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  • Open Access


    Cyclic Softening Modeling with the Distribution of Non Linear Relaxation (Dnlr) Approach

    L. Dieng1, A. Abdul-Latif2, M. Haboussi, C. Cunat3

    CMC-Computers, Materials & Continua, Vol.6, No.1, pp. 21-34, 2007, DOI:10.3970/cmc.2007.006.021

    Abstract Being of particular interest in this work, a complicated phenomenon related to cyclic softening of metallic polycrystals is modeled. As in the Waspaloy, this phenomenon can take place when a non-proportional tension-torsion cyclic loading of 90° out-of-phase is followed, after cyclic steady state, by a uniaxial one (tension-compression) with the same maximum equivalent plastic strain. By using the DNLR (Distribution of Non Linear Relaxation) model recently proposed by the authors describing the cyclic plasticity of metals, a new extension is here developed. It is recognized that such an extension can satisfactorily reproduce this softening phenomenon. More >

  • Open Access


    Prediction of Springback in Straight Flanging using Finite Element Method

    S. K. Panthi1,2, N. Ramakrishnan2, K. K. Pathak2, J. S. Chouhan3

    CMC-Computers, Materials & Continua, Vol.6, No.1, pp. 13-20, 2007, DOI:10.3970/cmc.2007.006.013

    Abstract One of the important features of flanging process is elastic recovery during unloading leading to springback. The elastic recovery is associated with various tool and material parameters. It is difficult to analytically predict the elastic recovery accurately owing to the complex material deformation behavior. In this investigation, a commercially available Finite Element software is used for elasto-plastic analysis of flanging process. The springback is studied varying geometrical, material and friction parameters. The results of the simulation are validated with a few published experimental results. More >

  • Open Access


    Characteristic of Waves in A Multi-Walled Carbon Nanotube

    G. Q. Xie1,2,3, X. Han2, S. Y. Long3

    CMC-Computers, Materials & Continua, Vol.6, No.1, pp. 1-12, 2007, DOI:10.3970/cmc.2007.006.001

    Abstract A multi-walled carbon nanotube is modeled as a multiple-elastic cylindrical structure. The numerical-analytical method is adopted to analyze the characteristics of harmonic waves propagating along an anisotropic carbon nanotube. Each wall of the carbon nanotube is divided into three-nodal-line layer elements. The deflections of two adjacent tubes are coupled through the van der Waals. The governing equation of element is obtained from Hamilton's principle. A set of system equation of dynamics equilibrium for the entire structure is obtained by the assembling of all the elements. From solution of the eigenvalue equations, the dispersive characteristics, group More >

  • Open Access


    Flutter of Thermally Buckled Composite Sandwich Plates

    Le-Chung Shiau1, Shih-Yao Kuo2

    CMC-Computers, Materials & Continua, Vol.5, No.3, pp. 213-222, 2007, DOI:10.3970/cmc.2007.005.213

    Abstract A high precision high order triangular plate element is developed for the linear flutter analysis of thermally buckled composite sandwich plates. Due to uneven thermal expansion in the two local material directions, the buckling mode of the plate may be shifted from one pattern to another for certain fiber orientation or plate aspect ratio as the aerodynamic pressure is present. This buckle pattern change alters the frequencies and modes of the plate and that in turn changes the flutter coalescent modes. Numerical results show that temperature has a destabilizing effect on the flutter boundary but More >

  • Open Access


    A Fin Design Problem in Determining the Optimum Shape of Non-Fourier Spine and Longitudinal Fins

    Cheng-Hung Huang1, Hsin-Hsien Wu2

    CMC-Computers, Materials & Continua, Vol.5, No.3, pp. 197-212, 2007, DOI:10.3970/cmc.2007.005.197

    Abstract The conjugate gradient method (CGM) is applied in an inverse fin design problem in estimating the optimum shapes for the non-Fourier spine and longitudinal fins based on the desired fin efficiency and fin volume at the specified time. One of the advantages in using CGM in the inverse design problem lies in that it can handle problems having a huge number of design parameters easily and converges very fast.
    The validity of using CGM in solving the present inverse design problem is justified by performing the numerical experiments. Several test cases involving different design fin efficiency, More >

  • Open Access


    A MLPG4 (LBIE) Formulation in Elastostatics

    V. Vavourakis, D. Polyzos1

    CMC-Computers, Materials & Continua, Vol.5, No.3, pp. 185-196, 2007, DOI:10.3970/cmc.2007.005.185

    Abstract Very recently, Vavourakis, Sellountos and Polyzos (2006) ({CMES: Computer Modeling in Engineering {\&} Sciences, vol. 13, pp. 171--184}) presented a comparison study on the accuracy provided by five different elastostatic Meshless Local Petrov-Galerkin (MLPG) type formulations, which are based on Local Boundary Integral Equation (LBIE) considerations. One of the main conclusions addressed in this paper is that the use of derivatives of the Moving Least Squares (MLS) shape functions decreases the solution accuracy of any MLPG(LBIE) formulation. In the present work a new, free of MLS-derivatives and non-singular MLPG(LBIE) method for solving elastic problems is More >

  • Open Access


    Boundary Conditions Generated by Dynamic Particles in SPH Methods

    A. J. C. Crespo1, M. Gómez-Gesteira1, R. A. Dalrymple2

    CMC-Computers, Materials & Continua, Vol.5, No.3, pp. 173-184, 2007, DOI:10.3970/cmc.2007.005.173

    Abstract Smoothed Particle Hydrodynamics is a purely Lagrangian method that can be applied to a wide variety of fields. The foundation and properties of the so called dynamic boundary particles (DBPs) are described in this paper. These boundary particles share the same equations of continuity and state as the moving particles placed inside the domain, although their positions and velocities remain unaltered in time or are externally prescribed. Theoretical and numerical calculations were carried out to study the collision between a moving particle and a boundary particle. The boundaries were observed to behave in an elastic More >

  • Open Access


    A Micromechanical Approach to Simulate Rubberlike Materials with Damage

    M. Timmel1, M. Kaliske1, S. Kolling2, R. Mueller3

    CMC-Computers, Materials & Continua, Vol.5, No.3, pp. 161-172, 2007, DOI:10.3970/cmc.2007.005.161

    Abstract A damage approach based on a material model with microstructural evolution is presented. In contrast to phenomenological constitutive laws, the material response is given by mechanisms at the microscale. At first, a micromechanical substructure is chosen, which represents the overall material behaviour. Then the system is described using a micromechanical model. A geometrical modification of the microstructure is allowed to minimize the total energy. Consequently, the global stiffness is reduced. In this context, thermodynamical considerations are based on configurational forces. With the help of the discussed approach, void growth phenomena of materials, which lead to More >

  • Open Access


    The Computation of Modified Landau-Lifshitz Equation under an AC Field

    Chein-Shan Liu1,2

    CMC-Computers, Materials & Continua, Vol.5, No.2, pp. 151-160, 2007, DOI:10.3970/cmc.2007.005.151

    Abstract An accurate magnetization requires that both the reversible and irreversible components be modeled. The classical Landau-Lifshitz model deals with only the irreversible component of magnetization. We first subject the Landau-Lifshitz equation to an AC external field by performing a computation through the closed-form solution and the resulting hysteresis loop is displayed to show its deficiency. Then we modify the Landau-Lifshitz model into a new one by including a reversible part and an irreversible part accompanying with the switching criteria between these two states. With the new solutions we display the influence of parameters on the More >

  • Open Access


    A Numerical Study of Strain Localization in Elasto-Thermo-Viscoplastic Materials using Radial Basis Function Networks

    P. Le1, N. Mai-Duy1, T. Tran-Cong1, G. Baker2

    CMC-Computers, Materials & Continua, Vol.5, No.2, pp. 129-150, 2007, DOI:10.3970/cmc.2007.005.129

    Abstract This paper presents a numerical simulation of the formation and evolution of strain localization in elasto-thermo-viscoplastic materials (adiabatic shear band) by the indirect/integral radial basis function network (IRBFN) method. The effects of strain and strain rate hardening, plastic heating, and thermal softening are considered. The IRBFN method is enhanced by a new coordinate mapping which helps capture the stiff spatial structure of the resultant band. The discrete IRBFN system is integrated in time by the implicit fifth-order Runge-Kutta method. The obtained results are compared with those of the Modified Smooth Particle Hydrodynamics (MSPH) method and More >

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