Stress intensity factor solutions for surface cracks with large aspect ratios in cylinders and plates

2021 ◽  
Vol 189 ◽  
pp. 104262
Author(s):  
Tairui Zhang ◽  
Kai Lu ◽  
Jinya Katsuyama ◽  
Yinsheng Li
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Surface Cracks ◽  
Aspect Ratios

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.

Stress Intensity Factors for Unusual Semi-Elliptical Surface Cracks With Ratio a/l Greater Than 0.5

2009 ◽  
Author(s):  
Christian Malekian ◽  
Eric Wyart ◽  
Michael Savelsberg ◽  
David Lacroix ◽  
Anne Teughels ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Finite Elements ◽  
Aspect Ratio ◽  
Intensity Factor ◽  
Crack Depth ◽  
Surface Cracks ◽  
Extended Finite Element ◽  
Aspect Ratios ◽  
Theoretical Limitation

Most of the literature about fracture mechanics treats cracks with a flaw aspect ratio a/l lower or equal to 0.5 where a is the crack depth and l the total length of the crack. The limitation to 0.5 corresponds to a semi-circular shape for surface cracks and to circular cracks for subsurface cracks. This limitation does not seem to be inspired by a theoretical limitation nor by a computational limit. Moreover, limiting the aspect ratio a/l to 0.5 may generate some unnecessary conservatism in flaw analysis. The present article deals with surface cracks in plates with more unusual aspect ratios a/l>0.5 (narrow cracks). A series of Finite-Elements calculations is made to compute the stress intensity factor KI for a large range of crack depths having an aspect ratio greater than 0.5. The KI values can be used with the same formalism as the ASME XI Appendix A, such that this approach can provide an extension above the inherent limitation to 0.5. Some of the results obtained are checked by using two different Finite-Elements softwares (Systus and Ansys), each one with a different cracked mesh. In addition, a comparison is made for some cases with results obtained by a XFEM approach (eXtended Finite-Element Method), where the crack does not need to be meshed in the same way as in classical Finite-Elements. The results show a reduction of stress intensity factor, sometimes significant, when considering a flaw aspect ratio above 0.5 instead of the conventional semi-circular flaw. They also show that it is not always possible to reduce the analysis of KI to only 2 points, namely the crack surface point and the crack deepest point. The growth by fatigue or by corrosion of a crack with such unusual shape should still be investigated.

Stress Intensity Factor Solutions for Circumferential Surface Cracks With Large Aspect Ratios in Pipes Subjected to Global Bending

2016 ◽  
Author(s):  
Kisaburo Azuma ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Do Jun Shim
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Depth ◽  
Piping System ◽  
Surface Cracks ◽  
Aspect Ratios ◽  
Piping Systems ◽  
Primary Water ◽  
Crack Depth Ratio

In some cracks attributed to primary water stress corrosion cracking, the crack depth a was greater than half-length of the crack 0.5ℓ. This paper presents details of stress intensity factor solutions for circumferential surface cracks with large aspect ratios a/ℓ in piping system subjected to global bending. The stress intensity factor solutions for semi-elliptical surface cracks were obtained by finite element analyses with quadratic hexahedron elements. Solutions at the deepest and the surface points of the cracks with various aspect ratio (0.5 ≤ a/ℓ ≤ 4.0), crack depth ratio (0.01 ≤ a/t ≤ 0.8) and pipe sizes ( 1/80 ≤ t/Ri ≤ 1/2) were investigated, where t and Ri are wall thickness and inner radius of pipe, respectively. Proposed stress intensity factor solutions for cracks with a/ℓ = 0.5 are consistent with the values reported in the previous study. The solutions developed in this study are widely applicable to various engineering problems related to crack evaluation in piping systems.

Closed-Form Stress Intensity Factor Solutions for Deep Surface Cracks in Cylinders Subjected to Global Bending

2017 ◽  
Author(s):  
Kisaburo Azuma ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Do Jun Shim
Keyword(s):  
Stress Intensity Factor ◽  
Water Stress ◽  
Stress Intensity ◽  
Aspect Ratio ◽  
Intensity Factor ◽  
Closed Form ◽  
Stress Corrosion Cracking ◽  
Surface Cracks ◽  
Aspect Ratios ◽  
Primary Water

Materials made of alloy 82/182/600 used in pressurized water reactors are known to be susceptible to primary water stress corrosion cracking. The depth, a, of flaws due to primary water stress corrosion cracking can be larger than half of the crack length c, which is referred to as cracks with large aspect ratios. The stress intensity factor solution for cracks plays an important role to predict crack propagation and failure. However, Section XI of the ASME Boiler and Pressure Vessel Code does not provide the solutions for cracks with large aspect ratio. This paper presents the stress intensity factor solutions for circumferential surface cracks with large aspect ratios in cylinders under global bending loads. Finite element solutions were used to fit closed-form equations with influence coefficients Ggb. The closed-form solutions for coefficient Ggb were developed at the deepest points and the surface points of the cracks with aspect ratio a/c ranged from 1.0 to 8.0.

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.

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