An Investigation of the Stress Intensity Factor Along a Corner Crack in Pressurizer Vent Nozzle Penetration Weld

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Sang-Min Lee ◽  
Jeong-Soon Park ◽  
Jin-Su Kim ◽  
Young-Hwan Choi ◽  
Hae-Dong Chung
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Structural Integrity ◽  
Operating Conditions ◽  
Corner Crack ◽  
Elastic Plastic ◽  
Material Fracture

Elastic–plastic fracture mechanics as well as linear-elastic fracture mechanics may be applied to evaluate a flaw in ferritic low alloy steel components for operating conditions when the material fracture resistance is controlled by upper shelf toughness behavior. In this paper, the distribution of the stress intensity factor (SIF) along a corner crack using elastic–plastic fracture mechanics technique is investigated to assess the effect of a structural factor on mechanical loads in pressurizer vent nozzle penetration weld. For this purpose, the stress intensity factor and the plastic-zone correction of a corner crack are calculated under internal pressure, thermal stress, and residual stress in accordance with Electric Power Research Institute (EPRI) equation and Irwin’s approach, respectively. The resulting stress intensity factor and the plastic-zone correction were compared with those obtained from Structural Integrity Associates (SIA) and Kinectrics Inc., and were observed to be in good agreement with Kinectrics results.

An Investigation of the Stress Intensity Factor Along a Corner Crack in Pressurizer Vent Nozzle Penetration Weld

2009 ◽  
Author(s):  
Sang-Min Lee ◽  
Jeong-Soon Park ◽  
Jin-Su Kim ◽  
Young-Hwan Choi ◽  
Hae-Dong Chung
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Structural Integrity ◽  
Operating Conditions ◽  
Corner Crack ◽  
Elastic Plastic ◽  
Material Fracture

Elastic-plastic fracture mechanics as well as linear-elastic fracture mechanics may be applied to evaluate a flaw in ferritic low alloy steel components for operating conditions when the material fracture resistance is controlled by upper shelf toughness behavior. In this paper, the distribution of the stress intensity factor along a corner crack using elastic-plastic fracture mechanics technique is investigated to assess the effect of a structural factor on mechanical loads in pressurizer vent nozzle penetration weld. For this purpose, the stress intensity factor and plastic zone correction of a corner crack are calculated under internal pressure, thermal stress and residual stress in accordance with Electric Power Research Institute (EPRI) equation and Irwin’s approach, respectively. The resulting stress intensity factor and plastic zone correction were compared with those obtained from Structural Integrity Associates (SIA) and Kinectrics, and were observed to be good agreement with Kinectrics results.

Application of 3D Fracture Mechanics for Improved Crack Growth Predictions of Gas Turbine Components

2017 ◽  
Author(s):  
Kanwardeep S. Bhachu ◽  
Santosh B. Narasimhachary ◽  
Sachin R. Shinde ◽  
Phillip W. Gravett
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Gas Turbine ◽  
Crack Growth ◽  
Structural Integrity ◽  
Crack Arrest ◽  
3D Crack Growth ◽  
Mechanics Analysis

Fracture mechanics analysis is essential for demonstrating structural integrity of gas turbine components. Usually, analyses based on simpler 2D stress intensity solutions provide reasonable approximations of crack growth. However, in some cases, simpler 2D solutions are too-conservative and does not provide realistic crack growth predictions; often due to its inability to account for actual 3D geometry, and complex thermal-mechanical stress fields. In such cases, 3D fracture mechanics analysis provides extra fidelity to crack growth predictions due to increased accuracy of the stress intensity factor calculations. Improved fidelity often leads to benefits for gas turbine components by reducing design margins, improving engine efficiency, and decreasing life cycle costs. In this paper, the application of 3D fracture mechanics analysis on a gas turbine blade for predicting crack arrest is presented. A comparison of stress intensity factor values from 3D and 2D analysis is also shown. The 3D crack growth analysis was performed by using FRANC3D in conjunction with ANSYS.

A Residual Stress Analysis of a Corner Crack in Pressurizer Vent Nozzle Penetration Weld

2009 ◽  
Author(s):  
Sang-Min Lee ◽  
Jeong-Soon Park ◽  
Young-Hwan Choi ◽  
Hae-Dong Chung ◽  
Doo-Ho Cho ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Welding Process ◽  
Corner Crack ◽  
Dissimilar Metal ◽  
Dissimilar Metal Welding ◽  
Metal Welding

There are some ferritic low alloy steel components including dissimilar metal welding parts in a nuclear power plant. Residual stress induced by welding process is one of the factors that may lead a sound component to have a defect. Therefore it is necessary that the distribution of residual stress is obtained to predict the behavior of a dissimilar metal welding part. In this paper, the distribution of residual stress obtained by finite element analysis is investigated to assess the stress intensity factor of a corner crack in pressurizer vent nozzle penetration weld. Then the stress intensity factor and plastic zone correction of a corner crack are calculated under internal pressure, thermal stress and residual stress in accordance with Electric Power Research Institute equation [1]. The resulting stress intensity factor and plastic-zone correction were compared with those obtained from Structural Integrity Associates.

Applicability of Stress Intensity Factor Solution for Flat Plate to Nozzle Crotch Corner Flaw

2016 ◽  
Author(s):  
Fuminori Iwamatsu ◽  
Katsumasa Miyazaki ◽  
Minoru Masuda ◽  
Fumihito Hirokawa
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Flat Plate ◽  
Structural Integrity ◽  
Nozzle Geometry ◽  
Plate Model ◽  
Flat Plates ◽  
Nozzle Geometries

The applicability of a stress intensity factor (SIF) solution for a flat plate with a surface flaw (flat plate model) to nozzle crotch corner flaw is investigated by using a 3-D finite element method (FEM). Flaws due to stress corrosion cracking (SCC), fatigue, etc. are frequently postulated or detected at discontinuity regions. To evaluate the structural integrity of flawed components, it is important to calculate fracture mechanics parameters rationally and appropriately. SIF is one of the key fracture mechanics parameters for linear elastic fracture mechanics evaluation. Therefore, almost all fitness-for-service codes, e.g. ASEM BPVC Section XI, JSME FFS Code and R6 provide SIF solutions. However, they essentially provide SIF solutions only for flat plates or cylinders with flaws. Since nozzle crotch corner suffers from stress concentration and there are a lot of nozzle geometry parameters, there is no direct SIF solution for arbitrary nozzle geometries. To estimate SIFs for nozzle crotch corner flaws rationally and appropriately, the applicability of the SIF solution for the flat plate model needs to be verified. SIFs were calculated by using 3-D FEM for a flawed nozzle, and the results were compared with those calculated by equations and coefficients in the code solution. Our comparison showed that the flat plate model is applicable to nozzle crotch corner flaws rationally and conservatively.

Evaluation of SCC Crack Growth Rate in BWR Water Based on Elastic-Plastic Fracture Mechanics Parameters

2015 ◽  
Author(s):  
Masahiro Takanashi ◽  
Yu Itabashi ◽  
Takashi Hirano
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Crack Growth Rate ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Elastic Plastic ◽  
Crack Growth Rates

This paper presents an applicability of elastic-plastic fracture mechanics parameters for evaluating a crack growth rate of stress corrosion cracking (SCC). Currently linear fracture mechanical approaches have been applied for the SCC crack growth evaluation, even though some cracks due to SCC are found in plastic deformation zones near welding where linear fracture mechanics is no longer applicable. In this paper, the authors have proposed an elastic-plastic parameter “equivalent stress intensity factor KJ” for evaluating the SCC crack growth rate based on the J-integral value, which is valid in both elastic and plastic stress fields. In order to verify the applicability of the evaluation by KJ, SCC crack growth tests were carried out in a simulated boiling water reactor (BWR) water. When the SCC crack growth rate was evaluated by the stress intensity factor K, no linear relationship between the K values and the crack growth rates was observed in the high K-value region, where a small-scale yielding condition was not met. The crack growth rates increased exponentially according to increasing the stress intensity factor to exceed the linear relationship. On the other hand, when the crack growth rate was evaluated by the elastic-plastic parameter KJ, a linear correlation between the KJ values and the crack growth rates was confirmed regardless the specimen size and the stress condition. This result suggests that by applying the elastic-plastic parameter KJ, the SCC crack growth rates in a wider range could be estimated easily with using a smaller specimen.

scholarly journals Optimisation Method for Determination of Crack Tip Position Based on Gauss-Newton Iterative Technique

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Bing Yang ◽  
Zhanjiang Wei ◽  
Zhen Liao ◽  
Shuwei Zhou ◽  
Shoune Xiao ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Relative Error ◽  
Crack Tip ◽  
Image Correlation ◽  
Preconditioned Conjugate Gradient ◽  
Loading Process ◽  
Tip Position

AbstractIn the digital image correlation research of fatigue crack growth rate, the accuracy of the crack tip position determines the accuracy of the calculation of the stress intensity factor, thereby affecting the life prediction. This paper proposes a Gauss-Newton iteration method for solving the crack tip position. The conventional linear fitting method provides an iterative initial solution for this method, and the preconditioned conjugate gradient method is used to solve the ill-conditioned matrix. A noise-added artificial displacement field is used to verify the feasibility of the method, which shows that all parameters can be solved with satisfactory results. The actual stress intensity factor solution case shows that the stress intensity factor value obtained by the method in this paper is very close to the finite element result, and the relative error between the two is only − 0.621%; The Williams coefficient obtained by this method can also better define the contour of the plastic zone at the crack tip, and the maximum relative error with the test plastic zone area is − 11.29%. The relative error between the contour of the plastic zone defined by the conventional method and the area of the experimental plastic zone reached a maximum of 26.05%. The crack tip coordinates, stress intensity factors, and plastic zone contour changes in the loading and unloading phases are explored. The results show that the crack tip change during the loading process is faster than the change during the unloading process; the stress intensity factor during the unloading process under the same load condition is larger than that during the loading process; under the same load, the theoretical plastic zone during the unloading process is higher than that during the loading process.

On notch fracture mechanics

2021 ◽  
Vol 87 (2) ◽  
pp. 56-64
Author(s):  
G. Pluvinage
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plastic Zone ◽  
Fracture Resistance ◽  
Notch Radius ◽  
Notch Stress Intensity Factor ◽  
Blunt Notch ◽  
Notch Stress

Different stress distributions for an elastic behavior are presented as analytical expressions for an ideal crack, a sharp notch and a blunt notch. The elastic plastic distribution at a blunt notch tip is analyzed. The concept of the notch stress intensity factor is deduced from the definition of the effective stress and the effective distance. The impacts of the notch radius and constraint on the critical notch stress intensity factor are presented. The paper ends with the presentation of the crack driving force Jρ for a notch in the elastic case and the impact of the notch radius on the notch fracture toughness Jρ,c. The notch fracture toughness Jρ,c is a measure of the fracture resistance which increases linearly with the notch radius due to the plastic work in the notch plastic zone. If this notch plastic zone does not invade totally the ligament, the notch fracture toughness Jρ,c is constant. This occurs when the notch radius is less than a critical one and there is no need to use the cracked specimen to measure a lower bound of the fracture resistance.

Structural Integrity of Penetration Nozzle of Reactor Pressure Vessel Head of PWR Plant

2008 ◽  
Author(s):  
Kiminobu Hojo ◽  
Naoki Ogawa ◽  
Yoichi Iwamoto ◽  
Kazutoshi Ohoto ◽  
Seiji Asada ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Complex Structure ◽  
Reactor Pressure Vessel ◽  
Reactor Pressure

A reactor pressure vessel (RPV) head of PWR has penetration holes for the CRDM nozzles, which are connected with the vessel head by J-shaped welds. It is well-known that there is high residual stress field in vicinity of the J-shaped weld and this has potentiality of PWSCC degradation. For assuring stress integrity of welding part of the penetration nozzle of the RPV, it is necessary to evaluate precise residual stress and stress intensity factor based on the stress field. To calculate stress intensity factor K, the most acceptable procedure is numerical analysis, but the penetration nozzle is very complex structure and such a direct procedure takes a lot of time. This paper describes applicability of simplified K calculation method from handbooks by comparing with K values from finite element analysis, especially mentioning crack modeling. According to the verified K values in this paper, fatigue crack extension analysis and brittle fracture evaluation by operation load were performed for initial crack due to PWSCC and finally structural integrity of the penetration nozzle of RPV head was confirmed.

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