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.

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.

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.

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.

Finite Element Analysis of Polyethylene Pipe Butt Fusion Joints with Circumferential Surface Cracks

2013 ◽  
Vol 785-786 ◽  
pp. 1151-1158
Author(s):  
Zhi Bin Zhu ◽  
Xiao Xiang Yang ◽  
Li Jing Chen ◽  
Nai Chang Lin ◽  
Zhi Tuo Wang ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Viscoelastic Material ◽  
Surface Crack ◽  
Crack Depth ◽  
Surface Cracks ◽  
Element Analysis ◽  
Polyethylene Pipe

Based on the viscoelastic material property of polyethylene pipe, software ANSYS was used to simulate and analyze the mechanical property of polyethylene pipe butt fusion joints with circumferential surface crack defects. The viscoelastic material creep parameters were characterized as Prony series and 1/4 node singular element was selected for meshing along the boundaries of the crack, then the stress intensity factor of polyethylene pipe butt fusion joints with circumferential surface crack was calculated under the uniform internal pressure. Through the finite element simulation, the result showed that polyethylene pipe were most likely to fracture failure when crack initiated. Thus the viscoelasticity of materials can be ignored when analyzing the stress intensity factor of circumferential surface cracks of polyethylene pipe. the main influencing factor of the circumferential crack defects was the ratio of the crack depth to the thickness of polyethylene pipe.

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.

Finite Element Analysis on the Stress Intensity Factor under Combined Bending and Torsion Loading

2011 ◽  
Vol 462-463 ◽  
pp. 1325-1330
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
M. Abdulrazzaq
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Depth ◽  
Crack Tip ◽  
Fe Model ◽  
Element Analysis ◽  
Loading Ratio

The stress intensity factor (SIF) under the combined bending and torsion loading were studied using a finite element (FE) analysis ANSYS. A 20-node iso-parametric element was used to model the crack tip and the square-root singularity of stress/strain was employed by shifting the mid-side node to the ¼ position to the crack tip. Different crack geometries and loading ratios were used and due to the non-symmetrical analysis involved, a full FE model was developed and analyzed. Remotely applied bending and torsion moment were subjected to the FE model and the SIF were then calculated along the crack front under such loadings. The SIF calculated using the finite element analysis (FEA) was compared with those results obtained using an effective combined SIF method. According to the comparisons, the discrepancies were dependent on the normalized coordinate, x/h, the relative crack depth, a/D, the crack aspect ratio, a/b and the loading ratio, .

J-Integral Analysis of Surface Cracks in Round Bars under Combined Loadings

2011 ◽  
Vol 214 ◽  
pp. 187-191 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Finite Element ◽  
Crack Front ◽  
Crack Depth ◽  
Limit Load ◽  
Strain Hardening Exponent ◽  
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 combined bending and torsion loadings by using ANSYS finite element analysis (FEA). Due to the non-symmetrical analysis, a full 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 in the region around the crack front. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under the loading was assumed to follow the Ramberg-Osgood relation with strain hardening exponent, 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.

J-Integral Analysis of Surface Cracks in Round Bars under Tension Loadings

2011 ◽  
Vol 52-54 ◽  
pp. 37-42
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Front ◽  
Crack Depth ◽  
Limit Load ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Reference Stress ◽  
Proposed Model ◽  
Square Root Singularity

This paper presents a non-linear numerical investigation of surface cracks in round bars under tension stresses 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 were modeled by shifting the mid-point nodes to the quarter-point locations in the region around the crack front. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under tension loading 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.

Dynamic Behaviour and Crack Detection of a Multi Cracked Rotating Shaft using Adaptive Neuro-Fuzzy-Inference System

2016 ◽  
Vol 6 (4) ◽  
pp. 1-10 ◽  
Author(s):  
Rajeev Ranjan
Keyword(s):  
Finite Element ◽  
Fuzzy Inference System ◽  
Crack Detection ◽  
Fuzzy Inference ◽  
Crack Depth ◽  
Multiple Cracks ◽  
Rotating Shaft ◽  
Element Analysis ◽  
Inference System ◽  
Neuro Fuzzy

The presence of crack changes the physical characteristics of a structure which in turn alter its dynamic response characteristics. So it is important to understand dynamics of cracked structures. Crack depth and location are the main parameters influencing the vibration characteristics of the rotating shaft. In the present study, a technique based on the measurement of change of natural frequencies has been employed to detect the multiple cracks in rotating shaft. The model of shaft was generated using Finite Element Method. In Finite Element Analysis, the natural frequency of the shaft was calculated by modal analysis using the software ANSYS. The Numerical data were obtained from FEA, then used to train through Adaptive Neuro-Fuzzy-Inference System. Then simulations were carried out to test the performance and accuracy of the trained networks. The simulation results show that the proposed ANFIS estimate the locations and depth of cracks precisely.

Analysis of Three-Dimensional Clamped Single Edge Notched Tension (SENT) Specimens

2018 ◽  
Author(s):  
Zheng Liu ◽  
Xu Chen ◽  
Xin Wang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Depth ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Width Ratio ◽  
Element Analysis ◽  
Out Of Plane ◽  
T Stress

In the present paper, three-dimensional clamped SENT specimens, which is one of the most widely used low-constraint and less-conservative specimen, are analyzed by using a crack compliance analysis approach and extensive finite element analysis. Considering the test standard (BS8571) recommended specimen sizes, the daylight to width ratio, H/W, is 10.0, the relative crack depth, a/W, is varied by 0.2, 0.3, 0.4, 0.5 or 0.6 and the relative plate thickness, B/W, is chosen by 1.0, 2.0 or 4.0, respectively. Complete solutions of fracture mechanics parameters, including stress intensity factor (K), in-plane T-stress (T11) and out-of-plane T-stress (T33) are calculated, and the results obtained from above two methods have a good agreement. Moreover, the combination of the effects of a/W and B/W on the stress intensity factor K, T11 and T33 stress are thus illustrated.

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