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Planman, T.*; Onizawa, Kunio; Server, W.*
Proceedings of 2009 ASME Pressure Vessels and Piping Division Conference (PVP 2009) (CD-ROM), 8 Pages, 2009/07
The fracture toughness transition curve shape in the Master Curve (MC) has been discussed since the original empirical definition of the curve in 1991. In most cases the standard MC approach, assuming a constant transition curve shape, has proven to give a realistic description for also highly irradiated ferritic steels. The fracture toughness data collected and analysed in the IAEA CRP-8 Topic Area 3 supports the validity of the curve shape assumption of ASTM E1921 also in case of irradiated steels and gives no rise to change the present definition. The Master Curve C-parameter (the shape parameter) estimation is proposed as an appropriate analysis method when there is need to estimate also the temperature dependence, whereas the SINTAP procedure is recommended for ensuring conservative lower bound estimates when material in homogeneity is suspected. The results show that irradiation may slightly lower the fracture toughness in the upper transition region in relation to that predicted by E1921, but the effect after moderate T0 shift values seems to be negligible.
Nanstad, R.*; Brumovsky, M.*; Callejas, R.*; Gillemot, F.*; Korshunov, M.*; Lee, B.*; Lucon, E.*; Scibetta, M.*; Minnebo, P.*; Nilsson, K.-F.*; et al.
Proceedings of 2009 ASME Pressure Vessels and Piping Division Conference (PVP 2009) (CD-ROM), 13 Pages, 2009/07
IAEA has developed a coordinated research project (CRP) to evaluate various issues associated with the fracture toughness Master Curve for application to light-water RPVs. Topic Area 1 of the CRP is focused on the issue of test specimen geometry effects, with emphasis on determination of reference temperature T
with the pre-cracked Charpy (PCC) specimen and the bias effect on T. Participating organizations for the experimental part of the CRP performed fracture toughness testing of various steels with various types of specimens under various conditions. Results from fracture toughness tests are compared with regard to effects of specimen size and type on the T. It is apparent from the results that the bias observed between the PCC specimen and larger specimens for Plate JRQ is not nearly as large as that obtained for other steels (-11
C to -45C). This observation is consistent with observations in the literature that show significant variations in the bias that are dependent on the specific materials being tested.
Planman, T.*; Onizawa, Kunio; Server, W.*; Rosinski, S.*
Proceedings of 2007 ASME Pressure Vessels and Piping Division Conference/8th International Conference on Creep and Fatigue at Elevated Temperatures (PVP 2007/CREEP-8) (CD-ROM), 9 Pages, 2007/07
In the Master Curve (MC) fracture model, a universal temperature dependence is assumed for reactor pressure vessel (RPV) steels. The assumed curve shape has been observed to be generally valid for highly irradiated materials. Lower than predicted fracture toughness behavior has been occasionally observed, however, in the upper transition range. One objective of the present IAEA CRP is to clarify the MC shape issue by collecting and analyzing relevant fracture toughness data on irradiated or thermally aged RPV steels. The data reviewed in this CRP show, in general, a very consistent fracture behavior with the basic MC model that further confirms the applicability of the assumed curve shape. In cases where the basic assumptions of the MC model were not satisfied due to high proportions of intergranular fracture, correspondence with the measured and predicted behavior could be markedly improved by applying available models developed to address inhomogeneous materials.