Application of CFS Model for T0 Estimation-I (original) (raw)
Related papers
Cleavage Fracture Stress Model for Estimating T0 from CVN Impact Tests
A semi-empirical cleavage fracture stress (CFS) model, mainly depending on the CFS, r f , has been derived for estimating the ASTM E1921 reference temperature (T 0 ) and demonstrated for ferritic steels with yield strength in the range 400-750 MPa. This requires only instrumented impact test of CVN specimens without precracking and static yield stress data. The T 0 estimate based on the CFS model, T Qcfs , lies within a 620 C band, being conservative for most of the steels, but less conservative than T QIGC based on the IGCprocedure (see Nomenclature for definition). Applicability and acceptability of the present calibration curves for highly irradiated steels need further examination.
Further application of the cleavage fracture stress model for estimating the T 0 of highly embrittled ferritic steels The semi-empirical cleavage fracture stress model (CFS), based on the microscopic cleavage fracture stress, r f , for estimating the ASTM E1921 reference temperature (T 0)o f ferritic steels from instrumented impact testing of unpre-cracked Charpy V-notch specimens is further confirmed by test results for additional steels, including steels highly embrittled by thermal aging or irradiation. In addition to the ferrite–pearlite, bainitic or tempered martensitic steels (which was examined earlier), acicular or polygonal ferrite, precipitation-strengthened or additional simulated heat affected zone steels are also evaluated. The upper limit for the applicability of the present CFS model seems to be T 41J *160 to 170 8Co rT 0 or T Qcfs (T 0 estimate from the present CFS model) *100 to 120 8C. This is not a clear-cut boundary, but indicative of an area of caution where generation and evaluation of further data are required. However, the present work demonstrates the applicability of the present CFS model even to substantially embrittled steels. The earlier doubts expressed about T Qcfs becoming unduly non-conservative for highly embrittled steels has not been fully substantiated and partly arises from the necessity of modifications in the T 0 evaluation itself at high degrees of embrittlement suggested in the literature.
Journal of Nuclear Materials, 2007
Irradiation embrittlement studies rely very often on Charpy impact data, in particular the ductile-to-brittle transition temperature (DBTT). However, while the DBTT-shift is equivalent to the increase of the fracture toughness transition temperature of ferritic steels, it is not the case for ferritic/martensitic steels. The aim of this study is to critically assess experimental data obtained on a 9%Cr-ferritic/martensitic steel, Eurofer-97, to better understand the underlying mechanisms involved during the fracture process. More specifically, a dedicated analysis using the load diagram approach allows to unambiguously reveal the actual effects of irradiation on physically rather than empirically based parameters. A comparison is made between a ferritic and ferritic/martensitic steel to better identify the possible similarities and differences. Tensile, Charpy impact and fracture toughness tests data are examined in a global approach to assess the actual rather than apparent irradiation effects. The adequacy or inadequacy of the Charpy impact test to monitor irradiation effects is extensively discussed.
Engineering Failure Analysis, 2010
The Master Curve (MC) methodology, originally proposed by Kim Wallin, is a standardised engineering tool for analysing the fracture toughness of ferritic steels in the ductile to brittle transition (DBT) region by means of the reference temperature T 0 . This temperature is normally estimated from quasi-static fracture toughness tests, nevertheless, it has been recently extended to the determination of dynamic fracture toughness. The aim of the present contribution is to characterise the fracture resistance in the DBT region under high strain rate conditions by applying the MC methodology to the steel of the Santa María de Garoña Spanish nuclear power plant (NPP). In this sense, 15 Charpy instrumented tests were performed on pre-cracked specimens from the surveillance program of the plant. The dynamic reference temperature, T 0,dyn , was obtained and compared with the quasi-static reference temperature, T 0,sta . The reliability of a semi-empirical formula proposed by Wallin to obtain T 0,dyn from T 0,sta has been analysed for this material.
Procedia Engineering, 2014
For physical reasons fracture toughness K Jc of ferritic steels in the brittle-to-ductile transition regime is affected by a pronounced scatter, which requires statistical methods to be applied for evaluation of test results as well as for application in safety analysis of structures. For this purposes the probabilistic Master-Curve-approach according to ASTM E1921 is often used. However, for engineering purposes like a screening safety analysis of a defect-containing component it is usually preferable to use a deterministic lower bound. However, within the framework of ASTM-standards there is no possibility to determine K Ic experimentally. So K Ic needs to be determined indirectly from the reference temperature T 0. In the present paper it is shown how lower bounds of fracture toughness-either plane strain K Ic for large components or thickness-dependent K Jc for smaller onescan be derived from T 0 , and how the latter can be determine with sufficient accuracy from one or a few K Jc values.
Fracture toughness of irradiated modified 9Cr–1Mo steel
Journal of Nuclear Materials, 2009
The effects of irradiation on fracture toughness of modified 9Cr-1Mo steel in the transition region were investigated. Half size precracked Charpy specimens were irradiated up to 1.2 Â 10 21 n/cm 2 (E > 0.1 MeV) at 340°C and 400°C in the Korean research reactor. The irradiation induced transition temperature shift for a modified 9Cr-1Mo was evaluated by using the Master Curve methodology. The T 0 temperature for the unirradiated specimens were measured as À67.7°C and À72.4°C from the tests with standard PCVN (precracked charpy V-notch) and half sized PCVN specimens, respectively. The T 0 shifts of specimens after irradiation at 340°C and 400°C were 70.7°C and 66.1°C, respectively. The Weibull slopes for the fracture toughness data obtained from the unirradiated and irradiated modified 9Cr-1Mo steels were determined to confirm the applicability of master curve methodology to modified 9Cr-1Mo steel.
International Journal of Fracture, 2017
Effect of loading rate on cleavage failure probability for ferritic/martensitic steels using Weibull stress analysis is studied. Calibration of Weibull slope for two grades of fusion reactor blanket steels namely, Indian Reduced Activation Ferritic/Martensitic Steel referred as In-RAFMS, F 82H and a non fusion grade modified 9Cr-1Mo steel (P91) are performed for the first time. The calibrated values of Weibull slope is used to predict the fracture behaviour of In-RAFMS at three different loading rates. The effect of loading rate is also examined on reference transition temperature using Wallin's correlation based on Zener-Hollomon strain rate parameter.