Probabilistic model for fracture toughness prediction based on the new local fracture criteria

Марголин, Б. З.; Gulenko, A. G.; Shvetsova, V. A.

doi:10.1016/s0308-0161(98)00005-2

Cited by 23 publications

(30 citation statements)

References 18 publications

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“…Another model for fracture toughness prediction based on a new local cleavage fracture criterion 10–12 was proposed in both a deterministic 10,13 and a probabilistic 14–17 manner. The probabilistic model (known now as Prometey model) was verified by application to various RPV steels in the initial (as‐produced), irradiated and highly embrittled conditions 14–18 …”

Section: Introductionmentioning

confidence: 99%

Application of a new cleavage fracture criterion for fracture toughness prediction for RPV steels

Марголин

Shvetsova

Gulenko

et al. 2006

Fatigue Fract Eng Mat Struct

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A B S T R A C T In the present paper, approaches for prediction of cleavage fracture proposed by authors over recent years are briefly reviewed. A new local criterion of cleavage fracture and its application are considered. Local criterion of cleavage fracture formulated in a probabilistic manner consists of cleavage microcrack nucleation condition and condition for their start and propagation through various barriers such as microstresses, grain and dislocation substructure boundaries. As distinct from universally accepted criterion in which microcrack nucleation occurs on the plastic deformation beginning (σ eq = σ Y ), cleavage microcrack nucleation according to the formulated condition depends on the maximum principal stress, plastic strain and temperature.On the basis of the proposed criterion, a probabilistic model for fracture toughness prediction (known now as Prometey model) was developed and verified by application to reactor pressure vessels (RPV) materials in the initial, moderately irradiated and highly embrittled states. The Prometey model and other applications of the proposed criterion are briefly considered. The predicted results are compared with test results and the Master Curve.Intensive development of local approach models over the past 30 years was stimulated, to a great extent, by the needs of assessing the structural integrity of reactor pressure vessels (RPV). A key input to calculation of the structural integrity of the RPV is known to be the fracture toughness of a material. It is important to determine how fracture toughness varies as a function of temperature, and how the fracture toughness versus temperature response changes with in-service material degradation due to irradiation.The neutron irradiation damage effect on RPV materials is estimated using data which are obtained from surveillance programs. These surveillance programs include irradiation and testing of small-sized specimens only. On the other hand, as it is well known, adequate determination of fracture toughness over wide temperature range requires full-sized specimen testing. Thus, the major problem arises how to predict the fracture toughness versus temperature curve, K IC (T) or K JC (T), for an irradiated steel on the basis of small-sized specimen testing.The application of a local approach for fracture toughness prediction in irradiated RPV materials appears to be the most promising way to solve this problem. This explains the reason why local approach models are now intensively developed.Currently, there are several brittle fracture models under development. These include the RKR model 1,2 and the Beremin model. 3 However, it was shown in 4,5 that fracture toughness prediction for irradiated RPV steels on the basis of the RKR and Beremin models is not correct. According to these models, the temperature dependence of fracture toughness K JC (T) is mainly determined by the temperature dependence of the yield stress σ Y (T). For RPV steels over the service temperature range 20 • C ≤ T ≤ 300 • C, the yield stress vari...

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Section: Introductionmentioning

confidence: 99%

Application of a new cleavage fracture criterion for fracture toughness prediction for RPV steels

Марголин

Shvetsova

Gulenko

et al. 2006

Fatigue Fract Eng Mat Struct

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“…In [18,19] a local approach in a probabilistic statement was proposed which is based on a new definition of the brittle fracture criterion. Now it is known as the Prometey model [13,20,21].…”

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“…For a probabilistic statement of criterion (3), σ d is taken as a stochastic parameter while the others as deterministic ones. This assumption is based on the analysis of stochastic nature of various critical parameters that govern brittle fracture in RPV steels [18]. 4.…”

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Probabilistic definition of local criterion for brittle fracture under complex thermomechanical loading

2005

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The new local criterion for brittle fracture in probabilistic definition, which was used by the authors earlier for the K Ic (T) prediction, is modified for the case of non-isothermal non-monotonic loading. An approach is put forward which allows predicting the brittle fracture probability for cracked elements under complex thermomechanical loading typical, for example, of the case of emergency cooldown of a reactor pressure vessel. The approach has been verified by comparing the calculated and experimental data of assessment of the influence of various thermomechanical pre-loading modes on the fracture toughness of reactor pressure vessel steels.

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“…This assumption is based on the analysis of stochastic nature of various critical parameters that govern brittle fracture in reactor pressure vessel steels [12].…”

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Prediction of Temperature Dependence of Fracture Toughness as a Function of Neutron Fluence for Pressure-Vessel Steels by Using the Unified Curve Method

et al. 2005

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Using the Unified Curve method as proposed by the authors earlier and a probabilistic model based on the local approach and physical background of the influence of impurities and carbide size on the local strength of material, a method has been elaborated for predicting a variation of the temperature dependence of fracture toughness with neutron fluence. The results calculated by this method are compared to the available experimental data.Keywords: fracture toughness, Unified Curve method, Master Curve method, probabilistic model, local criterion, neutron fluence, pressure vessel.Introduction. The authors have developed a new engineering method whereby the temperature dependence of fracture toughness for pressure vessel (PV) steels is predicted from the results of fracture toughness testing of specimens at one or several temperatures [1]. The method is similar to the widely accepted Master Curve method [2-5] but, unlike the latter, it allows for a change in shape of the K T Jc ( ) curve depending on the degree of embrittlement of material. It is called the Unified Curve method. It was demonstrated earlier [1] that the Master Curve method is a particular case of the Unified Curve method.Here are the basic principles of the Unified Curve method. 1. The temperature dependence of fracture toughness of ferrite-pearlite structural steels with a fracture probability P f = 0 5. for specimens of thickness B = 25 mm can be represented by a single relationship

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Probabilistic model for fracture toughness prediction based on the new local fracture criteria

Cited by 23 publications

References 18 publications

Application of a new cleavage fracture criterion for fracture toughness prediction for RPV steels

Application of a new cleavage fracture criterion for fracture toughness prediction for RPV steels

Probabilistic definition of local criterion for brittle fracture under complex thermomechanical loading

Prediction of Temperature Dependence of Fracture Toughness as a Function of Neutron Fluence for Pressure-Vessel Steels by Using the Unified Curve Method

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