Stress Intensity Factor for Corner Cracks of Pressurized Tees

1980 ◽  
Vol 102 (1) ◽  
pp. 121-123 ◽  
Author(s):  
M. A. Mohamed ◽  
J. Schroeder
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Intensity Factor ◽  
Local Stress ◽  
Numerical Techniques ◽  
Intensity Factors ◽  
Local Stress Concentration ◽  
Corner Cracks ◽  
Good Agreement

A method based on local stress concentration is employed to estimate stress intensity factors for corner cracks at the crotch corner of pressurized tees. The method yields results which are in good agreement with data obtained using other advanced numerical techniques.

Evolution of Tenacity in Mixed Mode Fracture – Volumetric Approach

2020 ◽  
Vol 22 (4) ◽  
pp. 931-938
Author(s):  
O. Zebri ◽  
H. El Minor ◽  
A. Bendarma
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Mixed Mode ◽  
Local Stress ◽  
Critical Stress Intensity Factor ◽  
Mixed Mode Fracture ◽  
Intensity Factors ◽  
Singular Stress

AbstractIn fracture mechanics most interest is focused on stress intensity factors, which describe the singular stress field ahead of a crack tip and govern fracture of a specimen when a critical stress intensity factor is reached. In this paper, stress intensity factors which represents fracture toughness of material, caused by a notch in a volumetric approach has been examined, taking into account the specific conditions of loading by examining various U-notched circular ring specimens, with various geometries and boundary conditions, under a mixed mode I+II. The bend specimens are computed by finite element method (FEM) and the local stress distribution was calculated by the Abaqus/CAE. The results are assessed to determine the evolution of the stress intensity factor of different notches and loading distances from the root of notch. This study shows that the tenacity is not intrinsic to the material for all different geometries notches.

Stress Intensity Factor Interaction for Subsurface to Surface Flaw Transformations Under Stress Concentration Fields

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Pierre Dulieu ◽  
Valéry Lacroix ◽  
Kunio Hasegawa
Keyword(s):  
Stress Intensity Factor ◽  
Free Surface ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Concentration Field ◽  
Surface Flaw ◽  
Intensity Factors ◽  
Surface Proximity

If a single subsurface flaw is detected that is close to a component's free surface, a flaw-to-surface proximity rule is used to determine whether the flaw should be treated as a subsurface flaw, or transformed to a surface flaw. The transformation from subsurface to surface flaw is adopted as flaw-to-surface proximity rules in all fitness-for-service (FFS) codes. These proximity rules are applicable when the component's free surface is without a stress concentration. On the other hand, subsurface flaws have been found under notches, such as roots of bolts, toes in welded joints, or geometrical discontinuities of components. The stress intensity factors of the subsurface flaws are affected by the stress concentrations caused by the notches. The stress intensity factor of the subsurface flaw increases with increasing stress concentration factor of the notch and decreasing ligament distance between tip of the subsurface flaws and the notch, for a given notch width. Such subsurface flaws are transformed to surface flaws at a distance from the notch tip for conservative evaluations. This paper shows the interactions of stress intensity factors of subsurface flaws under stress concentration fields. Based on the interaction, a flaw-to-surface proximity criterion is proposed for a circular flaw under the stress concentration field induced by a notch.

Stress Intensity Factors for Unequal Longitudinal-Radial Cracks in Thick-Walled Cylinders

1991 ◽  
Vol 113 (1) ◽  
pp. 22-27 ◽  
Author(s):  
J. L. Desjardins ◽  
D. J. Burns ◽  
R. Bell ◽  
J. C. Thompson
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Finite Elements ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Two Dimensional ◽  
Intensity Factors ◽  
Radial Cracks ◽  
Good Agreement

Finite elements and two-dimensional photoelasticity have been used to analyze thick-walled cylinders which contain arrays of straight-fronted, longitudinal-radial cracks of unequal depth. The stress intensity factor K1 has been computed for the dominant crack and for some of the surrounding cracks. Cylinders with 2, 4, 6, 8, 16, 36 and 40 cracks have been considered. Good agreement has been obtained between the experimental and the numerical results and, for cylinders with 2 or 4 cracks, with previously published predictions. The results for all of the foregoing cases are used to develop simple, approximate techniques for estimating K1 for the dominant crack, when the total number of cracks is different from those that have been considered herein. Estimates of K1 obtained by these techniques agree well with corresponding finite element results.

Stress Intensity Factors for Reactor Vessel Nozzle Cracks

1978 ◽  
Vol 100 (2) ◽  
pp. 141-149 ◽  
Author(s):  
C. W. Smith ◽  
W. H. Peters ◽  
M. I. Jolles
Keyword(s):  
Stress Intensity Factor ◽  
Data Analysis ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Three Dimensional ◽  
Reactor Vessel ◽  
Intensity Factors ◽  
Independent Estimate ◽  
Self Similar ◽  
Corner Cracks

A method consisting of a marriage between frozen stress photoelasticity and a computerized least-squares data analysis for extracting stress intensity factor (SIF) distributions in three-dimensional cracked body problems is reviewed. Results from the application of the method to three programs dealing with nozzle corner cracks are discussed. The importance of using actual flaw shapes in analysis is stressed. It is concluded that the flaw growth in such problems is generally not self-similar due to the complexity and variety of boundary shapes. The experimental technique described appears to offer a viable independent estimate of SIF distributions for such problems.

Evaluation of stress intensity factors

1975 ◽  
Vol 10 (4) ◽  
pp. 217-224 ◽  
Author(s):  
D J Cartwright ◽  
D P Rooke
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Shape Factor ◽  
Intensity Factors ◽  
Crack Problems

Some of the more useful methods of evaluating stress intensity factors are presented in a concise form. The stress intensity factor is defined and compared with the more familiar stress concentration factor. The shape factor, the parameter which characterizes the shape of the crack, the orientation of the crack and the proximity of other boundaries, is introduced; the techniques for determining the shape factor are divided into theoretical and experimental. Each method is described with a minimum of mathematical detail; references are given to papers where the methods are more fully described and used to solve specific crack problems. The accuracy and usefulness of the methods is summarized.

Stress Intensity Factor Interaction of Subsurface Flaws Under Notches

2017 ◽  
Author(s):  
Kunio Hasegawa ◽  
Pierre Dulieu ◽  
Valery Lacroix
Keyword(s):  
Stress Intensity Factor ◽  
Free Surface ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Concentration Field ◽  
Surface Flaw ◽  
Intensity Factors ◽  
Surface Proximity

If a single subsurface flaw is detected that is close to the component free surface, a flaw-to-surface proximity rule is used to determine whether the flaw should be treated as a subsurface flaw, or transformed to a surface flaw. The transformation from subsurface to surface flaw is adopted as flaw-to-surface proximity rules in all fitness-for-service (FFS) codes. These proximity rules are used under the condition of the component free surface without stress concentration. On the other hand, subsurface flaws have been found under the notches, such as roots of bolts, toes in welded joints or geometrical discontinuities of components. The stress intensity factors of the subsurface flaws are affected by the stress concentrations caused by the notches. The interaction of stress intensity factor increases with increasing stress concentration factor and decreasing the ligament distance between the tips of the subsurface flaws and the notches for a given notch width. Such subsurface flaws shall be transformed to surface flaws at far distance of the notch tips for conservative evaluations. This paper shows the interactions of stress intensity factors of subsurface flaws under stress concentration fields. Based on the interaction, a flaw-to-surface proximity criterion for a circular flaw is proposed under the stress concentration field induced by a notch.

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.

A Procedure for Estimating the Stress Intensity Factor of a Flattened Surface Crack at a Nozzle Corner

1979 ◽  
Vol 101 (2) ◽  
pp. 181-183 ◽  
Author(s):  
A. S. Kobayashi ◽  
A. F. Emery ◽  
W. J. Love ◽  
A. Antipas
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Surface Crack ◽  
Finite Thickness ◽  
Normal Stresses ◽  
Intensity Factors ◽  
Qualitative Comparison ◽  
Crack Penetration ◽  
Corner Cracks ◽  
Crack Contour

A flattened surface crack at a nozzle corner is modeled by a segment of a semi-elliptical crack in a finite thickness plate with matching crack contour and crack pressure corresponding to the normal stresses in the uncracked nozzle corner. Lacking other solutions for comparison, a qualitative comparison was made between nondimensionalized stress intensity factors at the deepest crack penetration with those obtained experimentally for similar corner cracks in epoxy models.

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