Evaluation of Fracture Toughness by Master Curve Approach Using Miniature C(T) Specimens

2010 ◽  
Author(s):  
Naoki Miura ◽  
Naoki Soneda
Keyword(s):  
Fracture Toughness ◽  
Test Temperature ◽  
Master Curve ◽  
Evaluation Method ◽  
Practical Method ◽  
Reference Temperature ◽  
Surveillance Program ◽  
Astm Standard ◽  
Master Curve Method ◽  
Curve Method

The fracture toughness Master Curve gives a universal relationship between the median of fracture toughness and temperature in the ductile-brittle transition temperature region of ferritic steels such as reactor pressure vessel (RPV) steels. The Master Curve approach specified in the ASTM standard theoretically provides the confidence levels of fracture toughness in consideration of the inherent scatter of fracture toughness. The authors have conducted a series of fracture toughness tests for typical Japanese RPV steels with various specimen sizes and shapes, and ascertained that the Master Curve can be well applied to the specimens with the thickness of 0.4-inches or larger. Considering the possible application of the Master Curve method coexistent with the present surveillance program for operating RPVs, the utilization of miniature specimens which can be taken from broken halves of surveillance specimens is quite important for the efficient determination of the Master Curve from the limited volume of the materials of concern. In this study, fracture toughness tests were conducted for typical Japanese RPV steels, SFVQ1A forging and SQV2A plate materials, using the miniature C(T) specimens with the thickness of 4 mm following the procedure of the ASTM standard. The results showed that the differences in test temperature, evaluation method, and specimen size did not affect the Master Curves, and the fracture toughness indexed by the reference temperature, T0, obtained from miniature C(T) specimens were consistent with those obtained from standard and larger C(T) specimens. It was also found that valid reference temperature can be determined with the realistic number of miniature C(T) specimens, less than ten, if the test temperature was appropriately selected. Thus, the Master Curve method using miniature C(T) specimens could be a practical method to determine the fracture toughness of actual RPV steels.

Evaluation of Fracture Toughness by Master Curve Approach Using Miniature C(T) Specimens

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Naoki Miura ◽  
Naoki Soneda
Keyword(s):  
Fracture Toughness ◽  
Test Temperature ◽  
Master Curve ◽  
Evaluation Method ◽  
Practical Method ◽  
Surveillance Program ◽  
Astm Standard ◽  
Master Curve Method ◽  
Curve Method ◽  
Miniature Specimens

The fracture toughness master curve shows the relationship between the median of fracture toughness and temperature in the ductile–brittle transition temperature region of ferritic steels such as reactor pressure vessel (RPV) steels. The master curve approach specified in the ASTM standard theoretically provides the confidence levels of fracture toughness in consideration with the inherent scatter of fracture toughness. The authors have conducted several fracture toughness tests for typical Japanese RPV steels with various specimen sizes and shapes and ascertained that the master curve can be accurately applied to the specimens with a thickness of 0.4-in. or larger. With respect to using the master curve method with the current surveillance program for operating RPVs, the utilization of miniature specimens is important. Miniature specimens, which can be taken from the broken halves of surveillance specimens, are necessary for the efficient determination of the master curve from the limited volume of the available materials. In this study, fracture toughness tests were conducted for typical Japanese RPV steels, particularly SFVQ1A forged and SQV2A plate materials, using the miniature C(T) specimens with a thickness of 4 mm, following the procedure in the ASTM standard. The results show that the differences in the test temperature, evaluation method, and specimen size did not affect the master curves, and the fracture toughness indexed by the reference temperature, To, obtained from miniature C(T) specimens were consistent with those obtained from the standard and larger C(T) specimens. It was also found that valid reference temperatures can be determined with a realistic number of miniature C(T) specimens, i.e., less than ten, if the test temperature was appropriately selected. Thus, the master curve method using miniature C(T) specimens could be a practical method to determine the fracture toughness of actual RPV steels.

Fracture Toughness Transferability Study Between the Master Curve Method and a Pressure Vessel Nozzle Using Local Approach

2003 ◽  
Author(s):  
Anssi Laukkanen ◽  
Pekka Nevasmaa ◽  
Heikki Keina¨nen ◽  
Kim Wallin
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Structural Integrity ◽  
Reference Temperature ◽  
Cleavage Crack ◽  
Local Approach ◽  
Master Curve Method ◽  
Curve Method ◽  
Constitutive Parameters

Local approach methods are to greater extent used in structural integrity evaluation, in particular with respect to initiation of an unstable cleavage crack. However, local approach methods have had a tendency to be considered as methodologies with ‘qualitative’ potential, rather than quantitative usage in realistic analyses where lengthy and in some cases ambiguous calibration of local approach parameters is not feasible. As such, studies need to be conducted to illustrate the usability of local approach methods in structural integrity analyses and improve upon the transferability of their intrinsic, material like, constitutive parameters. Improvements of this kind can be attained by constructing improved models utilizing state of the art numerical simulation methods and presenting consistent calibration methodologies for the constitutive parameters. The current study investigates the performance of a modified Beremin model by comparing integrity evaluation results of the local approach model to those attained by using the constraint corrected Master Curve methodology. Current investigation applies the Master Curve method in conjunction with the T-stress correction of the reference temperature and a modified Beremin model to an assessment of a three-dimensional pressure vessel nozzle in a spherical vessel end. The material information for the study is extracted from the ‘Euro-Curve’ ductile to brittle transition region fracture toughness round robin test program. The experimental results are used to determine the Master Curve reference temperature and calibrate local approach parameters. The values are then used to determine the cumulative failure probability of cleavage crack initiation in the model structure. The results illustrate that the Master Curve results with the constraint correction are to some extent more conservative than the results attained using local approach. The used methodologies support each other and indicate that with the applied local approach and Master Curve procedures reliable estimates of structural integrity can be attained for complex material behavior and structural geometries.

Investigation of Mechanical Properties and Ductile-Brittle Transition Behaviors of SA738Gr.B Steel Used as Reactor Containment

2019 ◽  
Vol 795 ◽  
pp. 66-73
Author(s):  
Ya Lin Zhang ◽  
Hu Hui
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Steel Plate ◽  
Reference Temperature ◽  
Impact Performance ◽  
Brittle Transition ◽  
Containment Vessel ◽  
Master Curve Method ◽  
Nuclear Containment ◽  
Curve Method

The low temperature tensile properties, Charpy-V notch impact performance and fracture toughness of SA738Gr.B steel plate for domestic CAP1400 containment vessel were tested. On this basis, the reference temperature T0 of the master curve method was obtained. The fracture toughness distribution of the steel in the whole ductile-brittle transition zone is predicted and its applicability is verified by the theoretical basis of the master curve method. The results show that the reference temperature of SA738Gr.B steel master curve method is-123.6 °C. The master curve method is appropriate for SA738Gr.B steel with domestic nuclear containment vessel.

Correlations Between Charpy V-Notch Impact Energy and Fracture Toughness of Nuclear Reactor Pressure Vessel (RPV) Steels

2015 ◽  
Author(s):  
Meifang Yu ◽  
Zhen Luo ◽  
Y. J. Chao
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Test Data ◽  
Impact Energy ◽  
Master Curve ◽  
Reference Temperature ◽  
Master Curve Method ◽  
Curve Method ◽  
Reactor Pressure ◽  
Actual Test

Both Charpy V-notch (CVN) impact energy and fracture toughness are parameters reflecting toughness of the material. Charpy tests are however easy to perform compared to standard fracture toughness tests, especially when the material is irradiated and quantity is limited. Correlations between the two parameters are therefore of great significance, especially for reactor pressure vessel (RPV) structural integrity assessment. In this paper, correlations between CVN impact energy and fracture toughness of three commonly used RPV steels, namely Chinese A508-3 steel, USA A533B steel, Euro 20MnMoNi55 steel, are investigated with two methods. One method applies a direct conversion using empirical formulas and the other adopts the Master Curve method. It is found that when the empirical formula is used, the difference between the predicted fracture toughness (from the CVN impact energy) and actual test data is relatively small in upper shelf, lower shelf and the bottom of transition region, while relatively large in other parts of the transition region. When the Master Curve method is adopted, whether the reference temperature T0 is estimated through temperature at 28J or 41J CVN impact energy, the predicted fracture toughness values of the three steels are consistent with actual test data. The reference temperature T0 is also estimated through the IGC-parameter correlation and through a combination of empirical formula and multi-temperature method. Both procedures show excellent agreement with test results. The mean value of T0 estimated from T28J, T41J, IGC-parameters and the combination method is denoted by TQ-ave and is then used as the final reference temperature T0 for the Master Curve determination. Accuracy of TQ-ave (and therefore the Master Curve method) is demonstrated by comparison with actual test data of the three RPV steels. It is concluded that Master Curve method provides a reliable procedure for predicting fracture toughness in the transition region utilizing limited CVN impact energy data from open literature.

A Round Robin Program of Master Curve Evaluation Using Miniature C(T) Specimens: First Round Robin Test on Uniform Specimens of Reactor Pressure Vessel Material

2012 ◽  
Author(s):  
Masato Yamamoto ◽  
Akihiko Kimura ◽  
Kunio Onizawa ◽  
Kentaro Yoshimoto ◽  
Takuya Ogawa ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Evaluation Method ◽  
Round Robin ◽  
Machining Process ◽  
Reference Temperature ◽  
Surveillance Program ◽  
Test Technique ◽  
Actual Application ◽  
The Difference

Reference temperature evaluation method by Master Curve approach for the fracture toughness evaluation had been standardized recently in Japan, and expected to be a powerful tool to ensure the reliability of long term used RPV steels. In order to get sufficient number of data for the Master curve approach coexistent with the present surveillance program for RPVs, the utilization of miniature specimens, which can be taken from broken halves of surveillance Charpy specimens, is important. CRIEPI had developed the test technique for the miniature C(T) specimens (Mini-CT), whose dimensions are 4 × 10 × 10 mm, and verified the basic applicability of Master Curve approach by means of Mini-CT for the determination of fracture toughness of typical Japanese RPV steels. A round robin program is organized with the participation of Japanese academia, industries and a government institute. The program aims to verify the reliability and robustness of experimental data of Mini-CT, and to pick out further investigation items to be solved before the actual application of the technique. As the first step of this program, four institutes separately carried out a series of Master Curve evaluation in conformity to ASTM E1921-10e1 by means of Mini-CT specimens, whose material (Japanese RPV material, SFVQ1A), machining process and pre-cracking process are in common in all the specimens. Valid reference temperature T0 could be successfully obtained in all of the institutes by means of Mini-CT specimen. However, the value, T0, have large difference with maximum of 34 °C among the institutes. The difference shows strong correlation with the difference in loading rate, which is selected by each organization to be meet the testing standard ASTM E1921-10e1.

Applicability of Master Curve Method to Japanese Reactor Pressure Vessel Steels

2006 ◽  
Author(s):  
Naoki Miura ◽  
Naoki Soneda ◽  
Taku Arai ◽  
Kenji Dohi
Keyword(s):  
Fracture Toughness ◽  
Test Temperature ◽  
Pressure Vessel ◽  
Master Curve ◽  
Loading Rate ◽  
Specimen Size ◽  
Master Curves ◽  
Master Curve Method ◽  
Curve Method ◽  
Reactor Pressure

The Master Curve method has been proposed and recognized worldwide as an alternative approach to evaluate fracture toughness of reactor pressure vessel (RPV) steels in brittle-to-ductile transition temperature range. This method theoretically provides the confidence levels of fracture toughness in consideration of the statistical distribution, which is an inherent property of fracture toughness. In this study, a series of fracture toughness tests was conducted for typical Japanese RPV steels, SFVQ1A and SQV2A, to identify the effects of test temperature, specimen size, and loading rate, and the applicability of the Master Curve method was experimentally validated. The differences in test temperature and specimen size did not affect master curves. In contrast, increasing loading rate significantly shifted master curves to higher temperatures. The lower bound curve based on the master curve could conservatively envelop all of the experimental fracture toughness data. The present rule, in which the lower limit of fracture toughness is indirectly determined by Charpy impact test results, can be too conservative, while the application of the Master Curve method may significantly reduce the conservativity of the allowable level of fracture toughness.

scholarly journals Master Curve Fracture Toughness Characterization of Eurofer97 Using Miniature Multi-Notch Bend Bar Specimens for Fusion Applications

2018 ◽  
Author(s):  
Xiang Chen ◽  
Mikhail A. Sokolov ◽  
Yutai Katoh ◽  
Michael Rieth ◽  
Logan N. Clowers
Keyword(s):  
Fracture Toughness ◽  
Power Plants ◽  
Master Curve ◽  
Reference Temperature ◽  
Irradiation Damage ◽  
First Wall ◽  
Irradiation Embrittlement ◽  
Master Curve Method ◽  
Fusion Applications ◽  
Curve Method

Eurofer97 is one of leading candidates of reduced activation ferritic martensitic (RAFM) steels for first wall structural materials of early demonstration fusion power plants. During fusion plant operation, high neutron irradiation damage on first wall materials can cause irradiation embrittlement and reduce the fracture toughness of RAFM steels. Therefore, it is critical to select proper testing techniques to characterize the fracture toughness of RAFM steels with high fidelity. In this manuscript, we present the feasibility study of using pre-cracked miniature multi-notch bend bar specimens (M4CVN) with a dimension of 45mm (length) × 3.3mm (width) × 1.65mm (thickness) to characterize the transition fracture toughness of Eurofer97 steel based on the ASTM E1921 Master Curve method. The testing yielded a provisional Master Curve reference temperature ToQ of −89°C of unirradiated Eurofer97 steel heat J362A in the normalized and tempered condition. The results are within the normal scatter range of Master Curve reference temperature T0 for Eurofer97 steel, indicating suitability of applying M4CVN specimens for characterizing the transition fracture toughness of Eurofer97 steel.

Fracture Toughness Estimation of Miniature Specimens by Considering Geometry Effects

2010 ◽  
Author(s):  
Shin-Beom Choi ◽  
Young-Jin Kim ◽  
Yoon-Suk Chang
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Context Effects ◽  
Equivalent Stress ◽  
Scale Factor ◽  
Surveillance Program ◽  
Master Curve Method ◽  
Curve Method ◽  
Geometry Effects ◽  
Miniature Specimens

Since small-sized specimens are widely used for fracture toughness tests to assure safety of a reactor pressure vessel in service, as a part of surveillance program, various geometry parameters affecting on the stress level near the crack-tip should be investigated for realistic assessment of cleavage fracture behavior. The aim of the present paper is to improve the current master curve method for typical miniature specimens, especially pre-cracked Charpy V-notched (PCVN) specimens. In this context, effects of thickness and side-grooves were quantified from comparing finite element (FE) analyses results in use of various PCVN specimens with and without side-grooves. Then, a scale factor to deal with geometry effects was suggested by employing the fracture toughness diagram, which was derived from FE analyses data of compact tension specimens and PCVN specimens. The scale factor was applied to calculate equivalent stress intensity factors influencing on the reference temperature embodied in the master curve method. The approach proposed in this paper will be useful to estimate fracture toughness of PCVN specimen made of SA508 carbon steel.

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