Crack Analysis using Discontinuous Boundary Elements

1993 ◽  
Vol 207 (1) ◽  
pp. 41-45 ◽  
Author(s):  
A Elzein ◽  
R A Adey
Keyword(s):  
Aerospace Industry ◽  
Three Dimensional ◽  
Boundary Elements ◽  
Intensity Factors ◽  
Convergence Results ◽  
Discontinuous Boundary ◽  
Crack Problems ◽  
Axisymmetric Problems ◽  
Analysis System ◽  
Line Elements

A simple and efficient approach is proposed for the analysis of crack problems occurring in mechanical components widely used in the aerospace industry. A linear stress analysis of the cracked components is performed using discontinuous boundary elements at the crack tip. The engineering analysis system BEASY is used to derive accurate predictions of the stress intensity factors corresponding to either of the three modes KI, KII or KIII. With the proposed approach, the user has to model only the surface of the component, as opposed to its volume in finite elements. Thus, line elements in two-dimensional and axisymmetric problems and surface quadrilaterals or triangles in three-dimensional problems are used to mesh the components. The approach clearly results in substantial savings in mesh preparation effort. The paper will describe the application of the system to problems in the aerospace field and the convergence results that demonstrate the high accuracy and reliability of the technique.

Development of the Next-Generation Computational Fracture Mechanics Simulator on the Earth Simulator 2

2012 ◽  
Author(s):  
Kaworu Yodo ◽  
Hiroshi Kawai ◽  
Hiroshi Okada ◽  
Masao Ogino ◽  
Ryuji Shioya
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Large Scale ◽  
Three Dimensional ◽  
Intensity Factors ◽  
Element Analysis ◽  
Mechanics Analysis ◽  
Analysis System

Fracture mechanics analysis using the finite element method has been one of the key methodologies to evaluate structural integrity for aging infrastructures such as aircraft, ship, power plants, etc. However, three-dimensional crack analyses for structures with highly complex three-dimensional shapes have not widely been used, because of many technical difficulties such as the lack of enough computational power. The authors have been developing a fracture mechanics analysis system that can deal with arbitrary shaped cracks in three-dimensional structures. The system consists of mesh generation software, a finite element analysis program and a fracture mechanics module. In our system, a Virtual Crack Closure-Integral Method (VCCM) for the quadratic tetrahedral finite elements is adopted to evaluate the stress intensity factors. This system can perform the three-dimensional fracture analyses. Fatigue and SCC crack propagation analyses with more than one cracks of arbitrary complicated shapes and orientations. The rate and direction of crack propagation are predicted by using appropriate formulae based on the stress intensity factors. When the fracture mechanics analysis system is applied to the complex shaped aging structures with the cracks which are modeled explicitly, the size of finite element analysis tends to be very large. Therefore, a large scale parallel structural analysis code is required. We also have been developing an open-source CAE system, ADVENTURE. It is based on the hierarchical domain decomposition method (HDDM) with the balancing domain decomposition (BDD) pre-conditioner. A general-purpose parallel structural analysis solver, ADVENTURE_Solid is one of the solver modules of the ADVENTURE system. In this paper, we combined VCCM for the tetrahedral finite element with ADVENTURE system and large-scale fracture analyses are fully automated. They are performed using the massively parallel super computer ES2 (Earth Simulator 2) which is owned and run by JAMSTEC (Japan Agency for Marine-Earth Science and Technology).

A Surface Crack in Shells Under Mixed-Mode Loading Conditions

1988 ◽  
Vol 55 (4) ◽  
pp. 795-804 ◽  
Author(s):  
P. F. Joseph ◽  
F. Erdogan
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Mixed Mode ◽  
Shallow Shell ◽  
Crack Problem ◽  
Three Dimensional ◽  
Loading Conditions ◽  
Intensity Factors ◽  
Crack Problems

The problem of a shallow shell containing a surface crack and subjected to general loading conditions is considered. It is shown that, as in the three-dimensional elasticity formulation, the mode I state can be separated whereas modes II and III remain coupled. A line spring model is developed to formulate the part-through crack problem under mixed-mode conditions. A shallow shell of arbitrary curvature having a part-through crack located on the outer or the inner surface of the shell is then considered. Reissner’s transverse shear theory is used to formulate the problem by assuming that the shell is subjected to all five moment and stress resultants. The uncoupled antisymmetric problem is solved for cylindrical and toroidal shells having a surface crack in various orientations and the primary and the secondary stress intensity factors are given. The results show that, unlike the through crack problems, in surface cracks the effect of shell curvature on the stress intensity factors is relatively insignificant.

Fracture Analysis of Cracks in Anisotropic Materials Using 3DFAS and ANSYS®

2006 ◽  
Author(s):  
U. Ozkan ◽  
A. C. Kaya ◽  
A. Loghin ◽  
A. O. Ayhan ◽  
H. F. Nied
Keyword(s):  
Finite Element ◽  
Numerical Solutions ◽  
Parametric Design ◽  
Three Dimensional ◽  
Crack Tip ◽  
Fracture Analysis ◽  
Anisotropic Materials ◽  
Finite Element Software ◽  
Crack Problems ◽  
Analysis System

The analysis of two and three dimensional fracture mechanics problems in anisotropic materials using ANSYS finite element software and 3DFAS (Three Dimensional Fracture Analysis System) is examined in this study. The methodology uses analytically derived generalized plane strain crack tip fields in anisotropic materials and is implemented into an ANSYS Macro using ANSYS Parametric Design Language. It is shown that quarter-point finite element approach is still a very effective technique for general three dimensional crack problems in homogeneous anisotropic materials. The expressions of the crack tip asymptotic displacement field are summarized and numerical examples of two and three dimensional crack problems in orthotropic, directionally solidified, and single crystal materials are presented. The stress intensity factors are compared with two-dimensional analytical and numerical solutions available in the literature and with numerical solutions obtained from FRAC3D [1, 2], a three dimensional fracture analysis program using enriched finite elements. Very good agreement is obtained between the different numerical techniques or with the analytical solutions.

Benchmark for the Calculation of Quasi-Laminar Elliptical Cracks Interaction Under Bi-Axial Loading

2015 ◽  
Author(s):  
Pierre Dulieu ◽  
Valéry Lacroix ◽  
Do Jun Shim ◽  
Frederick (Bud) Brust
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Axial Loading ◽  
Intensity Factors ◽  
Interaction Factor ◽  
Crack Problems ◽  
Cracks Interaction

In the frame of the Structural Integrity demonstration of the Doel 3 and Tihange 2 RPVs flawed with quasi-laminar cracks, alternative proximity rules based on 3D eXtended Finite Element Method (X-FEM) calculations have been developed by Tractebel Engineering. The calculations have been performed with the X-FEM software Morfeo Crack. This software uses the Level-Sets method allowing a very straightforward cracks modelling. A large part of the development of these proximity rules for quasi-laminar flaws has been dedicated to the validation of the models and the calculations. This validation has been done through a benchmark with Engineering Mechanics Corporation of Columbus (Emc2). This company uses: • The Finite Element Alternating Method (FEAM) for calculating stress intensity factors through the FRAC@ALT program. The FEAM is a state-of-the-art method for obtaining stress intensity factors for three-dimensional surface and embedded crack problems. • The X-FEM functionality as implemented in Abaqus software. The benchmark consists of the Stress Intensity Factor calculation of interacting quasi-laminar flaws and of the interaction factor assessment as well.

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