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  • Open Access

    ARTICLE

    A Combination of Group Preserving Scheme and Runge-Kutta Method for the Integration of Landau-Lifshitz Equation

    Chein-Shan Liu, Yu-Ling Ku

    CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 151-178, 2005, DOI:10.3970/cmes.2005.009.151

    Abstract In this paper we are concerned with the integration of a semi-discretized version of the Landau-Lifshitz equation, which is fundamental to describe the magnetization dynamics in micro/nano-scale magnetic systems. The resulting ordinary differential equations at the interior grid points are numerically integrated by a combination of the group preserving scheme derived by Liu (2004a) and the fourth-order Runge-Kutta method, abbreviated as GPS-RK4. The new method not only conserves the magnetization magnitude and has the fourth-order accuracy, but also preserves the Lyapunov property of the Landau-Lifshitz equation, namely the free energy is decreasing with time. In the limit of zero damping,… More >

  • Open Access

    ARTICLE

    Finite Element Approaches to Non-classical Heat Conduction in Solids

    S. Bargmann, P. Steinmann1

    CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 133-150, 2005, DOI:10.3970/cmes.2005.009.133

    Abstract The present contribution is concerned with the modeling and computation of non-classical heat conduction. In the 90s Green and Naghdi presented a new theory which is fully consistent. We suggest a solution method based on finite elements for the spatial as well as for the temporal discretization. A numerical example is compared to existing experimental results in order to illustrate the performance of the method. More >

  • Open Access

    ARTICLE

    Vibrations of Cracked Euler-Bernoulli Beams using Meshless Local Petrov-Galerkin (MLPG) Method

    U. Andreaus1,3, R.C. Batra2, M. Porfiri2, 3

    CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 111-132, 2005, DOI:10.3970/cmes.2005.009.111

    Abstract Structural health monitoring techniques based on vibration data have received increasing attention in recent years. Since the measured modal characteristics and the transient motion of a beam exhibit low sensitivity to damage, numerical techniques for accurately computing vibration characteristics are needed. Here we use a Meshless Local Petrov-Galerkin (MLPG) method to analyze vibrations of a beam with multiple cracks. The trial and the test functions are constructed using the Generalized Moving Least Squares (GMLS) approximation. The smoothness of the GMLS basis functions requires the use of special techniques to account for the slope discontinuities at the crack locations. Therefore, a… More >

  • Open Access

    ARTICLE

    Dynamic Simulation of Long Flexible Fibers in Shear Flow

    Wenzhong Tang1, Suresh G. Advani1

    CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 165-176, 2005, DOI:10.3970/cmes.2005.008.165

    Abstract An optimization method is proposed to simulate the motion of long flexible fibers in shear flow. The fiber is modeled as spheres connected by massless rigid rods and ball-socket joints. The optimization method is mathematically justified and used to obtain the position of a fiber at the next time step from its current position. Results for a single fiber in simple shear flow agree well with those reported in the literature. The usefulness of the method is demonstrated by simulating the motion of two interactive fibers subjected to shear flow field, and by studying the viscosity of dilute suspensions of… More >

  • Open Access

    ARTICLE

    An Efficient Time-Domain BEM/FEM Coupling for Acoustic-Elastodynamic Interaction Problems

    D. Soares Jr.1, W.J. Mansur1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 153-164, 2005, DOI:10.3970/cmes.2005.008.153

    Abstract A coupling procedure is described to perform time-domain numerical analyses of dynamic fluid-structure interaction. The fluid sub-domains, where acoustic waves propagate, are modeled by the Boundary Element Method (BEM), which is quite suitable to deal with linear homogeneous unbounded domain problems. The Finite Element Method (FEM), on the other hand, models the structure sub-domains, adopting a time marching scheme based on implicit Green's functions. The BEM/FEM coupling algorithm here developed is very efficient, eliminating the drawbacks of standard and iterative coupling procedures. Stability and accuracy features are improved by the adoption of different time steps in each sub-domain of the… More >

  • Open Access

    ARTICLE

    Multiscale Simulations Using Generalized Interpolation Material Point (GIMP) Method And SAMRAI Parallel Processing

    J. Ma1, H. Lu1, B. Wang1, S. Roy1, R. Hornung2, A. Wissink2, R. Komanduri1,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 135-152, 2005, DOI:10.3970/cmes.2005.008.135

    Abstract In the simulation of a wide range of mechanics problems including impact/contact/penetration and fracture, the material point method (MPM), Sulsky, Zhou and Shreyer (1995), demonstrated its computational capabilities. To resolve alternating stress sign and instability problems associated with conventional MPM, Bardenhagen and Kober (2004) introduced recently the generalized interpolation material point (GIMP) method and implemented for one-dimensional simulations. In this paper we have extended GIMP to 2D and applied to simulate simple tension and indentation problems. For simulations spanning multiple length scales, based on the continuum mechanics approach, we present a parallel GIMP computational method using the Structured Adaptive Mesh… More >

  • Open Access

    ARTICLE

    Computational Modelling of Isotropic Multiplicative Growth

    G. Himpel, E. Kuhl, A. Menzel, P. Steinmann1

    CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 119-134, 2005, DOI:10.3970/cmes.2005.008.119

    Abstract The changing mass of biomaterials can either be modelled at the constitutive level or at the kinematic level. This contribution attends on the description of growth at the kinematic level. The deformation gradient will be multiplicatively split into a growth part and an elastic part. Hence, in addition to the material and the spatial configuration, we consider an intermediate configuration or grown configuration without any elastic deformations. With such an ansatz at hand, contrary to the modelling of mass changes at the constitutive level, both a change in density and a change in volume can be modelled. The algorithmic realisation… More >

  • Open Access

    ARTICLE

    Acoustic Scattering from Complex Shaped Three Dimensional Structures

    B. Chrasekhar1, S. M. Rao2

    CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 105-118, 2005, DOI:10.3970/cmes.2005.008.105

    Abstract In this work, a simple, robust, and an efficient numerical algorithm to calculate the scattered acoustic fields from complex shaped objects such as aircrafts and missiles, subjected to a plane wave incidence is presented. The work is based on the recently proposed method of moments (MoM) and the potential theory, unlike the standard Helmholtz integral equation (HIE) solution method. For the numerical solution, the scattering structure is approximated by planar triangular patches. For the MoM solution of complex bodies involving open/closed/intersecting surfaces, a unified set of basis functions to approximate the source distribution is defined. These basis functions along with… More >

  • Open Access

    ARTICLE

    Time-Resolved Penetration of B4C Tiles by the APM2 Bullet

    Charles E. Anderson, Jr.1, Matthew S. Burkins2, James D. Walker1, William A. Gooch2

    CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 91-104, 2005, DOI:10.3970/cmes.2005.008.091

    Abstract A modification of Wilkins computational ceramics model is used to simulate experiments of the impact of the APM2 bullet against boron carbide/aluminum targets. Flash radiography provides time-resolved penetration histories. The simulation results are compared to the experimental data; generally, agreement is very good, including capturing dwell and then the onset of penetration. Crater width and debris diameter are also reproduced by the simulations reasonably well. A critical discussion of deficiencies of this computational engineering model is provided. More >

  • Open Access

    ARTICLE

    Computational Characterization and Evaluation of Deformation Behavior of Spherulite of High Density Polyethylene in Mesoscale Domain

    Y. Tomita 1, M. Uchida 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 239-248, 2005, DOI:10.3970/cmes.2005.010.239

    Abstract In this study, we clarified the micro- to mesoscopic deformation behavior of a semicrystalline polymer by employing a large-deformation finite element homogenization method. The crystalline plasticity theory with a penalty method for the inextensibility of the chain direction and the nonaffine molecular chain network theory were applied for the representation of the deformation behavior of the crystalline and amorphous phases, respectively, in the composite microstructure of the semicrystalline polymer. The 3D structure of lamellae in the spherulite of high-density polyethylene was modeled, and the tensile and compressive deformation behaviors were investigated. A series of computational simulations clarified the difference in… More >

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