The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Yiming Zhang - One of the best experts on this subject based on the ideXlab platform.

  • cracking Elements a self propagating strong discontinuity embedded approach for quasi brittle fracture
    Finite Elements in Analysis and Design, 2018
    Co-Authors: Yiming Zhang, Xiaoying Zhuang
    Abstract:

    Abstract In this paper, we present a self-propagating Strong Discontinuity embedded Approach (SDA) for quasi-brittle fracture. The method is based on the Statically Optimal Symmetric formulation (SOS) of the SDA using the 8-node Quadrilateral Element which avoids local stress locking. A non-continuous crack path is assumed such that the crack is modelled by a set of disconnected cracking segments. Hence, no complex crack tracking procedure and no explicit (or implicit) representation of the crack surface are needed. A local fracture criteria is proposed for determining the orientation of the crack. Several numerical tests with irregular discretizations are performed, demonstrating the effectiveness and robustness of the presented method.

  • strong discontinuity embedded approach with standard sos formulation Element formulation energy based crack tracking strategy and validations
    Computer Methods in Applied Mechanics and Engineering, 2015
    Co-Authors: Yiming Zhang, Roman Lackner, Matthias Zeiml, Herbert A Mang
    Abstract:

    Abstract The Strong Discontinuity embedded Approach (SDA) has proved to be a robust numerical method for simulating fracture of quasi-brittle materials such as glass and concrete. Three different numerical formulations are used in the SDA: (i) Statically Optimal Symmetric (SOS), (ii) Kinematically Optimal Symmetric (KOS), (iii) Statically and Kinematically Optimal Nonsymmetric (SKON). While the SOS formulation (standard version) of the SDA is simple for coding and provides good numerical stability (considering standard Galerkin method), several researchers have pointed out that this formulation encounters serious stress-locking. In this paper, an SOS formulation of the SDA is presented, considering Elements with linear and quadratic interpolation for the displacement field. The performance of the proposed model of crack simulation is investigated by re-analysis of a pulling test, a three-point bending test, and an L-shaped panel with prescribed crack paths. The obtained results show that Elements with linear interpolation encounter significant stress-locking, whereas Elements with quadratic interpolation give good results without locking. Based on the eight-node Quadrilateral Element, which showed the best performance in the aforementioned re-analysis of the tests, an energy-based crack-tracking strategy, originally used in the framework of the XFEM, is modified and implemented into the SDA model. Several numerical benchmark tests, including an L-shaped panel test, a tension-shear test, a notched panel test, four-point bending tests with single and double notches, and a pull-out test are performed, illustrating the good performance with respected to the SDA model and the robustness of the proposed crack-tracking strategy.

Hong Zheng - One of the best experts on this subject based on the ideXlab platform.

  • Four-Node Quadrilateral Element with Continuous Nodal Stress for Geometrical Nonlinear Analysis
    International Journal of Computational Methods, 2017
    Co-Authors: Yongtao Yang, Hong Zheng, Xuhai Tang, Quansheng Liu
    Abstract:

    In this paper, the performance of a hybrid ‘FE-Meshfree’ Quadrilateral Element with continuous nodal stress (Quad4-CNS) is investigated for geometrical nonlinear solid mechanic problems. By combining finite Element method (FEM) and meshfree method, this Quad4-CNS synergizes the individual strengths of these two methods, which leads to higher accuracy, better convergence rate, as well as high tolerance to mesh distortion. Therefore, Quad4-CNS is attractive for geometrical nonlinear solid mechanic problems where excessive distorted meshes occur. For geometrical nonlinear analysis, numerical results show that the results of Quad4-CNS Element are much better than those of four-node isoparametric Quadrilateral Element (Quad4), and are comparable to quadratic Quadrilateral Element (Quad8) and other hybrid ‘FE- Meshfree’ Elements.

  • A Three-Node Triangular Element with Continuous Nodal Stress (Trig3-CNS) for Geometry Nonlinear Solid Mechanics Problems
    International Journal of Computational Methods, 2017
    Co-Authors: Guanhua Sun, Yongtao Yang, Hong Zheng
    Abstract:

    This paper investigates the performance of the three-node triangular Element with continuous nodal stress (Trig3-CNS) for geometry nonlinear solid mechanic problems. This Trig3-CNS Element was recently proposed to improve accuracy of the finite Element method (FEM). By synergizing the individual strengths of meshfree method and FEM, the Trig3-CNS Element achieves higher accuracy and convergence rate. Furthermore, Trig3-CNS presents high tolerance to mesh distortion. Therefore, it is potentially useful for geometry nonlinear solid mechanics problems in which mesh distortion takes place. Compared with the traditional hybrid “FE-Meshfree” Elements, Trig3-CNS naturally processes CNS without requiring any extra operation in post-processing. Numerical tests in the present work show that for geometry nonlinear analysis, the results of the Trig3-CNS Element are better than the 3-node triangular Element (Trig3) and 4-node isoparametric Quadrilateral Element (Quad4). In addition, the performance of Trig3-CNS is com...

  • A partition-of-unity based three-node triangular Element with continuous nodal stress using radial-polynomial basis functions
    Science China Technological Sciences, 2017
    Co-Authors: Yongtao Yang, Hong Zheng
    Abstract:

    A partition-of-unity (PU) based “FE-Meshfree” three-node triangular Element (Trig3-RPIM) was recently developed for linear elastic problems. This Trig3-RPIM Element employs hybrid shape functions that combine the shape functions of three-node triangular Element (Trig3) and radial-polynomial basis functions for the purpose of synergizing the merits of both finite Element method and meshfree method. Although Trig3-RPIM Element is capable of obtaining higher accuracy and convergence rate than the Trig3 Element and four-node iso-parametric Quadrilateral Element without adding extra nodes or degrees of freedom (DOFs), the nodal stress field through Trig3-RPIM Element is not continuous and extra stress smooth operations are still needed in the post processing stage. To further improve the property of Trig3-RPIM Element, a new PU-based triangular Element with continuous nodal stress, called Trig3-RPIMcns, is developed. Numerical examples including several linear, free vibration and forced vibration test problems, have confirmed the correctness and feasibility of the proposed Trig3-RPIMcns Element.

  • Application of the ‘FE-Meshfree’ QUAD4 with continuous nodal stress using radial-polynomial basis functions for vibration and geometric nonlinear analyses
    Engineering Analysis With Boundary Elements, 2017
    Co-Authors: Yongtao Yang, Hong Zheng
    Abstract:

    Abstract A hybrid ‘FE-Meshfree’ four-node Quadrilateral Element with continuous nodal stress using radial-polynomial basis functions (Quad4-RPIMcns), was recently proposed for static analysis. The Quad4-RPIMcns Element can be considered as a development of the previous partition-of-unity (PU) based ‘FE-Meshfree’ QUAD4 Element (Quad4-RPIM) which uses FE shape functions to construct the PU and radial-polynomial basis functions to construct the local approximation (LA), so as to synergize the individual strengths of finite Element and meshfree methods. As a result, high order global approximations in Quad4-RPIMcns Element could be easily constructed without adding extra nodes and DOFs, thereby achieving high accuracy and convergence rate. In this paper, the Element is further applied to conduct free vibration, forced vibration and geometric nonlinear analyses of two-dimensional solids. Several numerical test problems are solved and the performance of the Element is compared with that of the three-node triangular Element (Trig3) and four-node isoparametric Quadrilateral Element (Quad4). Numerical results show that Quad4-RPIMcns Element has higher tolerance to mesh distortion and gives more accurate solution as compared to Trig3 and Quad4 Elements.

  • a four node Quadrilateral Element fitted to numerical manifold method with continuous nodal stress for crack analysis
    Computers & Structures, 2016
    Co-Authors: Yongtao Yang, Guanhua Sun, Hong Zheng
    Abstract:

    Formulations of the Quad4-CNS (NMM) Element for crack problems are presented.The derivatives of Quad4-CNS (NMM) shape function are continuous at nodes.Quad4-CNS (NMM) Element is able to achieve continuous nodal stress without any smoothing operation.Quad4-CNS (NMM) Element is very suitable for solving crack propagation problems.Comparing to extended Quadrilateral Element (XQ4), Quad4-CNS (NMM) Element can obtain better results. Formulations of a four-node Quadrilateral Element fitted to numerical manifold method (NMM) with continuous nodal stress called Quad4-CNS (NMM) Element for two-dimensional (2D) crack analysis are presented. This Quad4-CNS (NMM) Element can be considered as a development of the recently published four-node Quadrilateral Element with continuous nodal stress (Quad4-CNS). In contrast to the four-node iso-parametric Quadrilateral Element (Quad4), the Quad4-CNS Element has higher order of global approximations, much better accuracy and continuous nodal stress. Moreover, it is free from the linear dependence which otherwise cripples many of the partition of unity (PU) based methods with high order global approximations. Due to the adoption of two cover systems, namely, the mathematical cover and physical cover, the NMM is capable of solving continuous and discontinuous problems in a unified way. The purpose of this paper is to synergize the advantages of both the Quad4-CNS Element and the NMM to precisely model linear elastic fracture problems. A number of numerical examples indicate the accuracy and robustness of the present Quad4-CNS (NMM) Element.

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

  • a Quadrilateral shallow shell Element based on the third order theory for functionally graded plates and shells and the inaccuracy of rule of mixtures
    European Journal of Mechanics A-solids, 2015
    Co-Authors: S. Kapuria, Mayank Patni, Yaqoob M Yasin
    Abstract:

    Abstract A four-node Quadrilateral Element is developed for the dynamic analysis of doubly curved functionally graded material (FGM) shallow shells, using the refined third order theory. Two micromechanics models, the Voigt's rule of mixtures (ROM) and the Mori–Tanaka model, are considered for computing the effective material properties at a point. The accuracy of the Element is examined by comparing with various three dimensional elasticity and two dimensional (2D) analytical and finite Element solutions available in the literature for static and free vibration responses of FGM plates and shells. It is shown that the present Element, with the least number of degrees of freedom, achieves similar or better accuracy compared to other available 2D finite Elements some of which are even based on higher order theories. Using this Element, we also make a systematic assessment of the accuracy of the widely used ROM in predicting the behavior of FGM structures, for different values of the inhomogeneity parameter, and different geometrical parameters, boundary conditions, and material combinations. It is revealed that there can be very significant error in the deflection, stresses and natural frequencies predicted by the ROM, depending primarily on the inhomogeneity parameter and the difference in the material properties of the constituents.

  • active vibration control of smart plates using directional actuation and sensing capability of piezoelectric composites
    Acta Mechanica, 2013
    Co-Authors: S. Kapuria, Yaqoob M Yasin
    Abstract:

    The efficacy of directional actuation and sensing using piezoelectric fiber-reinforced composite (PFRC) actuators and sensors in active vibration suppression is examined for the first time for smart fiber metal laminate (FML) plates. A recently developed Quadrilateral Element with four physical nodes and one electric node, based on an efficient layer-wise theory, is employed for the structural analysis. The linear quadratic Gaussian (LQG) control strategy is employed for the active vibration control. The optimal direction of PFRC fibers to achieve the minimum control voltage is obtained for skew plates of cantilever and simply supported boundary conditions for different skew angles.

  • Free vibration analysis of composite and sandwich plates using an improved discrete Kirchhoff Quadrilateral Element based on third-order zigzag theory
    Computational Mechanics, 2008
    Co-Authors: S. D. Kulkarni, S. Kapuria
    Abstract:

    The new improved discrete Kirchhoff Quadrilateral Element based on the third-order zigzag theory developed earlier by the present authors for the static analysis of composite and sandwich plates is extended for dynamics and assessed for its performance for the free vibration response. The Element is free from the shear locking. The finite Element formulation is validated by comparing the results for simply supported plates with the analytical Navier solution of the zigzag theory. Comparison of the present results for the natural frequencies with those of a recently developed triangular Element based on the zigzag theory, for composite and sandwich plates, establishes the superiority of the present Element in respect of simplicity, accuracy and computational efficiency. The accuracy of the zigzag theory is assessed for composite and sandwich plates with various boundary conditions and aspect ratio by comparing the finite Element results with the 3D elasticity analytical and finite Element solutions.

  • an efficient Quadrilateral Element based on improved zigzag theory for dynamic analysis of hybrid plates with electroded piezoelectric actuators and sensors
    Journal of Sound and Vibration, 2008
    Co-Authors: S. Kapuria, S. D. Kulkarni
    Abstract:

    Abstract An efficient four-node Quadrilateral Element is developed using a coupled improved zigzag theory for the dynamic analysis of hybrid plates with segmented piezoelectric sensors and actuators. The theory considers a third-order zigzag approximation for inplane displacements, a layerwise quadratic approximation for the electric potential and a layerwise variation of the deflection to account for the piezoelectric transverse normal strain. The conditions on transverse shear stresses at the interfaces and at the top and bottom are satisfied exactly in the presence of electric loading. In a novel concept, the degrees of freedom (dof) corresponding to the quadratic component of the electric potential distribution are associated with the physical nodes and the electric potentials of the electroded piezoelectric surfaces are attached to separate electric nodes. The requirement of C 1 continuity of interpolation functions of the deflection is circumvented by employing an improved discrete Kirchhoff constraint technique. Comparison of the present results for natural frequencies and mode shapes for a variety of bimorph, hybrid composite and sandwich plates, with three-dimensional (3D) analytical and FE solutions, and those of other available Elements establishes the superiority of the present Element with respect to accuracy, robustness and computational efficiency. The comparison also establishes the superiority of the zigzag theory over the smeared third-order theory having the same number of dof.

  • an improved discrete kirchhoff Quadrilateral Element based on third order zigzag theory for static analysis of composite and sandwich plates
    International Journal for Numerical Methods in Engineering, 2007
    Co-Authors: S. Kapuria, S. D. Kulkarni
    Abstract:

    A new improved discrete Kirchhoff Quadrilateral Element based on the third-order zigzag theory is developed for the static analysis of composite and sandwich plates. The Element has seven degrees of freedom per node, namely, the three displacements, two rotations and two transverse shear strain components at the mid-surface. The usual requirement of C1 continuity of interpolation functions of the deflection in the third-order zigzag theory is circumvented by employing the improved discrete Kirchhoff constraint technique. The Element is free from the shear locking. The finite Element formulation and the computer program are validated by comparing the results for simply supported plate with the analytical Navier solution of the zigzag theory. Comparison of the present results with those using other available Elements based on zigzag theories for composite and sandwich plates establishes the superiority of the present Element in respect of simplicity, accuracy and computational efficiency. The accuracy of the zigzag theory is assessed by comparing the finite Element results of the square all-round clamped composite plates with the converged three-dimensional finite Element solution obtained using ABAQUS. The comparisons also establish the superiority of the zigzag theory over the smeared third-order theory having the same number of degrees of freedom. Copyright © 2006 John Wiley & Sons, Ltd.

Xiaoying Zhuang - One of the best experts on this subject based on the ideXlab platform.

  • cracking Elements a self propagating strong discontinuity embedded approach for quasi brittle fracture
    Finite Elements in Analysis and Design, 2018
    Co-Authors: Yiming Zhang, Xiaoying Zhuang
    Abstract:

    Abstract In this paper, we present a self-propagating Strong Discontinuity embedded Approach (SDA) for quasi-brittle fracture. The method is based on the Statically Optimal Symmetric formulation (SOS) of the SDA using the 8-node Quadrilateral Element which avoids local stress locking. A non-continuous crack path is assumed such that the crack is modelled by a set of disconnected cracking segments. Hence, no complex crack tracking procedure and no explicit (or implicit) representation of the crack surface are needed. A local fracture criteria is proposed for determining the orientation of the crack. Several numerical tests with irregular discretizations are performed, demonstrating the effectiveness and robustness of the presented method.

Yongtao Yang - One of the best experts on this subject based on the ideXlab platform.

  • Four-Node Quadrilateral Element with Continuous Nodal Stress for Geometrical Nonlinear Analysis
    International Journal of Computational Methods, 2017
    Co-Authors: Yongtao Yang, Hong Zheng, Xuhai Tang, Quansheng Liu
    Abstract:

    In this paper, the performance of a hybrid ‘FE-Meshfree’ Quadrilateral Element with continuous nodal stress (Quad4-CNS) is investigated for geometrical nonlinear solid mechanic problems. By combining finite Element method (FEM) and meshfree method, this Quad4-CNS synergizes the individual strengths of these two methods, which leads to higher accuracy, better convergence rate, as well as high tolerance to mesh distortion. Therefore, Quad4-CNS is attractive for geometrical nonlinear solid mechanic problems where excessive distorted meshes occur. For geometrical nonlinear analysis, numerical results show that the results of Quad4-CNS Element are much better than those of four-node isoparametric Quadrilateral Element (Quad4), and are comparable to quadratic Quadrilateral Element (Quad8) and other hybrid ‘FE- Meshfree’ Elements.

  • A Three-Node Triangular Element with Continuous Nodal Stress (Trig3-CNS) for Geometry Nonlinear Solid Mechanics Problems
    International Journal of Computational Methods, 2017
    Co-Authors: Guanhua Sun, Yongtao Yang, Hong Zheng
    Abstract:

    This paper investigates the performance of the three-node triangular Element with continuous nodal stress (Trig3-CNS) for geometry nonlinear solid mechanic problems. This Trig3-CNS Element was recently proposed to improve accuracy of the finite Element method (FEM). By synergizing the individual strengths of meshfree method and FEM, the Trig3-CNS Element achieves higher accuracy and convergence rate. Furthermore, Trig3-CNS presents high tolerance to mesh distortion. Therefore, it is potentially useful for geometry nonlinear solid mechanics problems in which mesh distortion takes place. Compared with the traditional hybrid “FE-Meshfree” Elements, Trig3-CNS naturally processes CNS without requiring any extra operation in post-processing. Numerical tests in the present work show that for geometry nonlinear analysis, the results of the Trig3-CNS Element are better than the 3-node triangular Element (Trig3) and 4-node isoparametric Quadrilateral Element (Quad4). In addition, the performance of Trig3-CNS is com...

  • A partition-of-unity based three-node triangular Element with continuous nodal stress using radial-polynomial basis functions
    Science China Technological Sciences, 2017
    Co-Authors: Yongtao Yang, Hong Zheng
    Abstract:

    A partition-of-unity (PU) based “FE-Meshfree” three-node triangular Element (Trig3-RPIM) was recently developed for linear elastic problems. This Trig3-RPIM Element employs hybrid shape functions that combine the shape functions of three-node triangular Element (Trig3) and radial-polynomial basis functions for the purpose of synergizing the merits of both finite Element method and meshfree method. Although Trig3-RPIM Element is capable of obtaining higher accuracy and convergence rate than the Trig3 Element and four-node iso-parametric Quadrilateral Element without adding extra nodes or degrees of freedom (DOFs), the nodal stress field through Trig3-RPIM Element is not continuous and extra stress smooth operations are still needed in the post processing stage. To further improve the property of Trig3-RPIM Element, a new PU-based triangular Element with continuous nodal stress, called Trig3-RPIMcns, is developed. Numerical examples including several linear, free vibration and forced vibration test problems, have confirmed the correctness and feasibility of the proposed Trig3-RPIMcns Element.

  • Application of the ‘FE-Meshfree’ QUAD4 with continuous nodal stress using radial-polynomial basis functions for vibration and geometric nonlinear analyses
    Engineering Analysis With Boundary Elements, 2017
    Co-Authors: Yongtao Yang, Hong Zheng
    Abstract:

    Abstract A hybrid ‘FE-Meshfree’ four-node Quadrilateral Element with continuous nodal stress using radial-polynomial basis functions (Quad4-RPIMcns), was recently proposed for static analysis. The Quad4-RPIMcns Element can be considered as a development of the previous partition-of-unity (PU) based ‘FE-Meshfree’ QUAD4 Element (Quad4-RPIM) which uses FE shape functions to construct the PU and radial-polynomial basis functions to construct the local approximation (LA), so as to synergize the individual strengths of finite Element and meshfree methods. As a result, high order global approximations in Quad4-RPIMcns Element could be easily constructed without adding extra nodes and DOFs, thereby achieving high accuracy and convergence rate. In this paper, the Element is further applied to conduct free vibration, forced vibration and geometric nonlinear analyses of two-dimensional solids. Several numerical test problems are solved and the performance of the Element is compared with that of the three-node triangular Element (Trig3) and four-node isoparametric Quadrilateral Element (Quad4). Numerical results show that Quad4-RPIMcns Element has higher tolerance to mesh distortion and gives more accurate solution as compared to Trig3 and Quad4 Elements.

  • a four node Quadrilateral Element fitted to numerical manifold method with continuous nodal stress for crack analysis
    Computers & Structures, 2016
    Co-Authors: Yongtao Yang, Guanhua Sun, Hong Zheng
    Abstract:

    Formulations of the Quad4-CNS (NMM) Element for crack problems are presented.The derivatives of Quad4-CNS (NMM) shape function are continuous at nodes.Quad4-CNS (NMM) Element is able to achieve continuous nodal stress without any smoothing operation.Quad4-CNS (NMM) Element is very suitable for solving crack propagation problems.Comparing to extended Quadrilateral Element (XQ4), Quad4-CNS (NMM) Element can obtain better results. Formulations of a four-node Quadrilateral Element fitted to numerical manifold method (NMM) with continuous nodal stress called Quad4-CNS (NMM) Element for two-dimensional (2D) crack analysis are presented. This Quad4-CNS (NMM) Element can be considered as a development of the recently published four-node Quadrilateral Element with continuous nodal stress (Quad4-CNS). In contrast to the four-node iso-parametric Quadrilateral Element (Quad4), the Quad4-CNS Element has higher order of global approximations, much better accuracy and continuous nodal stress. Moreover, it is free from the linear dependence which otherwise cripples many of the partition of unity (PU) based methods with high order global approximations. Due to the adoption of two cover systems, namely, the mathematical cover and physical cover, the NMM is capable of solving continuous and discontinuous problems in a unified way. The purpose of this paper is to synergize the advantages of both the Quad4-CNS Element and the NMM to precisely model linear elastic fracture problems. A number of numerical examples indicate the accuracy and robustness of the present Quad4-CNS (NMM) Element.