Statistical and Constraint Loss Size Effects on Cleavage Fracture–Implications to Measuring Toughness in the Transition

2005 ◽  
Vol 128 (3) ◽  
pp. 305-313 ◽  
Author(s):  
H. J. Rathbun ◽  
G. R. Odette ◽  
T. Yamamoto ◽  
M. Y. He ◽  
G. E. Lucas
Keyword(s):  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Size Effects ◽  
Three Dimensional ◽  
Crack Tip ◽  
Systematic Investigation ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Point Bend ◽  
The Individual

A systematic investigation of the effects of specimen size on the cleavage fracture toughness of a typical pressure vessel steel is reported. Size dependence arises both from: (i) statistical effects, related to the volume of highly stressed material near the crack tip, that scales with the crack front length (B) and (ii) constraint loss, primarily associated with the scale of plastic deformation compared to the un-cracked ligament dimension (b). Previously, it has been difficult to quantify the individual contributions of statistical versus constraint loss size effects. Thus, we developed a single variable database for a plate section from the Shoreham pressure vessel using a full matrix of three point bend specimens, with B from 8 to 254 mm and b from 3.2 to 25.4 mm, that were tested at a common set of conditions. The University of California Santa Barbara (UCSB) b-B database was analyzed using three-dimensional finite element calculation of the crack tip fields combined with a cleavage model calibrated to the local fracture properties of the Shoreham steel. This paper focuses on the possible significance of these results to the Master Curve standard as formulated in ASTM E 1921. The statistical scaling procedure to treat variations in B used in E 1921 was found to be reasonably consistent with the UCSB b-B database. However, constraint loss for three point bend specimens begins at a deformation level that is much lower than the censoring limit specified in E 1921. Unrecognized constraint loss leads to a nonconservative, negative bias in the evaluation of To, estimated to be typically on the order of −10°C for pre-cracked Charpy specimens.

Statistical and Constraint Loss Size Effects on Cleavage Fracture: Implications to Measuring Toughness in the Transition

2003 ◽  
Author(s):  
H. J. Rathbun ◽  
G. R. Odette ◽  
T. Yamamoto ◽  
M. Y. He ◽  
G. E. Lucas
Keyword(s):  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Size Effects ◽  
Three Dimensional ◽  
Crack Tip ◽  
Systematic Investigation ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Master Curve Method ◽  
The Individual

A systematic investigation of the effects of specimen size on the cleavage fracture toughness of a typical pressure vessel steel is reported. Size dependence arises both from: i) statistical effects, related to the volume of highly stressed material near the crack tip, that scales with the crack front length (B); and ii) constraint loss, primarily associated with the scale of plastic deformation compared to the uncracked ligament dimension (b). Previously, it has been difficult to quantify the individual contributions of statistical versus constraint loss to size effects. Thus, we developed a single variable database for a plate section from the Shoreham pressure vessel using a full matrix of bend specimens, with B from 8 to 254 mm and b from 3.2 to 25.4 mm, that were tested at a common set of conditions. The University of California Santa Barbara (UCSB) b-B database was analyzed using three-dimensional finite element simulations of the crack tip fields combined with a cleavage model calibrated to the local fracture properties of the Shoreham steel. This paper focuses on the possible significance of these results to the Master Curve Method Standard as formulated ASTM E 1921-97. The statistical scaling procedure used in E 1921-97 to treat variations in B was found to be reasonably consistent with the UCSB b-B database. However, constraint loss for bend specimens begins at a deformation level that is much lower than the censoring limit specified in E 1921-97. Unrecognized constraint loss leads to a non-conservative, negative bias in the evaluation of To, estimated to be typically on the order of a −10°C for pre-cracked Charpy specimens.

scholarly journals A Local Approach to Assess Effects of Specimen Geometry on Cleavage Fracture Toughness in Reactor Pressure Vessel Steels

2018 ◽  
Author(s):  
Diego F. B. Sarzosa ◽  
Rafael Savioli ◽  
Claudio Ruggieri ◽  
Andrey Jivkov ◽  
Jack Beswick
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Crack Size ◽  
Size Ratio ◽  
Additional Contribution ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Shallow Crack

This work presents recent improvements in the micromechanical failure criterion based on the Weibull stress (σw) concept for prediction of cleavage fracture in ferritic steels. The model is applied in SE(B) specimens extracted from an ASTM A533 pressure vessel steel having different levels of stress triaxiality at the crack tip. Nonlinear 3D finite element models with dimensions matching the tested specimens were built to provide the necessary crack tip stresses at the fracture process zone for calculation of the σw-J evolution from wich the variation of characteristic toughness values (J0) between different cracked geometries can be estimated. Application of this methodology for the material used at this study is able to predict J0 for SE(B) specimens with very shallow crack size ratio a/W = 0.05, short crack a/W = 0.2 and deep crack a/W = 0.4. The reported fracture toughness values for specimens having very shallow crack size ratio is an additional contribution of this study.

scholarly journals Micromagnetic Characterization of Operation-Induced Damage in Charpy Specimens of RPV Steels

2021 ◽  
Vol 11 (7) ◽  
pp. 2917
Author(s):  
Madalina Rabung ◽  
Melanie Kopp ◽  
Antal Gasparics ◽  
Gábor Vértesy ◽  
Ildikó Szenthe ◽  
...  
Keyword(s):  
Neutron Irradiation ◽  
Pressure Vessel ◽  
Operating Conditions ◽  
Magnetic Characteristics ◽  
Pressure Vessel Steel ◽  
Training Procedure ◽  
Vessel Steel ◽  
Before And After ◽  
The Individual ◽  
Magnetic Adaptive Testing

The embrittlement of two types of nuclear pressure vessel steel, 15Kh2NMFA and A508 Cl.2, was studied using two different methods of magnetic nondestructive testing: micromagnetic multiparameter microstructure and stress analysis (3MA-X8) and magnetic adaptive testing (MAT). The microstructure and mechanical properties of reactor pressure vessel (RPV) materials are modified due to neutron irradiation; this material degradation can be characterized using magnetic methods. For the first time, the progressive change in material properties due to neutron irradiation was investigated on the same specimens, before and after neutron irradiation. A correlation was found between magnetic characteristics and neutron-irradiation-induced damage, regardless of the type of material or the applied measurement technique. The results of the individual micromagnetic measurements proved their suitability for characterizing the degradation of RPV steel caused by simulated operating conditions. A calibration/training procedure was applied on the merged outcome of both testing methods, producing excellent results in predicting transition temperature, yield strength, and mechanical hardness for both materials.

Effects of microstructure on cleavage fracture in pressure vessel steel

1986 ◽  
Vol 34 (6) ◽  
pp. 1121-1131 ◽  
Author(s):  
P. Bowen ◽  
S.G. Druce ◽  
J.F. Knott
Keyword(s):  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Pressure Vessel Steel ◽  
Vessel Steel

AE Evaluation of Relationship between AE Signals and Fracture Mechanisms for the Weldment of Pressure Vessel Steel

2007 ◽  
Vol 26-28 ◽  
pp. 1181-1186
Author(s):  
Eui Gyun Na ◽  
Seung Kee Koh ◽  
Dong Whan Lee
Keyword(s):  
Pressure Vessel ◽  
Phase Particle ◽  
Fracture Mechanisms ◽  
Second Phase ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Ae Signal ◽  
Point Bend ◽  
Ae Counts ◽  
Ae Signals

The purpose of this study is to find out the AE characteristics and fracture mechanisms through AE signal analysis for the weldment, PWHT specimen and basemetal of the pressure vessel steel. Charpy sized specimens were taken from the multi-passed weld block. Specimens were given to four point bend and AE tests. Lots of AE signals were emitted from the weldment compared with the basemetal and PWHT specimen. Besides, amplitude for the weldment was the largest, followed by PWHT specimen and basemetal and more AE counts for the weldment were emitted in the process of deformation. Lots of microcracks around the notch for the weldment were formed so that more AE signals were produced. In addition, second phase particle such as MgO for the basemetal acts as AE source. However, in case of weldment, debonding mechanisms between matrix and hard oxides which are formed during welding in air attributed to the emission of AE signals and softened particles for the PWHT specimen cause to produce the low level AE signals.

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