bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic finite element analysis of viscoelastic composite plates in the time domain
Authors: Yi Sung , Hilton Harry H. 
Published: August 2005

AbstractNumerical procedures for analysing transient responses of anisotropic viscoeiastic composite plates have been developed in the time domain using variational principles and a direct time integration method. Recursion relationships have been formulated in order to reduce computer storage substantially. The method developed herein requires only two previous lime solutions to evaluate the next time solution and the necessary storage is independent of the number of the time steps. Verification studies were conducted to evaluate the accuracy and convergence of the present numerical algorithm and they show that the numerical solutions agree well with analytical ones. As examples, dynamic transient responses of viscoeiastic composite plates subjected to unit step loads were calculated using the presently developed procedure.
Spatial stability and free vibration of shear flexible thin‐walled elastic beams. I: Analytical approach
Authors: Kim Moon‐Young , Chang Sung‐Pil , Kim Sung‐Bo 
Published: August 2005

AbstractAn improved formulation for spatial stability and free vibration analysis of thin‐walled elastic beams is presented by applying Hellinger–Reissner principle and introducing Vlasov's assumption. It includes shear deformation effects due to flexural shear and restrained warping stress, rotary inertia effects and bendirsg–torsional coupling effects due to unsymmetric cross sections. Closed‐form solutions for determining flexural–torsional buckling loads and natural frequencies of unsymmetric simply supported beam‐columns subjected to eccentric axial force are newiy derived and also, the tangent stiffness matrix and stability functions for symmetric thin‐walled beam elements subjected to axial force are presented. In a companion paper,26 these analytic solutions are compared with the finite element solutions according to the increase of shear deformation effects.
Charge iteration: A procedure for the finite element computation of unbounded electrical fields
Authors: Aiello G. , Alfonzetti S. , Coco S. 
Published: August 2005

AbstractAn iterative procedure is presented for the finite element computation of unbounded electrical fields created by voltaged conductors. The procedure is based on successive evaluations of the potential on a fictitious boundary enclosing all the conductors, according to the charge lying on their surface. The convergence of the procedure to the solution of the unbounded field problem is demonstrated. Indications for the optimal placement of the fictitious boundary are provided, also taking into account the accuracy of the solution. The way in which computational efficiency can be reached is also discussed. The main advantage of this procedure lies in its simplicity of implementation in the context of a standard FE code for bounded problems, because a very limited amount of additional software is required; moreover, 2‐D and axisymmetric versions can be implemented with minor changes from a suitable 3‐D one. Examples of application are given in order to illustrate the practical use of the procedure and to validate it by comparisons with available solutions.
A modal aeroelastic finite element analysis method for advanced turbomachinery stages
Authors: Jacquet‐Richardet G. , Henry R. 
Published: August 2005

AbstractThis paper presents a formulation suitable for the flutter analysis of rotating bladed assemblies. The blades are modelled using the finite element method. The aeroelastic displacements, expressed in terms of travelling wave co‐ordinates, are written as a linear combination of a number of undamped modes leading to a complex eigenvalues eigenvectors problem. The associated unsteady aerodynamic model is either two or three dimensional, leading for both cases to a consistent and flexible aeroelastic analysis method.Three numerical applications are presented which illustrate the theory and emphasize the possible effects of blade cross‐section (chord) deformation on aeroelastic damping.
A fixed grid method for the numerical solution of phase change problems
Authors: Clavier L. , Arquis E. , Caltagirone J. P. , Gobin D. 
Published: August 2005

AbstractA fixed grid method using an updated iterative implicit scheme is developed to solve one‐dimensional phase change problems. The temperature field is deduced from the resolution of the governing equations whose discretization takes into account the discontinuous variation of the temperature derivative at the phase change front. At each iteration an updated position of the moving front is found from the resolution of the energy conservation at the solid‐liquid interface. The accuracy of the proposed numerical method has been checked on three test problems.
Reduced minimization of Mindlin plate
Authors: Oak‐Key Min , Yong‐Woo Kim 
Published: August 2005

AbstractThe use of inconsistent displacement fields for Mindlin plate elements causes unmatched coefficients to appear in shear strain interpolations. The role of the numerical integration order in relation to these unmatched coefficients, and the existence of optimal stress points are explained through the use of the reduced minimization concept. This concept makes it possible to test whether assumed displacement fields or shear strain fields result in inconsistent strain fields which contain spurious constraints. We have included applications of reduced minimization to the conventional C0‐continuous elements, which employ reduced integration, and to quadrilateral Mindlin plate elements of Hinton and Huang to demonstrate how these elements alleviate shear locking.
Flow chart for numerical coupling of dynamic problems in elastic media
Authors: Martin Vincent , Peseux Bernard 
Published: August 2005

AbstractFrom the starting point of dynamic coupling problems in the harmonic field, such as fluid/fluid, fluid/structure, fluid/structure/fluid problems, a single procedure capable of resolving the couplage is shown when only one domain is under study. The notions of impedance transfer familiar in analytical methods in the dynamic harmonic field are introduced into numerical methods especially when transferring the structure to the fluid. The proposed work goes beyond the problems themselves and the methods currently applied io solve them (modal series, integral method, finite element method) and suggests how the ideas developed here could simplify greatly the way more complex problems might be tackled.
Sensitivity analysis of the non‐linear dynamic viscoplastic response of 2‐D structures with respect to material parameters
Authors: Kulkarni Makarand , Noor Ahmed K. 
Published: August 2005

AbstractA computational procedure is presented for evaluating the sensitivity coefficients of the viscoplastic response of structures subjected to dynamic loading. A state of plane stress is assumed to exist in the structure, a velocity strain‐Cauchy stress formulation is used, and the geometric non‐linearities arising from large strains are incorporated. The Jaumann rate is used as a frame indifferent stress rate. The material model is chosen to be isothermal viscoplasticity, and an associated flow rule is used with a von Mises effective stress. The equations of motion emanating from a finite element semi‐discretization are integrated using an explicit central difference scheme with an implicit stress update. The sensitivity coefficients are evaluated using a direct differentiation approach. Since the domain of integration is the current configuration, the sensitivity coefficients of the spatial derivatives of the shape functions must be included. Numerical results are presented for a thin plate with a central circular cutout subjected to an in‐plane compressive loading. The sensitivity coefficients are generated by evaluating the derivatives of the response quantities with respect to Young's modulus, and two of the material parameters characterizing the viscoplastic response. Time histories of the response and sensitivity coefficients, and spatial distributions at selected times are presented.
A Chebyshev collocation method for computing the eigenvalues of the Laplacian
Authors: Lu Ya Yan 
Published: August 2005

AbstractChebyshev collocation techniques are developed in this paper to compute the eigenvalues of the Laplacian based on a boundary integral formulation for two‐dimensional domains with piecewise smooth boundaries. Unlike the traditional domain methods (for example, the finite element method) which discretizes the eigenfunctions on the two‐dimensional domain, only a one‐dimensional function defined on the boundary is discretized. Global expansions in terms of Chebyshev polynomials are used in each smooth piece of the boundary to solve the integral equation. Comparing with the boundary element method, this method obtains higher accuracy for a smaller discretized matrix. Finally, an efficient algorithm for generating the discretized matrix (say, n × n) is developed that requires only O(n2 log n) operations.
Calculation of flows using three‐dimensional overlapping grids and multigrid methods
Authors: Tu J. Y. , Fuchs L. 
Published: August 2005

AbstractA computational methodology combining overlapping grid techniques with multigrid methods has been developed for three‐dimensional flow calculations in or around complex geometries. The computational accuracy, efficiency and capability of the present approach are investigated in this paper. The incompressible Navier–Stokes equations are discretized using a finite volume method on a semi‐staggered grid. The discrete problem is solved by a multigrid algorithm. Some numerical examples are chosen for evaluating numerical accuracy: (a) a straight pipe for which the exact solution is known; (b) curved pipes where previous experimental and numerical data are available; (c) an axisymmetric sudden expansion. The performance of the multigrid method on overlapping grids is assessed. Several cases of flows in stationary and time‐dependent complex geometries are given to demonstrate the capability and the potential of the methods that we employ.
The dual boundary element formulation for elastoplastic fracture mechanics
Authors: Leitão V. , Aliabadi M. H. , Rooke D. P. 
Published: August 2005

AbstractIn this paper the extension of the dual boundary element method (DBEM) to the analysis of elastoplastic fracture mechanics (EPFM) problems is presented. The dual equations of the method are the displacement and the traction boundary integral equations. When the displacement equation is applied on one of the crack surfaces and the traction equation on the other, general mixed‐mode crack problems can be solved with a single‐region formulation. In order to avoid collocation at crack tips, crack kinks and crack‐edge corners, both crack surfaces are discretized with discontinuous quadratic boundary elements. The elastoplastic behaviour is modelled through the use of an approximation for the plastic component of the strain tensor on the region expected to yield. This region is discretized with internal quadratic, quadrilateral and/or triangular cells. This formulation was implemented for two‐dimensional domains only, although there is no theoretical or numerical limitation to its application to three‐dimensional ones. A centre‐cracked plate and a slant edge‐cracked plate subjected to tensile load are analysed and the results are compared with others available in the literature. J‐type integrals are calculated.
Finite element simulation of combined buoyancy and thermocapillary driven convection in open cavities
Authors: Chippada S. , Jue T. C. , Ramaswamy B. 
Published: August 2005

AbstractThermocapillary‐induced and buoyancy‐driven convective flows that commonly occur in crystal growth are numerically simulated using Galerkin finite element method. The physical domain comprises of a open cavity with aspect ratio one and differentially heated vertical walls. The top gas–melt interface is free to deform subject to 90° contact angle boundary conditions at the two vertical walls. The unsteady two‐dimensional Navier–Stokes equations are discretized in time using Chorin‐type splitting scheme and pressure is determined from the Poisson's equation. The free surface is taken to be resting on vertical spines and its evolution in time is determined from the kinematic free surface equation. The governing equations for heat and momentum are solved in the Arbitrary Lagrangian Eulerian frame of reference to handle the moving boundary. The influence of Grashof number, Marangoni number, Bond number, Ohnesorge number and Prandtl number on the flow field and heat transfer is investigated.
A new strategy for solving fluid‐structure problems
Authors: Sandberg Göran 
Published: August 2005

AbstractA scheme for treating unsymmetrical coupled systems is outlined. Such systems occur naturally in connection with fluid–structure interaction, where an acoustic fluid is contained in an elastic structure. The discretization is performed by means of the finite element method, using displacement formulation in the structure and either pressure or displacement potential in the fluid. Based on the eigenvalues of each subdomain some simple steps give a standard eigenvalue problem. It might also be concluded that the unsymmetrical matrices have real eigenvalues.
A Galerkin least‐squares finite element method for the two‐dimensional Helmholtz equation
Authors: Thompson Lonny L. , Pinsky Peter M. 
Published: August 2005

AbstractIn this paper a Galerkin least‐squares (GLS) finite element method, in which residuals in least‐squares form are added to the standard Galerkin variational equation, is developed to solve the Helmholtz equation in two dimensions. An important feature of GLS methods is the introduction of a local mesh parameter that may be designed to provide accurate solutions with relatively coarse meshes. Previous work has accomplished this for the one‐dimensional Helmholtz equation using dispersion analysis. In this paper, the selection of the GLS mesh parameter for two dimensions is considered, and leads to elements that exhibit improved phase accuracy. For any given direction of wave propagation, an optimal GLS mesh parameter is determined using two‐dimensional Fourier analysis. In general problems, the direction of wave propagation will not be known a priori. In this case, an optimal GLS parameter is found which reduces phase error for all possible wave vector orientations over elements. The optimal GLS parameters are derived for both consistent and lumped mass approximations. Several numerical examples are given and the results compared with those obtained from the Galerkin method. The extension of GLS to higher‐order quadratic interpolations is also presented.
A comparison of the finite element and control volume numerical solution techniques applied to timber drying problems below the boiling point
Authors: Ferguson W. J. , Turner I. W. 
Published: August 2005

AbstractDrying is a process which involves heat and mass transfer both inside the porous material, where a phase change in moisture occurs from the liquid to the gaseous state, and in the external boundary layer of the convected hot dry air, which heats the porous medium. The equations which govern this process consist of three tightly coupled, highly non‐linear partial differential equations for the unknown system variables of moisture content, temperature and pressure. Due to the inherently complex boundary conditions and intricate physical geometries in any practical drying problem, an analytical solution is not possible. In order to obtain a transient drying solution it is necessary to resort to a numerical technique. The numerical solution techniques which were employed in this research were the finite element method and the control volume method. The transient numerical results were compared and contrasted for two timber drying problems, first, at a dry bulb temperature of 50°C, and secondly, at 80°C, both cases being below the boiling point of water.
Condensation algorithms for the regular mesh substructuring
Authors: Xiao‐Lin Liu , Lam Y. C. 
Published: August 2005

AbstractThis paper describes and analyses the implementation of two static condensation algorithms used to exploit the regular patterns created by two schemes of regular mesh substructuring. Computer resources required by the implementation are assessed in terms of the number of multiplications, the total CPU time, the core and the disk storage requirements. It is discovered that, when implemented for the regular mesh substructuring, the newly proposed condensation algorithm is generally more cost effective than the one proposed by Han and Abel, and modified for the regular mesh substructuring by the present authors.
Large‐eddy simulations of plane impinging jets
Authors: Voke Peter R. , Gao Shian , Leslie David 
Published: August 2005

AbstractThe methods used for the study of the impingement of a thermally inhomogeneous plane jet on a solid plate, using large‐eddy simulation, are described. Innovative numerical methods have been introduced to produce the thermally inhomogeneous jet, to study the transmission of thermal fluctuations into the solid plate, and to prevent overshoot in the thermal computation. We have studied the impingement of water on a perspex plate in three different geometries, and also one case of the impingement of liquid sodium on a steel plate. Comparison is made with available experimental data and closure calculations.
The hybrid Laplace transform/finite element method applied to the quasi‐static and dynamic analysis of viscoelastic Timoshenko beams
Authors: Chen Tzer‐Ming 
Published: August 2005

AbstractThe quasi‐static and dynamic responses of a linear viscoelastic beam are solved numerically by using the hybrid Laplace transform/finite element method. In the analysis, the Timoshenko beam theory, which includes the transverse shear and rotatory inertia effect and conventional beam theory, are used to solve this problem. The temperature field is assumed to be constant and homogeneous and that the relaxation modulus has the form of the Prony series. In the hybrid method, the Laplace transform with respect to time is applied to the coupled equations and the finite element model is developed by applying Hamilton's variational principle without any integral transformation. The numerical results of quasi‐static and dynamic responses for the models of Maxwell fluid and three parameter solid types are presented and discussed.
Unit‐impulse response matrix of unbounded medium by finite‐element based forecasting
Authors: Song Chongmin , Wolf John P. 
Published: August 2005

AbstractIn this novel forecasting algorithm to calculate the unit‐impulse response matrix of an unbounded medium to analyse dynamic medium‐structure interaction in the time domain based on the substructure method, a finite‐element region adjacent to the structure–medium interface consisting of two or three rows only is introduced. Its exterior boundary is chosen to be similar to the interior boundary which coincides with the structure–medium interface. At similar boundaries of the unbounded medium the unit‐impulse response matrices are a function of the dimensionless time. The unit‐impulse response matrix at the exterior boundary can be forecasted from that at the interior boundary via this dimensionless time by taking advantage of the time delay of waves propagating between these two boundaries. The forecasting algorithm based solely on the finite‐element method is exact in the finite‐element sense in modelling the unbounded medium.
A parallel Monte‐Carlo finite‐element procedure for the analysis of multicomponent random media
Authors: Cruz Manuel E. , Patera Anthony T. 
Published: August 2005

AbstractWe present a new first‐principle framework for the prediction of effective properties and statistical correlation lengths for multicomponent random media. The methodology is based upon a variational hierarchical decomposition procedure which recasts the original multiscale problem as a sequence of three scale‐decoupled subproblems. The focus of the current paper is the computationally intensive mesoscale subproblem, which comprises: Monte‐Carlo acceptance–rejection sampling; domain generation and parallel partition based on Voronoi tesselation; parallel Delaunay mesh generation; homogenization‐theory formulation of the governing equations; finite‐element discretization; parallel iterative solution procedures; and implementation on message‐passing multicomputers, here the Intel iPSC/860 hypercube. Two (two‐dimensional) problems of practical importance are addressed: heat conduction in random fibrous composites, and creeping flow through random fibrous porous media.
A quadrilateral mixed finite element with two enhanced strain modes
Authors: Piltner R. , Taylor R. L. 
Published: August 2005

AbstractAn improved plane strain/stress element is derived using a Hu–Washizu variational formulation with bilinear displacement interpolation, seven strain and stress terms, and two enhanced strain modes. The number of unknowns of the four‐node element is increased from eight to ten degrees of freedom. For linear and non‐linear applications, the two unknowns associated with the enhanced strain terms can be eliminated by static condensation so that eight displacement degrees of freedom remain for the proposed element, which is denoted by QE2. The excellent performance of the proposed element is demonstrated using several linear and non‐linear examples.
A cubic‐spline boundary integral method for two‐dimensional free‐surface flow problems
Authors: Sen Debabrata 
Published: August 2005

AbstractA cubic‐spline boundary‐integral‐equation method is presented for solution of free‐surface potential problems in two dimensions. In this scheme, it is possible to enforce a condition of conitnuous velocity through a geometric corner point in addition to the condition of continuous potential. Only the latter condition is possible in a linear‐element version of the model. A detailed description of the method is provided. Test computations concerning a propagating linear wave show a remarkable improvement in the performance of the method compared to the linear and constant‐element versions, both of which are prevalent in free‐surface hydrodynamics applications. What is particularly emphasized is the level of accuracy that can be achieved from the presented method both globally and locally at and near the corner.
A continuum‐based shell theory for non‐linear applications
Authors: Parisch H. 
Published: August 2005

AbstractThe paper introduces a non‐linear shell theory, which provides a complete three‐dimensional state of stress. Since the theory is derived from simple three‐dimensional continuum mechanics, it is very easy to understand. As an example, the theory is applied to quadrilateral shell elements, which provide only displacement degrees of freedom located at nodes on the outer surfaces and one degree of freedom at the middle surface. It is proposed to eliminate this degree of freedom on element level, so that the elements have the same layout as the equivalent brick elements, but have a better behaviour in bending, have stress resultants and are cheaper with respect to computational effort. The advantages with respect to implementation in a finite element program, as well as in special applications, are obvious. However, well‐known conditioning problems in thin shell applications must be expected. Therefore emphasis is put on this issue in the example problems. It is shown that the elements can give acceptable answers in engineering applications and offer a potential for material non‐linear applications, which will be considered in a forthcoming paper.