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  • Open Access


    An Adaptive Extended Kalman Filter Incorporating State Model Uncertainty for Localizing a High Heat Flux Spot Source Using an Ultrasonic Sensor Array

    M.R. Myers1, A.B. Jorge2, D.E. Yuhas3, D.G. Walker1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.3, pp. 221-248, 2012, DOI:10.3970/cmes.2012.083.221

    Abstract An adaptive extended Kalman filter is developed and investigated for a transient heat transfer problem in which a high heat flux spot source is applied on one side of a thin plate and ultrasonic pulse time of flight is measured between spatially separated transducers on the opposite side of the plate. The novel approach is based on the uncertainty in the state model covariance and leverages trends in the extended Kalman filter covariance to drive changes to the state model covariance during convergence. This work is an integral part of an effort to develop a system capable of locating the… More >

  • Open Access


    T-Trefftz Voronoi Cell Finite Elements with Elastic/Rigid Inclusions or Voids for Micromechanical Analysis of Composite and Porous Materials

    L. Dong1, S. N. Atluri2

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.2, pp. 183-220, 2012, DOI:10.32604/cmes.2012.083.183

    Abstract In this paper, we develop T-Trefftz Voronoi Cell Finite Elements (VCF -EM-TTs) for micromechanical modeling of composite and porous materials. In addition to a homogenous matrix in each polygon-shaped element, three types of arbitrarily-shaped heterogeneities are considered in each element: an elastic inclusion, a rigid inclusion, or a void. In all of these three cases, an inter-element compatible displacement field is assumed along the element outer-boundary, and interior displacement fields in the matrix as well as in the inclusion are independently assumed as T-Trefftz trial functions. Characteristic lengths are used for each element to scale the T-Trefftz trial functions, in… More >

  • Open Access


    Comparison between a Cohesive Zone Model and a Continuum Damage Model in Predicting Mode-I Fracture Behavior of Adhesively Bonded Joints

    K.I. Tserpes1, A.S. Koumpias1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.2, pp. 169-182, 2012, DOI:10.32604/cmes.2012.083.169

    Abstract In this work, a comparison between a cohesive zone model and a continuum damage model in predicting the mode-I fracture behavior of adhesively bonded joints is performed on the basis of reliability and applicability. The cohesive zone model (CZM) is based on an exponential traction law characterizing the behavior of the interface elements. The continuum damage model (CDM) is based on the stiffness degradation of adhesive elements imposed by a damage parameter. Both models have been implemented by means of a 3D finite element model. Mode-I fracture behavior of the bonded joints was characterized using the DCB specimen. Firstly, the… More >

  • Open Access


    Stochastic Finite Element Analysis and Reliability Of Steel Telecommunication Towers

    M.M. Kamiński1, J. Szafran1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.2, pp. 143-168, 2012, DOI:10.32604/cmes.2012.083.143

    Abstract The main issue in this article is computational probabilistic analysis and reliability assessment of the steel telecommunication towers subjected to material and environmental uncertainty. Such a discussion is important since very wide, frequent and relatively modern application of these structures, which are subjected to various sources of uncertainty and having at this moment no rich and time-dependent failure evidence. Numerical analysis is based on the generalized stochastic perturbation technique implemented as the Stochastic Finite Elements using the Response Function Method applied with the use of computer algebra system. A simultaneous usage of the engineering FEM system and mathematical package enables… More >

  • Open Access


    A Linear Strain, Curvature-Driven Triangular Element for the Analysis of Membrane Structures

    P.D.Gosling1, L. Zhang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.2, pp. 97-142, 2012, DOI:10.32604/cmes.2012.083.097

    Abstract The analysis of membrane structures is made complex by the essentially anti-clastic geometry and flexibility introducing significant geometric non-linearities. With the increasing application of these structures in high-profile projects, the introduction of new materials in the form of ETFE foil, for example, and the impending requirements of a membrane structures-specific Eurocode, the need for high quality analysis capabilities is paramount. Existing formulations lag behind shell element counterparts and are based on a range of principles, from discrete to continua, and uniaxial to plane stress constitutive laws. In this paper, we present a linear strain triangular element for the efficient and… More >

  • Open Access


    A Physically Meaningful Level Set Method for Topology Optimization of Structures

    Zhen Luo1,2, Nong Zhang1,3, Yu Wang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.1, pp. 73-96, 2012, DOI:10.3970/cmes.2012.083.073

    Abstract This paper aims to present a physically meaningful level set method for shape and topology optimization of structures. Compared to the conventional level set method which represents the design boundary as the zero level set, in this study the boundary is embedded into non-zero constant level sets of the level set function, to implicitly implement shape fidelity and topology changes in time via the propagation of the discrete level set function. A point-wise nodal density field, non-negative and value-bounded, is used to parameterize the level set function via the compactly supported radial basis functions (CSRBFs) at a uniformly defined set… More >

  • Open Access


    Fluid Flow Simulation Using Particle Method and Its Physics-based Computer Graphics

    Kazuhiko Kakuda1, Shunsuke Obara1, Jun Toyotani1, Mitsuhiko Meguro1, Masakazu Furuichi1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.1, pp. 57-72, 2012, DOI:10.3970/cmes.2012.083.057

    Abstract The application of a particle method to incompressible viscous fluid flow problem and its physics-based computer graphics are presented. The method is based on the MPS (Moving Particle Semi-implicit) scheme using logarithmic weighting function to stabilize the spurious oscillatory solutions for the pressure fields which are governed by Poisson equation. The physics-based computer graphics consist of the POV-Ray (Persistence of Vision Raytracer) rendering using marching cubes algorithm as polygonization. The standard MPS scheme is widely utilized as a particle strategy for the free surface flow, the problem of moving boundary, multi-physics/multi-scale ones, and so forth. Numerical results demonstrate the workability… More >

  • Open Access


    New Optimization Algorithms for Structural Reliability Analysis

    S.R. Santos1, L.C. Matioli2, A.T. Beck3

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.1, pp. 23-56, 2012, DOI:10.3970/cmes.2012.083.023

    Abstract Solution of structural reliability problems by the First Order method require optimization algorithms to find the smallest distance between a limit state function and the origin of standard Gaussian space. The Hassofer-Lind-Rackwitz-Fiessler (HLRF) algorithm, developed specifically for this purpose, has been shown to be efficient but not robust, as it fails to converge for a significant number of problems. On the other hand, recent developments in general (augmented Lagrangian) optimization techniques have not been tested in aplication to structural reliability problems. In the present article, three new optimization algorithms for structural reliability analysis are presented. One algorithm is based on… More >

  • Open Access


    Modeling Train Movement for Moving-Block Railway Network Using Cellular Automata

    Yonghua Zhou1, Chao Mi1

    CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.1, pp. 1-22, 2012, DOI:10.3970/cmes.2012.083.001

    Abstract Cellular automata (CAs), model the dynamics of complex systems as the state update of cells restricted from their own neighbors. This paper regards the tempo-spatial constraints as dummy neighborhoods of cells for train movement, such as scheduled movement authority and speed restriction, equivalent to the maximum displacements during the future certain time steps and each time step, respectively. Under the framework of CA modeling, this paper attempts to propose an improved CA model for moving-block railway network which incorporates the tempo-spatial constraints to capture the restrictive, synergistic and autonomous dynamics. We divide the one-dimensional cell lattice into several segments, called… More >

  • Open Access


    Creation of Imperfections for Welding Simulations

    L. Novotný1, M. Tsunori2

    CMES-Computer Modeling in Engineering & Sciences, Vol.82, No.3&4, pp. 253-264, 2011, DOI:10.32604/cmes.2011.082.253

    Abstract The welding simulation is carried out by an uncoupled thermal and mechanical analysis or by a coupled thermo-mechanical analysis. For weld-induced distortion and residual stress simulation, nonlinear mechanical analysis is required. Nonlinearities are caused by both nonlinear behaviour of the material and geometrical nonlinearity. Usually, the element birth technique is used to incorporate the filler material in the model. The ideal straight geometry may be altered by imperfections to enable buckling behaviour. Real component shapes contain various imperfections (e.g. geometrical, material). The finite element mesh may contain geometrical imperfections too. When a simple weld model is used, the mode of… More >

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