Investigating the Interaction Behavior Between Two Arbitrarily Oriented Surface Cracks Using Multilevel Substructuring

2002 ◽  
Vol 124 (4) ◽  
pp. 440-445 ◽  
Author(s):  
Walied A. Moussa
Keyword(s):  
Crack Depth ◽  
Plate Thickness ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Release Rates ◽  
Element Analysis ◽  
Wide Range ◽  
Total Failure ◽  
Energy Release Rates

The existence of arbitrarily oriented multiple cracks is a common problem in brittle materials. Some of these materials, such as ceramics, are used in mechanical and aerospace structures that suffer from aging. Because of that, such structures have shown some signs of sudden partial or total failure. The interaction and coalescence of multiple cracks may significantly affect the designed lives of aging structures. Knowledge of the growth behavior of interacting cracks is still limited. In this paper, a novel submodeling meshing algorithm is used to construct different cases of arbitrarily oriented identical surface cracks in a plate subjected to remote tension. These cases are solved using finite element analysis (FEA) and covered a wide range of crack geometries. The stress intensity factors (SIFs) and the energy release rates (G) for these cracks are calculated as a function of their relative orientation and the position along the interaction crack-front. In this paper, the studied ratio of crack depth to plate thickness, a/t, and to crack length, a/c, are kept at 0.2 and 0.3, respectively. Where possible, a comparison of the 3-D results with 2-D ones is also considered.

Investigating the Effect of Crack Shape on the Interaction Behavior of Noncoplanar Surface Cracks Using Finite Element Analysis

2002 ◽  
Vol 124 (2) ◽  
pp. 234-238 ◽  
Author(s):  
Walied A. Moussa ◽  
R. Bell ◽  
C. L. Tan
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Crack Depth ◽  
Plate Thickness ◽  
Infinite Plate ◽  
Multiple Cracks ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Mechanics Model

In the last two decades, multiple cracks are often found in aging aerospace and mechanical structures. The interaction and coalescence of multiple cracks may significantly affect the service lives of these aging structures. Knowledge of the behavior of interacting cracks is still limited. The calculation of the crack-tip stress intensity factor, SIF, along the interacting crack fronts is considered a major contribution for the application of any linear fracture mechanics model to investigate the growth life of these cracks. In this paper, a parametric study is presented for two parallel surface cracks in an infinite plate subjected to remote tension or to pure bending loads. This study focuses on constructing a finite element (FE) model that combines the submodeling technique with its ability to generate crack submodels of different lengths and depths, and a mesh generator that can build up a mesh grid based on the size, depth, and orientation of the interacting crack sub-models. The stress intensity factors for these cracks are calculated as a function of the crack front position, depth, shape, and plate thickness. In this paper, the values of the studied crack depth to length ratio, a/c, are 0.33, 0.5, 0.67, and 1.0. Where possible, a comparison of the 3-D with 2-D results is also considered.

On the Interaction of Non-Coplanar Embedded Crack With Surface Crack in 3D Using FE and Multi-Level Sub-Structuring

2002 ◽  
Author(s):  
Walied A. Moussa
Keyword(s):  
Surface Crack ◽  
Crack Depth ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Infinite Plate ◽  
Separation Distance ◽  
Multiple Cracks ◽  
Element Analysis ◽  
Weld Toe ◽  
Embedded Crack

The interaction and coalescence of multiple cracks may significantly affect the designed lives of aging pressure vessel structures. Knowledge of the growth behavior of interacting cracks is still limited. In this paper, a novel sub-modeling meshing algorithm is used in three-dimensional linear finite element analysis to investigate the interaction between two identical, non-coplanar, semi-elliptical cracks. One of these cracks is modeled as a surface crack while the other is modeled as an embedded crack under a weld toe. Both interacting cracks are assumed to be in an infinite plate subjected to a remote tension loading condition. The energy release rates (G) and the Stress Intensity Factors (SIF’s) for these cracks are calculated along the interacting crack-front. And, a parametric study involving the variation of the relative horizontal separation distance between the two interacting cracks is carried out for a specific crack depth to plate thickness ratio, a/t, of 0.2. The crack shape aspect ratio, a/c, is also varied in this study within a range that extend between 1.0 and 0.33. An empirical formula is derived that relates the effects of the relative positions of these cracks to their SIFs.

Mode III Stress Intensity Factors of Surface Crack in Round Bars

2011 ◽  
Vol 214 ◽  
pp. 192-196 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Crack Tip ◽  
Bending Moment ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Mode Iii ◽  
Element Analysis ◽  
Proposed Model

This study presents a numerical investigation on the stress intensity factors (SIF), K of surface cracks in round bars that were obtained under pure torsion loadings or mode III. ANSYS finite element analysis (FEA) was used to determine the SIFs along the crack front of surface cracks embedded in the solid circular bars. 20-node isoparametric singular elements were used around the crack tip by shifting the mid-side node ¼-position close to a crack tip. Different crack aspect ratio, a/b were used ranging between 0.0 to 1.2 and relative crack depth, a/D were ranged between 0.1 to 0.6. Mode I SIF, KI obtained under bending moment was used to validate the proposed model and it was assumed this proposed model validated for analyzing mode III problems. It was found that, the mode II SIF, FII and mode III SIF, FIII were dependent on the crack geometries and the sites of crack growth were also dependent on a/b and a/D.

scholarly journals Stress-Intensity Factors for Internal Surface Cracks in Cylindrical Pressure Vessels

1980 ◽  
Vol 102 (4) ◽  
pp. 342-346 ◽  
Author(s):  
J. C. Newman ◽  
I. S. Raju
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Intensity ◽  
Wall Thickness ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Internal Surface ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Wide Range

The purpose of this paper is to present stress-intensity factors for a wide range of semi-elliptical surface cracks on the inside of pressurized cylinders. The ratio of crack depth to crack length ranged from 0.2 to 1; the ratio of crack depth to wall thickness ranged from 0.2 to 0.8; and the ratio of wall thickness to vessel radius was 0.1 to 0.25. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employ singularity elements along the crack front and linear-strain elements elsewhere. The models had about 6500 degrees of freedom. The stress-intensity factors were evaluated from a nodal-force method. An equation for the stress-intensity factors was obtained from the results of the present analysis. The equation applies over a wide range of configuration parameters and was within about 5 percent of the present results. A comparison was also made between the present results and other analyses of internal surface cracks in cylinders. The results from a boundary-integral equation method were in good agreement (± 2 percent) and those from another finite-element method were in fair agreement (± 8 percent) with the present results.

Development of Stress Intensity Factors for Cracks With Large Aspect Ratios in Pipes and Plates

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Makoto Udagawa
Keyword(s):  
Stress Intensity ◽  
Wall Thickness ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Influence Coefficient ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Pipe Radius

The stress intensity factors (SIFs) for pipes containing semi-elliptical surface cracks with large aspect ratios were calculated by finite-element analysis (FEA). The cracks were circumferential and axial surface cracks inside the pipes. The parameters of the SIFs are crack aspect ratio, crack depth, and the ratio of pipe radius to wall thickness. In comparing SIFs for plates and pipes, it can be clarified that SIFs for both plates and thin pipes with t/Ri ≤ 1/10 are almost the same, and the SIFs for plates can be used as a substitute for pipes with t/Ri ≤ 1/10, where t is the pipe wall thickness, and Ri is the inner radius of the pipe. This means that it is not necessary to provide SIF solutions for pipes with t/Ri ≤ 1/10, and it is suggested that the number of tables for influence coefficient values for pipes can be significantly reduced.

Stress intensity factors for semi-elliptical surface cracks in semicircularly notched tension plates

1997 ◽  
Vol 32 (3) ◽  
pp. 229-236 ◽  
Author(s):  
X B Lin ◽  
R A Smith
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Finite Thickness ◽  
J Integral ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Wide Range ◽  
Half Length ◽  
Half Thickness

Stress intensity factors for semi-elliptical surface cracks located at the centre of a semicircular edge notch in a finite thickness plate subjected to a remote tensile load are presented in a tabulated format. A wide range of geometry ratios are considered. They are all combinations of the following ratios: the ratio of crack surface half-length to plate half-thickness, c/t = 0.2, 0.4, 0.6, 0.8 and 0.95; the ratio of crack depth to surface half-length, a/c = 0.2, 0.4, 0.6, 0.8 and 1; and the ratio of notch radius to plate half-thickness, r/t = 0.5, 1, 2 and 3. Both the quarter-point displacement and J.-integral methods based on three-dimensional finite element analyses were employed for the calculation of stress intensity factors. The calculation accuracy was studied by analysing the J.-integral path independence and comparing stress intensity factor results with other solutions available in the literature.

The Interaction of Two Parallel Semi-Elliptical Surface Cracks Under Tension and Bending

1999 ◽  
Vol 121 (3) ◽  
pp. 323-326 ◽  
Author(s):  
W. A. Moussa ◽  
R. Bell ◽  
C. L. Tan
Keyword(s):  
Stress Intensity ◽  
Crack Depth ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Infinite Plate ◽  
Multiple Cracks ◽  
Surface Cracks ◽  
Engineering Structures ◽  
Mechanics Model ◽  
Front Position

Multiple cracks are often observed in engineering structures; and their interaction and coalescence may significantly affect their life. Knowledge of the behavior of interacting cracks is very limited. A major component of any linear fracture mechanics model for fatigue crack growth is the calculation of the crack-tip stress intensity factor, SIF. In this paper, a parametric study is presented for two parallel surface cracks in an infinite plate subjected to remote tension or to pure bending loads. The stress intensity factors for these cracks as a function of the crack-front position, depth, shape, and plate thickness are calculated using three-dimensional (3-D) finite element, (FE) analysis. The ratios of crack depth to plate thickness, a/t, and to crack length, a/c, range from 0.1 to 0.62 and 0.1 to 1.0, respectively. Where possible, a comparison of 3-D with 2-D results is also considered.

Development of Stress Intensity Factors for Deep Surface Cracks in Pipes and Plates

2015 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li
Keyword(s):  
Stress Intensity ◽  
Wall Thickness ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Influence Coefficients ◽  
Pipe Radius

Stress intensity factors (SIFs) for pipes with semi-elliptical cracks containing large aspect ratios were calculated by finite element analysis. The cracks were circumferential and axial surface cracks inside the pipes. The parameters of the SIFs are crack aspect ratio, crack depth and the ratio of pipe radius to wall thickness. In comparing SIFs for plates and pipes, it can be clarified that SIFs for both plates and thin pipes with t/Ri ≤1/10 are almost the same, and the SIFs for plates are used as a substitute for pipes with t/Ri ≤1/10, where t is the pipe wall thickness and Ri is the inner radius of the pipe. This means that it is not necessary to provide SIF solutions for pipes with t/Ri ≤1/10, and it is suggested that number of tables for influence coefficients G values for pipes can significantly reduce.

J-Integral Analysis of Surface Cracks in Round Bars under Bending Moments

2011 ◽  
Vol 52-54 ◽  
pp. 43-48 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Crack Tip ◽  
Bending Moment ◽  
Limit Load ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Reference Stress ◽  
Proposed Model

This paper presents a non-linear numerical investigation of surface cracks in round bars under bending moment by using ANSYS finite element analysis (FEA). Due to the symmetrical analysis, only quarter finite element (FE) model was constructed and special attention was given at the crack tip of the cracks. The surface cracks were characterized by the dimensionless crack aspect ratio, a/b = 0.6, 0.8, 1.0 and 1.2, while the dimensionless relative crack depth, a/D = 0.1, 0.2 and 0.3. The square-root singularity of stresses and strains was modeled by shifting the mid-point nodes to the quarter-point locations close to the crack tip. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under remotely applied bending moment was assumed to follow the Ramberg-Osgood relation with n = 5 and 10. J values were determined for all positions along the crack front and then, the limit load was predicted using the J values obtained from FEA through the reference stress method.

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