Overview of NESC-IV Cruciform Specimen Test Results

2002 ◽  
Author(s):  
N. Taylor ◽  
R. Bass
Keyword(s):  
Pressure Vessel ◽  
Best Practice ◽  
Biaxial Loading ◽  
Production Quality ◽  
Standard Test ◽  
Reactor Pressure Vessel ◽  
Test Analysis ◽  
Post Test ◽  
Specimen Test ◽  
Reactor Pressure

NESC-IV is an experimental/analytical program to develop validated analysis methods for transferring fracture toughness data generated on standard test specimens to shallow flaws in reactor pressure vessel welds subject to biaxial loading in the lower-transition temperature region. It is the fourth major project of the Network for Evaluating Structural Components (NESC). The testing program has exploited material removed from a production-quality reactor pressure vessel. In Part A six clad cruciform specimens containing shallow surface-breaking flaws located in weld material were successfully tested. For Part B a further four beam tests were performed using an innovative test piece design with a simulated embedded flaw. Post-test analysis is now in progress. The implications for current best-practice procedures for evaluation of RPV shallow are also being considered.

Fracture Analysis of Surface-Breaking Shallow Flaw Behaviour in the NESC-IV Bend Beam Tests

2004 ◽  
Author(s):  
N. Taylor ◽  
I. Sattari-Far ◽  
D. Siegele ◽  
I. Varfolomeyev ◽  
L. Stumpfrock
Keyword(s):  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Biaxial Loading ◽  
Production Quality ◽  
Standard Test ◽  
Reactor Pressure Vessel ◽  
Weld Material ◽  
Post Test ◽  
Analytical Program ◽  
Reactor Pressure

NESC-IV is an experimental/analytical program to develop validated analysis methods for transferring fracture toughness data generated on standard test specimens to shallow flaws in reactor pressure vessel welds subject to biaxial loading in the lower-transition temperature region. The testing program exploited material from a production-quality reactor pressure vessel. In Part A six clad cruciform specimens containing shallow surface-breaking flaws located in weld material were successfully tested. Post-test fracture mechanics analyses have been conducted by several organizations to determine fracture mechanics parameters such as K, J, Q and T at the flaws. These have been used to interpret the results with respect to the Master Curve, giving particular attention to constraint aspects.

Use of Master Curve Technology for Assessing Shallow Flaws in a Reactor Pressure Vessel Material

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
N. Taylor ◽  
P. Minnebo ◽  
B. R. Bass ◽  
D. Siegele ◽  
K. Wallin ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Master Curve ◽  
Biaxial Loading ◽  
Production Quality ◽  
Pressure Vessels ◽  
Reactor Pressure Vessel ◽  
Test Pieces ◽  
Fracture Tests ◽  
Vessel Material ◽  
Reactor Pressure

In the NESC-IV project, an experimental/analytical program was performed to develop validated analysis methods for transferring fracture toughness data to shallow flaws in reactor pressure vessels subject to biaxial loading in the lower-transition temperature region. Within this scope, an extensive range of fracture tests was performed on material removed from a production-quality reactor pressure vessel. The master curve analysis of these data is reported and its application to the assessment of the project feature tests on large beam test pieces is discussed.

Use of Master Curve Technology for Assessing Shallow Flaws in a Reactor Pressure Vessel Material

2006 ◽  
Author(s):  
N. Taylor ◽  
P. Minnebo ◽  
R. B. Bass ◽  
D. Siegele ◽  
K. Wallin ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Master Curve ◽  
Biaxial Loading ◽  
Production Quality ◽  
Pressure Vessels ◽  
Reactor Pressure Vessel ◽  
Test Pieces ◽  
Fracture Tests ◽  
Vessel Material ◽  
Reactor Pressure

In the NESC-IV project an experimental/analytical program was performed to develop validated analysis methods for transferring fracture toughness data to shallow flaws in reactor pressure vessels subject to biaxial loading in the lower-transition temperature region. Within this scope an extensive range of fracture tests was performed on material removed from a production-quality reactor pressure vessel. The Master Curve analysis of this data is reported and its application to the assessment of the project feature tests on large beam test pieces.

Microstructural Banding and Biaxial Fracture Toughness Tests in a Specially Heat-Treated Reactor Pressure Vessel Steel

2004 ◽  
Author(s):  
Randy K. Nanstad ◽  
Mikhail A. Sokolov ◽  
Philip J. Maziasz
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Biaxial Loading ◽  
Reactor Pressure Vessel ◽  
Biaxial Test ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Oak Ridge ◽  
Heat Treated ◽  
Reactor Pressure

The Heavy-Section Steel Technology (HSST) Program at Oak Ridge National Laboratory (ORNL) includes a task to investigate the effects of constraint on the cleavage initiation fracture toughness of reactor pressure vessel (RPV) steels in the lower transition temperature region using relatively large cruciform fracture toughness specimens under varying degrees of biaxial loading. One of the materials used for the project was a plate of A533 grade B steel (HSST Plate 14A) which was specially heat treated to result in a yield strength comparable to that of a radiation-sensitive RPV steel near the end of design life. During the testing phase to characterize the fracture toughness behavior of the plate with uniaxial three-point bend specimens, some relatively low fracture toughness values were observed. Subsequent metallography revealed the presence of varying degrees of dark bands in the microstructure. These observations prompted an investigation of the relationship between the experimentally determined fracture toughness results and the microstructure of the plate steel used for the biaxial-loading effects project, especially with regard to the results obtained from the biaxial test specimens. The primary issue in the investigation is whether the fracture toughness results obtained from the biaxially loaded specimens were influenced by the steel microstructure in a biased manner, i.e., were the observation regarding effects of biaxial loading on fracture toughness significantly affected by the microstructural segregation in heat treated HSST Plate 14A. A secondary issue is whether segregated microstructures are common in steels used for RPV construction and if the current procedures for evaluating fracture toughness of RPV steels adequately account for such microstructures. Various metallurgical tools, including metallography, microhardness testing, scanning electron fractography, electron microprobe analysis, and analytical electron microscopy were used to characterize the nature of the bands and evaluate the potential effects on the fracture toughness results.

An Investigation of Cladding Effects on Shallow-Flaw Fracture Toughness of Reactor Pressure Vessel Steel Under Prototypic Biaxial Loading

1999 ◽  
Vol 121 (3) ◽  
pp. 257-268 ◽  
Author(s):  
B. R. Bass ◽  
W. J. McAfee ◽  
J. W. Bryson ◽  
W. E. Pennell
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Biaxial Loading ◽  
Reactor Pressure Vessel ◽  
Biaxial Stress ◽  
Pressure Vessel Steel ◽  
Test Results ◽  
Vessel Steel ◽  
Nonlinear Stress ◽  
Reactor Pressure

Potential structural-integrity benefits or liabilities of the stainless steel cladding on the inner surface of a reactor pressure vessel (RPV) are important considerations in the effort to refine or improve safety assessment procedures applied to RPVs. Clad-beam tests were carried out to investigate and quantify effects of the clad structure on fracture initiation toughness of through-clad shallow surface flaws in RPV material. A cruciform beam specimen was developed at ORNL to introduce a prototypic, far-field, out-of-plane biaxial stress component that provides a linear approximation of the nonlinear stress distribution generated by thermo-mechanical loading transients in an RPV. The cruciform specimens (102-mm-thick test section) were fabricated from RPV shell segments available from a canceled pressurized-water reactor plant. The specimens were tested under biaxial load ratios ranging from 0.0 (uniaxial) to 1.0 (full biaxial), the ratio being defined as the total load applied to the transverse beam arms divided by that applied to the longitudinal arms. The test results imply that biaxial loading is effective in reducing the shallow-flaw fracture toughness of the clad/heat-affected zone/structural-weld region of the RPV shell below that determined from uniaxial loading conditions. The lowest toughness value from the clad cruciform specimens tested under biaxial loading is only slightly above the ASME Section XI KIc curve. For all biaxiality ratios, the test results imply that shallow-flaw fracture toughness data from the RPV structural weld material are significantly lower than that obtained from a high-yield strength plate material.

Models of the Temperature Dependence and Scatter in J-R and J0.1 for Ferritic Reactor Pressure Vessel Steels

2015 ◽  
Author(s):  
Mark Kirk ◽  
Marjorie Erickson ◽  
Gary Stevens
Keyword(s):  
Fracture Toughness ◽  
Temperature Dependence ◽  
Pressure Vessel ◽  
Standard Test ◽  
Reactor Pressure Vessel ◽  
Test Method ◽  
Confidence Bounds ◽  
The Mean ◽  
Reactor Pressure ◽  
Curve Index

At the 2014 ASME Pressure Vessel and Piping Conference, these authors and others presented a paper that drew together a number of models describing the fracture toughness of ferritic reactor pressure vessel (RPV) steels. That paper summarized models of both the temperature dependence and scatter in a number of fracture toughness metrics (i.e., KJc, KIa, JIc, and J0.1). That paper also provided equations that quantify the interrelationships between these toughness metrics, and how these interrelationships are affected by hardening. Significantly, all of these models and interrelationships are linked via a single parameter: the Master Curve index temperature, To, which can be measured as described in ASTM Standard Test Method E1921. Work is currently underway within the ASME Section XI Working Group on Flaw Evaluation (WGFE) to develop a revision to Code Case N-830 that incorporates all of these models, and provides information on how to apply them in a flaw evaluation. As part of that work, an effort was initiated to augment these models by the addition of a model that can be used to predict the temperature variation of, and the scatter in, J-R curve behavior. A J-R curve model is also expected to support on-going WGFE efforts to in development of acceptance criteria for flaws in ferritic components operating in the upper shelf temperature range. The work presented in this paper provides a model of the J-R behavior of ferritic RPV steels. When combined with other fracture toughness models to be published in Code Case N-830-1, this model allows prediction of the mean J-R curve, confidence bounds on the mean, and the temperature dependence of J-R all based only on input of To. The J-R model described herein has equivalent or better accuracy to other models described in the literature, and generally has fewer fitting parameters than those other models. Because the full J-R curve is predicted, this model is also useful for prediction of J0.1.

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