scholarly journals Stress-Intensity-Factor Influence Coefficients for Semielliptical Inner-Surface Flaws in Clad Pressure Vessels

2009 ◽  
pp. 430-430-14 ◽  
Author(s):  
JA Keeney ◽  
JW Bryson
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Pressure Vessels ◽  
Influence Coefficients ◽  
Surface Flaws ◽  
Inner Surface

Stress Intensity Factor Influence Coefficients for External Surface Flaws in Boiling Water Reactor Pressure Vessels

2009 ◽  
Author(s):  
Shengjun Yin ◽  
Terry L. Dickson ◽  
Paul T. Williams ◽  
B. Richard Bass
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
External Surface ◽  
Pressure Vessels ◽  
Water Reactor ◽  
Influence Coefficients ◽  
Surface Flaws ◽  
Reactor Pressure

Over the service life of a nuclear power plant, the Boiling Water Reactor (BWR) may undergo many cool-down and heat-up thermal-hydraulic transients associated with, for example, scheduled refueling outages and other normal operational transients, or even possible overcooling transients. These thermal-hydraulic events can act on postulated surface flaws in BWRs and therefore impose potential risk on the structure integrity of Reactor Pressure Vessels (RPVs). Internal surface flaws are of interest for the BWRs under overcooling accidental scenarios, while external surface flaws are more vulnerable when the BWRs are subjected to heat-up transients. Stress Intensity Factor Influence Coefficient (SIFIC) databases for application to linear elastic fracture mechanics analyses of BWR pressure vessels which typically have an internal radius to wall thickness ratio (Ri/t) between 15 and 20 were developed for external surface breaking flaws. This paper presents three types of surface flaws necessary in fracture analyses of BWRs: (1) finite-length external surface flaws with aspect ratio of 2, 6, and 10. (2) infinite-length axial external surface flaws; and (3) 360° circumferential external surface flaws. These influence coefficients have been implemented and validated in the FAVOR fracture mechanics code developed at Oak Ridge National Laboratory (ORNL) for the US Nuclear Regulatory Commission (NRC). Although these SIFIC databases were developed in application to RPVs subjected to thermal-hydraulic transients, they could also be applied to RPVs under other general loading conditions.

Revision to Stress Intensity Factor Equations for ASME Section XI Appendix C-4000: Determination of Failure Mode

2018 ◽  
Author(s):  
Kiminobu Hojo ◽  
Steven Xu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Failure Mode ◽  
Inside Surface ◽  
Screening Procedure ◽  
Real Surface ◽  
Screening Criteria ◽  
Influence Coefficients ◽  
Surface Flaws

In ASME Section XI Appendix C for analytical evaluation of flaws in piping, a screening procedure is prescribed to determine the failure mode and analysis method for the flawed pipe. The end-of-evaluation period flaw dimensions, temperature, material properties, and pipe loadings are considered in the screening procedure. Equations necessary to calculate components of the screening criteria (SC) include stress intensity factor (K) equations. The K-equation for a pipe with a circumferential inside surface flaw in the 2017 Edition Section XI Appendix C-4000 is for a fan-shaped flaw. Real surface flaws are closer to semi-elliptical shape. As part of Section XI Working Group on Pipe Flaw Evaluation (WGPFE) activities, revision to stress intensity factor equations for circumferential surface flaws in Appendix C-4000 has been proposed. The proposed equations include closed-form equations for stress intensity influence coefficients G0 for membrane stress and Ggb for global bending stress for circumferential inside surface flaws. The rationale for the Code changes and technical basis for the proposed stress intensity factor equations are provided in this paper.

Closed-Form Relations for Stress Intensity Factor Influence Coefficients for Axial ID Surface Flaws in Cylinders for Appendix A of ASME Section XI

2014 ◽  
Author(s):  
Steven X. Xu ◽  
Darrell R. Lee ◽  
Douglas A. Scarth ◽  
Russell C. Cipolla
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Weight Function ◽  
Closed Form ◽  
Nuclear Power ◽  
Cubic Equation ◽  
Evaluation Procedures ◽  
Influence Coefficients ◽  
Surface Flaws

Analytical evaluation procedures for determining the acceptability of flaws detected during in-service inspection of nuclear power plant components are provided in Section XI of the ASME Boiler and Pressure Vessel Code. Linear elastic fracture mechanics based evaluation procedures in ASME Section XI require calculation of the stress intensity factor. In Article A-3000 of Appendix A of the 2013 Edition of ASME Section XI, the calculation of stress intensity factor for a surface crack is based on characterization of stress field with a cubic equation and use of stress intensity factor influence coefficients. The influence coefficients are only provided for a flat plate geometry. The ASME Section XI Working Group on Flaw Evaluation is in the process of rewriting Article A-3000 of Appendix A. Major updates include the implementation of an alternate method for calculation of the stress intensity factor for a surface flaw that makes explicit use of the Universal Weight Function Method and does not require a polynomial fit to the actual stress distribution, and the inclusion of stress intensity factor influence coefficients for the cylinder geometry. Tabular data of influence coefficients for the cylinder geometry are available in API 579-1/ASME FFS-1 2007. Effort has been made to develop closed-form relations for the stress intensity factor influence coefficients for the cylinder geometry based on API data. With the inclusion of the explicit weight function approach and the closed-form relations for influence coefficients, the procedures of Appendix A for the calculation of stress intensity factors can be used more efficiently. The development of closed-form relations for stress intensity factor influence coefficients for axial ID surface flaws in cylinders is described in this paper.

Stress Intensity Factor Solutions for Internal Longitudinal Semi-Circular Surface Flaws in a Cylinder Under Arbitrary Loading

1983 ◽  
Vol 105 (4) ◽  
pp. 309-315 ◽  
Author(s):  
Y. S. Lee ◽  
M. Raymund
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Degrees Of Freedom ◽  
Pressure Vessels ◽  
Loading Conditions ◽  
Arbitrary Loading ◽  
Surface Flaws ◽  
Circular Surface ◽  
Inside Radius

The behavior of semi-circular surface flaws in cylinders is of interest in the technology of pressure vessels. The object of this study is to determine the stress intensity factor distribution around the crack front under arbitrary loading conditions for a longitudinal semi-circular flaw with Ri/t = 10; where Ri is the inside radius of the cylinder, and t is the cylinder thickness. Six crack depths are studied under various loading conditions: a/t = 0.10, 0.25, 0.50, 0.65, 0.80, and 0.90, where a is the circular flaw radius. In general, the finite element method is used to determine the displacement solution. Parks’ stiffness derivative method is used to find the stress intensity factor distribution around the semi-circle. The immediate crack tip geometry is modeled by use of a “macro-element” containing over 1600 degrees of freedom. Four separate loadings are considered: 1) constant, 2) linear, 3) quadratic, and 4) cubic crack surface pressure. From these loadings, nondimensional magnification factors are derived to represent the resulting stress intensity factors. Comparisons are made with other investigators and results agree within 5 percent of published results.

Plasticity Correction on the Stress Intensity Factor Evaluation for Underclad Cracks Under Pressurized Thermal Shock Events

2016 ◽  
Author(s):  
Kai Lu ◽  
Jinya Katsuyama ◽  
Yinsheng Li
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Thermal Shock ◽  
Structural Integrity ◽  
Correction Method ◽  
Pressure Vessels ◽  
Ductile Material ◽  
Pressurized Thermal Shock ◽  
Inner Surface

When conducting structural integrity assessments for reactor pressure vessels (RPVs) under pressurized thermal shock (PTS) events, the stress intensity factor (SIF) is evaluated for a surface crack which is postulated near the inner surface of RPVs. It is known that cladding made of the stainless steel is a ductile material which is overlay-welded on the inner surface of RPVs for corrosion protection. Therefore, the plasticity of cladding should be considered in the SIF evaluation for a postulated underclad crack. In our previous study, we performed three-dimensional (3D) elastic and elastic-plastic finite element analyses (FEAs) for underclad cracks during PTS transients and discussed the conservatism of a plasticity correction method prescribed in the French code. In this study, additional FEAs were performed to further investigate the plasticity correction on SIF evaluation for underclad cracks. Based on the 3D FEA results, a new plasticity correction method was proposed for Japanese RPVs subjected to PTS events. In addition, the applicability of the new method was verified by studying the effects of the RPV geometry, cladding thickness and loading conditions. Finally, it is concluded that the newly proposed plasticity correction method can provide a more rational evaluation with a margin to some extent on SIFs of underclad cracks in Japanese three-loop RPVs.

Comparison of the Stress Intensity Factor Influence Coefficients for Axial ID Surface Cracks in Cylinders of RSE-M and API 579-1

2015 ◽  
Author(s):  
Patrick Le Delliou ◽  
Stéphane Chapuliot
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Nuclear Power ◽  
Crack Depth ◽  
Wall Stress ◽  
Surface Point ◽  
Evaluation Procedures ◽  
Influence Coefficients ◽  
Wide Range

Analytical evaluation procedures for determining the acceptability of flaw detected during in-service inspection of nuclear power plant components are provided in Appendix 5.4 of the French RSE-M Code. Linear elastic fracture mechanics based evaluation procedures require calculation of the stress intensity factor (SIF). In Appendix 5.4 of the RSE-M Code, influence coefficients needed to compute the SIF are provided for a wide range of surface axial or circumferential flaws in cylinders, the through-wall stress field being represented by a cubic equation. On the other hand, Appendix C of API 579-1 FFS procedure provides also a very complete set of influence coefficients. The paper presents the comparison of the influence coefficients from both documents, focused on axial ID semi-elliptical surface flaws in cylinders. The cylinder and crack geometries are represented by three ratios: Ri/t, a/t, and a/c, where Ri, t, a, and c are respectively the inner radius, the wall thickness, the crack depth and one-half of the crack length. The solutions for the coefficients G0 and G1 at the deepest point and at the surface point are investigated. At the deepest point, the agreement between the solutions is good, the relative difference being lower than 2 %, except for the plate (Ri/t = ∞) at a/c = 0.125 and 0.0625 and a/t = 0.8 (around 5 %). At the surface point, the agreement between both solutions is not so good. At this point, the relative differences depend strongly on the a/c ratio, being larger for elongated cracks (with low a/c ratios). However, it must be recalled that the absolute values of the coefficients are low at the surface point for elongated cracks, and that for these cracks the critical point regarding the stress intensity factor is the deepest point.

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