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  • Open Access

    ARTICLE

    Investigation of the Effect of Frictional Contact in III-Mode Crack under Action of the SH-Wave Harmonic Load

    A.N. Guz1, V.V. Zozulya2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 119-128, 2007, DOI:10.3970/cmes.2007.022.119

    Abstract The frictional contact interaction of the edges of a finite plane crack is studied for the case of normal incidence of a harmonic SH-shear wave which produces antiplane deformation. The forces of contact interaction and displacement discontinuity are analyzed. Influence of the wave frequency on the stress intensity factor for different coefficients of friction is studied here. More >

  • Open Access

    ARTICLE

    A New Uncertain Optimization Method Based on Intervals and An Approximation Management Model

    C. Jiang1, X. Han1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 97-118, 2007, DOI:10.3970/cmes.2007.022.097

    Abstract A new uncertain optimization method is developed based on intervals and an approximation management model. A general uncertain optimization problem is considered in which the objective function and constraints are both nonlinear and uncertain, and intervals are used to model the uncertainty existing in the system. Based on a possibility degree of interval,anonlinear interval number programming (NINP) method is proposed. A deterministic objective function is constructed to maximize the possibility degree of the uncertain objective function, and the uncertain constraints are changed into deterministic ones by introducing some possibility degree levels. If the optimal possibility degree of the objective function… More >

  • Open Access

    ARTICLE

    A Comparative Study of Non-separable Wavelet and Tensor-product Wavelet in Image Compression

    Jun Zhang1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 91-96, 2007, DOI:10.3970/cmes.2007.022.091

    Abstract The most commonly used wavelets for image processing are the tensor-product of univariate wavelets, which have a disadvantage of giving a particular importance to the horizontal and vertical directions. In this paper, a new class of wavelet, non-separable wavelet, is investigated for image compression applications. The comparative results of image compression preprocessed with two different kinds of wavelet transform are presented: (1) non-separable wavelet transform; (2) tensor-product wavelet transform. The results of our experiments show that in the same vanishing moment, the non-separable wavelets perform better than the tensor-product wavelets in dealing with still images. More >

  • Open Access

    ARTICLE

    Modeling of Degraded Composite Beam Due to Moisture Absorption For Wave Based Detection.

    Shamsh Tabrez, Mira Mitra, S. Gopalakrishnan1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 77-90, 2007, DOI:10.3970/cmes.2007.022.077

    Abstract In this paper, wave propagation is studied in degraded composite beam due to moisture absorption. The obtained wave responses are then used for diagnosis of the degraded zone. Moisture absorption causes an irreversible hygrothermal deterioration of the material. The change in temperature and moisture absorption changes the mechanical properties. Thus this affects the structure in dimensional stability as well as material degradation due to reduction in mechanical properties. Here, the composite beam is modeled as Timoshenko beam using wavelet based spectral finite element (WSFE) method. The WSFE technique is especially tailored for simulation of wave propagation. It involves Daubechies scaling… More >

  • Open Access

    ARTICLE

    Meshless Local Petrov-Galerkin Collocation Method for Two-dimensional Heat Conduction Problems

    WU XueHong1, SHEN ShengPing2, TAO WenQuan1,3

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 65-76, 2007, DOI:10.3970/cmes.2007.022.065

    Abstract Meshless local Petrov-Galerkin collocation method is applied to compute two-dimensional heat conduction problems in irregular domain. By taking the Dirac's Delta function as the test function, the local domain integration is avoided. The essential boundary conditions can be implemented easily in this method. A case that has analytical solution shows the present method can obtain desired accuracy and efficient. Two cases in engineering are computed to validate the approach by comparing the present method with the finite volume method (FVM) solutions obtained from a commercial CFD package FLUENT 6.3. The results show that the present method is in good agreement… More >

  • Open Access

    ARTICLE

    Fictitious Domain with Least-Squares Spectral Element Method to Explore Geometric Uncertainties by Non-Intrusive Polynomial Chaos Method

    L. Parussini1, V. Pediroda2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 41-64, 2007, DOI:10.3970/cmes.2007.022.041

    Abstract In this paper the Non-Intrusive Polynomial Chaos Method coupled to a Fictitious Domain approach has been applied to one- and two-dimensional elliptic problems with geometric uncertainties, in order to demonstrate the accuracy and convergence of the methodology. The main advantage of non-intrusive formulation is that existing deterministic solvers can be used. A new Least-Squares Spectral Element method has been employed for the analysis of deterministic differential problems obtained by Non-Intrusive Polynomial Chaos. This algorithm employs a Fictitious Domain approach and for this reason its main advantage lies in the fact that only a Cartesian mesh needs to be generated. Excellent… More >

  • Open Access

    ARTICLE

    Non-Equilibrium Molecular Dynamics Simulation of Water Flow around a Carbon Nanotube

    Wenzhong Tang1, Suresh G. Advani1,2

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 31-40, 2007, DOI:10.3970/cmes.2007.022.031

    Abstract In this paper, non-equilibrium molecular dynamics (MD) simulations were performed to investigate water flow around a single-walled carbon nanotube. In the simulation, the nanotube was modeled as a rigid cylinder of carbon atoms. Water molecules were described with the extended simple point charge (SPC/E) model. The nanotube-water interactions were calculated with a Lennard-Jones potential between carbon-oxygen pairs. The water-water interactions comprised a Lennard-Jones potential between the oxygen-oxygen pairs and a Coulomb potential between all charge sites on interactive water molecules. It was shown that classical continuum mechanics does not hold when the drag forces on the nanotube are considered. In… More >

  • Open Access

    ARTICLE

    Structural Analysis of the Right Rear Lug of American Airlines Flight 587*

    I.S. Raju1, E.H. Glaessgen1, B.H. Mason1, T. Krishnamurthy1, C.G. Davila1

    CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 1-30, 2007, DOI:10.3970/cmes.2007.022.001

    Abstract A detailed finite element analysis of the right rear lug of the American Airlines Flight 587 - Airbus A300-600R was performed as part of the National Transportation Safety Board's failure investigation of the accident that occurred on November 12, 2001. The loads experienced by the right rear lug were evaluated using global models of the vertical tail, local models near the right rear lug, and a global-local analysis procedure. The right rear lug was analyzed using two modeling approaches. In the first approach, solid-shell type modeling was used, and in the second approach, layered-shell type modeling was used. The solid-shell… More >

  • Open Access

    ARTICLE

    An Inverse Problem in Estimating Simultaneously the Time-Dependent Applied Force and Moment of an Euler-Bernoulli Beam

    Cheng-Hung Huang1,2, Chih-Chun Shih1

    CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.3, pp. 239-254, 2007, DOI:10.3970/cmes.2007.021.239

    Abstract An inverse forced vibration problem, based on the Conjugate Gradient Method (CGM), (or the iterative regularization method), is examined in this study to estimate simultaneously the unknown time-dependent applied force and moment for an Euler-Bernoulli beam by utilizing the simulated beam displacement measurements. The accuracy of this inverse problem is examined by using the simulated exact and inexact displacement measurements. The numerical experiments are performed to test the validity of the present algorithm by using different types of applied force and moment, sensor locations and measurement errors. Results show that excellent estimations on the applied force and moment can be… More >

  • Open Access

    ARTICLE

    On Hole Nucleation in Topology Optimization Using the Level Set Methods

    S.Y. Wang1,2, K.M. Lim2,3, B.C. Khoo2,3, M.Y. Wang4

    CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.3, pp. 219-238, 2007, DOI:10.3970/cmes.2007.021.219

    Abstract Hole nucleation is an important issue not yet fully addressed in structural topology optimization using the level set methods. In this paper, a consistent and robust nucleation method is proposed to overcome the inconsistencies in the existing implementations and to allow for smooth hole nucleation in the conventional shape derivatives-based level set methods to avoid getting stuck at a premature local optimum. The extension velocity field is constructed to be consistent with the mutual energy density and favorable for hole nucleation. A negative extension velocity driven nucleation mechanism is established due to the physically meaningful driving force. An extension velocity… More >

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