The Charpy Impact Test as an Evaluation of 4 K Fracture Toughness

The monitoring of neutron induced embrittlement of nuclear power plants is provided using Charpy impact test in the surveillance program. However structural integrity assessments require the fracture toughness. Some empirical formulas have been developed but no direct relationship was found. The aim of our study is to determine the fracture toughness of a Reactor Pressure Vessel steel from instrumented Charpy impact test using local approach to fracture. This non-empirical method has been applied in the brittle domain as well as in the ductile to brittle transition for an A508 C1.3 steel. In the brittle domain, fracture occurs by cleavage and can be modeled with the Beremin model. Fracture toughness has been successfully determined from Charpy impact tests results and the influence of several parameters (mesh design, Beremin model with one or two parameters, number of Charpy impact tests results) on the results was considered. In the ductile to brittle transition, cleavage fracture is preceded by ductile crack growth. Ductile tearing has been accounted for in the simulations with the Rousselier model whereas cleavage fracture is still described with the Beremin model. The determination of fracture toughness from Charpy impact tests gave encouraging results but finite element simulations have to be refined in order to improve predictions.

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Prediction of fracture toughness KIc of steel from Charpy impact test results.

Journal of the Society of Materials Science Japan ◽

10.2472/jsms.35.873 ◽

1986 ◽

Vol 35 (395) ◽

pp. 873-879

Author(s):

Tadao IWADATE ◽

Yasuhiko TANAKA ◽

Hiroyuki TAKEMATA ◽

Shuhei TERASHIMA

Keyword(s):

Fracture Toughness ◽

Impact Test ◽

Charpy Impact ◽

Charpy Impact Test ◽

Test Results

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Validation of the Master Curve Approach With Various Welding Conditions: Groove Shapes, Heat Inputs and Welding Processes

Volume 3: Materials Technology ◽

10.1115/omae2020-18653 ◽

2020 ◽

Author(s):

Jin Ho Lee ◽

Ji Hoon Kim ◽

Myung Hyun Kim

Keyword(s):

Fracture Toughness ◽

Master Curve ◽

Impact Test ◽

Structural Integrity ◽

Charpy Impact ◽

Test Sample ◽

Charpy Impact Test ◽

Theoretical Background ◽

Reference Temperature ◽

Welding Processes

Abstract Engineering critical assessment (ECA) is a procedure for evaluating the soundness of structures with flaws and has been widely applied for assessing the structural integrity. ECA procedure requires reliable fracture toughness data to assess the effect of defects. Ideal data are typically obtained from samples taken during construction of an engineering structure or from the structure afterward, but there are cases in which removal of the test samples is impossible due to the continued operation of the structure. To this end, Appendix J of the BS 7910 provides a procedure for estimating fracture toughness values from appropriate Charpy impact test data. However, the correlation between Charpy impact energy and fracture toughness is known to be overly conservative with not sufficient theoretical background in fracture mechanics perspective. In this regard, the revised BS 7910:2019 provides an improved method for calculating the reference temperature by applying the yield strength and the Charpy upper shelf energy based on empirical data. The target of this study is to validate the master curve approach in the modified BS 7910 for two common offshore grade steels with explicit considerations for various groove shapes, heat inputs and welding processes. For the purpose, the master curves are compared in terms of the reference temperature calculated from Charpy impact test according to BS 7910:2013 and the newly revised 2019 version of BS 7910. The modified master curve resulted in less conservative fracture toughness values anticipated from the decreased reference temperature. The estimated fracture toughness values exhibited a good correlation with experimentally obtained toughness values. The influence of various groove shapes, heat inputs and welding processes in estimating fracture toughness based on the master curve approach is discussed. In addition, the effect of impact test sample locations within weld metals toward estimated fracture toughness values is evaluated.

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Thermal Aging Behavior of Grade CF3M Cast Austenitic Stainless Steels

Volume 1A: Codes and Standards ◽

10.1115/pvp2017-65959 ◽

2017 ◽

Author(s):

Yasufumi Miura ◽

Takashi Sawabe ◽

Kiyoshi Betsuyaku ◽

Taku Arai

Keyword(s):

Fracture Toughness ◽

Stainless Steels ◽

Thermal Aging ◽

Impact Test ◽

Charpy Impact ◽

Charpy Impact Test ◽

Ferrite Phase ◽

Absorbed Energy ◽

Aging Conditions ◽

Charpy Absorbed Energy

In this study, CASSs which were thermally aged at 275–400°C for up to 30000 hrs were investigated using atom probe tomography, Charpy impact test, hardness test, and fracture toughness test in order to evaluate the effects of chemical composition and ferrite content on thermal aging embrittlement. Test materials were 4 types of statically casted grade CF3M stainless steels which are used in Japanese BWR plants. As a result of the tests, Charpy absorbed energy at room temperature of all thermal aging conditions were obtained. We also obtained the microstructural evolution in ferrite phase, hardness of ferrite phase, and J–R curves of several aging conditions. The fracture toughness and the Charpy absorbed energy of all materials aged at 275°C for up to 15000 hrs were approximately same as those of unaged materials. On the other hand, reduction of the fracture toughness and the Charpy absorbed energy were observed in the materials aged at 300°C, 320°C, 350°C and 400°C. For the Charpy impact test in this study, the absorbed energy of the material with highest molybdenum was lower than that of the material with highest ferrite content. After the tests, the fracture toughness estimation model for grade CF8M in NUREG/CR-4513 and the method in PVP2005-71528 (H3T model) were discussed in order to confirm the applicability of the prediction methods to CF3M.

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Fracture toughness of filament wound BFR and GFR arc shaped specimens with Charpy impact test method

Composites Part B Engineering ◽

10.1016/j.compositesb.2014.04.015 ◽

2014 ◽

Vol 66 ◽

pp. 7-14 ◽

Cited By ~ 18

Author(s):

Mehmet Turan Demirci ◽

Necmettin Tarakçıoğlu ◽

Ahmet Avcı ◽

Ömer Faruk Erkendirci

Keyword(s):

Fracture Toughness ◽

Impact Test ◽

Charpy Impact ◽

Charpy Impact Test ◽

Test Method ◽

Filament Wound

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Evaluation of Shear Area of DWTT Fracture Surface With Instrumented System

Volume 3: Pipeline and Riser Technology ◽

10.1115/omae2009-79407 ◽

2009 ◽

Author(s):

Seong Soo Ahn ◽

You Sun Ham

Keyword(s):

Fracture Toughness ◽

Fracture Surface ◽

Dynamic Loading ◽

Impact Test ◽

Charpy Impact ◽

Charpy Impact Test ◽

Displacement Curve ◽

Absorbed Energy ◽

Long Time ◽

Shear Area

The test method to evaluate fracture toughness can be divided by the loading type to specimen. A static load is given to specimen for testing KIC, JIC, CTOD, etc. while a dynamic load is given to those for testing Charpy impact test, DWTT, etc. In case of fracture toughness tests with static loading, the data of load and displacement should be gathered during test because they were driven from fracture mechanics. In case of fracture toughness tests with dynamic loading, however, we don’t gather any data during specimen broken. We measure an absorbed energy for fracture and shear area from fracture surface after Charpy impact test and a shear area from fracture surface after DWTT. To analyze the results from these toughness tests of dynamic loading type with using fracture mechanics, recently, an instrumented system is installed to these dynamic loading test machines. An instrumented system can measure load and displacement during specimen broken. On the displacement-load curve made with data from an instrumented system, in general, the area in the region before peak-force is the energy for crack initiation while area in the region after peak-force is that for crack propagation. Meanwhile, it takes a long time and effort to evaluate the shear area from both fracture surfaces after Charpy impact test and DWTT test. For Charpy impact test, the method how to calculate the shear area with the information from a load-displacement curve has been studied for a long time. So the method for it is well established and known. For DWTT, however, the method how to calculate the shear area from a load-displacement curve was not known well. In this paper, a shear area could be calculated from an instrumented data without any more time or effort in addition to test. A shear area could be expressed as a function of total absorbed energy, fractured area, maximum force, time at 50kN and time at maximum force. Especially, the material with shear area more than 85% could be distinguished from that with shear area less than 85% because the transition curve of DWTT changes dramatically around 85% shear area.

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