Abstract An efficient technique for evaluating stress intensity factors is presented. The method, based on the crack closure integral, can be used with a constant strain finite element stress analysis and a coarse grid. The technique also permits evaluation of both Mode I and Mode II stress intensity factors from the results of a single analysis. Example computations are performed for a double cantilever beam test specimen, a finite width strip with a central crack, and a pin loaded circular hole with radial cracks. Close agreement between numerical results given by this approach and reference solutions were found in all cases.

The development of a generalized quadrilateral finite element that includes a singular point at a corner node is presented. Inter-element conformability is maintained so that monotone convergence is preserved. The global-local concept of finite elements is used to formulate the complete set of equations. Examples of crack tip singularities are given.

#1M. F. Kanninen(Battelle Memorial Institute)H-Index: 18

An improved analytical model for the double cantilever beam fracture specimen is developed by treating a finite length beam which is partly free and partly supported by an elastic foundation. The results obtained are shown to be in excellent agreement with established data for initial crack extension. Some preliminary computational results for unstable crack propagation are also presented.

Abstract : The report summarizes the first phase of the development of computer programs for calculating elastic stress intensity factors at the critical (fatigue-prone) details of pressure hulls. The work is part of a broader study aimed at the development of analytical methods for fatigue and fracture analysis of submarine hulls. Two new techniques are introduced. One is based on direct application of the linear elastic fracture mechanics relations between the stress intensity factors and the ...

Since the theoretical stresses and strains at the tip of a V-notched crack in an elastic continuum are infinite, the question arises as to the accuracy of strain energy as calculated from finite element computer programs for systems containing such a crack. Two geometries for which analytical solutions are available were analyzed using a plane stress finite element computer program. Results show that accuracy in both cases depended upon proper selection of a grid network. Several methods of calc...

Last. W.K. Wilson(Westinghouse Electric)H-Index: 5

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Abstract The usefulness of the finite element method for the computation of crack tip stress intensity factors is established. Although ordinary finite element methods lack the ability to represent crack tip stress singularity, meaningful values for crack tip stress intensity factors can be obtained by a simple process. The results are compared not only to the results of other analytical solutions, but additional correlation is made of two different fracture test specimen types.

#1Esben Byskov(DTU: Technical University of Denmark)H-Index: 10

The calculation of stress intensity factors for complicated crack configurations in finite plates usually presents substantial difficulty. A version of the finite element method solves such problems approximately by means of special cracked elements. A general procedure for evaluating the stiffness matrix of a cracked element is developed, and numerical results obtained by the simplest elements are compared with those provided by other methods.

#1V.B. Watwood(PNNL: Pacific Northwest National Laboratory)H-Index: 1

Abstract A direct method of computation of the stress intensity factor, K , of linear fracture mechanics is discussed. Poor accuracy of the method, unless extremely small elements are used near the crack tip, leads to its abandonment in favor of direct computation of the strain energy release rate which is equivalent to K . This procedure consists of computing the strain energy for two slightly different crack lengths and employing numerical differentiation to determine the strain energy release...

Abstract null null Pultruded Fiber-Reinforced Polymers (FRP) are innovative structural elements that are experiencing a steady increase in use for different structural applications. Due to their appealing properties that set them apart from traditional construction materials, such as magnetic transparency and excellent strength-to-weight ratio, numerous experimental and numerical studies have been performed in the last decades to assess their performance as structural components. The description...

#2Golam Newaz(WSU: Wayne State University)H-Index: 20

Single hat sectioned hybrid beams composed of aluminum and Carbon Fiber Reinforced Polymeric materials (CFRP), intended for structural applications in the automotive and aviation sectors, have been studied from the point of their energy absorption capabilities when submitted to transverse low-velocity impact loading. Carbon fiber-epoxy composite prepregs were placed on the inside of the single hat sectioned aluminum sheet and completely cured in the autoclave under the recommended curing cycle. ...

Abstract null null Physical fatigue tests and numerical simulation were conducted to verify the effectiveness of cold reinforcement methods of distortion-induced fatigue cracks at web gaps in steel girder bridges. Test results indicate that stop-holes could temporarily arrest crack growth. However, bolting and bonding angle could effectively arrest further cracking, and reduce distortions and fatigue stresses. Numerical simulation analysis results show that the equivalent stress intensity factor...

Last. Luigi Lazzeri(UniPi: University of Pisa)H-Index: 23

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Abstract null null The study investigates fatigue growth and shape evolution of a corner crack in a pin-loaded hole by means of three-dimensional FE analyses. The constraint factor/plasticity-induced crack closure strategy was tuned to reproduce experimentally measured crack front shapes. The study quantitatively determines the LEFM acceptability regions using elastic–plastic simulations. It also assesses the sensitivity of crack propagation and shape evolution to the stress distribution along t...

#2Yujie Wei(CAS: Chinese Academy of Sciences)H-Index: 38

Abstract null null Propagating cracks may deflect due to dynamic instability, running into pre-existing weak regions of heterogeneous media, or encountering variation in driving forces. The mechanical analysis of a kinked crack is of engineering significance for safety control and crack-network formation. Existing theories for kinked cracks relied on the perturbation method, as befit small kinks. The stress intensity factors (SIFs) are valid in the close proximity of the primary crack tip. As to...

Last. Hongniao Chen(Guida: Guizhou University)H-Index: 1

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Abstract null null In order to study the fracture performance of nuclear graphite, numerical simulations were performed on single-edge notched graphite beam subjected to three-point bending by using XFEM, CZM and VCCT in ABAQUS. The dependence of peak load Pc on the element size was analyzed and numerical results indicated that the Pc is sensitive to the mesh size using the three methods and it is the most sensitive using VCCT. For the three models, the influences of critical parameters such as ...

Abstract null null A computational framework is presented for the delamination propagation analysis in laminated composite strips that combines an extended high-order layerwise model and a spectral finite element with high-order spatial approximation in the plane of the structure. The extended layerwise laminate mechanics approximate the through-thickness fields using Hermite cubic splines, while the discontinuities in displacement induced by a delamination crack are treated as generalized damag...

#1Yan-Ping Liu(China University of Geosciences (Wuhan))

#2Tian-Jun Li(China University of Geosciences (Wuhan))

Abstract null null This paper proposes an approach for calculating the stress intensity factor (SIF) based on the virtual crack closure technique (VCCT) using tetrahedral finite elements. An important feature of this approach is that tetrahedral element meshes with no strict requirements of shape can be employed to calculate the SIF with the VCCT. Therefore, structures with cracks can be meshed automatically and easily using arbitrary tetrahedral elements. Two cases with different crack shapes a...