scholarly journals An Interim Approach to Determine Dynamic Ductile Fracture Resistance of Modern High Toughness Pipeline Steels

2000 ◽  
Author(s):  
N. Pussegoda ◽  
L. Malik ◽  
A. Dinovitzer ◽  
B. A. Graville ◽  
A. B. Rothwell
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Total Energy ◽  
Ductile Fracture ◽  
Initiation Toughness ◽  
Low Carbon ◽  
Initial Portion ◽  
High Toughness ◽  
Test Parameters ◽  
Ductile Fracture Toughness

The ductile fracture toughness of steel is used to assess the ability of a pipeline to resist long running ductile fractures in a burst event. In modern low carbon clean steels with high toughness, conventional measures of ductile fracture toughness (standard Charpy and DWTT energy) are under review, and alternatives are being studied. The major factor causing concern is the inability of these tests to isolate the energy associated with crack propagation from the total energy absorbed during the specimen fracture. This is significant in modern high toughness steels because their initiation toughness is extremely high. To resolve crack propagation energy, a novel modification was evaluated for both Charpy and DWTT specimens by employing a back-slot including a snug fitting shim to replace the removed material. In most cases, this modification was effective in curtailing the load-displacement trace when the propagating crack interacted with the slot on the backside of the specimen, without affecting the initial portion of the trace; this allowed crack propagation energies to be resolved. The propagation energy determined by this method is compared with the total energy and conventional test parameters. The crack propagation energy values inferred based on this should be validated, in future burst test.

scholarly journals Review of CTOA as a Measure of Ductile Fracture Toughness

2000 ◽  
Author(s):  
L. N. Pussegoda ◽  
S. Verbit ◽  
A. Dinovitzer ◽  
W. Tyson ◽  
A. Glover ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Ductile Fracture ◽  
Pipeline Steel ◽  
Opening Angle ◽  
Low Carbon ◽  
Pipeline Steels ◽  
Crack Tip Opening Angle ◽  
Ductile Fracture Toughness ◽  
Crack Tip Opening

The ductile fracture toughness of steel is used to assess the ability of a pipeline to resist long running ductile fractures in a burst event. With the introduction of modern low carbon clean steels with ultra high toughness, conventional measures of ductile fracture toughness (standard Charpy and DWTT energy) are under review, and alternatives are being studied. The crack tip opening angle (CTOA) was investigated to evaluate its appropriateness as a measure of modern pipeline steel ductile fracture toughness. At first, fracture mechanics tests at quasi-static rate were analyzed to examine the constancy of CTOA with crack growth. The results of this initial review are based on four pipeline steels with a range of ductile fracture toughness. The CTOA values are also compared with appropriate parameters from conventional tests to examine potential relationships that may be used to indicate the relative resistance of pipeline steels to ductile fracture propagation. The final objective is to compare CTOA values determined by the simple two specimen method and those developed through a formal fracture mechanics based technique.

Effect of inclusion density on ductile fracture toughness and roughness

2014 ◽  
Vol 63 ◽  
pp. 62-79 ◽  
Author(s):  
A. Srivastava ◽  
L. Ponson ◽  
S. Osovski ◽  
E. Bouchaud ◽  
V. Tvergaard ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Ductile Fracture ◽  
Ductile Fracture Toughness

About Relation Between Irradiation Hardening of Ferritic Steels and Ductile Fracture Toughness Decrease

2009 ◽  
Author(s):  
Jiri Novak
Keyword(s):  
Fracture Toughness ◽  
Temperature Dependence ◽  
Ductile Fracture ◽  
Stress Level ◽  
Deformation Theory ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Irradiation Hardening ◽  
Ductile Fracture Toughness

We showed recently that temperature dependence of the ductile fracture toughness can be predicted on the base of two assumptions: 1) assumption of constant characteristic length, 2) assumption of proportionality between J-R curve slope and deformation work in unit volume, evaluated from zero to critical strain for initiation of deformation bands determined in plane strain geometry for material modeled by deformation theory of plasticity. Temperature dependence of ductile fracture toughness results simply from temperature dependence of the stress-strain curve. Irradiation hardening changes stress-strain behavior in a qualitatively different way: It is observed that irradiation hardening to certain yield stress level changes the stress-strain curve of the material in the same way as prestraining of the unirradiated material to the same flow stress level does. Equivalence of irradiation and prestraining concerns all key properties of deformation theory; namely the secant modulus should be taken from the stress-strain curve of unirradiated material. With exception of this specific feature, the task of finding relative fracture toughness decrease by irradiation is the same as prediction of relative decrease of fracture toughness by temperature change. In the frame of the corresponding theory, relative decrease of ductile fracture toughness expressed by J-R curve slope can be obtained from the stress-strain curve of unirradiated material and irradiation hardening level. Quantitative results are presented for the weld metals 72W and 73W, studied in the Fifth Irradiation Series in the Heavy-Section Steel Irradiation Program, and compared with experimental data.

A Procedure for the Determination of Ductile Fracture Toughness Values Using J Integral Techniques

1979 ◽  
Vol 7 (1) ◽  
pp. 49 ◽  
Author(s):  
RT Horstman ◽  
KC Lieb ◽  
RL Meltzer ◽  
MB Vieth ◽  
GA Clarke ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Ductile Fracture ◽  
J Integral ◽  
Ductile Fracture Toughness

Establishment of Unified Correlation of In-Plane and Out-of-Plane Constraints with Ductile Fracture Toughness of Steel

2016 ◽  
Vol 853 ◽  
pp. 22-27 ◽  
Author(s):  
Bo Rui Yan ◽  
G.Z. Wang ◽  
Fu Zhen Xuan ◽  
Shan Tung Tu
Keyword(s):  
Fracture Toughness ◽  
Ductile Fracture ◽  
Structural Integrity ◽  
Damage Model ◽  
Equivalent Plastic Strain ◽  
Specimen Thickness ◽  
Wide Range ◽  
Out Of Plane ◽  
Correlation Line ◽  
Ductile Fracture Toughness

In this paper, the finite element method (FEM) based on GTN damage model was used to obtain ductile fracture toughness and investigate the establishment method of unified correlation of in-plane and out-of-plane constraints with ductile fracture toughness of steels. The unified constraint parameter Ap at different equivalent plastic strain (εp) isolines has been calculated and analyzed for SEN(B) specimens with a wide range of in-plane and out-of-plane constraints. The results show that the average Ap along the specimen thickness (Apave) can well characterize a wide range of in-plane and out-of-plane constraints. The suitable εpisolines range for establishing the unified correlation between Apave and ductile fracture toughness of the steel has been obtained. For the specimens with lower constraint, the higher εp values should be used. The results also show that the correlation line of JC/Jref-Apave1/2is independent of the selections of the suitable εp isolines and the reference specimen. This may bring convenience for the establishment and application of the JC/Jref-Apave1/2correlation lines. Using ductile fracture toughness data of a small number of specimens with different constraints (such as three specimens with different a/W) together with FEM calculations of the parameter Ap, the correlation line of JC/Jref-Apave1/2can be established. The correlation line may be used in structural integrity assessments incorporating both in-plane and out-of-plane constraints.

Fracture Toughness of Aged Stainless Steel Primary Piping and Reactor Vessel Materials

1987 ◽  
Vol 109 (4) ◽  
pp. 440-448 ◽  
Author(s):  
W. J. Mills
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Ductile Fracture ◽  
Thermal Aging ◽  
Fracture Resistance ◽  
Reactor Vessel ◽  
Initiation Toughness ◽  
Second Phase ◽  
Premature Failure ◽  
Fracture Properties

The ductile fracture toughness behavior of FFTF primary piping and reactor vessel construction materials was characterized using the multiple-specimen JR-curve technique before and after 10,000-hr thermal aging treatments. The test materials included Types 304 and 316 stainless steel (SS) and Types 308 and 16–8–2 SS welds. In the unaged condition, these alloys exhibited very high Jc initiation toughness and tearing modulus values at elevated temperatures (427–538°C). The fracture resistance for the 316 SS piping was found to be dependent on orientation; Jc values for the axial (C–L) direction were 60 to 70 percent lower than those for the circumferential (L–C) orientation. The lower fracture properties in the C–L orientation resulted from premature failure of stringers aligned in the axial direction. Thermal aging at 427° C caused no degradation in fracture resistance, while 482 and 566° C agings resulted in a modest 10 to 20 percent reduction in Jc for both base and weld metals. Residual toughness levels after aging are adequate for precluding any possibility of nonductile fracture. Hence, conventional stress and strain limits, such as those provided by the ASME Code, are sufficient to guard against ductile fracture for SS components that have accumulated 10,000-hr exposures at or below 566° C. Metallographic and fractographic examinations revealed that the degradation in fracture properties was associated with aging-induced second-phase precipitation.

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