15.2 to 18.3 m/s), whereas the fracture speed in the full-scale pipe test is 300 to 1,000 fps (91.4 to 305 m/s). Recently, the authors have extended the DWTT work and developed a modified back-slot DWTT specimen to obtain higher fracture speeds. One aspect of this modified specimen was to increase the width of DWTT sample from the standard 3-inch (76.2 mm) to 5-inch (127 mm). This was done to increase the ligament length in a relatively deep back-slotted specimen to capture more steady-state data. The initial experimental results demonstrated that this type of specimen can be used to obtain higher fracture speeds. Furthermore, the experimental results clearly showed the effect of fracture speed on the ductile fracture resistance. In this paper, to extend the work on modified back-slot DWTT specimens, the tup was instrumented to measure the load during dynamic impact. From this, the load-displacement curve, steady-state energy (or energy per area) was obtained for the modified back-slot DWTT specimens. These results were compared to those obtained from the standard 3-inch specimens. These results also clearly showed the effect of fracture speed on fracture resistance.

Effect of Fracture Speed on Ductile Fracture Resistance: Part 2—Results and Application

2010 ◽  
Author(s):  
Da-Ming Duan ◽  
Joe Zhou ◽  
Do-Jun Shim ◽  
Gery Wilkowski
Keyword(s):  
Fracture Toughness ◽  
Steady State ◽  
Ductile Fracture ◽  
High Speed ◽  
Material Selection ◽  
Basic Material ◽  
Pipe Material ◽  
High Grade ◽  
Control Plan ◽  
Material Fracture

One of the many aspects of natural gas pipeline design and material selection is the consideration of propagation and arrest of high-speed axial ductile fracture in the line pipes. Understanding the material ductile fracture behavior is essential for establishing an integrated fracture control plan. This is particularly important for pipelines of high design pressures utilizing large-diameter and high-grade line pipes. The procedure of Battelle Two-Curve Method (TCM) has been most commonly used in ductile fracture analysis in the prediction of fracture speed and minimum arrest toughness for axially running cracks. In the past decades, discussions and research have been in that the TCM approach, among with others, could not accurately predict either fracture speed or minimum arrest fracture toughness for high-grade pipes, and with pipe grade increasing the prediction errors are getting larger. Recent research work at TransCanada indicates that for a better prediction of pipeline ductile fracture, understanding the basic material mechanical behavior and its fundamental fracture mechanism is essential. One of the important findings of the work is that pipe material fracture toughness is not a constant as being commonly treated, rather the fracture toughness, in terms of both steady-state CTOA and steady-state DWTT fracture energy is fracture speed dependent, being decreasing with increasing fracture speed. Corresponding modifications have been made to the traditional TCM by introducing speed-dependent fracture toughness. The improved model gives much better predictions in both fracture speed and toughness for high grade pipes. This paper presents recent work at TransCanada, together with its industry partner Engineering Mechanics Corporation of Columbus (EMCC), on high-speed pipe-material fracture testing technique (using the modified back-slot DWTT specimen) and high-grade material testing data. The test data supports the predictions of early published work on speed-dependent fracture toughness. The fracture speeds obtained from the modified back-slot DWTT specimens were very close to actual full-scale pipeline ductile fracture speeds and this in turn enhanced the applicability of the modified TCM model.

scholarly journals Fracture resistance of railway ballast rock under tensile and tear loads

2021 ◽  
Vol 9 (3) ◽  
pp. 271-280 ◽  
Author(s):  
A. Bahmani ◽  
S. Nemati
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Crack Propagation ◽  
Fracture Resistance ◽  
Propagation Path ◽  
Tensile Fracture ◽  
Fracture Test ◽  
Railway Ballast ◽  
Point Bend ◽  
Loading Type

The influence of loading type on tensile and tearing fracture resistance of ballast rock was assessed using edge-notched diametrically compressed disc (ENDC) and edge-notched disc bend (ENDB) test geometries. The geometry of these two specimens was similar; however, their loading type (i.e., three-point bend and diametral compressive) was different affecting the geometry factors. The obtained pure tensile fracture toughness (KIc) using the ENDB test was higher than the ENDC test. In contrast to tensile fracture toughness, the pure tearing fracture toughness (KIIIc) in the ENDC test was higher than the ENDB fracture test. The obtained experimental data were explained in terms of crack propagation path, since two distinct trajectories were observed for both configurations under tearing deformation.

Determination of the Region of Steady-State Crack Growth From Impact Tests

2002 ◽  
Author(s):  
Gery M. Wilkowski ◽  
David L. Rudland ◽  
Yong-Yi Wang ◽  
David Horsley ◽  
Alan Glover ◽  
...  
Keyword(s):  
Steady State ◽  
Ductile Fracture ◽  
Crack Growth ◽  
Fracture Resistance ◽  
Crack Tip ◽  
Opening Angle ◽  
Test Results ◽  
Crack Tip Opening Angle ◽  
Linepipe Steels ◽  
Crack Tip Opening

Large-diameter gas pipelines typically have a design requirement to ensure that the toughness is sufficient to avoid brittle or ductile fractures from occurring. New pipeline design requirements with richer gases, higher-grade steels, higher operating pressures, and in some cases lower operating temperatures require considerable extrapolation of the current ductile fracture design equations. To obtain a better understanding of ductile fracture arrest toughness, TCPL has funded efforts to assess the steady-state fracture toughness from specimens that can be used in mill applications. This paper reviews past efforts to assess the regions of steady-state ductile crack growth in test specimens, as well as current test results from numerous highly instrumented impact specimens. The new test results were for X52, X70, and X80 linepipe steels, whereas the past efforts were from linepipe steels, aerospace materials, as well as ferritic and austenitic nuclear piping steels. All of these results show that there is a limited region over which the steady-state fracture resistance can be determined. The fracture energy associated with steady-state fracture is the total energy minus; (1) the energy associated with initiation of the crack (including indentation energy and global yielding of the specimen), (2) the transient crack growth from initiation to reaching steady-state fracture, and (3) a non-steady-state fracture region at the end of the test record. Instrumented load versus load-line displacement data were linked to high-speed digital video data of the crack growth, crack-tip-opening angle (within 2 mm of the crack tip), and crack-mouth-opening displacement. These data allowed for comparison of J-R curves and crack-tip-opening angle values during crack growth to help determine the regions of steady-state crack growth. The results from these efforts are an important consideration in the development of a single test specimen method that can be used for determining the ductile fracture resistance of high-strength and high-toughness linepipe steels.

An Updated Fracture Resistance Dataset of Pipeline Ductile Fracture Propagation Based on High Speed DWTT Tests

2014 ◽  
Author(s):  
Da-Ming Duan ◽  
James Ferguson ◽  
Joe Zhou ◽  
Mohammed Uddin ◽  
Do-Jun Shim
Keyword(s):  
Fracture Toughness ◽  
Steady State ◽  
Ductile Fracture ◽  
High Speed ◽  
Fracture Propagation ◽  
Gas Pipeline ◽  
Charpy Specimen ◽  
Low Grade ◽  
Speed Dependence ◽  
Fracture Control

One of the major research topics in the area of gas pipeline fracture control is the suitability of using Charpy energy for ductile fracture control for modern and/or high strength line pipes. A common understanding is that, for pipe body crack self-arresting, the deviation of the actual required Charpy energy from those predicted using the traditional procedure of Battelle Two-Curve Method (TCM) is getting larger with higher strength pipes. DWTT is being paid more attention to because of its larger and full thickness specimen that can better capture the fracture process than a Charpy specimen does. Previous work at TransCanada indicated that various fracture speeds can be achieved in DWTT specimens and it is the steady-state fracture speed that is representative to the actual fracture propagation in a gas pipeline. It has also been found that the steady-state fracture toughness, in terms of either fracture energy or CTOA, is fracture speed dependent with lower fracture toughness for higher fracture speeds. Previous analysis also indicated by considering the speed dependent toughness, better predictions can be obtained for both self-arresting fracture toughness requirement and the fracture propagation speed. Previous DWTT fracture toughness data published by the authors exhibited a strong speed dependence and it was demonstrated that if the actual speed dependence is plugged into the modified TCM, both the fracture toughness and fracture speed would be over predicted. The assumption was that the original TCM was calibrated using pipe fracture data that also had speed dependent fracture toughness but the speed dependence was less strong than those for the modern pipes. This paper presents an updated DWTT fracture dataset that expands the previously published data by adding high speed DWTT test results of modern line pipe steels with a range of grades X70-X100 and three old vintage pipe materials that is representative to the pipes that were used for the original TCM testing and calibration. The toughness data for the low grade pipes also shows speed dependence which purports the previous assumption.

Holdup and holdup profiles in the reciprocating plate extractor VPE

1990 ◽  
Vol 55 (11) ◽  
pp. 2648-2661 ◽  
Author(s):  
Helena Sovová ◽  
Vladislav Bízek ◽  
Jaroslav Procházka
Keyword(s):  
Steady State ◽  
Experimental Results ◽  
Model Parameters ◽  
Dispersed Phase ◽  
Pulse Form ◽  
Sieve Plates

In this work measurements of mean holdup of dispersed phase, of axial holdup profiles and of flooding points in a reciprocating plate contactor with both the VPE-type plates and the sieve plates were carried out. The experimental results were compared with a monodisperse model of steady-state column hydrodynamics and the model parameters were evaluated. Important differences in the behaviour of the two plate types could be identified. Comparison was also made between two reciprocating drives of different pulse form.

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