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  • Open Access


    Discrete Dislocation Dynamics Simulation of Interfacial Dislocation Network in Gamma/Gamma-Prime Microstructure of Ni-based Superalloys

    K. Yashiro1, Y. Nakashima1, Y. Tomita1

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.2, pp. 73-80, 2006, DOI:10.3970/cmes.2006.011.073

    Abstract A simple back force model is proposed for a dislocation cutting into γ' precipitate, taking the work formaking and recovering an anti-phase boundary (APB) into account. The first dislocation, or a leading partial of a superdislocation, is acted upon by a back force whose magnitude is equal to the APB energy. The second dislocation, or a trailing partial of a superdislocation, is attracted by the APB with a force of the same magnitude. The model is encoded in the 3D discrete dislocation dynamics (DDD) code and applied to the cutting behavior of dislocations at a γ/γ' interface covered by an… More >

  • Open Access


    A Quasicontinuum Method for Deformations of Carbon Nanotubes

    Jong Youn Park1, Young-Sam Cho2, Sung Youb Kim1, Sukky Jun3, Seyoung Im1

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.2, pp. 61-72, 2006, DOI:10.3970/cmes.2006.011.061

    Abstract We present a coarse-graining computation for deformations of CNTs (carbon nanotubes) via QC (quasicontinuum), particularly targeting analysis of multi-walled carbon nanotubes. Higher order triangular elements are utilized for proper interpolation of atom positions of the CNT on the basis of QC approach. The computing scheme enables one to differentiate between the fully atomistic zone and the coarse-grained zone in the framework of the multiscale computing. Several numerical examples demonstrate the effectiveness and accuracy of the present methodology. More >

  • Open Access


    Dimple Fracture Simulation of Fracture Specimen under Different Constraint Conditions

    Masanori Kikuchi 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.2, pp. 49-60, 2006, DOI:10.3970/cmes.2006.011.049

    Abstract Three kinds of fracture specimens are tested under different constraint conditions. By the SEM(Scanning Electron Microscope) observation, it is shown that the roughness of fracture surface is different from each other largely. This is the effect of constraint condition. The dimple fracture process is simulated by the finite element method using Gurson’s constitutive equation, and the crack tip stress fields are obtained. The distributions of stress triaxiality qualitatively agree with the experimental results. The J-R curves obtained also qualitatively agree with those of experiments, and the fracture surface roughness is well simulated. More >

  • Open Access


    The Bauschinger Effect's Impact on the 3-D Combined SIFs for Radially Cracked Fully or Partially Autofrettaged Thick-Walled Cylinders

    M. Perl1, C. Levy 2, V. Rallabhandy 2

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.1, pp. 37-48, 2006, DOI:10.3970/cmes.2006.011.037

    Abstract The Bauschinger Effect (BE) impact on KIN– the combined, Mode I, 3-D Stress Intensity Factor (SIF) distributions for arrays of radial, internal, surface cracks emanating from the bore of a fully or partially autofrettaged thick-walled cylinder is investigated. A in-depth comparison between the combined SIFs for a “realistic” - Bauschinger Effect Dependent Autofrettage (BEDA) and those for an “ideal” - Bauschinger Effect Independent Autofrettage (BEIA) is performed. The 3- D finite element (FE) analysis is performed employing the submodeling technique and singular elements along the crack front. Both autofrettage residual stress fields, BEDA and BEIA, are simulated using an equivalent… More >

  • Open Access


    Passive Electric Potential CT Method Using Piezoelectric Material for Identification of Plural Cracks

    Daiki Shiozawa1, Shiro Kubo2, Takahide Sakagami2, Masaaki Takagi2

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.1, pp. 27-36, 2006, DOI:10.3970/cmes.2006.011.027

    Abstract The passive electric potential CT (computed tomography) method using piezoelectric film was applied to the identification of plural through cracks. The use of piezoelectric material made it possible to obtain electric potential field without applying electric current. For identification of cracks an inverse analysis scheme based on the least residual method was applied, in which square sum of residuals is evaluated between the measured electric potential distributions and those computed by using the finite element method. Akaike information criterion (AIC) was used to estimate the number of cracks. Numerical simulations were carried out on the identification of plural cracks and… More >

  • Open Access


    MATES : Multi-Agent based Traffic and Environment Simulator -- Theory, Implementation and Practical Application

    S. Yoshimura 1

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.1, pp. 17-26, 2006, DOI:10.3970/cmes.2006.011.017

    Abstract This paper describes a development of an advanced traffic simulator based on a multi-agent approach which is named MATES (Multi-Agent based Traffic and Environment Simulator). City traffic phenomena are essentially regarded as complex systems consisting of a number of human beings. Each element creating traffic phenomena such as car (driver), traffic signal, pedestrian and others is modeled as an intelligent agent that possesses its own logic of behavior and preference. The environment surrounding each agent consists of other cars, road network, traffic signals, pedestrian and others. Interaction among numerous agents simulates nonlinear behaviors of city traffic phenomena. First we describe… More >

  • Open Access


    Prediction of Crack Growth in Steam Generator Tubes Using Monte Carlo Simulation

    Jae Bong Lee1, Jai Hak Park1, Sung Ho Lee2, Hong-Deok Kim2, Han-Sub Chung2

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.1, pp. 9-16, 2006, DOI:10.3970/cmes.2006.011.009

    Abstract The growth of stress corrosion cracks in steam generator tubes is predicted using the Monte Carlo simulation and statistical approaches. The statistical parameters that represent the characteristics of crack growth and crack initiation are derived from in-service inspection (ISI) non-destructive evaluation (NDE) data. Based on the statistical approaches, crack growth models are proposed and applied to predict crack distribution at the end of cycle (EOC). Because in-service inspection (ISI) crack data is different from physical crack data, a simple method for predicting the physical number of cracks from periodic in-service inspection data is proposed in this study. Actual number of… More >

  • Open Access


    Nonlinear Dynamic Response Analysis of Steel Frames under Seismic Action

    T. Yoda1, N. Kodama2

    CMES-Computer Modeling in Engineering & Sciences, Vol.11, No.1, pp. 1-8, 2006, DOI:10.3970/cmes.2006.011.001

    Abstract A nonlinear dynamic response analysis of a box section steel rigid frame under seismic action is proposed on the basis of a beam model. The average stress-strain relation of the beam model can be formulated for transverse stiffener spacing, in which stress-strain relation after local buckling is assumed. As a result of the present study, the maximum lateral displacements and the residual displacements of a box section steel rigid frame were well estimated by the proposed beam element model that considers the deterioration effect due to local buckling. More >

  • Open Access


    MLPG Method Based on Rankine Source Solution for Simulating Nonlinear Water Waves

    Q.W. Ma1

    CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 193-210, 2005, DOI:10.3970/cmes.2005.009.193

    Abstract Recently, the MLPG (Meshless Local Petrov-Galerkin Method) method has been successfully extended to simulating nonlinear water waves [Ma, (2005)]. In that paper, the author employed the Heaviside step function as the test function to formulate the weak form over local sub-domains, acquiring an expression in terms of pressure gradient. In this paper, the solution for Rankine sources is taken as the test function and the local weak form is expressed in term of pressure rather than pressure gradient. Apart from not including pressure gradient, velocity gradient is also eliminated from the weak form. In addition, a semi-analytical technique is developed… More >

  • Open Access


    3-D Modeling of a composite material reinforced with multiple thickly coated particles using the infinite element method

    D.S. Liu1,2 , C.Y. Chen2 , D.Y. Chiou3

    CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 179-192, 2005, DOI:10.3970/cmes.2005.009.179

    Abstract A three-dimensional heterogeneous infinite element method (HIEM) for modeling inclusions with interphases in composite materials is presented. This special element is formulated based on the conventional finite element method (FEM) using the similarity stiffness property and matrix condensation operations. An HIE-FE coupling scheme is also developed and implemented using the commercial software ABAQUS to conduct the elastostatic analysis. The proposed approach was validated first to study heterogeneous material containing one spherical inclusion. The displacement and stress variations around the inclusion vicinity are verified against conventional FEM. The proposed approach was next applied to analyze the effective modulus of single-particle and… More >

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