CMES-Vol. 17, No. 1, 2007

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ARTICLE

Highly Accurate Computation of Spatial-Dependent Heat Conductivity and Heat Capacity in Inverse Thermal Problem
Chein-Shan Liu¹, Li-Wei Liu², Hong-Ki Hong²
CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 1-18, 2007, DOI:10.3970/cmes.2007.017.001
Abstract In this paper we are concerned with the parameters identification of the inverse heat conduction problems governed by linear parabolic partial differential equations (PDEs). It is the first time that one can construct a closed-form estimation method for the inverse thermal problems of estimating the spatial-dependent thermophysical parameters. The key points hinge on an establishment of a one-step group preserving scheme (GPS) for the semi-discretization of PDEs, as well as a closed-form solution of the resulting algebraic equations. The new method, namely the Lie-group estimation method, has four advantages: it does not require any prior More >

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An Explicit Multi-Level Time-Step Algorithm to Model the Propagation of Interacting Acoustic-Elastic Waves Using Finite Element/Finite Difference Coupled Procedures
D. Soares Jr.^1,2, W.J. Mansur¹, D.L. Lima³
CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 19-34, 2007, DOI:10.3970/cmes.2007.017.019
Abstract The present paper discussion is concerned with the development of robust and efficient algorithms to model propagation of interacting acoustic and elastic waves. The paper considers acoustic-elastic, acoustic-acoustic and elastic-elastic partitioned analyses of coupled systems; however, the focus here is the acoustic-elastic coupling considering finite elements and the acoustic-acoustic coupling considering finite elements and finite differences (other coupling procedures can be implemented analogously). One important feature of the algorithms presented is that they allow considering different time-steps for different sub-domains; so it is possible to substantially improve efficiency, accuracy and stability of the central difference More >

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Dynamic Analysis of Piezoelectric Structures by the Dual Reciprocity Boundary Element Method
G. Dziatkiewicz¹ and P. Fedelinski¹
CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 35-46, 2007, DOI:10.3970/cmes.2007.017.035
Abstract The aim of the present work is to show the formulation and application of the dual reciprocity boundary element method (BEM) to free vibrations of two-dimensional piezoelectric structures. The piezoelectric materials are modelled as homogenous, linear -- elastic, transversal isotropic and dielectric. Displacements and electric potentials are treated as generalized displacements and tractions and electric charge flux densities are treated as generalized tractions. The static fundamental solutions, which are required in the proposed approach, are derived using the Stroh formalism. The domain inertial integral is transformed to the equivalent boundary integral using the dual reciprocity More >

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Cumulative Nonlinear Effects in Acoustic Wave Propagation
Ivan Christov¹, C.I. Christov², P.M. Jordan³
CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 47-54, 2007, DOI:10.3970/cmes.2007.017.047
Abstract Two widely-used weakly-nonlinear models of acoustic wave propagation --- the inviscid Kuznetsov equation (IKE) and the Lighthill--Westervelt equation (LWE) --- are investigated numerically using a Godunov-type finite-difference scheme. A reformulation of the models as conservation laws is proposed, making it possible to use the numerical tools developed for the Euler equations to study the IKE and LWE, even after the time of shock-formation. It is shown that while the IKE is, without qualification, in very good agreement with the Euler equations, even near the time of shock formation, the same cannot generally be said for More >

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General Corotational Rate Tensor and Replacement of Material-time Derivative to Corotational Derivative of Yield Function
K. Hashiguchi¹
CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.1, pp. 55-62, 2007, DOI:10.3970/cmes.2007.017.055
Abstract Constitutive equation describing the mechanical properties of material has to be formulated in an identical form independent of coordinate systems by which it is described even if there exist any mutual configuration and/or mutual rotation between the material and coordinate systems. This mechanical requirement is attained by describing rate variables as corotational rate tensors with objectivity in constitutive equations in rate form. Besides, in order to use the material-time derivative of yield condition as a consistency condition it has to be replaced to the corotational derivative. In this note a general corotational rate for tensors More >

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