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.

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 Plates

2017 ◽  
Author(s):  
Kisaburo Azuma ◽  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Steven Xu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Corrosion ◽  
Closed Form ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Influence Coefficient ◽  
Surface Cracks ◽  
Deep Surface

Materials made of Alloy 82/182/600 used in light-water reactors are known to be susceptible to stress corrosion cracking. It is known that the depth a of some cracks due to primary water stress corrosion cracking is larger than the half-length c. 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 ratios a/c. In this study, closed-form stress intensity factor influence coefficients for deep surface cracks in plates are discussed. The crack tip stress distribution is represented by a fourth degree polynomial equation. Influence coefficient tables obtained by using finite element analysis in previous studies are used for curve fitting. The closed-form solutions for the coefficient were developed at the surface points and the deepest points of the cracks with aspect ratio a/c ranged from 1.0 to 8.0. The solutions for the points where the stress intensity factor reaches maximum were also investigated.

Stress-Intensity Factor for a Short Edge-Notched Specimen Subjected to Three-Point Loading

1967 ◽  
Vol 89 (1) ◽  
pp. 7-12 ◽  
Author(s):  
H. T. Akao ◽  
A. S. Kobayashi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Aspect Ratio ◽  
Intensity Factor ◽  
Numerical Technique ◽  
Bending Moment ◽  
Mapping Function ◽  
Notched Specimen ◽  
Short Edge ◽  
Aspect Ratios

Stress-intensity factors for a short edge-notched specimen with an aspect ratio of appoximately 2.7:1 and subjected to three-point loading were obtained by using Bowie’s numerical technique of expanding a mapping function. Numerical relations between the mapping function, aspect ratios, and crack depths of different specimens as well as numerical difficulty in convergence of the procedure are discussed. The results are compared with the nondimensionalized experimental results obtained by Kies, et al., for a larger aspect ratio of 8:1. The proportionality factor between bending moment and stress-intensity factor was approximately 10 percent lower than the corresponding factor for Kies’ specimen and is in substantial agreement with Gross’ results.

Interaction Relationship for High Aspect Ratio Semi-Elliptical Internal Surface Cracks in CO2 Pipelines

2013 ◽  
Vol 774-776 ◽  
pp. 581-584
Author(s):  
Qiao Jin
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Aspect Ratio ◽  
Intensity Factor ◽  
High Aspect Ratio ◽  
Internal Surface ◽  
Surface Cracks ◽  
Interaction Relationship

Surface cracks with aspect ratio can occur in pipelines subjected to corrosion attacks. There are few studies on interaction relationship for double semi-elliptical surface cracks with such high aspect ratio. This paper attempts to develop a finite element method to determine on interaction of two semi-elliptical internal surface cracks with high aspect ratio by analyzing two key fracture mechanics parameters, i.e., the stress intensity factor and the-stress. The numerical results prove that the existing flaw-interaction criteria are too general to lose the worthy of application especially in pipeline engineering.

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