Numerical Analysis of Asymmetrically Bonded Composite Patch Repair and Effect of In-Plane Skewed Crack Front on the SIF

2017 ◽  
Vol 30 ◽  
pp. 11-22 ◽  
Author(s):  
Baltach Abdelghani ◽  
Aid Abdelkarim ◽  
Abdelkader Djebli ◽  
Belabbes Bachir Bouiedjra ◽  
Benhamena Ali
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Crack Front ◽  
Patch Repair ◽  
Growth Stages ◽  
Initial State ◽  
Element Analysis ◽  
Composite Patch

A nonlinear 3-D finite element analysis was conducted to analyze the crack front behavior of a center cracked aluminum plate, asymmetrically repaired with composite patch. According to experimental observations, the crack front was modeled as an inclined shape from the initial state where the crack front is straight and parallel to the thickness direction from the patched side toward the un-patched side. The skew degree is found to strongly influence the stress intensity factor (SIF) distribution along the crack front. In effect, the obtained trends of the SIF’s distribution are different and changes during crack growth stages. The main finding is that regardless the crack front shape (inclination), the average stress intensity factor through the crack front remains constant and consequently, it means to be an effective parameter to estimate the fatigue life and crack growth of the asymmetrically patched structures. The performed models gave good results compared to the literature and the different findings correlate well with the experimental observations and make sense with a realistic crack development.

Study on the Relationship Between Interaction Factors and Stress Intensity Factor for Elliptical Flaws

2017 ◽  
Author(s):  
Kisaburo Azuma ◽  
Yinsheng Li ◽  
Kunio Hasegawa
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Front ◽  
Elastic Solid ◽  
Element Analysis ◽  
Linear Elastic ◽  
Close Proximity ◽  
Interaction Factors ◽  
The Relationship

The interaction of multiple flaws in close proximity to one another may increase the stress intensity factor of the flaw in structures and components. This interaction effect is not distributed uniformly along the crack front. For instance, the strongest interaction is generally observed at the point closest to a neighboring flaw. For this reason, the closest point could show a higher value of the stress intensity factor than all other points in some cases, even if the original value at the point of the single flaw is relatively low. To clarify the condition when the closest point shows the maximum stress intensity factor, we investigated the interaction of two similar elliptical flaws in an infinite model subjected to remote tension loading. The stress intensity factor of the elliptical flaws was obtained by performing finite element analysis of a linear elastic solid. The results indicated that the interaction factors along the crack front can be expressed by a simple empirical formula. Finally, we show the relationship between geometrical features of the flaw and the stress intensity factor at the closest point to a neighboring flaw.

Stress Intensity Factor of an Elliptical Crack With a Wavy Crack Front

2016 ◽  
Author(s):  
Masayuki Arai
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Front ◽  
Perturbation Technique ◽  
Three Dimensional ◽  
Elastic Field ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, the stress intensity factor KI for the crack front line a − ε(1 + cosmθ), which is slightly perturbed from a complete circular line with a radius of a, is determined. The method used in this study is based upon the perturbation technique developed by Rice for solving the elastic field of a crack whose front slightly deviates from some reference geometry. It is finally shown that the solution for the stress intensity factor matches the results of a three-dimensional finite element analysis.

Analysis of Stress Intensity Factor and Crack Propagation for Alloy X-750 Pressure Vessel with a Blunting Crack

2010 ◽  
Vol 303-304 ◽  
pp. 63-83
Author(s):  
Ehsan Mahdavi ◽  
Mahmoud Mosavi Mashhadi ◽  
M. Amidpour
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Crack Growth ◽  
Pressure Vessel ◽  
Element Analysis ◽  
Linear Elastic ◽  
The Stability

It is well known that the crack growth rate fatigue and stress corrosion cracking can be approximated by a power function of the stress intensity factor. In this study, stress intensity factor for elliptical crack under the uniform tension in linear elastic fracture mechanics (LEFM) is investigated therefore for this purpose, a pressure vessel modeled by finite element. A crack modeled on the pressure vessel and then the stress intensity factor for crack propagation in different methods is evaluated. Finite element analysis calculates stress intensity factor in the values of the J-integral are based on the stress intensity factors, JK, and by evaluating the contour integral directly, JA. The stability of crack growth is considered so the ductile crack extension is determined by pursuing the equilibrium between loading and crack resistance. Using especial method of meshing caused to have accurate results. This method causes to decrease run time and considerable accuracy. Then stress intensity factor is calculated for different position of the crack such as crack front and then compared to each other.

Stress Intensity Factor Distributions and Crack Growth in Pressure Vessel Problems by the Frozen Stress Method

2004 ◽  
Author(s):  
C. W. Smith ◽  
C. T. Liu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Crack Front ◽  
Pressure Vessel ◽  
A Priori ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Crack Shape

This paper describes the application of a laboratory based experimental method [1] to three dimensional cracked body problems in pressure vessels in order to determine the crack shape and stress intensity factor (SIF) distribution along the crack front when the crack shape is not known a-priori. Results for specific problems are presented and conditions and limitation of the method are described.

The Effect of Crack Shape Idealisation on Leak-Before-Break Assessment

2016 ◽  
Author(s):  
Renaud Bourga ◽  
Bin Wang ◽  
Philippa Moore ◽  
Yin Jin Janin
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Crack Front ◽  
Structural Integrity ◽  
Crack Opening ◽  
Integrity Assessment ◽  
Crack Shape ◽  
Leak Before Break

Based on detailed 3D finite element (FE) analyses, idealized and non-idealized axial through-wall flaws were evaluated in a cylinder under internal pressure. The key parameters (Stress Intensity Factor, Reference stress, and Crack Opening Area) from widely accepted structural integrity assessment procedures (BS 7910 and API 579-1/ASME FFS-1) were explored and compared between idealized (perpendicular straight-sided flaw) and non-idealized geometry. The effect of crack shape on the evolution of stress intensity factors and crack opening areas along the crack front were also investigated. Non-idealized crack shapes have been modelled assuming a straight crack front with different internal and external crack lengths. The influence of crack shape has been evaluated by varying the crack front location and lengths ratios. The current findings highlight the significance of assessing a more realistic crack shape and should be considered in a leak-before-break (LBB) analysis. A non-idealized crack has a significantly smaller crack opening area than the equivalent idealized through-wall crack. Therefore the leakage rate at this stage of crack growth will be lower than predicted by standard solutions. Stress intensity factor solutions should also take the crack shape variation into account with regards to fatigue crack growth as a surface flaw propagates through-thickness.

Bonded Composite Repairs of Aluminum Alloy 2024T3 Cracked Plates

2014 ◽  
Author(s):  
F. Benyahia ◽  
A. Albedah ◽  
B. Bachir Bouiadjra
Keyword(s):  
Stress Intensity Factor ◽  
Aluminum Alloy ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Front ◽  
Three Dimensional ◽  
Fatigue Tests ◽  
Patch Repair ◽  
Bonded Composite ◽  
Three Dimensional Finite Element

In this study, the behavior of repaired cracks, located in aluminum alloy sheets 2024T3, with bonded composite patch is analyzed experimentally and numerically. The experimental study has been conducted through fatigue tests on aluminum cracked plate repaired with Carbon/epoxy patch. In the numerical analysis, the stress intensity factor at the crack front is computed using three-dimensional finite element method. The obtained results show that the stress intensity factor at the crack front is highly reduced by the presence of the patch repair. Therefore, the fatigue life of the damaged structure can be significantly improved especially if the patch repair is applied at small crack lengths.

The Distribution of the Stress Intensity Factor Along the Front of the Growing Crack in an Optical Glass Fiber

1992 ◽  
Vol 114 (4) ◽  
pp. 403-406 ◽  
Author(s):  
M. Muraoka ◽  
H. Abe´ ◽  
N. Aizawa
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Front ◽  
Crack Velocity ◽  
Optical Glass ◽  
Fiber Surface ◽  
Element Analysis ◽  
Growing Crack ◽  
Silica Optical Fiber

The stress intensity factor K1 along the front edge of a growing small crack in a silica optical fiber was evaluated by 3-D boundary element analysis based on the crack geometry observed during the delayed fracture test. The variation of K1 was shown to be little along the front of the growing crack. The crack velocity in the direction normal to the crack front was able to be expressed as a power function of K1 at each position on the crack front. The crack velocity was also shown to be larger at a position closer to the fiber surface for each value of K1.

Stress Intensity Factor for Repaired Circumferential Cracks in Pipe With Bonded Composite Wrap

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
F. Benyahia ◽  
A. Albedah ◽  
B. Bachir Bouiadjra
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Criterion ◽  
Three Dimensional ◽  
Element Analysis ◽  
Composite Systems ◽  
Bonded Composite ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The use of composite systems as a repair methodology in the pipeline industry has grown in recent years. In this study, the analysis of the behavior of circumferential through cracks in repaired pipe with bonded composite wrap subjected to internal pressure is performed using three-dimensional finite element analysis. The fracture criterion used in the analysis is the stress intensity factor (SIF). The obtained results show that the bonded composite repair reduces significantly the stress intensity factor at the tip of repaired cracks in the steel pipe, which can improve the residual lifespan of the pipe.

Crack Growth in Stainless Steel 304 under Creep-Fatigue Loading

2007 ◽  
Vol 353-358 ◽  
pp. 485-490 ◽  
Author(s):  
Y.M. Baik ◽  
K.S. Kim
Keyword(s):  
Stress Intensity Factor ◽  
Stainless Steel ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Growth Rates ◽  
Static Loading ◽  
Fatigue Loading ◽  
Creep Fatigue ◽  
Crack Growth Rates

Crack growth in compact specimens of type 304 stainless steel is studied at 538oC. Loading conditions include pure fatigue loading, static loading and fatigue loading with hold time. Crack growth rates are correlated with the stress intensity factor. A finite element analysis is performed to understand the crack tip field under creep-fatigue loading. It is found that fatigue loading interrupts stress relaxation around the crack tip and cause stress reinstatement, thereby accelerating crack growth compared with pure static loading. An effort is made to model crack growth rates under combined influence of creep and fatigue loading. The correlation with the stress intensity factor is found better when da/dt is used instead of da/dN. Both the linear summation rule and the dominant damage rule overestimate crack growth rates under creep-fatigue loading. A model is proposed to better correlate crack growth rates under creep-fatigue loading: 1 c f da da da dt dt dt Ψ −Ψ     =         , where Ψ is an exponent determined from damage under pure fatigue loading and pure creep loading. This model correlates crack growth rates for relatively small loads and low stress intensity factors. However, correlation becomes poor as the crack growth rate becomes large under a high level of load.

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