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Dungan Wang - One of the best experts on this subject based on the ideXlab platform.
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mode i stress Intensity Factor solutions for spot welds in lap shear specimens
International Journal of Solids and Structures, 2007Co-Authors: Dungan WangAbstract:The analytical solutions of the mode I stress Intensity Factor for spot welds in lap-shear specimens are investigated based on the classical Kirchhoff plate theory for linear elastic materials. First, closed-form solutions for an infinite plate containing a rigid inclusion under counter bending conditions are derived. The development of the closed-form solutions is then used as a guide to develop approximate closed-form solutions for a finite square plate containing a rigid inclusion under counter bending conditions. Based on the J integral, the closed-form solutions are used to develop the analytical solutions of the mode I stress Intensity Factor for spot welds in lap-shear specimens of large and finite sizes. The analytical solutions of the mode I stress Intensity Factor based on the solutions for infinite and finite square plates with an inclusion are compared with the results of the three-dimensional finite element computations of lap-shear specimens with various ratios of the specimen half width to the nugget radius. The results indicate that the mode I stress Intensity Factor solution based on the finite square plate model with an inclusion agrees well with the computational results for lap-shear specimens for the ratio of the half specimen width to the nugget radius between 4 and 15. Finally, a set of the closed-form stress Intensity Factor solutions for lap-shear specimens at the critical locations are proposed for future applications.
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a computational study of local stress Intensity Factor solutions for kinked cracks near spot welds in lap shear specimens
International Journal of Solids and Structures, 2005Co-Authors: Dungan WangAbstract:In this paper, the local stress Intensity Factor solutions for kinked cracks near spot welds in lap-shear specimens are investigated by finite element analyses. Based on the experimental observations of kinked crack growth mechanisms in lap-shear specimens under cyclic loading conditions, three-dimensional and two-dimensional plane-strain finite element models are established to investigate the local stress Intensity Factor solutions for kinked cracks emanating from the main crack. Semi-elliptical cracks with various kink depths are assumed in the three-dimensional finite element analysis. The local stress Intensity Factor solutions at the critical locations or at the maximum depths of the kinked cracks are obtained. The computational local stress Intensity Factor solutions at the critical locations of the kinked cracks of finite depths are expressed in terms of those for vanishing kink depth based on the global stress Intensity Factor solutions and the analytical kinked crack solutions for vanishing kink depth. The three-dimensional finite element computational results show that the critical local mode I stress Intensity Factor solution increases and then decreases as the kink depth increases. When the kink depth approaches to 0, the critical local mode I stress Intensity Factor solution appears to approach to that for vanishing kink depth based on the global stress Intensity Factor solutions and the analytical kinked crack solutions for vanishing kink depth. The two-dimensional plane-strain computational results indicate that the critical local mode I stress Intensity Factor solution increases monotonically and increases substantially more than that based on the three-dimensional computational results as the kink depth increases. The local stress Intensity Factor solutions of the kinked cracks of finite depths are also presented in terms of those for vanishing kink depth based on the global stress Intensity Factor solutions and the analytical kinked crack solutions for vanishing kink depth. Finally, the implications of the local stress Intensity Factor solutions for kinked cracks on fatigue life prediction are discussed.
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geometric functions of stress Intensity Factor solutions for spot welds in lap shear specimens
International Journal of Solids and Structures, 2005Co-Authors: Dungan WangAbstract:In this paper, the stress Intensity Factor solutions for spot welds in U-shape specimens are investigated by finite element analyses. Three-dimensional finite element models are developed for U-shape specimens to obtain accurate stress Intensity Factor solutions. In contrast to the existing investigations of the stress Intensity Factor solutions based on the finite element analyses, various ratios of the sheet thickness, half specimen width, half specimen length, and corner radius to the nugget radius are considered in this investigation. The computational results confirm the functional dependence on the nugget radius and sheet thickness of Zhang’s analytical solutions. The computational results provide a geometric function in terms of the normalized half specimen width, normalized half specimen length, and normalized corner radius to Zhang’s analytical solutions. The computational results also provide a geometric function in terms of the aspect ratio of the specimen to complete Lin and Pan’s analytical solution. Finally, based on the analytical and computational results, the dimensions of U-shape specimens are suggested.
Bel Abbes Bachir Bouiadjra - One of the best experts on this subject based on the ideXlab platform.
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Stress Intensity Factor analysis for notched cracked structure repaired by composite patching
Materials & Design, 2009Co-Authors: Djamel Ouinas, Nouredine Benderdouche, Mohamed Sahnoune, Bel Abbes Bachir BouiadjraAbstract:In this paper, we investigated the crack growth behaviour of cracked thin aluminium plate repaired with bonded composite patch. The finite element method is used to study the performance of the bonded composite reinforcement or repair for reducing the stress concentration at a semicircular lateral notch and repairing cracks starting from this kind of notch. The effects of the adhesive properties and the patch size on the stress Intensity Factor variation at the crack tip in mode I and mixed mode are highlighted. The obtained results show that the stress concentration Factor at the semicircular notch root and the stress Intensity Factor of a crack starting from notch are reduced with the increase of the diameter and the number of the semicircular patch. The maximum reduction of stress Intensity Factor is about 42% and 54%, respectively for single and double patch. However, the gain in the patch thickness increases with the increase of the crack length and it decreases when the patch thickness increases. The adhesive properties must be optimised in order to increase the performance of the patch repair or reinforcement.
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Disbond effect on the stress Intensity Factor for repairing cracks with bonded composite patch
Computational Materials Science, 2004Co-Authors: Abdelkader Megueni, Bel Abbes Bachir Bouiadjra, M BelhouariAbstract:It is well known that the stress Intensity Factor is considerably reduced by the bonded composite repair. The finite element method is used to compute the stress Intensity Factor for repairing cracks with bonded composite patch taking account of the disbond. In the case of a disbond, the increase of patch thickness reduce the negative effects of disbond. The curves plotted show the concordance with the model [Thermal residual stresses in composite repairs on cracked metal structures, Ph.D. Thesis, University of British Columbia, 1998].
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computation of the stress Intensity Factor for patched crack with bonded composite repair in pure mode ii
Composite Structures, 2003Co-Authors: Abdelkader Megueni, Bel Abbes Bachir Bouiadjra, Benali BoutaboutAbstract:The finite element method is carried out to analyse the performance of the bonded composite patch for repairing cracks in pure mode II by computing the stress Intensity Factor at the crack tip. The effects of the patch size and the adhesive thickness on the stress Intensity Factor variation are highlighted. The comparison between double and single patch repairs is also given in this study. The obtained results shows that, like in pure mode I, the mode II stress Intensity Factor exhibits an asymptotic behaviour as the crack length increases. There is a significant difference in the reduction of the SIF between the single and double sided patch.
Sergei Alexandrov - One of the best experts on this subject based on the ideXlab platform.
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A numerical method for determining the strain rate Intensity Factor under plane strain conditions
Continuum Mechanics and Thermodynamics, 2016Co-Authors: Sergei Alexandrov, Y.-r. JengAbstract:Using the classical model of rigid perfectly plastic solids, the strain rate Intensity Factor has been previously introduced as the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. Since then, many strain rate Intensity Factors have been determined by means of analytical and semi-analytical solutions. However, no attempt has been made to develop a numerical method for calculating the strain rate Intensity Factor. This paper presents such a method for planar flow. The method is based on the theory of characteristics. First, the strain rate Intensity Factor is derived in characteristic coordinates. Then, a standard numerical slip-line technique is supplemented with a procedure to calculate the strain rate Intensity Factor. The distribution of the strain rate Intensity Factor along the friction surface in compression of a layer between two parallel plates is determined. A high accuracy of this numerical solution for the strain rate Intensity Factor is confirmed by comparison with an analytic solution. It is shown that the distribution of the strain rate Intensity Factor is in general discontinuous.
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A Numerical Method for Calculating the Strain Rate Intensity Factor
2015Co-Authors: Sergei Alexandrov, Chih-yu KuoAbstract:The strain rate Intensity Factor is the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. In the case of rigid perfectly plastic solids, the maximum friction law postulates that the friction stress at sliding is equal to the shear yield stress. The equivalent strain rate approaches infinity near maximum friction surfaces. Therefore, the strain rate Intensity Factor cannot be calculated by means of standard finite element packages. On the other hand, the strain rate Intensity Factor can be used to predict the generation of fine grain layers in the vicinity of friction surfaces in metal forming processes. In order to develop a model that connects the strain rate Intensity Factor and parameters characterizing such layers, it is necessary to propose a numerical method for calculating the strain rate Intensity Factor with a high accuracy. In the present paper, the strain rate Intensity Factor is expressed in terms of quantities that are found by means of conventional numerical methods based on the theory of characteristics. Then, an available numerical method is complemented with an additional procedure to find the strain rate Intensity Factor. The new method is used to calculate the strain rate Intensity Factor in compression of a plastic layer between parallel plates. The approach proposed is restricted to plane strain deformation of rigid perfectlyplastic material.
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The Strain Rate Intensity Factor and Its Applications: A Review
Materials Science Forum, 2009Co-Authors: Sergei AlexandrovAbstract:The present paper concerns with the concept of the strain rate Intensity Factor in rigid plastic solids. The strain rate Intensity Factor is the coefficient of the principal singular term in the expansion of the equivalent strain rate in a series in the vicinity of maximum friction surfaces. Such singular velocity fields appear in solutions based on several rigid plastic models. Because of this singularity in the velocity field, many conventional evolution equations for material properties are not compatible with such rigid plastic solutions. On the other hand, qualitative behaviour of the singular rigid plastic solutions in the vicinity of maximum friction surfaces is in agreement with a number of experimental results. Therefore, the primary objective of research in this direction is to develop an approach to relate parameters of the singular velocity fields and parameters characterizing material properties. The approaches proposed in previous works are based on the strain rate Intensity Factor. In the case of analytical and semi-analytical solutions the strain rate Intensity Factor can be found by means of an asymptotic analysis of the solutions. A number of such solutions obtained by inverse methods are reviewed in the present paper and the strain rate Intensity Factor is found. An effect of process parameters on its magnitude is shown and discussed.
J.j. Mason - One of the best experts on this subject based on the ideXlab platform.
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Dynamic stress Intensity Factor due to concentrated loads on a propagating semi-infinite crack in orthotropic materials
International Journal of Fracture, 2002Co-Authors: Cindy Rubio-gonzález, J.j. MasonAbstract:The elastodynamic response of an infinite orthotropic material with a semi-infinite crack propagating at constant speed under the action of concentrated loads on the crack faces is examined. Solution for the stress Intensity Factor history around the crack tip is found for the loading modes I and II. Laplace and Fourier transforms along with the Wiener-Hopf technique are employed to solve the equations of motion. The asymptotic expression for the stress near the crack tip is analyzed which lead to a closed-form solution of the dynamic stress Intensity Factor. It is found that the stress Intensity Factor for the propagating crack is proportional to the stress Intensity Factor for a stationary crack by a Factor similar to the universal function k(v) from the isotropic case. Results are presented for orthotropic materials as well as for the isotropic case.
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Dynamic stress Intensity Factor for a propagating semi-infinite crack in orthotropic materials
International Journal of Engineering Science, 2000Co-Authors: Cindy Rubio-gonzález, J.j. MasonAbstract:Abstract The elastodynamic response of an infinite orthotropic material with a semi-infinite crack propagating at constant speed is examined. Solution for the stress Intensity Factor history around the crack tip is found for the loading modes I and II. Laplace and Fourier transforms along with the Wiener–Hopf technique are employed to solve the equations of motion. The asymptotic expression for the stress near the crack tip is analyzed which lead to a closed-form solution of the dynamic stress Intensity Factor. It is found that the stress Intensity Factor for the propagating crack is proportional to the stress Intensity Factor for a stationary crack by a Factor similar to the universal function k ( v ) from the isotropic case. Results are presented for orthotropic materials as well as for the isotropic case.
Xin Wang - One of the best experts on this subject based on the ideXlab platform.
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the stress Intensity Factor solutions for edge cracks in a padded plate geometry under general loading conditions
International Journal of Fatigue, 2007Co-Authors: R Bell, Xin WangAbstract:Abstract The stress Intensity Factor weight function for a single edge crack originating from the T-plate weld toe was derived from a general weight function form and two reference stress Intensity Factors. The coefficients of the weight function are given. The weight function together with the stress distribution on the crack plane was used to obtain the stress Intensity Factor solutions. The validity of the weight function for the T-plate was verified by the comparison with the numerical data. Good agreement was achieved. The derived weight function is valid for the relative depth a/t ⩽ 0.8. It is also shown that this weight function is suitable for the stress Intensity Factor calculation for the cracked laser-welded padded plate geometries under general loading conditions.
