Application of Local Approach Concept of Cleavage Fracture to VVER Materials

2002 ◽  
Author(s):  
B. Z. Margolin ◽  
G. P. Karzov ◽  
V. A. Shvetsova ◽  
E. Keim ◽  
R. Chaouadi
Keyword(s):  
Cleavage Fracture ◽  
Master Curve ◽  
Future Application ◽  
Surveillance Program ◽  
Model Parameters ◽  
Local Approach ◽  
Initial State ◽  
Master Curve Method ◽  
Rpv Steel ◽  
Curve Method

The Prometey local approach of cleavage fracture has been applied within the TACIS R2.06/96 project: “Surveillance Program for VVER 1000 Reactors”, sponsored by the European Commission. The main tasks are: • perform special experiments on smooth cylindrical and pre-cracked Charpy (PCC) specimens for VVER 1000 RPV material in initial, embrittled and irradiated state; • perform fracture toughness tests on 2T-CT specimens for RPV steel in initial and embrittled state; • predict the KJC(T) curves by this model; • compare the calculated and experimental results with the Master Curve results. The local approach of cleavage fracture is applied to predict KJC(T) curves in the transition regime of RPV materials in the initial state, embrittled by thermal heat treatment and irradiated, samples in the latter cases taken from surveillance capsules of a VVER 1000 NPP. The test data of large fracture mechanics specimens (2T-CT) could be well described over a wide temperature range for the initial state and the embrittled material, when the test results of PCC specimens at one temperature are used for the calibration of the model parameters. It is recommended for future application cases to use PCC specimens for the calibration of the parameters. A comparison of the Prometey local approach with the Master Curve approach lead to a good agreement for all investigated materials apart from the thermally embrittled material which has a very high embrittlement level (DBTT shift). The KJC(T) curves of VVER1000 RPV steels with low and moderate embrittlement level could be well predicted by both methods. Because the Master Curve method is already accepted as an international standard, it might be easier to apply in more routine cases. The Prometey probabilistic model may be also used for the prediction of KJC(T) curves of RPV steels with a high embrittlement level.

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.

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.

Applicability of Miniature C(T) Specimens for the Master Curve Evaluation of RPV Weld Metal

2015 ◽  
Author(s):  
Masato Yamamoto ◽  
Naoki Miura
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Master Curve ◽  
Master Curve Method ◽  
Rpv Steel ◽  
Steel Base ◽  
Toughness Evaluation ◽  
Curve Method ◽  
The Difference

The Master Curve approach for the fracture toughness evaluation is expected to be a powerful tool to ensure the reliability of long term used reactor pressure vessel (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 that can be taken from the broken halves of the surveillance Charpy specimens is important. CRIEPI has developed the test technique for the miniature C(T) specimens, whose dimensions are 4 × 10 × 9.6 mm, and has verified the basic applicability of the Master Curve approach by means of the miniature C(T) for the determination of the fracture toughness of typical Japanese RPV steel base metals [1]. A series of round robin tests on RPV steel base metals [2–4] demonstrated that the miniature C(T) specimen can be used for the determination of the reference temperature (To) with no specific difficulties in test techniques. The present paper addresses the applicability of the fracture toughness evaluation by the miniature C(T) specimens on a RPV weld metal with multi-layer weld bead structure. The distribution of the fracture toughness and the trend in fracture toughness change with temperature were confirmed to show a good agreement with the assumption of the Master Curve method [5]. Fracture surface of the specimens were in cleavage fracture mode regardless of the difference in fracture toughness level. The relevance of the specimen size correction in the Master Curve method was confirmed. The difference of To values were only in a few degrees Celsius between the data obtained with 0.5 inch-thickness C(T) specimens and the miniature C(T) specimens. The effect of local loss of constraint nearby the specimen side surface was examined by comparing with the datasets from the specimens with and without side grooves. The difference of To was only 3 degree centigrade and no remarkable effect of side grooving could be seen. From overall examination results, it was concluded that the miniature C(T) specimen can be used for the Master Curve evaluation of tested PRV weld metal.

Application of the Master Curve Method to the Japanese RPV Materials

2005 ◽  
Author(s):  
Hiroomi Funakoshi ◽  
Yasushi Kanazawa ◽  
Takashi Hirano ◽  
Naoki Kojima ◽  
Kouichi Matsumoto ◽  
...  
Keyword(s):  
Master Curve ◽  
Charpy Impact ◽  
Pressure Vessels ◽  
Surveillance Program ◽  
Master Curve Method ◽  
Curve Method ◽  
Static Fracture ◽  
Impact Data ◽  
Reactor Pressure ◽  
Mc Method

In application of the Master Curve (MC) method to the surveillance program of the BWR plants in Japan, we need to address two issues. The first one is to confirm the validity of the MC method to the steels typical to the Japanese reactor pressure vessels (RPVs), and the second is to find a procedure, which allows us to smoothly switch from the current Charpy-based surveillance program to the MC-based surveillance program. In this study, we present results to address the two different issues mentioned above. First, we study the application of the ASTM E 1921 procedure to determine the To values and the MCs for the unirradiated model steels for the Japanese BWR plants. We investigate the basic aspects of the MC method. Second, we investigate the applicability of instrumented Charpy impact data to estimate static fracture toughness Jc values.

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.

scholarly journals Non-Isothermal Kinetic Analysis of the Crystallization of Metallic Glasses Using the Master Curve Method

Materials ◽  
2011 ◽  
Vol 4 (12) ◽  
pp. 2231-2243 ◽  
Author(s):  
Joan Torrens-Serra ◽  
Shankar Venkataraman ◽  
Mihai Stoica ◽  
Uta Kuehn ◽  
Stefan Roth ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Metallic Glasses ◽  
Master Curve ◽  
Master Curve Method ◽  
Curve Method ◽  
Isothermal Kinetic Analysis ◽  
Isothermal Kinetic

A Monte Carlo Implementation of the James-Ford-Jivkov Micro-Structurally Informed Local Approach Applied to Predict Fracture Toughness Including Low Constraint Conditions

2015 ◽  
Author(s):  
Michael Ford ◽  
Peter James
Keyword(s):  
Fracture Toughness ◽  
Monte Carlo ◽  
Transition Region ◽  
Crack Size ◽  
Model Parameters ◽  
Local Approach ◽  
Rpv Steel ◽  
Low Constraint ◽  
Constraint Effects ◽  
Monte Carlo Implementation

The need to predict changes in fracture toughness for materials where the tensile properties change through life, such as with irradiation, whilst accounting for geometric constraint effects, such as crack size, are clearly important. Currently one of the most likely approaches by which to develop such ability are through application of local approach models. These approaches appear to be sufficient in predicting lower shelf toughness under high constraint conditions, but may fail when attempting to predict toughness in the transition region or for low constraint geometries when using the same parameters, making predictions impossible. Cleavage toughness predictions in the transition regime that are then extended to low constraint conditions are here made with a stochastic, Monte Carlo implementation of the recently proposed James-Ford-Jivkov model. This implementation is based around the creation of individual initiators following the experimentally observed distribution for specific RPV steel, and determining if these initiators form voids or cause cleavage failure using the model’s improved criterion for particle failure. The model has shown to predict experimentally measured locations of cleavage initiators. Further, initial results from the Monte Carlo implementation of the model predicts the fracture toughness in a large part of the transition region, demonstrates an ability to predict the constraint shift and shows a level of scatter similar to that observed experimentally. All results presented, for a given material, are obtained without changes in the model parameters. This suggests that the model can be used predicatively for assessing toughness changes due to constraint- and temperature-driven plasticity changes.

Sign in / Sign up

Export Citation Format

Share Document