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.

A Round Robin Program of Master Curve Evaluation Using Miniature C(T) Specimens: First Round Robin Test on Uniform Specimens of Reactor Pressure Vessel Material

2012 ◽  
Author(s):  
Masato Yamamoto ◽  
Akihiko Kimura ◽  
Kunio Onizawa ◽  
Kentaro Yoshimoto ◽  
Takuya Ogawa ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Evaluation Method ◽  
Round Robin ◽  
Machining Process ◽  
Reference Temperature ◽  
Surveillance Program ◽  
Test Technique ◽  
Actual Application ◽  
The Difference

Reference temperature evaluation method by Master Curve approach for the fracture toughness evaluation had been standardized recently in Japan, and 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 Master Curve approach by means of Mini-CT for the determination of fracture toughness of typical Japanese RPV steels. A round robin program is organized with the participation of Japanese academia, industries and a government institute. The program aims to verify the reliability and robustness of experimental data of Mini-CT, and to pick out further investigation items to be solved before the actual application of the technique. As the first step of this program, four institutes separately carried out a series of Master Curve evaluation in conformity to ASTM E1921-10e1 by means of Mini-CT specimens, whose material (Japanese RPV material, SFVQ1A), machining process and pre-cracking process are in common in all the specimens. Valid reference temperature T0 could be successfully obtained in all of the institutes by means of Mini-CT specimen. However, the value, T0, have large difference with maximum of 34 °C among the institutes. The difference shows strong correlation with the difference in loading rate, which is selected by each organization to be meet the testing standard ASTM E1921-10e1.

A Round Robin Program of Master Curve Evaluation Using Miniature C(T) Specimens: 3rd Report — Comparison of T0 Under Various Selections of Temperature Conditions

2014 ◽  
Author(s):  
Masato Yamamoto ◽  
Akihiko Kimura ◽  
Kunio Onizawa ◽  
Kentaro Yoshimoto ◽  
Takuya Ogawa ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Test Temperature ◽  
Master Curve ◽  
Testing Procedure ◽  
Round Robin ◽  
Surveillance Program ◽  
Rate Dependency ◽  
Test Technique ◽  
The Difference ◽  
Selection Of

The 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 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 Master Curve approach by means of Mini-CT for the determination of fracture toughness of typical Japanese RPV steels. A round robin program is organized in order to assure the robustness of the testing procedure to the difference in testing machines or operators. The first and second round robin tests (PVP2012-78661 [1], PVP2013-97936 [2]) suggested that the reference temperature T0 evaluation technique by Mini-CT specimen potentially is fairly robust in regard to difference in testing machines and operators, and gives similar loading rate dependency to the larger C(T) specimens. As the final year of the round robin program, “blind tests” were carried out. Here, detailed material information such as the type of materials, estimated T0, existing fracture toughness data for the material, were not given with the specimen, and 6 organizations independently selected the test temperature based on Charpy full curve of the tested material. The selection of test temperature has the variation of −120 °C to −150 °C among the organizations. 8 to 20 specimens in a set were subjected to the Master Curve evaluation and all the 6 organizations successfully obtained valid T0. The scatter range in T0 was at most 16 °C, which was within the acceptable scatter range specified in ASTM E1921-10e1. The selection of test temperature seems to give limited effect as like as that in larger specimens.

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.

Effect of loading rate on cohesive parameters of the adhesive Araldite 2015

2020 ◽  
Vol 62 (9) ◽  
pp. 943-950
Author(s):  
Engin Erbayrak ◽  
Halil Ozer
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Fracture Energy ◽  
Transition Region ◽  
Cantilever Beam ◽  
Epoxy Matrix ◽  
Loading Rate ◽  
Double Cantilever Beam ◽  
Loading Rates ◽  
Softening Behavior

Abstract This study addresses the effect of loading rates on cohesive parameters and microstructural composition of the Araldite 2015 adhesive. Double Cantilever Beam (DCB) samples were tested under the loading rates of 1, 5, 10, 20, 100 and 200 mm × min-1. The Park-Paulinho-Roeser model (PPR model) was used to get cohesive parameters. In modelling of the softening behavior, inverse analyses were performed using the date obtained from the PPR softening curves. It was seen that the fracture energy and cohesive parameters are decreasing with increasing the loading rate. However, there seems to be a transition region where the fracture energy nearly remains constant. Microstructural analyses were implemented in order to study the effects of the loading rates on the characteristics of the fracture surfaces. It was concluded that the loading rates greatly influence the distribution of micro-voids in the epoxy matrix. Moreover, the presence of voids in epoxy matrix improved the plastic deformation around the crack tip and increased the fracture toughness.

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.

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.

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.

Fracture Toughness Evaluation of Reactor Pressure Vessel Steels by Master Curve Method Using Miniature Compact Tension Specimens

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Tohru Tobita ◽  
Yutaka Nishiyama ◽  
Takuyo Ohtsu ◽  
Makoto Udagawa ◽  
Jinya Katsuyama ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Loading Rate ◽  
Compact Tension ◽  
Master Curve Method ◽  
Toughness Evaluation ◽  
Curve Method ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure

We conducted fracture toughness testing on five types of commercially manufactured steel with different ductile-to-brittle transition temperatures. This was performed using specimens of different sizes and shapes, including the precracked Charpy-type (PCCv), 0.4T-CT, 1T-CT, and miniature compact tension specimens (0.16T-CT). Our objective was to investigate the applicability of 0.16T-CT specimens to fracture toughness evaluation by the master curve method for reactor pressure vessel (RPV) steels. The reference temperature (To) values determined from the 0.16T-CT specimens were overall in good agreement with those determined from the 1T-CT specimens. The scatter of the 1T-equivalent fracture toughness values obtained from the 0.16T-CT specimens was equivalent to that obtained from the other larger specimens. Furthermore, we examined the loading rate effect on To for the 0.16T-CT specimens within the quasi-static loading range prescribed by ASTM E1921. The higher loading rate gave rise to a slightly higher To, and this dependency was almost the same for the larger specimens. We suggested an optimum test temperature on the basis of the Charpy transition temperature for determining To using the 0.16T-CT specimens.

Application of Master Curve Approach to Surveillance Test Data for WWER-1000 Reactor Pressure Vessels

2017 ◽  
Author(s):  
Volodymyr M. Revka ◽  
Liudmyla I. Chyrko
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Test Data ◽  
Master Curve ◽  
Pressure Vessels ◽  
Reference Temperature ◽  
Transition Curve ◽  
Surveillance Program ◽  
Data Set ◽  
Reactor Pressure

An important issue in the safety operation of WWER-1000 type reactor is a decrease in fracture toughness for reactor pressure vessel steels due to neutron irradiation. This effect for RPV metal is known as radiation embrittlement. The radiation induced temperature shift of the fracture toughness transition curve is considered as a measure of the embrittlement rate. The Charpy impact and fracture toughness specimens are included in the surveillance program for an assessment of changes in fracture toughness of RPV materials. The present analysis is based on a large data set which includes mostly experimental results for pre-cracked Charpy specimens from a WWER-1000 RPV surveillance program. A Master curve approach is applied to analyze the surveillance test data with respect to a shape of the fracture toughness transition curve and a scatter of KJC values. The RPV base and weld metal in unirradiated, thermally aged and irradiated conditions are considered in this study. The maximum shift in a reference temperature T0 due to irradiation is 107 degree Celsius. It is shown that the Master curve, 5 % and 95 % tolerance bounds describe adequately the temperature dependence and the statistical scatter of KJC values for WWER-1000 RPV steels both in unirradiated condition and after irradiation up to design as well as long term operation neutron fluence. Furthermore, a development of the Weibull plots for considered data sets is shown that the Weibull slope is close to the expected one of 4 on average. Finally, a comparison of the reference temperature T0 and a scatter of KJC values derived from the pre-cracked Charpy and 0,5T C(T) specimens of base and weld metal in unirradiated condition is done. The analysis has shown a significant discrepancy between the T0 values derived from the two different types of specimens for both RPV metals.

IAEA Coordinated Research Project on Master Curve Approach to Monitor Fracture Toughness of RPV Steels: Effect of Loading Rate

2007 ◽  
Author(s):  
Hans-Werner Viehrig ◽  
Enrico Lucon
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Loading Rate ◽  
Crack Arrest ◽  
Dynamic Fracture Toughness ◽  
Current Status ◽  
Research Project ◽  
Topic Area ◽  
Loading Rates ◽  
Data Assessment

In the final evaluation for the application of the Master Curve in the IAEA Coordinated Research Project Phase 5 (CRP-5), one of the areas which was identified as needing further work concerned the effects of loading rate on the reference temperature To up to impact loading conditions. This subject represents one of the three topic areas within the current CRP-8. The effect of loading rate can be broken down into two distinct aspects: 1) the effect of loading rate on the Master Curve To values for loading rates within the specified in ASTM E1921-05 for quasi-static loading (0.1–2 MPa√m/s); 2) the effect of loading rate on To values for higher loading rates, including impact conditions using instrumented precracked Charpy (PCC) specimens. The new CRP includes both aspects, but primarily focuses on the second element of loading rate effects, i.e. loading rates above 2 MPa√m/s. These issues are investigated within the topic area #2 of CRP-8 (Loading Rate Effect). The mandatory portion of this topic area required participation in a round-robin exercise (RRE) to validate the application of the Master Curve approach to PCC specimens tested in the ductile-to-brittle transition region using an instrumented pendulum (10 tests per participant on the JRQ material). The current status of the RRE is presented in [1]. The non-mandatory portion of this topic area consists in providing Master Curve data obtained at different loading rates on various RPV steels, in order to assess the loading rate dependence of To and compare it with an empirical model proposed by Wallin. Moreover, additional topics will be addressed, such as: • comparison of results from unloading compliance and monotonic loading in the quasi-static range; • estimation of fracture toughness from Charpy V-notch data; • assessment of crack arrest properties from instrumented Charpy results; • effect of irradiation on the relationship between static and dynamic fracture toughness.

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