A Closer Look at Effects of the Loading Rate on Fracture Toughness in the Ductile-to-Brittle Transition Regime of a Ferritic Steel

2014 ◽  
Vol 43 (3) ◽  
pp. 20120321 ◽  
Author(s):  
Hans-Jakob Schindler ◽  
Dietmar Kalkhof
Keyword(s):  
Fracture Toughness ◽  
Ferritic Steel ◽  
Loading Rate ◽  
Transition Regime ◽  
Brittle Transition ◽  
Ductile To Brittle Transition

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.

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

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

scholarly journals Incorporation of Obstacle Hardening into Local Approach to Cleavage Fracture to Predict Temperature Effects in the Ductile to Brittle Transition Regime

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1224
Author(s):  
Maria S. Yankova ◽  
Andrey P. Jivkov ◽  
Rajesh Patel
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Cleavage Crack ◽  
Pressure Vessel Steel ◽  
Transition Regime ◽  
Vessel Steel ◽  
Integrity Assessment ◽  
Brittle Transition ◽  
Ductile To Brittle Transition ◽  
Weibull Stress

Ductile-to-brittle-transition refers to observable change in fracture mode with decreasing temperature—from slow ductile crack growth to rapid cleavage. It is exhibited by body-centred cubic metals and presents a challenge for integrity assessment of structural components made of such metals. Local approaches to cleavage fracture, based on Weibull stress as a cleavage crack-driving force, have been shown to predict fracture toughness at very low temperatures. However, they are ineffective in the transition regime without the recalibration of Weibull stress parameters, which requires further testing and thus diminishes their predictive capability. We propose new Weibull stress formulation with thinning function based on obstacle hardening model, which modifies the number of cleavage-initiating features with temperature. Our model is implemented as a post-processor of finite element analysis results. It is applied to analyses of standard compact tension specimens of typical reactor pressure vessel steel, for which deformation and fracture toughness properties in the transition regime are available. It is shown that the new Weibull stress is independent of temperature, and of Weibull shape parameter, within the experimental error. It accurately predicts the fracture toughness at any temperature in the transition regime without relying upon empirical fits for the first time.

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