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

2019 ◽  
Author(s):  
Xiang Chen ◽  
Mikhail A. Sokolov ◽  
Arunodaya Bhattacharya ◽  
Logan N. Clowers ◽  
Tim Graening ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Cumulative Probability ◽  
Fracture Toughness Testing ◽  
Master Curve Method ◽  
Fusion Applications ◽  
Curve Method ◽  
Toughness Testing ◽  
Reasonable Prediction

Abstract In this study, we performed fracture toughness testing of ten Eurofer97 steel variants using precracked miniature multi-notch bend bar (M4CVN) specimens based on the Master Curve method in the ASTM E1921 standard. Additional Vickers microhardness and room temperature tensile testing complemented the fracture toughness testing. Compared with standard Eurofer97, the ten variants didn’t show a comprehensive improvement of mechanical properties. The Master Curve method was found to yield a reasonable prediction of fracture toughness results obtained from M4CVN specimens with most valid fracture toughness data within the 2% and 98% tolerance boundaries of the Master Curve. The three-parameter Weibull distribution with Weibull exponent b = 4 also yielded excellent prediction of the relationship between fracture toughness results KJc and the cumulative probability for failure pf for one steel variant.

Fracture Toughness Testing Using Non-Standard PCVN Specimens: Experiments and Specimen Geometry Effects on T0 Reference Temperature

2018 ◽  
Author(s):  
Vitor Scarabeli Barbosa ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Master Curve ◽  
High Strength ◽  
Potential Effect ◽  
Reference Temperature ◽  
Fracture Toughness Testing ◽  
Toughness Testing ◽  
Additional Support

This work addresses an experimental investigation on the cleavage fracture behavior of a high strength, low alloy structural steel using non-standard PCVN specimens. The primary purpose is to investigate the effects of increased specimen span on experimentally measured fracture toughness values and implications for the characterization of the temperature dependence of toughness based on the Master Curve methodology. Fracture toughness testing conducted on various PCVN geometries with increased specimen span extracted from an A572 Grade 50 steel plate provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc. The experimental results show a potential effect of specimen span on Jc-values which can help mitigating the effects of constraint loss often observed in smaller fracture specimens. An exploratory application to determine the reference temperature, T0, derived from the Master Curve methodology also provides additional support for using non-standard bend specimens in routine fracture applications.

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.

scholarly journals Post-Irradiation Evaluation of Eurofer97 Fracture Toughness Using Miniature Multinotch Bend Bar Specimens

2020 ◽  
Author(s):  
Xiang Chen ◽  
Logan A. Clowers ◽  
Tim Graening ◽  
Arunodaya Bhattacharya ◽  
Anne A. Campbell ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Vickers Microhardness ◽  
National Laboratory ◽  
Irradiation Temperature ◽  
Irradiation Hardening ◽  
Oak Ridge ◽  
Master Curve Method ◽  
Curve Method

Abstract In this study, we performed fracture toughness characterization of ten neutron-irradiated Eurofer97 variants using precracked miniature multi-notch bend bar (M4CVN) specimens based on the Master Curve method in the ASTM E1921 standard. The neutron irradiation was performed in the flux trap position of the High Flux Isotope Reactor (HFIR) of the Oak Ridge National Laboratory (ORNL) with the nominal irradiation temperature of 300°C and irradiation dose of 2.5 displacements per atom (dpa). Depending on the irradiation temperature and materials, we observed different degrees of irradiation hardening and embrittlement for ten Eurofer97 variants. The upper shift in the Master Curve reference temperature T0Q vs. the increase in Vickers microhardness values showed a liner relationship for only a few materials indicating different irradiation responses of the Eurofer97 variants.

Prediction of Fracture Toughness for WWER RPV Integrity Assessment on the Basis of the Unified Curve Approach and Surveillance Specimens Testing

2009 ◽  
Author(s):  
Boris Margolin ◽  
Victoria Shvetsova ◽  
Alexander Gulenko ◽  
Valentin Fomenko
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Present Report ◽  
Temperature Shift ◽  
Curve Shape ◽  
Integrity Assessment ◽  
Master Curve Method ◽  
Curve Method ◽  
Unified Curve ◽  
Surveillance Specimens

For construction of the fracture toughness temperature curve that may be used for WWER RPV integrity assessment on the basis of tests of cracked surveillance specimens, the issues have to be solved as follows. First of all, it is important to determine how fracture toughness varies as a function of temperature, and how the fracture toughness vs. temperature dependence, KJC(T), changes with in-service material degradation due to neutron irradiation. These variations of KJC(T) curve are known to be the shift of KJC(T) curve to higher temperature range and change in the KJC(T) curve shape. At present, two advanced engineering methods are known that allow the prediction of KJC(T) curve on the basis of small-size fracture toughness specimens (for example, pre-cracked Charpy specimens), namely, the Master Curve and the Unified Curve methods. Procedures of test result treatment for the Master Curve and the Unified Curve are very similar. The Master Curve method uses the lateral temperature shift condition and, therefore, does not describe possible change in the KJC(T) curve shape. The Unified Curve method has an advantage as compared with the Master Curve as the Unified Curve describes a variation of the KJC(T) curve shape when degree of embrittlement increases. This advantage becomes important for RPV integrity assessment when the reference KJC(T) curve is recalculated to the crack front length of the postulated flaw that is considerable larger than thickness of surveillance specimens. Application of the KJC(T) curve determined from test results of cracked surveillance specimens to RPV integrity assessment requires also to introduce some margins. These margins have to take into account the type and number of tested specimens and the uncertainty connected with spatial non-homogeneity of RPV materials. Indeed, there is sufficient number of experimental data showing variability in fracture toughness for various parts of RPV. Therefore, situation is possible when the material properties near the postulated flaw will be worse than the properties of surveillance specimens. In the present report, advanced approaches are considered for prediction of fracture toughness for WWER RPV integrity assessment that allow one: • to construct the KJC(T) curve for irradiated RPV steels with any degree of embrittlement; • to provide transferability of fracture toughness data from cracked surveillance specimens to calculation of resistance to brittle fracture of RPV with a postulated flaw.

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.

Influence of Microstructural Variation in Thick Section Steels on the Characterisation of Fracture Toughness Using Sub-Size Specimens

2019 ◽  
Author(s):  
Philippa Moore ◽  
Borislava Yordanova ◽  
Yong Lu ◽  
Yin Jin Janin
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Plate Thickness ◽  
High Strength ◽  
Steel Plates ◽  
Full Thickness ◽  
Master Curve Method ◽  
Sampling Locations ◽  
Curve Method ◽  
Thick Material

Abstract The challenges of performing full-thickness fracture toughness tests on steel plates of 100mm thickness and greater means that the use of sub-size specimens is desirable. In this work, 100mm thick parent plate of S690 high strength steel was characterised using SENB fracture toughness specimens with thickness of 12mm, 25mm, 50mm and 100mm. Sub-size specimens were extracted at two different locations through the plate thickness; mid-wall and quarter wall. Sufficient specimens were tested to apply the Master Curve method in ASTM E1921 to predict the behaviour of 100mm thick material from each set of sub-size specimens. The through-thickness microstructural variation in these heavy-wall steel plates meant that significantly different predictions of full-thickness fracture toughness were obtained from the two sampling locations. However, when sampled from the mid-wall location, sub-size specimens down to 25mm thick were able to conservatively predict full-thickness fracture toughness using Master Curve methods.

Adjustments to Master Curve Methodology and Development of Fracture Toughness Estimation

2011 ◽  
Author(s):  
R. S. Kulka
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Driving Force ◽  
Master Curve ◽  
Structural Components ◽  
Fracture Test ◽  
Element Analysis ◽  
Master Curve Method ◽  
Curve Method ◽  
Constraint Effects

In conventional fracture mechanics assessments, there is often an inadequate treatment of in-plane constraint effects on the apparent toughness of structural components, leading to significant conservatism. Modifications to the Master Curve method, to account for these effects, have previously been suggested. A study of these proposed modifications has identified that less conservative toughness estimates could be made from the analysis of fracture mechanics test specimens. An approach has been developed for allowing a comparison of a variation of fracture toughness values throughout a component, to a variation of the localised effective driving force. Cracked-body finite element analysis has been used to assess fracture test specimens with varying levels of in-plane constraint, to provide fracture mechanics data for use with the approach that has been developed.

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.

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