scholarly journals Two-Dimensional Stress Intensity Factor Analysis of Cracks in Anisotropic Bimaterial

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Chia-Huei Tu ◽  
Jia-Jyun Dong ◽  
Chao-Shi Chen ◽  
Chien-Chung Ke ◽  
Jyun-Yong Jhan ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Numerical Technique ◽  
Intensity Factors ◽  
Straight Crack ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Anisotropic Bimaterials

This paper presents a 2D numerical technique based on the boundary element method (BEM) for the analysis of linear elastic fracture mechanics (LEFM) problems on stress intensity factors (SIFs) involving anisotropic bimaterials. The most outstanding feature of this analysis is that it is a singledomain method, yet it is very accurate, efficient, and versatile (i.e., the material properties of the medium can be anisotropic as well as isotropic). A computer program using the BEM formula translation (FORTRAN 90) code was developed to effectively calculate the stress intensity factors (SIFs) in an anisotropic bi-material. This BEM program has been verified and showed good accuracy compared with the previous studies. Numerical examples of stress intensity factor calculation for a straight crack with various locations in both finite and infinite bimaterials are presented. It was found that very accurate results can be obtained using the proposed method, even with relatively simple discretization. The results of the numerical analysis also show that material anisotropy can greatly affect the stress intensity factor.

Examination of Ellipticity and Stress Intensity Factors by Photoelastic and Caustic Methods

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1898-1903
Author(s):  
Tsutomu Ezumi ◽  
Katsunao Suzuki
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Experimental Methods ◽  
Intensity Factors ◽  
Linear Elastic ◽  
Freezing Method ◽  
Elastic Fracture ◽  
Caustics Method

In the field of linear elastic fracture mechanics, the stress intensity factor approach has been widely accepted as a valid means for predicting the behavior of a material in the presence of a crack or flaw. To optimize their dimension and to ensure their safety in service, a practical study of the strength under centrifugal force is important. In this paper, it is investigated that the stress intensity factors K_ and K_ on the rotating elliptic disks having outside cracks by means of combining the photoelastic freezing method and the caustics method. Stress intensity factors K and K were determined by using two experimental methods, as a function of ellipticity of the elliptic disk and at two different velocities. The results of these experimental methods was nearly agreement, and attracted the interest.

Numerical Determination of Stress Intensity Factors Using ABAQUS

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Intensity Factors ◽  
Element Analysis ◽  
Linear Elastic ◽  
Displacement Extrapolation Method

Crack assessments for pressure vessels often need to quantify the crack driving force — stress intensity factor K with the linear-elastic fracture mechanics methods. Different numerical methods have been developed to calculate the stress intensity factors for complex cracks. Of which, four typical methods, i.e., the displacement extrapolation method, the virtual crack closure technique (VCCT), the J-integral conversion method, and the direct K output method are selected and evaluated in this paper using the finite element analysis (FEA) and ABAQUS software. The evaluations are performed based on the benchmark FEA calculations in the linear-elastic conditions for the central-cracked panel (CCP) specimen in the two-dimensional (2D) plane strain conditions. The “best method” is then determined and used to calculate the stress intensity factor for the CCP specimen with a through-thickness crack in the three-dimensional (3D) conditions. The results show that ABAQUS can simply determine very accurate K values for both 2D and 3D cracks.

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.

Propose of Simplified Stress Intensity Factor Equation for SCC Extension of the Pipe Welds

2008 ◽  
Author(s):  
Mayumi Ochi ◽  
Kiminobu Hojo ◽  
Itaru Muroya ◽  
Kazuo Ogawa
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Crack Extension ◽  
Crack Depth ◽  
Alloy 600 ◽  
Intensity Factors ◽  
Axial Crack ◽  
Extension Analysis

Alloy 600 weld joints have potential for primary water stress corrosion cracks (PWSCC). At the present time it has been understood that PWSCC generates and propagates in the Alloy 600 base metal and the Alloy 600 weld metal and there has been no observation of cracking the stainless and the low alloy steel. For the life time evaluation of the pipes or components the crack extension analysis is required. To perform the axial crack extension analysis the stress intensity database or estimation equation corresponding to the extension crack shape is needed. From the PWSCC extension nature mentioned above, stress intensity factors of the conventional handbooks are not suitable because most of them assume a semi-elliptical crack and the maximum aspect ratio crack depth/crack half length is one (The evaluation in this paper had been performed before API 579-1/ASME FFS was published). Normally, with the advance of crack extension in the thickness direction at the weld joint, the crack aspect ratio exceeds one and the K-value of the conventional handbook can not be applied. Even if those equations are applied, the result would be overestimated. In this paper, considering characteristics of PWSCC’s extension behavior in the welding material, the axial crack was modeled in the FE model as a rectangular shape and the stress intensity factors at the deepest point were calculated with change of crack depth. From the database of the stress intensity factors, the simplified equation of stress intensity factor with parameter of radius/thickness and thickness/weld width was proposed.

Consideration of Reduction in Stiffness due to Cracking and the Impact on Standard Stress Intensity Factor Solutions

2017 ◽  
Author(s):  
Daniel M. Blanks
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Nozzle Geometry ◽  
Intensity Factors ◽  
Factor Solution ◽  
Small Component ◽  
Embedded Crack ◽  
The Impact

An API 579-1/ASME FFS-1 Failure Assessment Diagram based Fitness-for-Service assessment was carried out on an embedded crack-like flaw found in a nozzle to shell weld in a pressure vessel. Stress intensity factors were initially calculated by utilizing stress results from a Finite Element Analysis (FEA) of an uncracked configuration, with the standard embedded crack stress intensity factor solution given in API 579-1/ASME FFS-1. Due to the complex nozzle geometry and flaw size, a second analysis was carried out, incorporating a crack into the FEA model, to calculate the stress intensity factors and evaluate if the standard solution could be applied to this geometry. A large difference in the resulting stress intensity factors was observed, with those calculated by the FEA with the crack incorporated into the model to be twice as high as those calculated by the standard solutions, indicating the standard embedded crack stress intensity factor solution may be non-conservative in this case. An investigation was carried out involving a number of studies to determine the cause of the difference. Beginning with an elliptical shaped embedded crack in a plate, the stress intensity factor calculated with an idealized 3D crack mesh agreed with the API 579-1/ASME FFS-1 solution. Examining other crack locations, and crack shapes, such as a constant depth embedded crack, revealed how the solution began to differ. The greatest difference was found when considering a crack mesh with a small component height (i.e. the distance measured perpendicular from the crack face to the top of the mesh). A close agreement was then found between the stress intensity factors calculated in the nozzle model and an idealized crack mesh with component heights representative of the true geometry. This revealed that reduced structural stiffness is a key factor in the calculation of the stress intensity factors for this geometry, due to the close proximity of the embedded crack to the inner surface of the nozzle. It was found that this reduction is potentially significant even with relatively small crack sizes. This paper details the investigation, and aims to provide the reader with an awareness of situations when the standard stress intensity factor solutions may no longer be valid, and offers general recommendations to consider when calculating stress intensity factors in these situations.

Variation of Stress Intensity Factor and Crack Distance Length for Double Edge Crack in Human Femur Bone

2014 ◽  
Vol 695 ◽  
pp. 580-583
Author(s):  
Noor A. Md Zain ◽  
Ruslizam Daud ◽  
W.Z.A.W. Muhamad ◽  
Khairul Salleh Basaruddin ◽  
Yazid Bajuri ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Parallel Edge ◽  
Linear Elastic ◽  
Femur Bone ◽  
Double Edge ◽  
Crack Tips ◽  
Elastic Fracture ◽  
Edge Cracks

The theory of linear elastic fracture mechanic (LEFM) has proven that we can evaluate the amount of stress located at the crack tip by determining the stress intensity factor (). The stress at the tip of a sharp crack has the highest stress which can lead to failure on the material. Thus, the cracks within human bones are quite complicated because of the bone microstructure. There are a few factors that can minimize the effect of the cracks so that patients can heal much faster. Hence, this paper focuses on how several crack distances, between two parallel edge cracks can affect the value of stress intensity factor (). Using the LEFM theory, the interaction between two neighboring crack tips was investigated.

Closed-Form Relations for Stress Intensity Factor Influence Coefficients for Axial Outside Surface Flaws in Cylinders for Appendix A of ASME Section XI

2016 ◽  
Author(s):  
Steven X. Xu ◽  
Darrell R. Lee ◽  
Douglas A. Scarth ◽  
Russell C. Cipolla
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Closed Form ◽  
Inside Surface ◽  
Linear Elastic ◽  
Evaluation Procedures ◽  
Influence Coefficients ◽  
Elastic Fracture ◽  
Flaw Location

Linear elastic fracture mechanics based flaw evaluation procedures in Section XI of the ASME Boiler and Pressure Vessel Code require calculation of the stress intensity factor. Article A-3000 of Appendix A in ASME Section XI prescribes a method to calculate the stress intensity factor for a surface or subsurface flaw by making use of the flaw location stress distribution obtained in the absence of the flaw. The 2015 Edition of ASME Section XI implemented a number of significant improvements in Article A-3000, including closed-form equations for calculating stress intensity factor influence coefficients for circumferential flaws on the inside surface of cylinders. Closed-form equations for stress intensity factor influence coefficients for axial flaws on the inside surface of cylinders have also been developed. Ongoing improvement efforts for Article A-3000 include development of closed-form relations for the stress intensity factor coefficients for flaws on the outside surface of cylinders. The development of closed-form relations for stress intensity factor coefficients for axial flaws on the outside surface of cylinders is described in this paper.

Effect of Weld Residual Stress Fitting on Stress Intensity Factor for Circumferential Surface Cracks in Pipe

2012 ◽  
Author(s):  
Do-Jun Shim ◽  
Matthew Kerr ◽  
Steven Xu
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Wall Thickness ◽  
Stress Intensity Factors ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Weld Residual Stress ◽  
Order Polynomial

Recent studies have shown that the crack growth of PWSCC is mainly driven by the weld residual stress (WRS) within the dissimilar metal weld. The existing stress intensity factor (K) solutions for surface cracks in pipe typically require a 4th order polynomial stress distribution through the pipe wall thickness. However, it is not always possible to accurately represent the through thickness WRS with a 4th order polynomial fit and it is necessary to investigate the effect of the WRS fitting on the calculated stress intensity factors. In this paper, two different methods were used to calculate the stress intensity factor for a semi-elliptical circumferential surface crack in a pipe under a given set of simulated WRS. The first method is the Universal Weight Function Method (UWFM) where the through thickness WRS distribution can be represented as a piece-wise cubic fit. In the second method, the through thickness WRS profiles are represented as a 4th order polynomial curve fit (both using the entire wall thickness data and only using data up to the crack-tip). In addition, three-dimensional finite element (FE) analyses (using the simulated weld residual stress) were conducted to serve as a reference solution. The results of this study demonstrate the potential sensitivity of stress intensity factors to 4th order polynomial fitting artifacts. The piece-wise WRS representations used in the UWFM was not sensitive to these fitting artifacts and the UWFM solutions were in good agreement with the FE results.

scholarly journals Experimental Study on the Caustics of Moving Cracks and Elliptical Curvature under Impact Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Haohao Luo ◽  
Renshu Yang ◽  
Yanbing Wang ◽  
Guoliang Yang ◽  
Chengxiao Li ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Impact Loading ◽  
Crack Tip ◽  
Test System ◽  
Moving Crack ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Crack Tip Stress

A dynamic caustics test system was used, and different moving cracks were analysed to study the interaction between the crack growth rate, stress intensity factor, and curvature of the elliptical end of a moving crack under impact loading. Based on the linear elastic fracture mechanics theory, linearly fitting of the crack tip stress intensity factor and the elliptical curvature were employed to obtain the specific functional expressions. ABAQUS software was used to numerically simulate the moving crack fracture process passing through different elliptical curvatures. The crack tip stress intensity factor was calculated by the stress extrapolation method. The stress intensity factor obtained from the numerical calculation and the caustics test was consistent. The test and numerical simulation results showed that the direction of moving cracks entering and passing through the elliptical defects shows a certain regularity. As the ellipse curvature increased, the moving crack stress intensity factor passing through the ellipse gradually decreased, and the moving crack also passed easily through oval defects.

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