scholarly journals Constraint Assessment for Specimens Tested Under Uniaxial and Biaxial Loading Conditions

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Yupeng Cao ◽  
Guian Qian ◽  
Yinbiao He ◽  
Markus Niffenegger ◽  
Yuh J. Chao
Keyword(s):  
Fracture Toughness ◽  
Material Property ◽  
Structural Integrity ◽  
Biaxial Loading ◽  
Compact Tension ◽  
Pressure Vessels ◽  
Test Method ◽  
Biaxial Stress ◽  
Operating Life ◽  
Integrity Assessment

In structural integrity analysis of reactor pressure vessels (RPVs), a postulated shallow crack is subjected to biaxial far-field stresses. However, the fracture toughness Kc or Jc, which is an important material property for the structural integrity assessment of RPVs, is usually obtained from testing deeply cracked compact tension (C(T)) or single-edged bending (SE(B)) specimens under uniaxial loading. Thus, the fracture toughness data do not reflect the biaxial loading state that cracks in a RPV are subjected to. Cruciform bending specimen was therefore developed to simulate the biaxial stress state. In this paper, a series of finite element (FE) simulations of the cruciform specimens containing different crack geometries and of different material properties are conducted. The crack tip stress fields are analyzed, and the constraint is investigated using the J–A2 theory. The results show that the biaxial effect is material property dependent which could be useful for the optimization of the test method and the better design of cruciform specimens. The trends about the biaxial loading effect revealed in this study would also be helpful in estimating the safe operating life of RPVs.

scholarly journals Constraint Assessment for Cruciform Specimens With a Semi-Elliptical Crack

2018 ◽  
Author(s):  
Yupeng Cao ◽  
Guian Qian ◽  
Yinbiao He ◽  
Yuh J. Chao
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Material Property ◽  
Structural Integrity ◽  
Biaxial Loading ◽  
Compact Tension ◽  
Biaxial Stress ◽  
Integrity Assessment ◽  
Shallow Crack ◽  
Crack Tip Constraint

A real crack to be assessed in a RPV is generally a shallow crack subjected to biaxial far-field stresses. However, the fracture toughness Kc or Jc, which is an important material property for the structural integrity assessment of RPV containing cracks, are usually tested on deep cracked compact tension [C(T)] or single-edged bending [SE(B)] specimens under uniaxial loading. The fracture toughness data do not reflect the realistic biaxial loading state that the cracks are subjected to. Cruciform bending [CR(B)] specimen is therefore developed to simulate the biaxial stress state. In this paper, a series of finite element (FE) simulations of the CR(B) specimens containing different semi-elliptical cracks are conducted. Stress-strain curves of materials of different yield strength and hardening behavior reflecting the variation in the mechanical properties of RPV steels due to aging or temperature change are implemented into the finite element models. The J-A2 theory is applied to analyze the crack tip constraint. The results show that the biaxial effect is material property dependent and affected by load levels.

scholarly journals Constraint Assessment for Specimens Tested Under Uniaxial and Biaxial Loading Conditions

2017 ◽  
Author(s):  
Yupeng Cao ◽  
Guian Qian ◽  
Yinbiao He ◽  
Yuh J. Chao ◽  
Markus Niffenegger
Keyword(s):  
Fracture Toughness ◽  
Material Property ◽  
Biaxial Loading ◽  
Compact Tension ◽  
Biaxial Stress ◽  
Integrity Assessment ◽  
Crack Tips ◽  
Shallow Crack ◽  
Crack Tip Constraint ◽  
Integrity Analysis

In the integrity analysis of a reactor pressure vessel (RPV), a postulated shallow crack is subjected to biaxial far-field stresses. However, the fracture toughness Kc or Jc, which is an important material property for the integrity assessment of a RPV, are usually tested with deeply-cracked compact tension [C(T)] or single-edged bending [SE(B)] specimens under uniaxial loading. Thus, the fracture toughness data do not reflect the biaxial loading state that the cracks in a RPV are subjected to. Cruciform bending specimen is therefore developed to simulate the biaxial stress state. In this paper, a series of finite element (FE) simulations of the cruciform specimens containing different crack geometries and of different material properties are conducted. The crack tip constraint is investigated using the J-A2 theory and the stress field near the crack tips is analyzed. The results show that the biaxial effect is material property dependent. This can contribute to the lifetime prediction of a RPV as well as better design of cruciform specimens.

Estimation of Through-Wall Cracking Frequency of RPV Under PTS Events Using PFM Analysis Method for Identifying Conservatism Included in Current Japanese Code

2014 ◽  
Author(s):  
Kazuya Osakabe ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Assessment Procedure ◽  
Analysis Method ◽  
Integrity Assessment ◽  
The U.S

To assess the structural integrity of reactor pressure vessels (RPVs) during pressurized thermal shock (PTS) events, the deterministic fracture mechanics approach prescribed in Japanese code JEAC 4206-2007 [1] has been used in Japan. The structural integrity is judged to be maintained if the stress intensity factor (SIF) at the crack tip during PTS events is smaller than fracture toughness KIc. On the other hand, the application of a probabilistic fracture mechanics (PFM) analysis method for the structural reliability assessment of pressure components has become attractive recently because uncertainties related to influence parameters can be incorporated rationally. A probabilistic approach has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. According to the PFM analysis method in the U.S., through-wall cracking frequencies (TWCFs) are estimated taking frequencies of event occurrence and crack arrest after crack initiation into consideration. In this study, in order to identify the conservatism in the current RPV integrity assessment procedure in the code, probabilistic analyses on TWCF have been performed for certain model of RPVs. The result shows that the current assumption in JEAC 4206-2007, that a semi-elliptic axial crack is postulated on the inside surface of RPV wall, is conservative as compared with realistic conditions. Effects of variation of PTS transients on crack initiation frequency and TWCF have been also discussed.

Development of Probabilistic Evaluation Models of Fracture Toughness KIc and KIa for Japanese RPV Steels

2015 ◽  
Author(s):  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa ◽  
Kazuya Osakabe ◽  
Kentaro Yoshimoto
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Fracture Probability ◽  
Pressure Vessels ◽  
Confidence Limits ◽  
Lognormal Distributions ◽  
Integrity Assessment ◽  
Probabilistic Evaluation ◽  
Evaluation Models ◽  
Reactor Pressure

Probabilistic fracture mechanics (PFM) analysis code PASCAL3 has been developed to apply the PFM analysis to the structural integrity assessment of domestic reactor pressure vessels (RPVs). In this paper, probabilistic evaluation models of fracture toughness KIc and KIa which have the largest scatter among the associated factors based on the database of Japanese RPV steels are presented. We developed probabilistic evaluation models for KIc and KIa based on the Weibull and lognormal distributions, respectively. The models are compared with the existing lower bound of fracture toughness in the Japanese code and probabilistic model in USA. As the results, the 5% confidence limits of the models established in present work corresponded to lower bounds of fracture toughness in the Japanese code. The comparison in the models between present work and USA showed significant differences that may have an influence on fracture probability of RPV.

Procedures on Fracture Toughness Estimation Safety Assessment and Life Extension for In-Service High Pressure Vessels

2004 ◽  
Author(s):  
Guohua Chen ◽  
Bonuan Chen
Keyword(s):  
Fracture Toughness ◽  
High Pressure ◽  
Safety Assessment ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Life Extension ◽  
Temper Brittleness ◽  
Integrity Assessment ◽  
Treatment Processes ◽  
Material Fracture

Based on the typical in-service high pressure vessels made of PCrNi3MoVA for producing synthetic crystal, a systematic technology of material fracture toughness estimation, structural integrity assessment, and life extension is carried out for the in-service equipment with the following aspects: macroscopically and microscopically analyzing, the tests including KIC, AKV, FATT (50%), the predicting method of fracture, system safety assessment, and the life extension technology. Some practical conclusions can be obtained from the test and analysis as follows: The main failure factors for this kind of high pressure vessels include heat treatment processes, temper brittleness, and stress corrosion; It is found that the value of FATT (50%) increased very significantly; The comparison between the test results and the predicted results of the value of KIC is also performed, and it is shown that the value of KIC of in-service equipment can be estimated by the formula presented by Barsom-Rolfe or in API 579 with the value of AKV, The test temperature is recommended at least to reach 25 C (or room temperature) for the repaired vessels; The life extension technologies are put forward for this kind of in-service super-high pressure vessels.

Study on Application of PFM Analysis Method to Japanese Code for RPV Integrity Assessment Under PTS Events

2015 ◽  
Author(s):  
Kazuya Osakabe ◽  
Koichi Masaki ◽  
Jinya Katsuyama ◽  
Genshichiro Katsumata ◽  
Kunio Onizawa ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Input Data ◽  
Structural Integrity ◽  
Probabilistic Approach ◽  
Pressure Vessels ◽  
Analysis Method ◽  
Integrity Assessment ◽  
Analysis Models ◽  
Reactor Pressure ◽  
The U.S

A probabilistic fracture mechanics (PFM) analysis method for pressure boundary components is useful to evaluate the structural integrity in a quantitative way. This is because the uncertainties related to influence parameters can be rationally incorporated in PFM analysis. From this viewpoint, the probabilistic approach evaluating through-wall cracking frequencies (TWCFs) of reactor pressure vessels (RPVs) has already been adopted as the regulation on fracture toughness requirements against PTS events in the U.S. As a study of applying PFM analysis to the integrity assessment of domestic RPVs, JAEA has been preparing input data and analysis models to calculate TWCFs using PFM analysis code PASCAL3. In this paper, activities have been introduced such as preparing input data and models for domestic RPVs, verification of PASCAL3, and formulating guideline on general procedures of PFM analysis for the purpose of utilizing PASCAL3. In addition, TWCFs for a model RPV evaluated by PASCAL3 are presented.

Size Effects on Fracture in Uncontained Plasticity Conditions in 304(L) Stainless Steel

2011 ◽  
Author(s):  
Andrew P. Wasylyk ◽  
Andrew H. Sherry
Keyword(s):  
Fracture Toughness ◽  
Plastic Zone ◽  
Crack Growth ◽  
Structural Integrity ◽  
Plastic Zone Size ◽  
Compact Tension ◽  
Specimen Size ◽  
Image Correlation ◽  
Local Approach ◽  
Integrity Assessment

In the structural integrity assessment of structures containing defects, ductile tearing and plastic collapse are treated as competing failure mechanisms. The validity of fracture toughness measurements in test specimens is limited by the development of plasticity ahead of the crack tip. Compact Tension (CT) specimens are commonly used to characterise the ductile fracture toughness. Three sizes of CT specimens (thickness 25, 15 and 10mm) were tested using the unloading compliance technique and the J-Resistance curve characterised. Concurrently, the development of the plastic zone was monitored on the surface of specimens using digital image correlation. This enabled the plastic zone size to be correlated with the evolution of crack growth. It was found that in all specimens no crack growth occurred prior to plastic yielding of the un-cracked ligament on the specimen surface. Furthermore, a reduction in initiation and tearing toughness was observed with reduction in specimen size. The Rice and Tracey local approach was developed to predict the specimen size effect.

Evolution of Plasticity in Relation to Ductile Tearing in 304(L) Stainless Steel

2010 ◽  
Author(s):  
Andrew P. Wasylyk ◽  
Andrew H. Sherry
Keyword(s):  
Fracture Toughness ◽  
Plastic Zone ◽  
Crack Growth ◽  
Structural Integrity ◽  
Plastic Zone Size ◽  
Compact Tension ◽  
Image Correlation ◽  
Ductile Tearing ◽  
Integrity Assessment ◽  
Unloading Compliance

In the structural integrity assessment of structures containing defects, ductile tearing and plastic collapse are treated as competing failure mechanisms. The validity of fracture toughness measurements in test specimens is limited by the development of plasticity ahead of the crack tip. Compact Tension (CT) specimens are commonly used to characterise the ductile fracture toughness. Two sizes of CT specimens (thickness 25 and 15mm) were tested using the unloading compliance technique and the J-Resistance curve characterised. Concurrently, the development of the plastic zone was monitored on the surface of specimens using digital image correlation. This enabled the plastic zone size to be correlated with the evolution of crack growth. It was found that in both specimens no crack growth had occurred prior to plastic yielding of the un-cracked ligament on the specimen surface.

Constraint Effect On Fracture Behavior of Underclad Crack in Reactor Pressure Vessel

2021 ◽  
Author(s):  
Masaki Shimodaira ◽  
Tohru Tobita ◽  
Hisashi Takamizawa ◽  
Jinya Katsuyama ◽  
Satoshi Hanawa
Keyword(s):  
Fracture Toughness ◽  
Surface Crack ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Compact Tension ◽  
Reactor Pressure Vessel ◽  
Local Approach ◽  
Integrity Assessment ◽  
Plastic Constraint ◽  
Reactor Pressure

Abstract According to JEAC4206-2016, in the structural integrity assessment of a reactor pressure vessel (RPV), the fracture toughness (KJc) should be higher than the stress intensity factor at the crack tip of a postulated underclad crack (UCC) near the inner surface of the RPV during a pressurized thermal shock event. Previous analytical studies show that the plastic constraint for UCC is lower than that for surface crack. Consequently, the apparent KJc for UCC is expected to be higher than that for surface crack. In this study, we performed three-point bending fracture toughness tests and finite element analyses (FEAs) for RPV steel containing a UCC or a surface crack to quantitatively investigate the effect of cladding on the plastic constraint and subsequent KJc evaluation. From the tests, we found that the apparent KJc for the UCC was considerably higher than that for the surface crack. Such a high KJc could be explained by the lower plastic constraint parameters, such as T-stress and Q-parameter, of the UCC compared with those for the surface crack. Additionally, local approach analysis showed that the KJc for the UCC was significantly higher than the master curve estimated from the fracture toughness tests using compact tension specimens.

French RPV PTS Assessment: An Overview of EDF Research and Development in Progress on Thermalhydraulic, Materials and Mechanical Aspects

2003 ◽  
Author(s):  
Dominique Moinereau ◽  
Jean-Michel Frund ◽  
Henriette Churier-Bossennec ◽  
Georges Bezdikian ◽  
Alain Martin
Keyword(s):  
Structural Integrity ◽  
Three Dimensional ◽  
Crack Arrest ◽  
Pressure Vessels ◽  
Short Description ◽  
Constraint Effect ◽  
Materials Properties ◽  
Integrity Assessment ◽  
Pressurized Thermal Shock ◽  
Reactor Pressure

A significant extensive Research & Development work is conducted by Electricite´ de France (EDF) related to the structural integrity re-assessment of the French 900 and 1300 MWe reactor pressure vessels in order to increase their lifetime. Within the framework of this programme, numerous developments have been implemented or are in progress related to the methodology to assess flaws during a pressurized thermal shock (PTS) event. The paper contains three aspects: a short description of the specific French approach for RPV PTS assessment, a presentation of recent improvements on thermalhydraulic, materials and mechanical aspects, and finally an overview of the present R&D programme on thermalhydraulic, materials and mechanical aspects. Regarding the last aspect on present R&D programme, several projects in progress will be shortly described. This overview includes the redefinition of some significant thermalhydraulic transients based on some new three-dimensional CFD computations (focused at the present time on small break LOCA transient), the assessment of vessel materials properties, and the improvement of the RPV PTS structural integrity assessment including several themes such as warm pre-stress (WPS), crack arrest, constraint effect ....

Sign in / Sign up

Export Citation Format

Share Document