scholarly journals Evaluation of Transition Temperature in Reactor Pressure Vessel Steels 6using the Fracture Energy Transition Curve from a Small Punch Test

2020 ◽  
Vol 58 (8) ◽  
pp. 522-532
Author(s):  
Tae-kyung Lee ◽  
Seokmin Hong ◽  
Jongmin Kim ◽  
Min-Chul Kim ◽  
Jae-il Jang
Keyword(s):  
Transition Temperature ◽  
Fracture Energy ◽  
Test Method ◽  
Transition Curve ◽  
Brittle Transition ◽  
Transition Behavior ◽  
Pressure Vessel Steels ◽  
Ductile To Brittle Transition ◽  
Transition Curves ◽  
Reactor Pressure

The small punch (SP) test is one of the small specimen test techniques, and standardization of the SP test method for evaluating the mechanical properties of metallic materials is in progress. In this study, the impact transition temperature of reactor pressure vessel steels (RPV) in nuclear power plants was estimated using the draft standard SP test method. The SP fracture energy (ESP) and normalized SP fracture energy (ENSP) of the RPV steels were evaluated at various temperatures, and their transition curves were derived and compared to the transition curve in the Charpy V notch (CVN) test. The SP transition region appeared at a much lower temperature range than that of the CVN owing to the size and notch effect. Ductile brittle transition temperature (DBTT) in the SP transition curve showed a linear relationship with DBTT and T41J in the CVN transition curve. The ductile to brittle transition behaviors of SP specimens were analyzed using fractographs and compared with the transition curves in ESP and ENSP. ENSP started to decrease at the temperature at which the SP ductile to brittle transition behavior occurred, and this means that the ENSP transition curves were in good agreement with transition behavior in the SP test. However, the ESP transition curves did not match transition behavior. Using DBTT in the ENSP transition curve is appropriate to estimate the CVNDBTT and T41J.

Bayesian Uncertainty Evaluation of Charpy Ductile-to-Brittle Transition Temperature for Reactor Pressure Vessel Steels

2020 ◽  
Author(s):  
Hisashi Takamizawa ◽  
Yutaka Nishiyama ◽  
Takashi Hirano
Keyword(s):  
Transition Temperature ◽  
Test Temperature ◽  
Pressure Vessel ◽  
Credible Interval ◽  
Irradiation Embrittlement ◽  
Brittle Transition ◽  
Pressure Vessel Steels ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Reactor Pressure

Abstract The irradiation embrittlement of reactor pressure vessel steels can be predicted using the ductile-to-brittle transition temperature (DBTT) shift obtained from Charpy impact tests. For the structural integrity assessment considering irradiation embrittlement, it is necessary to set margins for various uncertainties. It is important to understand what and how much factors contribute to the uncertainty. In the present study, a 34% credible interval value of Charpy DBTT at a 41J energy level (T41J) was evaluated by estimating the probability distributions of Charpy test data using Bayesian statistics. To fit the Charpy transition curves, a hyperbolic tangent with coefficients whose uncertainties depend on the test temperature was used. The probability distribution of T41J was estimated using Monte Carlo sampling and Bayesian inference. It was clarified that 34% of the credible-interval values of T41J before and after irradiation unchanged for base and weld metals when the number of specimens and test temperature were equivalent under un-irradiated and irradiated conditions. When the Charpy transition curve was determined by 12 specimens loaded in a surveillance test capsule, the estimated uncertainty of T41J was about 5 °C.

scholarly journals Fractographic Analysis Of Selected Boron Steels Subjected To Impact Testing

2015 ◽  
Vol 60 (3) ◽  
pp. 2373-2378 ◽  
Author(s):  
W. Dudziński ◽  
Ł. Konat ◽  
B. Białobrzeska
Keyword(s):  
Transition Temperature ◽  
Impact Testing ◽  
Transition Curve ◽  
Brittle Transition ◽  
Significant Difference ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Character Of Fracture ◽  
The Impact ◽  
Boron Steels

Abstract In this paper dynamic properties of low-alloy boron steels – Hardox 500, B27 and HTK 900H in delivered state (after hardening and tempering) are considered. Charpy V-notch (CVN) test results in connection with fractography in the ductile-to-brittle transition temperature region were analyzed. Obtained from CVN test the impact transition curve, not always predicts properly a behavior of materials in conditions of dynamic loading. So an analyze of character of fracture helps to evaluate the real behavior of materials. Tested samples were cut out longitudinally in relation to cold work direction. The results of CVN test for selected steels, in temperatures: −40°C, −20°C, 0°C and +20°C are presented. Regarding ductile-to-brittle transition temperature, there is a significant difference taking into account values of Charpy V energy absorbed and a character of fracture.

Fracture Testing of Existing Structures Without the Need for Repairs

2017 ◽  
Author(s):  
C. L. Walters ◽  
M. Bruchhausen ◽  
J.-M. Lapetite ◽  
W. Duvalois
Keyword(s):  
Pilot Project ◽  
Nuclear Industry ◽  
Test Method ◽  
Transition Curve ◽  
Structural Level ◽  
Crack Tip Opening Displacement ◽  
Fracture Testing ◽  
Existing Structures ◽  
Brittle Transition ◽  
Ductile To Brittle Transition

It is sometimes necessary to find the toughness of existing structures without damaging them. Examples of this scenario include situations in which the material is suspected of being brittle or service life extensions. However, fracture testing is inherently destructive. Removing material for Charpy or Crack Tip Opening Displacement (CTOD) specimens can result in expensive repairs. The Small Punch Test (SPT), which has been developed for monitoring programs in the nuclear industry, offers a test method that requires such small amounts of material that the test can be performed in a practically non-destructive way. A pilot project was conducted to determine if the SPT can be applied to steels of use in maritime and offshore applications. The results of the pilot project showed that the SPT can identify behavior related to the ductile to brittle transition for an example S355 steel. Therefore, the SPT can provide valuable information for predicting fracture properties relevant to structural-level behavior of steel, such as Charpy transition and estimates of CTOD values in the lower shelf and lower portion of the ductile to brittle transition curve. In the end of this paper, a theoretical framework for transferring results from SPT to CTOD or Charpy testing is outlined.

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