THE USE OF XFEM FOR STRESS INTENSITY FACTOR ESTIMATION OF SURFACE CRACKS

2017 ◽  
Author(s):  
Antonio Almeida Silva ◽  
Marco Antonio dos Santos ◽  
Gabriel Coêlho
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Surface Cracks ◽  
Factor Estimation

Stress Intensity Factors for Circular-Arc Cracks in Plates

2018 ◽  
Author(s):  
D. J. Shim ◽  
S. Tang ◽  
T. J. Kim ◽  
N. S. Huh
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Crack Model ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Element Analysis ◽  
Crack Face ◽  
Circular Arc

Stress intensity factor solutions are readily available for flaws found in pipe to pipe welds or shell to shell welds (i.e., circumferential/axial crack in cylinder). In some situations, flaws can be detected in locations where an appropriate crack model is not readily available. For instance, there are no practical stress intensity factor solutions for circular-arc cracks which can form in circular welds (e.g., nozzle to vessel shell welds and storage cask closure welds). In this paper, stress intensity factors for circular-arc cracks in finite plates were calculated using finite element analysis. As a first step, stress intensity factors for circular-arc through-wall crack under uniform tension and crack face pressure were calculated. These results were compared with the analytical solutions which showed reasonable agreement. Then, stress intensity factors were calculated for circular-arc semi-elliptical surface cracks under the lateral and crack face pressure loading conditions. Lastly, to investigate the applicability of straight crack solutions for circular-arc cracks, stress intensity factors for circular-arc and straight cracks (both through-wall and surface cracks) were compared.

Closed-Form Stress Intensity Factor Solutions for Surface Cracks With Large Aspect Ratios in Plates

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Kisaburo Azuma ◽  
Yinsheng Li ◽  
Steven Xu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Closed Form ◽  
Influence Coefficient ◽  
Maximum Point ◽  
Surface Cracks ◽  
Fourth Degree ◽  
Aspect Ratios ◽  
Influence Coefficients

Abstract Alloy 82/182/600, which is used in light-water reactors, is known to be susceptible to stress-corrosion cracking. The depth of some of these cracks may exceed the value of half-length on the surface. Although the stress intensity factor (SIF) for cracks plays an important role in predicting crack propagation and failure, Section XI of the ASME Boiler and Pressure Vessel Code does not provide SIF solutions for such deep cracks. In this study, closed-form SIF solutions for deep surface cracks in plates are discussed using an influence coefficient approach. The stress distribution at the crack location is represented by a fourth-degree-polynomial equation. Tables for influence coefficients obtained by finite element analysis in the previous studies are used for curve fitting. The closed-form solutions for the influence coefficients were developed at the surface point, the deepest point, and the maximum point of a crack with an aspect ratio a/c ranging from 1.0 to 8.0, where a is the crack depth and c is one-half of the crack length. The maximum point of a crack refers to the location on the crack front where the SIF reaches a maximum value.

Analytical Solutions and Tools for Assessment of Surface Cracks in Cylindrical Components

2008 ◽  
Author(s):  
Igor Varfolomeyev ◽  
Dieter Beukelmann
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fatigue Loading ◽  
Complex Stress ◽  
Radial Coordinate ◽  
Cylinder Wall ◽  
Crack Plane ◽  
Surface Cracks ◽  
Inner Radius

The paper reviews some advanced stress intensity factor solutions derived for analyses of axial and circumferential surface cracks in cylindrical components subjected to variable stress fields. The solutions are examined considering their validity ranges with respect to the crack and cylinder geometry, ability to account for a complex stress distribution in the pipe wall, as well as their accuracy. A method for estimating errors in numerical stress intensity factor solutions is introduced and applied to a particular set of data. Examples of a leak-before-break assessment and crack growth calculations under thermal fatigue loading are included to demonstrate the solutions performance. The considered analytical stress intensity factor solutions yield close results provided that the stress field in the prospective crack plane is described by a smooth function of the radial coordinate. For two-dimensional stress profiles as well as for variable ratios of the cylinder wall thickness to the inner radius, a selective use of the solutions is recommended considering their specific features and validity ranges.

Effect of Weld Residual Stress Fitting on Stress Intensity Factor for Circumferential Surface Cracks in Pipe

2012 ◽  
Author(s):  
Do-Jun Shim ◽  
Matthew Kerr ◽  
Steven Xu
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Wall Thickness ◽  
Stress Intensity Factors ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Weld Residual Stress ◽  
Order Polynomial

Recent studies have shown that the crack growth of PWSCC is mainly driven by the weld residual stress (WRS) within the dissimilar metal weld. The existing stress intensity factor (K) solutions for surface cracks in pipe typically require a 4th order polynomial stress distribution through the pipe wall thickness. However, it is not always possible to accurately represent the through thickness WRS with a 4th order polynomial fit and it is necessary to investigate the effect of the WRS fitting on the calculated stress intensity factors. In this paper, two different methods were used to calculate the stress intensity factor for a semi-elliptical circumferential surface crack in a pipe under a given set of simulated WRS. The first method is the Universal Weight Function Method (UWFM) where the through thickness WRS distribution can be represented as a piece-wise cubic fit. In the second method, the through thickness WRS profiles are represented as a 4th order polynomial curve fit (both using the entire wall thickness data and only using data up to the crack-tip). In addition, three-dimensional finite element (FE) analyses (using the simulated weld residual stress) were conducted to serve as a reference solution. The results of this study demonstrate the potential sensitivity of stress intensity factors to 4th order polynomial fitting artifacts. The piece-wise WRS representations used in the UWFM was not sensitive to these fitting artifacts and the UWFM solutions were in good agreement with the FE results.

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