Interrelation between Local and Global Characteristics of Cleavage Fracture

2013 ◽  
Vol 592-593 ◽  
pp. 221-224
Author(s):  
Vladimir Grishchenko ◽  
Sergiy Kotrechko ◽  
Sergey Mamedov ◽  
Oleksandra Zatsarna ◽  
Ivo Dlouhý
Keyword(s):  
Cleavage Fracture ◽  
High Strength Steels ◽  
High Strength ◽  
Fracture Initiation ◽  
Calibration Procedure ◽  
Local Approach ◽  
Notched Specimens ◽  
Distribution Parameters ◽  
Reactor Pressure

The complexity of calibration procedure for determination of Weibull distribution parameters as well as necessity to perform FEM calculations is one of the shortcomings of conventional versions of Local Approach (LA). This report presents an attempt to ascertain interrelation between local and global characteristics of fracture of pre-cracked and notched specimens of reactor pressure vessel steels, high-strength steels etc. Criterion of cleavage fracture initiation ahead of a crack (notch) is formulated. Dimensionless parameter characterizing the effect of embrittlement by the crack or notch is proposed on the basis of this criterion. Based on the findings of low-temperature tests of pre-cracked or notched specimens of structural steels, it is proved that this parameter may be determined by both local and global characteristics.

Effect of Prestrain at Elevated Temperature on the Fracture Behavior of High Strength Steels

1983 ◽  
Vol 105 (1) ◽  
pp. 16-20 ◽  
Author(s):  
K. Satoh ◽  
M. Toyoda ◽  
Y. Mutoh
Keyword(s):  
Elevated Temperature ◽  
Cleavage Fracture ◽  
Fracture Mechanism ◽  
Strain Aging ◽  
Fracture Behavior ◽  
Present Report ◽  
High Strength Steels ◽  
High Strength ◽  
Fracture Initiation ◽  
Initiation And Propagation

It is well known that fracture initiation behavior is influenced by weld thermal straining. In the present report, attention is focused on the influence of weld thermal straining on the fracture mechanism. The influence of prestrain at elevated temperature or strain-aging on the initiation and propagation behaviors of ductile and cleavage fracture in KD32 and HT80 steels is investigated. A relationship between the increase in the lowest temperature at which a tear dimple region can be observed (Ti) or the decrease in stretched zone width and the increase in hardness at the notch tip is found.

Method of Threshold Stress Determination for a Local Approach to Cleavage Fracture

2016 ◽  
Vol 258 ◽  
pp. 281-285 ◽  
Author(s):  
Sergiy Kotrechko ◽  
V. Gryshchenko ◽  
Vladislav Kozák ◽  
Ivo Dlouhý
Keyword(s):  
Cleavage Fracture ◽  
Threshold Stress ◽  
Liquid Nitrogen Temperature ◽  
Pressure Vessel Steel ◽  
Local Approach ◽  
Weibull Statistics ◽  
Vessel Steel ◽  
Reactor Pressure Vessel Steel ◽  
Reactor Pressure

The contribution is focused on a new methodology description for determination of threshold stress, as the third parameter in Beremin local approach to cleavage fracture that is using three-parameter Weibull statistics. Nature of the methodology lies in tensile testing of rounded notched specimens at liquid nitrogen temperature and corresponding calculations. Reactor pressure vessel steel was chosen as an example for the illustration.

Effect of Strain Paths on Formability Evaluation of TRIP Steels

2010 ◽  
Vol 89-91 ◽  
pp. 214-219 ◽  
Author(s):  
David Gutiérrez ◽  
A. Lara ◽  
Daniel Casellas ◽  
Jose Manuel Prado
Keyword(s):  
Strain Path ◽  
High Strength Steels ◽  
High Strength ◽  
Test Method ◽  
Forming Limit ◽  
Trip Steels ◽  
Advanced High Strength Steels ◽  
Strain Paths ◽  
Analysis System

The Forming Limit Diagrams (FLD) are widely used in the formability analysis of sheet metal to determine the maximum strain, which gives the Forming Limit Curve (FLC). It is well known that these curves depend on the strain path during forming and hence on the test method used to calculate them. In this paper, different stretching tests such as the Nakajima and the Marciniak tests were performed, with different sample geometries to obtain points in different areas of the FLD. An optical analysis system was used, which allows following the strain path during the test. The increasing use of advanced high-strength steels (AHSS) has created an interest in determining the mechanical properties of these materials. In this work, FLCs for a TRIP steel were determined using Nakajima and Marciniak tests, which revealed different strain paths depending on the type of test. Determination of the FLCs was carried out following the mathematical calculations indicated in the ISO 12004 standard and was also compared with an alternative mathematical method, which showed different FLCs. Finally, the tests were verified by comparing the strain paths of the Nakajima and Marciniak tests with a well-known mild steel.

Determination of global and local cleavage fracture characteristics of high strength bolt steels

2017 ◽  
Vol 59 (11-12) ◽  
pp. 945-950 ◽  
Author(s):  
Bo Wu ◽  
Benedikt Döbereiner ◽  
Zhengyin Piao ◽  
Björn Sabotke ◽  
Victoria Brinnel ◽  
...  
Keyword(s):  
Cleavage Fracture ◽  
High Strength ◽  
Fracture Characteristics ◽  
High Strength Bolt ◽  
Global And Local

Engineering Version of Local Approach to Fracture and its Application for RPV Lifetime Prediction

2019 ◽  
Vol 810 ◽  
pp. 15-20
Author(s):  
Sergiy Kotrechko ◽  
Galyna Zimina ◽  
Volodymyr Revka ◽  
Ivo Dlouhý
Keyword(s):  
Calibration Procedure ◽  
Pressure Vessel Steel ◽  
Brittle Strength ◽  
Local Approach ◽  
Vessel Steel ◽  
Reactor Pressure Vessel Steel ◽  
Cleavage Initiation ◽  
Radiation Induced ◽  
Surveillance Specimens ◽  
Reactor Pressure

Theoretical basis of the simplified (engineering) version of Local Approach (LA) to fracture is summarized, and the possibility of using this version to predict the lifetime of RPV steels is demonstrated. The concept of “effective” volume, , within which stresses and strains are uniformly distributed, but the magnitude of the probability of cleavage initiation are equal to their real values at given value of , underlies the proposed engineering version of LA. A function was selected to describe the temperature dependence of local cleavage stress, and a calibration procedure was proposed for determining the constants in this dependence from the results of tests of surveillance specimens. For weld metal of WWER-1000 reactors the dependences of brittle strength on fluence were obtained, and the maximum permissible fluence values were determined. It is shown that in addition to the radiation hardening, the radiation-induced reduction in the level of brittle strength, , has a significant effect on the radiation service life of reactor pressure vessel steel.

Application of Local Approach to Hydrogen Embrittlement Fracture Evaluation of High Strength Steels

2007 ◽  
Vol 539-543 ◽  
pp. 2155-2161 ◽  
Author(s):  
Shusaku Takagi ◽  
Satoshi Terasaki ◽  
Kaneaki Tsuzaki ◽  
Tadanobu Inoue ◽  
Fumiyoshi Minami
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Content ◽  
Fracture Property ◽  
Martensitic Steel ◽  
High Strength Steels ◽  
High Strength ◽  
New Method ◽  
Local Approach ◽  
Delayed Fracture ◽  
Ultra High Strength Steel

A new method for evaluating the hydrogen embrittlement (HE) susceptibility of ultra high strength steel was studied in order to propose a new method for assessing the delayed fracture property. The material used was 1400MPa tempered martensitic steel with the chemical composition 0.40C-0.24Si-0.81Mn-1.03Cr-0.16Mo(mass%). The local approach originally used for evaluating the brittle fracture property was applied to HE susceptibility assessment after modifying the method to include the effect of hydrogen content. Critical HE data used in the modified local approach was obtained by a stepwise test in which alternating processes of stress increase and stress holding were repeated until the specimen fractured. The specimen used in the stepwise test was 10 mm in diameter and the stress concentration factor was 4.9. Assessment of HE susceptibility for specimens with other dimensions entailed the use of a critical hydrogen content for failure, Hc, representing the maximum hydrogen content among the unfractured specimens in the HE test with constant loading. Matters to be noted for obtaining the material parameters are discussed.

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