Prediction of SENB Fracture Toughness From Charpy Data Using the Beremin Model in the Lower Transition Region

2013 ◽  
Author(s):  
Robin J. Smith ◽  
Andrew H. Sherry ◽  
Adam C. Bannister ◽  
Anthony J. Horn
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Cleavage Fracture ◽  
Ferritic Steel ◽  
Transition Curve ◽  
Charpy Specimen ◽  
Absorbed Energy ◽  
Brittle Transition ◽  
Lower Transition ◽  
Ductile To Brittle Transition

This work focuses on the application of a mechanistic local approach model to describe the statistical distribution of experimental Charpy (CVN) impact test data obtained at several temperatures in the ductile to brittle transition temperature range. The current objective is to develop a correlation in the lower transition regime between quasi-static CVN absorbed energy (CVE) and the J-integral fracture toughness (Jc) obtained from deeply pre-cracked Charpy (PCCVN) specimens tested quasi-statically to laboratory test standards. The Beremin model for cleavage fracture has been applied to a ferritic steel which has been comprehensively tested using standard CVN, shallow U-notched and PCCVN specimen types in the lower ductile to brittle transition. This has enabled a prediction to be made of the absorbed CVE at cleavage fracture initiation for a Charpy specimen tested quasi-statically in the lower part of the CVN transition curve. By applying the Beremin model to PCCVN single edge notch bend specimens at quasi-static rates it was possible to use the Weibull stress, to achieve a reliable correlation between CVE and Jc in the lower ductile to brittle transition region. The results from this work indicate that the Beremin model can provide a theoretically based correlation for CVE to Jc fracture toughness for a ferritic steel under quasi-static loading conditions. The overall objective of the project remains to predict dynamic CVN absorbed energy using micromechanical modelling and which is valid for all ferritic steels.

The Weibull Stress Model for Predicting Cleavage Fracture in the Ductile-to-Brittle Transition Region

2008 ◽  
Author(s):  
Xiaosheng Gao ◽  
Jason P. Petti ◽  
Robert H. Dodds
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Cleavage Fracture ◽  
Model Parameters ◽  
Ferritic Steels ◽  
Stress Model ◽  
Brittle Transition ◽  
Ductile To Brittle Transition ◽  
Constraint Effects ◽  
Weibull Stress

Transgranular cleavage fracture in the ductile-to-brittle transition region of ferritic steels often leads to spectacular and catastrophic failures of engineering structures. Due to the strongly stochastic effects of metallurgical scale inhomogenieties together with the nonlinear mechanical response from plastic deformation, the measured fracture toughness data exhibit a large degree of scatter and a strong dependence on constraint. This has stimulated an increasing amount of research over the past two decades, among which the Weibull stress model originally proposed by the Beremin group has gained much popularity. This model is based on weakest link statistics and provides a framework to quantify the relationship between macro and microscale driving forces for cleavage fracture. It has been successfully applied to predict constraint effects on cleavage fracture and on the scatter of macroscopic fracture toughness values. This paper provides a brief review of the research conducted by the authors in recent years to extend the engineering applicability of the Weibull stress model to predict cleavage fracture in ferritic steels. These recent efforts have introduced a threshold value in the Weibull stress model, introduced more robust calibration methods for determination of model parameters, predicted experimentally observed constraint effects, demonstrated temperature and loading rate effects on the model parameters, and expanded the original Beremin model to include the effects of microcrack nucleation.

scholarly journals Estimation of the Fracture Toughness Threshold of a Ferritic Steel at the Lower Ductile to Brittle Transition Region

2016 ◽  
Vol 19 (5) ◽  
pp. 1102-1107
Author(s):  
Carlos Berejnoi ◽  
Santiago Vacca ◽  
Claudia Galarza ◽  
Juan Elías Perez Ipiña
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Ferritic Steel ◽  
Brittle Transition ◽  
Ductile To Brittle Transition

An Engineering Procedure for Calculating Cleavage Fracture Toughness From Charpy Specimen Data Using a Mechanistic Approach for Ferritic Steels

2014 ◽  
Author(s):  
Robin J. Smith ◽  
Andrew H. Sherry ◽  
Anthony J. Horn ◽  
Adam C. Bannister
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Ferritic Steel ◽  
Fracture Behaviour ◽  
Micromechanical Modeling ◽  
Charpy Specimen ◽  
Equivalent Material ◽  
Notch Angle ◽  
Engineering Approach ◽  
Steel Material

This research develops an engineering approach which permits the treatment of Charpy specimen absorbed energy data in the lower transition of Charpy specimen fracture behaviour. The procedure has been shown to be applicable to a ferritic steel study material. The calculation method comprises several steps to correct the input Charpy data to the equivalent material fracture toughness of a ferritic steel under consideration. The engineering procedure develops existing methods for constraint and notch correction to data [Sherry et al, EFM 2005] [Horn and Sherry, IJPVP 2012]. Micromechanical modeling of cleavage fracture behaviour has been applied in conjunction with sequential experimental testing. This work addresses the important geometric differences between a single edge notch bend, SEN(B), fracture toughness specimen and the standard Charpy V-notch specimen. The engineering approach is demonstrated using a suitable study ferritic steel material and by undertaking an experimental laboratory testing programme comprising standard fracture toughness specimens and non-standard U-notch and V-notch Charpy sized specimens with a range of notch geometries. It has been found that constraint and notch assessment methodologies premised upon micro-mechanical modeling of cleavage fracture offer an accurate probabilistic description of fracture behaviour in these specimen geometries. Refinement of a notch angle correction is necessary within the procedure. These findings permit the extension of the approach to develop a material specific guidance to practitioners undertaking structural integrity assessments. The final extension of the research to Charpy impact data requires the measurement of ferritic steel material flow behaviour under dynamic conditions and represents further research.

scholarly journals Dynamic Effects on Fracture Toughness for Ferritic Steel in the Ductile-to-Brittle Transition

2016 ◽  
Author(s):  
C. Jacquemoud ◽  
I. Delvallée-Nunio ◽  
F. Balestreri
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Static Analysis ◽  
Ferritic Steel ◽  
Reference Temperature ◽  
Static Tests ◽  
Integrity Assessment ◽  
Brittle Transition ◽  
Thermal Chamber ◽  
Ductile To Brittle Transition

Dynamic loading effects on fracture toughness of ferritic steel have been evaluated in the ductile-to-brittle transition, considering loading rates representative of object drops. To verify that the design fracture toughness curve, initially defined from static tests, remains conservative for the integrity assessment of object submitted at low temperature to a dynamic impact due to a drop, experiments on 16MND5 ferritic steel have been performed. A three-point bending set-up and a thermal chamber have been designed in order to perform dynamic fracture tests on large Single Edge-notched Bending SE(B) specimens, at very low temperature. Considering that the reference temperature of the material is −122°C (defined from quasi-static tests), dynamic drop tests have been performed at −120°C, −80°C and 0°C in order to cover the ductile-to-brittle transition of the material. A shift of +80°C of the reference temperature has been observed with the increase in the stress intensity rate, from less than 1 MPa.m0.5/s in quasi-static tests to values up to 105 MPa.m0.5/s for the dynamic SE(B) tests. Numerical simulations of the tests, compared to classical static analysis, have confirmed that the effects of inertia and viscosity on fracture toughness are negligible at these temperatures (<0°C). Equivalent static analysis appears sufficient to study such dynamic tests.

Assessing the Loading Rate for a Fracture Toughness Test in the Ductile-to-Brittle Transition Region

2008 ◽  
Vol 5 (3) ◽  
pp. 101467
Author(s):  
Enrico Lucon ◽  
Marc Scibetta ◽  
R. Neu ◽  
K. Wallin ◽  
S. R. Thompson ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Transition Region ◽  
Loading Rate ◽  
Fracture Toughness Test ◽  
Brittle Transition ◽  
Toughness Test ◽  
Ductile To Brittle Transition
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