Fracture Toughness Analysis of the China RPV Steel with Miniaturized Specimen

2016 ◽  
Vol 850 ◽  
pp. 41-46 ◽  
Author(s):  
Yun Lin ◽  
Wen Yang ◽  
Zhen Feng Tong ◽  
Guang Sheng Ning
Keyword(s):  
Fracture Toughness ◽  
Nuclear Power ◽  
Master Curve ◽  
Initiation Site ◽  
Cleavage Crack ◽  
Test Technique ◽  
Rpv Steel ◽  
Specimen Test ◽  
Relationship Of ◽  
The Relationship

Reactor pressurized vessel (RPV), which determines the lifetime of the nuclear power plant (NPP), is mainly forged using A508-3 steel in China. In order to meet the requirement of the small specimen test technique in the nuclear application, the fracture toughness of A508-3 steel was tested under-100°C using 1/4 CT specimens, and analyzed using Master Curve according to ASTM E 1921. In this work, the relationship of the KIC and the distance between the cleavage crack initiation site and the front of the fatigue crack is studied, and the transition temperature T0 of A508-3 is-98.7 oC, which is quite close to the test temperature.

Effect of Sintering Temperature on Microstructure and Properties of VС/Fe Composite

2012 ◽  
Vol 430-432 ◽  
pp. 978-983
Author(s):  
Guo Jun Zhang ◽  
Zhi Ping Sun ◽  
Li Yan Zou
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Sintering Temperature ◽  
Growth Trend ◽  
Flexure Strength ◽  
Microstructure And Properties ◽  
Whole Process ◽  
Relationship Of ◽  
The Relationship ◽  
Composite Samples

VC/Fe composite samples were fabricated by sintering at 1050, 1100 and 1150°C in vacuum. The microstructure and mechanical properties of samples were examined, and the relationship of structure and mechanical properties for VC/Fe composite sintered at different temperature were studied. The results show that fracture toughness, hardness and density is increasing obviously at 1050-1100°Cwith the increasing sintering temperature, but the growth trend increases slowly at 1100-1150°C; in whole process with temperature increased, Flexure strength heighten trend obviously. The microstructure of VC/Fe composite changed from particles piled up together to the microstructure particles closely, VC particles set gradually into Fe with temperature increased, and the gap reduced gradually.

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.

Master Curve Approach for Some Japanese Reactor Pressure Vessel Steels

2008 ◽  
Author(s):  
Minoru Tomimatsu ◽  
Takashi Hirano ◽  
Seiji Asada ◽  
Ryoichi Saeki ◽  
Naoki Miura ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Power Plant ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Master Curve ◽  
Reactor Pressure Vessel ◽  
Pressure Vessel Steels ◽  
The World ◽  
Reactor Pressure ◽  
Plant Components

The Master Curve Approach for assessing fracture toughness of reactor pressure vessel (RPV) steels has been accepted throughout the world. The Master Curve Approach using fracture toughness data obtained from RPV steels in Japan has been investigated in order to incorporate this approach into the Japanese Electric Association (JEA) Code 4206, “Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components”. This paper presents the applicability of the Master Curve Approach for Japanese RPV steels.

The Master Curve Fracture Toughness Evaluation of Irradiated Plate Material JRQ Using Miniature-C(T) Specimens

2017 ◽  
Author(s):  
Masato Yamamoto
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Technical Difficulty ◽  
Plate Material ◽  
Test Technique ◽  
Toughness Evaluation ◽  
Standard Plate ◽  
Surveillance Programs ◽  
International Round ◽  
The Difference

The Master Curve approach is a powerful tool to evaluate material-specific fracture toughness of ferritic steels, such as RPV steels, using a limited number of specimens. However, preparing sufficient volume of material for the generally used 25.4mm-thickness fracture toughness specimens is difficult for irradiated reactor pressure vessel (RPV) steels of existing surveillance programs. Utilization of miniature specimens, which can be machined from broken halves of standard Charpy specimens, is a possible solution to address this issue. CRIEPI has been working on the development of test technique utilizing a miniature C(T) (Mini-C(T)) specimens, whose dimensions are 4×10×9.6 mm (0.16 inch thickness specimen). The basic applicability of the Mini-C(T) Master Curve approach on un-irradiated materials had been confirmed for the base metals of typical Japanese RPV steels [1]. International round robin tests [2–4] confirmed the reproducibility of fracture toughness data obtained by Mini-C(T) specimens. Applicability of the Mini-C(T) specimen on neutron irradiated materials is of another important subject to be ensured. In the present study, the European standard plate material JRQ, which is in irradiated state up to the fluence of 1.85×1019 n/cm2 was subjected to the Master Curve evaluation with Mini-C(T) specimens. Two laboratories, A and B, as well as CRIEPI were involved in this study. Both of the laboratories separately and successfully carried out machining, pre-cracking and fracture toughness testing without excessive technical difficulty even though the material was highly irradiated. Consistent reference temperature, To was estimated as 40°C (Lab. A) or 32°C (Lab. B). The difference between the two laboratories was reasonably small. To was also consistent with that by pre-cracked Charpy V-notch specimens (PCCv), or 1-inch thickness C(T) specimens examined in the former IAEA Coordinated Research Program [5]. As a results of the investigation, the relevance of using Mini-C(T) specimens for irradiated JRQ material was demonstrated.

A Round Robin Program of Master Curve Evaluation Using Miniature C(T) Specimens — 2nd Report: Fracture Toughness Comparison in Specified Loading Rate Condition

2013 ◽  
Author(s):  
Masato Yamamoto ◽  
Kunio Onizawa ◽  
Kentaro Yoshimoto ◽  
Takuya Ogawa ◽  
Yasuhiro Mabuchi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Master Curve ◽  
Loading Rate ◽  
Round Robin ◽  
Surveillance Program ◽  
Similar Amount ◽  
Test Technique ◽  
Rate Condition ◽  
Data Points

Master Curve approach for the fracture toughness evaluation is 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 the Master Curve approach by means of Mini-CT and larger specimens for the determination of fracture toughness of typical Japanese RPV steels. A round robin program was organized with the participation of a university, industries and a government institute in Japan. The first-round test results (PVP2012-78661[1]) with limited number of reference temperature To data points indicated the possible loading rate dK/dt dependence in To. However, increasing number of data points in second-round test, which was conducted in specified loading rate of 0.5 MPa m0.5 /sec, ensures that there is no clue of such a remarkable dK/dt dependency. Concerning the effect of large plastic deformation on dK/dt, dK/dt calculated by several definitions were compared with each other. Maximum one order difference was found between dK/dts with and without consideration of plastic deformation. dK/dt - T0 relationships showed similar amount of scatter in T0 regardless of dK/dt definitions. Difference in dK/dt definition seems less effective on scatter of T0 in the present results.

The Interrelationships of KIa, KIc, and JIc, and the Implications of These Relationships on Use of Fracture Models Over the Ranges of Hardening Observed in Ferritic Steels

2006 ◽  
Author(s):  
Marjorie EricksonKirk ◽  
Mark EricksonKirk ◽  
Tim Williams
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Master Curve ◽  
Crack Arrest ◽  
Nuclear Industry ◽  
Ferritic Steels ◽  
Initiation Toughness ◽  
Cleavage Crack ◽  
The Mean ◽  
Arrest Toughness

Models to predict the fracture and arrest behavior of ferritic steels, particularly those in use in the nuclear industry, have long been under development. The current, most widely accepted model of fracture toughness behavior is the ASTM E1921-02 “Master Curve” that is used to predict the variation of the mean cleavage fracture toughness with temperature in the transition temperature region as well as predicting the scatter of data about the mean at any given temperature. Recently, models describing the variation of arrest fracture toughness and of ductile initiation toughness with temperature have also been proposed. A study has been conducted with the goal of assessing how the scatter in cleavage initiation toughness may vary with temperature and level of irradiation embrittlement, which utilizes the crack arrest and ductile crack initiation models to redefine limits of applicability of the Master Curve-assumed Weibull distribution by developing empirically-derived interrelationships between the three models. These relationships are expected as all three parameters, KIc, KIa, and JIc, are controlled by the flow behavior of the material. There is a physical basis for viewing the crack arrest toughness as an absolute lower bound to the distribution of crack initiation toughness values for a fixed material condition and temperature. This physically based relationship, borne of the fact that both cleavage crack initiation toughness and cleavage crack arrest toughness are controlled by dislocation mobility, has brought about the suggestion that crack arrest toughness could be used to modify the lower tails of the crack initiation fracture toughness distribution. Using both empirical evidence and a hardening model proposed by Natishan and Wagenhofer, we investigate the relationship between initiation and arrest toughness and the implications on use of toughness models.

Unusual enhancer function in yeast rRNA transcription

1989 ◽  
Vol 9 (11) ◽  
pp. 4986-4993
Author(s):  
S P Johnson ◽  
J R Warner
Keyword(s):  
Transcription Initiation ◽  
Initiation Site ◽  
Transcription Unit ◽  
Rrna Genes ◽  
Yeast Saccharomyces Cerevisiae ◽  
Rrna Transcription ◽  
Enhancer Function ◽  
Polymerase I ◽  
Relationship Of ◽  
The Relationship

The rRNA genes in most eucaryotic organisms are present in a tandem array. There is substantial evidence that transcription of one of these genes may not be independent of transcription of others. In particular, in the yeast Saccharomyces cerevisiae, the enhancer of rRNA transcription that lies 2.2 kilobases 5' of the transcription initiation site is at least partly within the upstream transcription unit. To ask more directly about the relationship of the tandemness of these genes to their transcription, we have constructed a minirepeat containing two identifiable test genes, with or without enhancer(s). On integration into the URA3 locus, these genes were transcribed by RNA polymerase I. A single enhancer effectively stimulated transcription of both genes by 10- to 30-fold, even when it was located upstream of both or downstream of both. Two enhancers had roughly additive effects. These results suggest a model of enhancer function in tandemly repeated genes.

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