The Experts below are selected from a list of 6360 Experts worldwide ranked by ideXlab platform

S. N. Atluri - One of the best experts on this subject based on the ideXlab platform.

  • Finite element calculation of stress intensity factors for interfacial Crack using virtual Crack closure integral
    Computational Mechanics, 1995
    Co-Authors: W. T. Chow, S. N. Atluri
    Abstract:

    This paper presents a successful implementation of the virtual Crack closure integral method to calculate the stress intensity factors of an interfacial Crack. The present method would compute the mixed-mode stress intensity factors from the mixed-mode energy release rates of the interfacial Crack, which are easily obtained from the Crack opening displacements and the nodal forces at and ahead of the Crack tip, in a finite element model. The simple formulae which relate the stress intensity factors to the energy release rates are given in three separate categories: an isotropic bimaterial continuum, an orthotropic bimaterial continuum, and an anisotropic bimaterial continuum. In the example of a Central Crack in a bimaterial block under the plane strain condition, comparisons are made with the exact solution to determine the accuracy and efficiency of the numerical method. It was found that the virtual Crack closure integral method does lead to very accurate results with a relatively coarse finite element mesh. It has also been shown that for an anisotropic interfacial Crack under the generalized plane strain condition, the computed stress intensity factors using the virtual Crack closure method compared favorably with the results using the J integral method applied to two interacting Crack tip solutions. In order for the stress intensity factors to be used as physical variables, the characteristic length for the stress intensity factors must be properly defined. A study was carried out to determine the effects of the characteristic length on the fracture criterion based the mixed-mode stress intensity factors. It was found that the fracture criterion based on the quadratic mixture of the normalized stress intensity factors is less sensitive to the changes in characteristic length than the fracture criterion based on the total energy release rate along with the phase angle.

Filippo Berto - One of the best experts on this subject based on the ideXlab platform.

  • nsifs estimation based on the averaged strain energy density under in plane mixed mode loading
    Procedia structural integrity, 2016
    Co-Authors: Luca Pittarello, Filippo Berto, Alberto Campagnolo
    Abstract:

    Abstract In this work three methods for the rapid calculation of the NSIFs, based on the averaged strain energy density (SED), are compared. The first method was proposed by Lazzarin et al. and it is based on the calculation of the SED averaged in two different control volumes centred at the notch tip. The second one instead was recently presented by Treifi and Oyadiji and it takes advantage of the strain energy density averaged within two control volumes (semi-circular sector) centred at the notch tip. Then a new method based on the evaluation of the total and deviatoric strain energy density averaged over a control volume has been proposed. Finally, the described methods have been applied to plates weakened by different V-notch geometries: diamond-shaped notch, square hole and Central Crack in plates of finite and infinite extension. The values ​​of the NSIFs derived according to Gross and Mendelson have been compared with those obtained by means of the approximate methods, by using coarse FE meshes.

  • multiparametric full field representations of the in plane stress fields ahead of Cracked components under mixed mode loading
    International Journal of Fatigue, 2013
    Co-Authors: Filippo Berto, P Lazzarin
    Abstract:

    Abstract In some cases of engineering interest, the contribution of the higher order stress terms (besides the stress intensity factors and the T-stress) is not negligible in the Crack tip stress field. The main aim of the present investigation is to present a set of equations for accurately describing the Crack tip stress components particularly for those cases where the modes I and II stress intensity factors used in combination with the T-stress component, are unable to capture with satisfying precision the complete stress field ahead the Crack tip. The case of a plate with a Central Crack under mixed mode (I + II) loading is discussed to show the different contributions of the higher order terms in the overall stress field. The second example deals with a thin welded lap joint characterized by a jointing face width to thickness ratio d/t ranging from 0.5 to 5. The third example investigates the case of an inclined Crack departing from the slit tip of a welded lap joint. The strain energy averaged over a control volume can be analytically evaluated with high precision by taking into account only four additional terms besides KI, KII and T. Finally, the averaged SED is used to provide a demarcation line between the elastic and the elastic–plastic behaviors as well as to create a possible bridging with the CJP (Christopher, James and Patterson) model.

Subir Das - One of the best experts on this subject based on the ideXlab platform.

Youhe Zhou - One of the best experts on this subject based on the ideXlab platform.

  • thickness dependence of fracture behaviour in a superconducting strip
    Superconductor Science and Technology, 2013
    Co-Authors: Huadong Yong, Cu Xue, Youhe Zhou
    Abstract:

    When subjected to a magnetic field, a superconducting strip will undergo an electromagnetic body force induced by flux pinning. The magnitude of the body force is dependent on the critical current density. It is well known that the critical current density in the strip will decrease with increasing thickness. In addition, the mechanical behaviour of the strip will also be affected by the thickness of the strip. Thus, the strip thickness has an influence on both the electromagnetic and mechanical behaviours. In this paper, we analyse the fracture behaviour by considering the competition of electromagnetic and mechanical behaviours. In order to study the Central Crack problem of a superconducting strip with different thicknesses, we replace the electromagnetic body force with the total surface force. Using a Fourier transform method, the boundary value problem is reduced to a singular integral equation. By solving the singular integral equation, we obtain the stress intensity factors for two different Crack lengths during field descent. The results show that the stress intensity factor is not a monotonic function of the thickness and that two competing factors dominate in different field regions. It is necessary to obtain the optimized thickness by considering both the superconductivity and mechanical behaviour in the superconducting strip.

  • Crack problem for thin superconducting strip in a perpendicular magnetic field
    IEEE Transactions on Applied Superconductivity, 2012
    Co-Authors: Huadong Yong, Youhe Zhou
    Abstract:

    In this paper, we investigate fracture behavior for the superconducting strip with a Central Crack by means of the finite-element method. The Crack is assumed to be small enough such that the perturbations of the Crack on the shielding current and the magnetic field are negligible. The Bean model where jc is field independent is adopted. We consider two cases, i.e., superconducting film with and without substrate. The stress intensity factors in the thin strip for the decreasing field are obtained. Compared with the case without substrate, the effect of the substrate on the stress intensity factor depends on the applied field Ba.

  • edge Crack problem in a long cylindrical superconductor
    Journal of Applied Physics, 2008
    Co-Authors: Jun Zeng, Huadong Yong, Youhe Zhou
    Abstract:

    In this work, the general problem of a center Crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the Crack length and the applied field, is investigated. We presented a simple model in which the effect of the Crack on the critical current is taken into account. It is assumed that the Crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a Central Crack. The results show that the Crack length and the applied field have significant effects on the fracture behavior of the superconductor.

Kao-walter Sharon - One of the best experts on this subject based on the ideXlab platform.

  • Numerical simulation of buckling and post-buckling behavior of a Central notched thin aluminum foil with nonlinearity in consideration
    'MDPI AG', 2020
    Co-Authors: Shahmardani Mahdieh, Ståhle Per, Islam, Md. Shafiqul, Kao-walter Sharon
    Abstract:

    In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the Cracked area. This is due to local buckling and compression stresses near the Crack surfaces. This study aims to numerically study the buckling behavior of a thin sheet with a Central Crack under tension. A numerical model of a notched sheet under tensile loading is developed using the finite element method, which considers both material and geometrical nonlinearity. To overcome the convergence problem caused by the small thickness-to-length/width ratio and to stimulate the buckling, an imperfection is defined as a small perturbation in the numerical model. Both elastic and elasto-plastic behavior are applied, and the influence of them is studied on the critical buckling stress and the post-buckling behavior of the notched sheet. Numerical results for both elastic and elasto-plastic behavior reflect that very small perturbations need more energy for the activation of buckling mode, and a higher buckling mode is predominant. The influences of different parameters, including Poisson’s ratio, yield limit, Crack length-to-sheet-width ratio, and the sheet aspect ratio are also evaluated with a focus on the critical buckling stress and the buckling mode shape. With increase in Poisson’s ratio. First, the critical buckling stress reduces and then remains constant. A higher yield limit results in increases in the critical buckling stress, and no change in the buckling mode shape while adopting various Crack length-to-sheet-width ratios, and the sheet aspect ratio changes the buckling mode shape

  • Numerical simulation of buckling and post-buckling behavior of a Central notched thin aluminum foil with nonlinearity in consideration
    'MDPI AG', 2020
    Co-Authors: Shahmardani Mahdieh, Ståhle Per, Islam, Md. Shafiqul, Kao-walter Sharon
    Abstract:

    In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the Cracked area. This is due to local buckling and compression stresses near the Crack surfaces. This study aims to numerically study the buckling behavior of a thin sheet with a Central Crack under tension. A numerical model of a notched sheet under tensile loading is developed using the finite element method, which considers both material and geometrical nonlinearity. To overcome the convergence problem caused by the small thickness-to-length/width ratio and to stimulate the buckling, an imperfection is defined as a small perturbation in the numerical model. Both elastic and elasto-plastic behavior are applied, and the influence of them is studied on the critical buckling stress and the post-buckling behavior of the notched sheet. Numerical results for both elastic and elasto-plastic behavior reflect that very small perturbations need more energy for the activation of buckling mode, and a higher buckling mode is predominant. The influences of different parameters, including Poisson’s ratio, yield limit, Crack length-to-sheet-width ratio, and the sheet aspect ratio are also evaluated with a focus on the critical buckling stress and the buckling mode shape. With increase in Poisson’s ratio. First, the critical buckling stress reduces and then remains constant. A higher yield limit results in increases in the critical buckling stress, and no change in the buckling mode shape while adopting various Crack length-to-sheet-width ratios, and the sheet aspect ratio changes the buckling mode shape.Open accessMD3S - Model Driven Development and Decision Suppor

  • Numerical simulation of buckling and post-buckling behavior of a Central notched thin aluminum foil with nonlinearity in consideration
    'MDPI AG', 2020
    Co-Authors: Shahmardani Mahdieh, Ståhle Per, Islam, Md. Shafiqul, Kao-walter Sharon
    Abstract:

    In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the Cracked area. This is due to local buckling and compression stresses near the Crack surfaces. This study aims to numerically study the buckling behavior of a thin sheet with a Central Crack under tension. A numerical model of a notched sheet under tensile loading is developed using the finite element method, which considers both material and geometrical nonlinearity. To overcome the convergence problem caused by the small thickness-to-length/width ratio and to stimulate the buckling, an imperfection is defined as a small perturbation in the numerical model. Both elastic and elasto-plastic behavior are applied, and the influence of them is studied on the critical buckling stress and the post-buckling behavior of the notched sheet. Numerical results for both elastic and elasto-plastic behavior reflect that very small perturbations need more energy for the activation of buckling mode, and a higher buckling mode is predominant. The influences of different parameters, including Poisson’s ratio, yield limit, Crack length-to-sheet-width ratio, and the sheet aspect ratio are also evaluated with a focus on the critical buckling stress and the buckling mode shape. With increase in Poisson’s ratio. First, the critical buckling stress reduces and then remains constant. A higher yield limit results in increases in the critical buckling stress, and no change in the buckling mode shape while adopting various Crack length-to-sheet-width ratios, and the sheet aspect ratio changes the buckling mode shape.Open access