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  • Open Access

    ARTICLE

    Ionic Polymer Metal Composite Flapping Actuator Mimicking Dragonflies

    Sujoy Mukherjee1, Ranjan Ganguli1,2

    CMC-Computers, Materials & Continua, Vol.19, No.2, pp. 105-134, 2010, DOI:10.3970/cmc.2010.019.105

    Abstract In this study, variational principle is used for dynamic modeling of an Ionic Polymer Metal Composite (IPMC) flapping wing. The IPMC is an Electro-active Polymer (EAP) which is emerging as a useful smart material for `artificial muscle' applications. Dynamic characteristics of IPMC flapping wings having the same size as the actual wings of three different dragonfly species Aeshna Multicolor, Anax Parthenope Julius and Sympetrum Frequens are analyzed using numerical simulations. An unsteady aerodynamic model is used to obtain the aerodynamic forces. A comparative study of the performances of three IPMC flapping wings is conducted. Among More >

  • Open Access

    ARTICLE

    The Molecular Dynamic Finite Element Method (MDFEM)

    Lutz Nasdala1 , Andreas Kempe1 and Raimund Rolfes1

    CMC-Computers, Materials & Continua, Vol.19, No.1, pp. 57-104, 2010, DOI:10.3970/cmc.2010.019.057

    Abstract In order to understand the underlying mechanisms of inelastic material behavior and nonlinear surface interactions, which can be observed on macroscale as damping, softening, fracture, delamination, frictional contact etc., it is necessary to examine the molecular scale. Force fields can be applied to simulate the rearrangement of chemical and physical bonds. However, a simulation of the atomic interactions is very costly so that classical molecular dynamics (MD) is restricted to structures containing a low number of atoms such as carbon nanotubes. The objective of this paper is to show how MD simulations can be integrated… More >

  • Open Access

    ARTICLE

    Interface Effect on the Dynamic Stress around an Elliptical Nano-Inhomogeneity Subjected to Anti-Plane Shear Waves

    Xue-Qian Fang1,2, Xiao-Hua Wang1, Le-Le Zhang3

    CMC-Computers, Materials & Continua, Vol.16, No.3, pp. 229-246, 2010, DOI:10.3970/cmc.2010.016.229

    Abstract In the design of advanced micro- and nanosized materials and devices containing inclusions, the effects of surfaces/interfaces on the stress concentration become prominent. In this paper, based on the surface/interface elasticity theory, a two-dimensional problem of an elliptical nano-inhomogeneity under anti-plane shear waves is considered. The conformal mapping method is then applied to solve the formulated boundary value problem. The analytical solutions of displacement fields are expressed by employing wave function expansion method, the expanded mode coefficients are determined by satisfying the boundary conditions at the interfaces of the nano-inhomogeneity. Analyses show that the effect More >

  • Open Access

    ARTICLE

    Lattice Dynamics and Second and Third Order Elastic Constants of Iron at Elevated Pressures

    Hieu H. Pham1, Tahir Ça ˇgın1

    CMC-Computers, Materials & Continua, Vol.16, No.2, pp. 175-194, 2010, DOI:10.3970/cmc.2010.016.175

    Abstract We analyze the lattice dynamics of Fe in different crystal phases (bcc, fcc and hcp) by using density-functional theory. The study on equations of states indicates that bcc Fe is more stable than fcc and hcp Fe at low pressures. However, dynamical instabilities in lattice vibrations of bcc Fe predict a phase transformation from bcc to hcp at higher pressures. We reported a complete set of second-order and third-order elastic constants of Fe in these three phases. We observed a linear variation in the values of second order elastic constant as a function of increased More >

  • Open Access

    ARTICLE

    A Molecular Dynamics Study of Irradiation Induced Cascades in Iron Containing Hydrogen

    E. Hayward1, C. Deo1

    CMC-Computers, Materials & Continua, Vol.16, No.2, pp. 101-116, 2010, DOI:10.3970/cmc.2010.016.101

    Abstract Damage cascades representative of those that would be induced by neutron irradiation have been simulated in systems of pure iron and iron containing 0.01 at.% hydrogen. Results from molecular dynamics simulations using three different embedded-atom method (EAM) type potentials are compared for primary knock-on atom energies of 5, 10, and 20 keV to assess the effect of hydrogen on the primary damage state. We examine the influence of hydrogen on the primary damage state due to a single radiation cascade. These results can serve as an atomistic database for methods and simulations for long time More >

  • Open Access

    ARTICLE

    Molecular Dynamics Study of Dynamic Responses of Glassy Silica under Shock Impact

    Luming Shen1

    CMC-Computers, Materials & Continua, Vol.15, No.3, pp. 241-260, 2010, DOI:10.3970/cmc.2010.015.241

    Abstract In this study, molecular dynamics (MD) simulations are performed to form glassy silica from meltedb-cristobalite using cooling rates of 2, 20 and 200 K/ps. The resulting glassy silica samples are then shocked at particle velocities ranging from 0.3 to 11 km/s in the MD simulations. The effect of the cooling rate on the shock wave velocity is observed for particle velocities below 2 km/s. Moreover, the simulated pressure and density of the shocked glassy silica increase as the cooling rate increases. As compared with the experimental data, the MD simulation can approximately identify the initiation More >

  • Open Access

    ARTICLE

    Meshless Local Petrov-Galerkin (MLPG) Method for Laminate Plates under Dynamic Loading

    J. Sladek1, V. Sladek1, P. Stanak1, Ch. Zhang2

    CMC-Computers, Materials & Continua, Vol.15, No.1, pp. 1-26, 2010, DOI:10.3970/cmc.2010.015.001

    Abstract A meshless local Petrov-Galerkin (MLPG) method is applied to solve laminate plate problems described by the Reissner-Mindlin theory. Both stationary and transient dynamic loads are analyzed here. The bending moment and the shear force expressions are obtained by integration through the laminated plate for the considered constitutive equations in each lamina. The Reissner-Mindlin theory reduces the original three-dimensional (3-D) thick plate problem to a two-dimensional (2-D) problem. Nodal points are randomly distributed over the mean surface of the considered plate. Each node is the center of a circle surrounding this node. The weak-form on small More >

  • Open Access

    ARTICLE

    Anomaly Detection

    Nadipuram R. Prasad1, Salvador Almanza-Garcia1, Thomas T. Lu2

    CMC-Computers, Materials & Continua, Vol.14, No.1, pp. 1-22, 2009, DOI:10.3970/cmc.2009.014.001

    Abstract The paper presents a revolutionary framework for the modeling, detection, characterization, identification, and machine-learning of anomalous behavior in observed phenomena arising from a large class of unknown and uncertain dynamical systems. An evolved behavior would in general be very difficult to correct unless the specific anomalous event that caused such behavior can be detected early, and any consequence attributed to the specific anomaly following its detection. Substantial investigative time and effort is required to back-track the cause for abnormal behavior and to recreate the event sequence leading to such abnormal behavior. The need to automatically More >

  • Open Access

    ARTICLE

    Computer Modeling of Ionic Conductivity in Low Temperature Doped Ceria Solid Electrolytes

    Shu-Feng Lee1, Che-Wun Hong1,2

    CMC-Computers, Materials & Continua, Vol.12, No.3, pp. 223-236, 2009, DOI:10.3970/cmc.2009.012.223

    Abstract Solid oxides, such as ceria (CeO2) doped with cations of lower valance, are potential electrolytes for future solid oxide fuel cells. This is due to the theoretically high ionic conductivity at low operation temperature. This paper investigates the feasibility of two potential electrolytes which are samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) to replace the traditional yttria-stablized zirconia (YSZ). Molecular simulation techniques were employed to study the influence of different dopant concentrations at different operation temperatures on the ionic conductivity from the atomistic perspective. Simulation results show that the optimized ionic conductivity occurs at 11.11mol% concentration More >

  • Open Access

    ARTICLE

    Determination of Temperature-Dependent Elasto-Plastic Properties of Thin-Film by MD Nanoindentation Simulations and an Inverse GA/FEM Computational Scheme

    D. S. Liu1, C. Y. Tsai1, S. R. Lyu2

    CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 147-164, 2009, DOI:10.3970/cmc.2009.011.147

    Abstract This study presents a novel numerical method for extracting the tempe -rature-dependent mechanical properties of the gold and aluminum thin-films. In the proposed approach, molecular dynamics (MD) simulations are performed to establish the load-displacement response of the thin substrate nanoindented at temperatures ranging from 300-900 K. A simple but effective procedure involving genetic algorithm (GA) and finite element method (FEM) is implemented to extract the material constants of the gold and aluminum substrates. The material constants are then used to construct the corresponding stress-strain curve, from which the elastic modulus, yield stress and the tangent More >

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