Brittle Fracture Prevention Model for Pressure Based on Master Curve Approach

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
QingFeng Cui ◽  
Hu Hui ◽  
PeiNing Li ◽  
Feng Wang
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Impact Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Fracture Prevention ◽  
Pressure Vessels ◽  
New Model ◽  
Prevention Model ◽  
The Impact

The brittle fracture prevention model is of great importance to the safety of pressure vessels. Compared to the semi-empirical approach adopted in various pressure vessel standards, a model based on Master Curve technique is developed in this paper. Referring to ASME nuclear code, the safety features including the lower bound fracture toughness and a margin factor equal to 2 for the stress intensity factor produced by primary stress are adopted in the new model. The technical background of the brittle fracture model in ASME VIII-2 has been analyzed and discussed, and then its inappropriate items have been modified in the new model. Minimum design temperature curves, impact toughness requirements, and temperature adjustment for low stress condition are established on the basis of new model. The comparison with the relevant curves in ASME VIII-2 is also made. The applicability of the new model is verified by the measured fracture toughness and impact toughness data of several kinds of pressure vessel steels. The results suggest that the minimum design temperature and the impact test requirements derived by the new model are compatible with each other. More testing data of different steels to check this model is necessary for further engineering application.

Prediction of Fracture Toughness KIC Transition Curves of Pressure Vessel Steels From Charpy V-Notch Impact Test Results

1994 ◽  
Vol 116 (4) ◽  
pp. 353-358 ◽  
Author(s):  
T. Iwadate ◽  
Y. Tanaka ◽  
H. Takemata
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Prediction Method ◽  
Pressure Vessels ◽  
Life Extension ◽  
Low Alloy Steels ◽  
Excess Temperature ◽  
Pressure Vessel Steels ◽  
Transition Curves

A single and generalized prediction method of fracture toughness KIC transition curves of pressure vessel steels has been greatly desired by engineers in the petro-chemical and nuclear power industries, especially from the viewpoint of life extension of reactor pressure vessels. In this paper, the toughness degradation of Cr-Mo steels during long-term service was examined and the two prediction methods of fracture toughness KIC transition curves were studied using the data of 54 heats. 1) The toughness degradation of 2 1/4Cr-1Mo steels levels off within around 50,000 h service. 2) The FATT versus J-factor (=(Si+Mn)(P+Sn)×104) and/or X (=(10P+5Sb+4Sn+As)x10−2) relationships to estimate the maximum embrittlement of Cr-Mo steels were obtained. 3) A master curve method developed by authors et al.; that is, the method using a KIC/KIC−US versus excess temperature master curve of each material was presented for 2 1/4Cr-1Mo, 1 1/4Cr-1/2Mo, 1Cr and 1/2Mo chemical pressure vessel steels and ASTM A508 C1.1, A508 C1.2, A508 C1.3 and A533 Gr.B C1.1 nuclear pressure vessel steels, where KIC−US is the upper-shelf fracture toughness and excess temperature is test temperature minus FATT. 4) A generalized prediction method to predict the KIC transition curves of any low-alloy steels was developed. This method consists of KIC/KIC−US versus T–T0 master curve and temperature shift ΔT between fracture toughness and CVN impact transition curves versus yield strength relationship, where To is the temperature showing 50 percent KIC−US of the material. 5) The KIC transition curves predicted using both methods showed a good agreement with the lower bound of measured KJC values obtained from JC tests.

2 1/4% NICKEL STEEL

Alloy Digest ◽  
1980 ◽  
Vol 29 (11) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Brittle Fracture ◽  
Physical Properties ◽  
Heat Treating ◽  
Pressure Vessels ◽  
Nickel Steel ◽  
Subzero Temperatures ◽  
Steel Mills ◽  
Resistance To Brittle Fracture

Abstract The 21/4% Nickel Steel possesses a combination of moderate strength and superior resistance to brittle fracture at subzero temperatures. It is one of the most economical materials for the construction of equipment to operate at temperatures as low as -90 F. It is intended primarily for welded pressure vessels. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-378. Producer or source: Alloy steel mills and foundries.

scholarly journals Use of Mini-CT Specimens for Fracture Toughness Characterization of Low Upper-Shelf Linde 80 Weld Before and After Irradiation

2018 ◽  
Author(s):  
Mikhail A. Sokolov
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Collaborative Program ◽  
Before And After ◽  
Minimum Number ◽  
Real Practice ◽  
Reactor Pressure ◽  
Good Agreement

Mini-CT specimens are becoming a highly popular geometry for use in reactor pressure vessel (RPV) community for direct measurement of fracture toughness in the transition region using the Master Curve methodology. In the present study, Mini-CT specimens were machined from previously tested Charpy specimens of the Midland low upper-shelf Linde 80 weld in both, unirradiated and irradiated conditions. The irradiated specimens have been characterized as part of a joint ORNL-EPRI-CRIEPI collaborative program. The Linde 80 weld was selected because it has been extensively characterized in the irradiated condition by conventional specimens, and because of the need to validate application of Mini-CT specimens for low upper-shelf materials — a more likely case for some irradiated materials of older generation RPVs. It is shown that the fracture toughness reference temperatures, To, derived from these Mini-CT specimens are in good agreement with To values previously recorded for this material in the unirradiated and irradiated conditions. However, this study indicates that in real practice it is highly advisable to use a much larger number of specimens than the minimum number prescribed in ASTM E1921.

Fracture Toughness of Highly Irradiated Pressure Vessel Steels in the Upper Shelf Temperature

2006 ◽  
Author(s):  
Hiroshi Matsuzawa ◽  
Toru Osaki
Keyword(s):  
Fracture Toughness ◽  
Chemical Composition ◽  
Reference Material ◽  
Fast Neutron ◽  
Pressure Vessel ◽  
Charpy Impact ◽  
Pressure Vessels ◽  
Shelf Energy ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Nine Reactor Pressure Vessel (RPV) Steels and four RPV weld were irradiated up to 1.2 × 1024n/m2 fast neutron fluence (E>1MeV), and their fracture toughness and Charpy impact energy were measured. As chemical compositions, such as Cu, are known to affect the fracture toughness reduction due to neutron exposure, the above steels were fabricated by changing chemical composition widely to cover the chemical composition of the RPV materials of the operating Japanese nuclear power plants. 2.7 mm thick compact specimens were used to measure the upper shelf fracture toughness of highly irradiated materials, and their Charpy upper shelf energy was also measured. By correlating Charpy upper shelf energy to fracture toughness, the upper shelf fracture toughness evaluation formulae for highly irradiated reactor pressure vessel steels were developed. Both compact and V-notched Charpy impact specimens were irradiated in a test reactor. The fast neutron flux above 1MeV was about 5 × 1016n/(m2s). Charpy impact specimens made of Japanese PWR reference material containing 0.09w% Cu were irradiated simultaneously. The upper shelf energy of the reference material up to the medium fluence level showed little difference in the reduction of upper shelf energy to that which had been in the operating plant and which was irradiated to the same fluence. The developed correlation formulae have been adopted in the Japan Electric Association Code as new formulae to predict the fracture toughness in the upper shelf region of reactor pressure vessels. They will be applied to time limited ageing analysis of low upper shelf reactor pressure vessels in Japan, on a concrete technical basis in very high fluence regions.

Alternative RTNDT for Linde 80 Weld Materials

2002 ◽  
Author(s):  
K. K. Yoon ◽  
J. B. Hall
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Pressure Vessels ◽  
Screening Criteria ◽  
Master Curve Method ◽  
Asme Code ◽  
Curve Method

The ASME Boiler and Pressure Vessel Code provides fracture toughness curves of ferritic pressure vessel steels that are indexed by a reference temperature for nil ductility transition (RTNDT). The ASME Code also prescribes how to determine RTNDT. The B&W Owners Group has reactor pressure vessels that were fabricated by Babcock & Wilcox using Linde 80 flux. These vessels have welds called Linde 80 welds. The RTNDT values of the Linde 80 welds are of great interest to the B&W Owners Group. These RTNDT values are used in compliance of the NRC regulations regarding the PTS screening criteria and plant pressure-temperature limits for operation of nuclear power plants. A generic RTNDT value for the Linde 80 welds as a group was established by the NRC, using an average of more than 70 RTNDT values. Emergence of the Master Curve method enabled the industry to revisit the validity issue surrounding RTNDT determination methods. T0 indicates that the dropweight test based TNDT is a better index than Charpy transition temperature based index, at least for the RTNDT of unirradiated Linde 80 welds. An alternative generic RTNDT is presented in this paper using the T0 data obtained by fracture toughness tests in the brittle-to-ductile transition temperature range, in accordance with the ASTM E1921 standard.

Estimation of Master Curve Based RTTo Reference Temperature From CVN Data

2005 ◽  
Author(s):  
Kim R. W. Wallin ◽  
Gerhard Nagel ◽  
Elisabeth Keim ◽  
Dieter Siegele
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Brittle Failure ◽  
Master Curve ◽  
Simple Relation ◽  
Systematic Evaluation ◽  
Data Sets ◽  
Irradiation Embrittlement ◽  
Pressure Vessel Steels ◽  
Asme Code

The ASME code cases N-629 and N-631 permits the use of a Master Curve-based index temperature (RTTo ≡ T0 + 19.4°C) as an alternative to traditional RTNDT-based methods of positioning the ASME KIc, and KIR curves. This approach was adopted to enable use of Master Curve technology without requiring the wholesale changes to the structure of the ASME Code that would be needed to use all aspects of Master Curve technology. For the brittle failure analysis considering irradiation embrittlement additionally a procedure to predict the adjustment of fracture toughness for EOL from irradiation surveillance results must be available as by NRC R.G. 1.99 Rev. 2 e.g.: ART = Initial RTNDT + ΔRTNDT + Margin. The conservatism of this procedure when RTNDT is replaced by RTTo is investigated for western nuclear grade pressure vessel steels and their welds. Based on a systematic evaluation of nearly 100 different irradiated material data sets, a simple relation between RTToirr, RTToref and ΔT41JRG is proposed. The relation makes use of the R.G. 1.99 Rev. 2 and enables the minimizing of margins, necessary for conventional correlations based on temperature shifts. As an example, the method is used to assess the RTTo as a function of fluence for several German pressure vessel steels and corresponding welds. It is shown that the method is robust and well suited for codification.

Brittle Fracture Assessments on Piping Systems: MSOT Curves

2019 ◽  
Author(s):  
Ishita Chakraborty ◽  
Kannan Subramanian ◽  
Jorge Penso
Keyword(s):  
Brittle Fracture ◽  
Case Studies ◽  
Pressure Vessel ◽  
Iterative Process ◽  
Pressure Vessels ◽  
Temperature Changes ◽  
End Conditions ◽  
Piping Systems ◽  
Plant Personnel ◽  
Safe Operating

Abstract Brittle fracture assessments (BFAs) of pressure vessels based on API 579-1/ASME FFS-1, Section 3 procedures are frequently easier and more straightforward to implement in comparison to the BFAs on piping systems. Specifically, the development of the MSOT curves. This is due to the complexities involved in the piping systems due to the branch piping interactions, end conditions of piping systems such as nozzle flexibilities at the pressure vessel connections, temperature changes in the length of piping especially when the piping is significantly long as seen in flare header piping systems. MSOT curves that are alternatively used for MAT curves provide a better picture to the plant personnel in understanding the safe operating envelope. Development of MSOT curves is an iterative process and therefore involves significant number of piping stress analyses during their development. In this paper, an approach to develop the MSOT curves is discussed with two case studies that are of relevance to olefin plants.

Research on Synthesis and Properties of a Flexible Epoxy Curing Agent

2015 ◽  
Vol 744-746 ◽  
pp. 1463-1466
Author(s):  
Xi Wang
Keyword(s):  
Fracture Toughness ◽  
Impact Toughness ◽  
Epoxy Resin ◽  
Curing Agent ◽  
Pure Epoxy ◽  
Epoxy Curing ◽  
New Type ◽  
The Impact

This paper presents the synthesis of a new type of flexible epoxy curing agent and an approach to improve the toughness of epoxy resin by curing without reducing the strength and modulus of the resin-cured material. The results show that the degree of toughness reaches maximum values when the flexible curing agent is applied at weight percentages (wt.%) between 10% and 15%. When the amount of flexible curing agent added to epoxy resin weight is 10wt.%, the impact toughness and fracture toughness increases by 33.3% and 96.3%, respectively, compared with the pure epoxy resin. When the amount of flexible curing agent added to epoxy is 10wt.%, the resulting impact thoughness of the material is 19.5 kJ•m-2 at-50°C, the impact toughness of pure epoxy resin is only 7.96 kJ•m-2.

scholarly journals Analysis of the impact of position in fatigue cracks on the fracture toughness of thick-walled pressure vessel material

2016 ◽  
Vol 2 ◽  
pp. 2982-2988
Author(s):  
Nedeljko Vukojević ◽  
Nenad Gubeljak ◽  
Muamer Terzic ◽  
Fuad Hadžikadunić
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Fatigue Cracks ◽  
Vessel Material ◽  
The Impact

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.

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