bluuebunny/crossref_metadata_2025_split huggingface dataset:
F.E.M. in steady MHD duct flow problems
Authors: Scandiuzzi R. , Schrefler B. A. 
Published: November 2005

AbstractThe governing equations and the boundary conditions of steady incompressible magnetohydrodynamic (MHD) problems are adapted to the case of steady MHD flow in simply connected cross sections with arbitrary wall conductance. The problem is then solved numerically by means of the finite element method based on the weighted residual approach, and solutions for industrially relevant Hartmann numbers and non‐symmetric kinetic fields are presented.
Quasi‐Newton iterative strategies applied to the heat diffusion equation
Authors: Soria Antonio , Pegon Pierre 
Published: November 2005

AbstractSeveral iterative procedures have been used to solve the non‐linear heat diffusion equation taking into account radiation across internal cavities. Quasi‐Newton methods are compared with Picard iteration and Newton‐Raphson methods. Among them, the rank‐one quasi‐Newton update seems to be the most effective, specially in time‐dependent cases.
Beyond first‐order upwinding: The ultra‐sharp alternative for non‐oscillatory steady‐state simulation of convection
Authors: Leonard B. P. , Mokhtari Simin 
Published: November 2005

AbstractAlthough it is now well known that first‐order convection schemes suffer from serious inaccuracies attributable to artificial viscosity or numerical diffusion under high‐convection conditions, these methods continue to enjoy widespread popularity for numerical heat‐transfer calculations, apparently owing to a perceived lack of viable high‐accuracy alternatives. But alternatives are available. For example, non‐oscillatory methods used in gasdynamics, including currently popular ‘TVD’ schemes, can be easily adapted to multidimensional incompressible flow and convective transport. This, in itself, would be a major advance for numerical convective heat transfer, for example. But, as this paper shows, second‐order TVD schemes form only a small, overly restrictive, subclass of a much more universal, and extremely simple, non‐oscillatory flux‐limiting strategy which can be applied to convection schemes of arbitrarily high‐order accuracy, while requiring only a simple tridiagonal ADI line‐solver, as used in the majority of general‐purpose iterative codes for incompressible flow and numerical heat transfer. The new universal limiter and associated solution procedures form the so‐called ULTRA‐SHARP alternative for high‐resolution non‐oscillatory multidimensional steady‐state high‐speed convective modelling.
A layered composite shell element for elastic and thermoelastic stress and stability analysis at large deformations
Authors: Dorninger Konrad , Rammerstorfer Franz G. 
Published: November 2005

AbstractA finite shell element for layered fibre reinforced composite shells has been developed. The degeneration principle is used in combination with specific kinematic assumptions. The thermo‐elastic material is either described by the behaviour of the local components, i.e. fibre and matrix material laws and geometrical configuration in each layer, or by the overall orthotropic layer material laws.Thickness integration for obtaining the different contributions to the shell element's stiffness matrix is performed analytically and prior to the numerical in‐plane integration. This leads to a considerable saving in computer time during the incremental‐iterative analysis.Geometrical non‐linearities in terms of large deformations and material non‐linearities in terms of layer craccking are taken into account. Accompanying eigenvalue analyses allow the determination of the—sometimes rather complicated—buckling behaviour with non‐linear prebuckling deformations.
A triangular element based on Reissner‐Mindlin plate theory
Authors: Papadopoulos Panayiotis , Taylor Robert L. 
Published: November 2005

AbstractA new triangular plate bending element based on the Reissner‐Mindlin theory is developed through a mixed formulation emanating from the Hu‐Washizu variational principle. A main feature of the formulation is the use of a linear transverse shear interpolation scheme with discrete constraint conditions on the edges. The element is shown to avoid shear locking, converge to the Kirchhoff plate theory as the plate thickness approaches zero, and generally exhibit excellent behaviour on a series of standard problems and tests.
A hyperelastic‐based large strain elasto‐plastic constitutive formulation with combined isotropic‐kinematic hardening using the logarithmic stress and strain measures
Authors: Eterovic Adrian Luis , Bathe Klaus‐Jürgen 
Published: November 2005

AbstractThis paper addresses the formulation of a set of constitutive equations for finite deformation metal plasticity. The combined isotropic‐kinematic hardening model of the infinitesimal theory of plasticity is extended to the large strain range on the basis of three main assumptions: (i) the formulation is hyperelastic based, (ii) the stress‐strain law preserves the elastic constants of the infinitesimal theory but is written in terms of the Hencky strain tensor and its elastic work conjugate stress tensor, and (iii) the multiplicative decomposition of the deformation gradient is adopted. Since no stress rates are present, the formulation is, of course, numerically objective in the time integration. It is shown that the model gives adequate physical behaviour, and comparison is made with an equivalent constitutive model based on the additive decomposition of the strain tensor.
Three‐dimensional non‐linear fluid‐structure interaction problems: Formulation by the finite and infinite element method
Authors: Feng Y. Q. , Quevat J. P. 
Published: November 2005

AbstractUsing the perturbation method, the non‐linear exterior fluid‐structure interaction problem is separated into first‐ and second‐order problems. With the finite element method for the structure and the finite‐infinite element method for the fluid, we obtain a first‐order coupled matrix system and a second‐order coupled matrix system. By determining the frequencies of resonance of the structure, comparison of numerical results for a vertical cylinder and a horizontal floating cylinder shows the validity of the presented method for the resolution of three‐dimensional exterior hydroelastic problems.
Effect of the coupling between stretching and bending in the large displacement analysis of plates
Authors: Chang B. , Chen D. C. , Shabana A. A. 
Published: November 2005

AbstractThe effect of the rotary inertia on the non‐linear dynamics of plates that undergo a large reference displacement is examined in this paper. An assumed displacement field that accounts for the coupling between the stretching and bending of the plate as the result of considering the effect of the rotary inertia is used to identify the configuration of the plate. Furthermore, the coupling between the stretching and bending of the plate as the result of finite rotation is also considered in this investigation. Based on the assumed displacement field that accounts for the effect of the rotary inertia, a non‐linear finite element formulation is developed for the large displacement analysis of plates. The element equations of motion are expressed in terms of a set of element invariants that depend on the assumed displacement field as well as the rotary inertia. The use of the formulation presented in this paper is demonstrated using numerical examples.
Three‐dimensional finite element contact algorithm for metal forming
Authors: Marques Manuel J. M. Barata , Martins Paulo A. F. 
Published: November 2005

AbstractThis work presents a three‐dimensional rigid plastic finite element formulation. The workpiece is discretized with eight node hexahedral isoparametric elements. Friction is included in the formulation by means of a shear stress depending on the relative velocity between the workpiece and the tool. Special attention is given to the contact problems, and a three‐dimensional contact algorithm based on a discretization of the tool surface with triangular elements is presented.Finally, some selected examples are solved, in order to show the capabilities of the formulation.
Bulge predictions in steady state bar rolling processes
Authors: Lee Yong‐Shin , Dawson Paul R. , Dewhurst Timothy B. 
Published: November 2005

AbstractA new algorithm for free surface corrections in Eulerian finite element computations is presented and applied to a steady state bar rolling process to predict lateral spread. A variety of rolling geometries are examined, including differing height to width ratios and reductions. The bulge profiles, as well as the maximum and mean bulge amounts, are compared in detail with experiments.
An adaptive procedure for stabilizing convergence quality in frequency‐constrained design optimization of bar structures supporting non‐structural mass
Authors: Phan Khing F. , McGee Oliver G. 
Published: November 2005

AbstractThis paper presents an improved optimality criteria (OC) method for minimum‐weight design of bar structures supporting non‐structural mass and subjected to multiple natural frequency constraints and minimum gauge restrictions. The convergence quality of the OC method hinges on both the number of active constraints retained and the choice of a proper step size. This being the case, a criterion, which uses previous scaled designs to ‘adaptively’ tune the step size, is established with the purpose of dissolving the (sometimes violent) oscillations of scaled design weights in the iteration history. As the step size is tuned, the convergence rate is descreased. Hence, a modified Aitken's accelerator, which extrapolates from previous scaled designs to obtain an improved one, is used. Its effect is to both increase the overall rate and reduce the net cost of convergence by reducing the number of repeat finite element analyses. The method presented here is used to qualitatively survey the convergence of several OC recursive schemes compositely used to resize and to evaluate the Lagrange multipliers. Design examples are presented to demonstrat the method. The method is adaptable, as it eliminates the need for adjustments of internal parameters during the redesign stage.
A numerical study of the deviation of the crack ending at the interface in a multilayer
Authors: El Abdi R. 
Published: November 2005

AbstractThe study of the deviation of a crack reaching the interface separating two materials in a multilayer in a 4‐point deflection is considered. This study is based on the use of special isoparametric finite elements.1 (The elements surrounding the crack tip have nodes placed at a distance α from the crack tip, and in this way we impose a singularity of the stresses in the neighbourhood of the crack.)The Erdogan2 criterion that estimates the deviation angle shows that this angle is a function of the initial angle of the crack, and the properties of each component of the multilayer.
An implicit finite‐element method for high‐speed flows
Authors: Hassan O. , Morgan K. , Peraire J. 
Published: November 2005

AbstractA fast algorithm is presented for constructing continuous lines, made up of element sides, which pass once through each node of a general unstructured triangular mesh and which are generally aligned in prescribed directions. The lines are used as the basis of an adaptive fully implicit unstructured grid procedure for the solution of two‐dimensional problems of steady compressible inviscid and laminar viscous high‐speed flows, where the equation system is solved by line relaxation using a block tridiagonal equation solver. For three‐dimensional laminar viscous simulations it is proposed to utilize an implicit/explicit finite‐element formulation. In the vicinity of solid walls a grid exhibiting structure in the normal direction is employed while, away from this region, the grid will be totally unstructured. In the structured region, lines in the normal direction to the wall are readily identified, while lines in the surfaces parallel to the solid wall are constructed using the proposed two‐dimensional procedure. The implicit algorithm is then used in the structured region and the equation solution is achieved via line relaxation. An explicit form of the solution algorithm is used elsewhere. To illustrate the performance of the proposed method, solutions are obtained for both transonic inviscid and transonic and hypersonic laminar viscous problems in two dimensions. The application of the proposed procedure to the solution of three‐dimensional hypersonic laminar viscous flow over a double ellipsoid configuration is also described.
New predictor/corrector algorithms with improved energy balance for a recent formulation of dynamic vehicle/structure interaction
Authors: Vu‐Quoc L. , Olsson M. 
Published: November 2005

AbstractA new class of predictor/corrector algorithms is proposed to solve the complex system of differential equations that arises from a Galerkin spatial discretization of the equations of motion in a recent formulation of dynamic vehicle/structure interaction. The applicability of the concept of a building‐block vehicle/structure interaction model developed in our previous work—where the vehicle nominal motion is not prescribed a priori, but is part of the unknown motion of the system—is demonstrated through the construction of a simple vehicle model. In the new algorithms, the presence of the accelerations of the vehicle component is eliminated in the predictor structural equations, making these equations different from the corrector structural equations. The special treatment of the predicted axial motion that provides an artificial damping to eliminate unstable oscillations in the numerical results as proposed in the old algorithms is avoided. Accurate results from numerical simulations using the new algorithms are obtained, and there are no unstable oscillations that were observed in some other predictor/corrector schemes. The system energy balance is also better preserved compared with the old algorithms.
Phase‐space representation of iterative design processes
Authors: Burns Scott A. 
Published: November 2005

AbstractA large variety of design optimization methods have been proposed in recent years. Comparison of the relative performance of each method is a difficult task, and attempts to do so are often based on a limited number of numerical experiments. Recently, a ‘basins of attraction’ construction has been proposed as a graphical tool for investigating global performance of iterative design optimization methods, and as a basis for comparison of different methods. The phase‐space representation presented in this paper is a companion to the basins of attraction construction. Basins of attraction reveal the relationship between starting design and final outcome of the solution process; the phase‐space construction reveals that nature of the paths connecting the starting design and final outcome. The two constructions complement one another in summarizing the performance of design optimization processes. Both constructions are demonstrated in this paper, applied to the optimal design of an elastic grillage structure using Newton's method and the stress ratio method.
A numerical method for the solution of two‐dimensional inverse heat conduction problems
Authors: Reinhardt H.‐J. 
Published: November 2005

AbstractA numerical method for the solution of inverse heat conduction problems in two‐dimensional rectangular domains is established and its performance is demonstrated by computational results. The present method extends Beck's8 method to two spatial dimensions and also utilizes future times in order to stabilize the ill‐posedness of the underlying problems. The approach relies on a line approximation of the elliptic part of the parabolic differential equation leading to a system of one‐dimensional problems which can be decoupled.
On the numerical integration of a class of pressure‐dependent plasticity models with mixed hardening
Authors: Lee J. H. , Zhang Y. 
Published: November 2005

AbstractRadial return algorithms, for both three‐dimensional and plane stress situations, are developed for a class of pressure‐dependent plasticity models (formulated in state variables) with mixed hardening. The consistent tangent matrix has been developed which, among other advantages, does not require numerical inversion. The algorithms, for Gurson's mixed hardening model, are incorporated in a finite element program to solve several simple uniaxial tension problems. When compared with numerically integrated solutions, the results from the finite element analysis show excellent agreement. Finally, results of the axisymmetric necking problem, using Gurson's mixed hardening model, are presented as an example of application.
A comparative study of the behaviour of a direct solver and a preconditioned iterative solver for the equations arising from the discretization by Chebyshev collocation of a second‐order partial differential equation on a square
Authors: Kjellmert Bo 
Published: November 2005

AbstractThe behaviour is compared of two solvers for the discrete equations arising from the discretization using Chebyshev collocation of a second‐order linear partial differential equation on a square. The alternative solvers considered are a direct solver and an iterative solver based on preconditioning with the matrix arising from finite‐difference discretization of the governing equation. The total error of the collocation derivatives and the separate contributions from round‐off and discretization error are examined. The efficiency of the two solvers is compared. The iterative solver is more efficient than the direct solver on fine grids for equations similar to the Poisson equation, provided that there are Dirichlet boundary conditions on at least three of the sides of the square.
Forced harmonic vibration of rotating beam systems in space analysed by use of exact finite elements
Authors: Lundblad H. Mikael 
Published: November 2005

AbstractA general computational technique is developed for the accurate analysis of forced non‐synchronous harmonic vibration of linear structures rotating with constant speed about a fixed axis in the inertial space. The structures studied are built up from piecewise uniform straight Rayleigh‐Timoshenko beam members having coinciding cross‐sectional centres of geometry, shear and mass, and vibrating in coupled tension, torsion, bending and shearing. Hysteretic and viscous dampings in the beam material and in a Winkler‐type ambient medium are considered. Rigid bodies and modal bodies and also discrete masses, springs and dampers can be included in the structure. The six coupled scalar partial linear differential equations governing the motion of a loaded beam are established in a corotating local co‐ordinate system. A transcendentally frequency‐dependent non‐symmetric complex‐valued 12 × 12 stiffness matrix is derived, over a state‐space analogy and an associated eigenproblem, for a harmonically vibrating beam member non‐synchronously excited at its ends. This matrix is exact in the sense that no assumed shape functions and no lumped masses are used. The general computational technique is here applied to a simple beam rotating about (1) its longitudinal axis and (2) about a transverse axis. The study clarifies the influence of gyroscopic effects and of material and support dampings on the dynamical behaviour of the beam at different rotational speeds and forcing frequencies. Resonance frequencies are found. Frequency response functions and frequency maps are plotted.
A comparison of adaptive‐grid redistribution and embedding for steady transonic flows
Authors: Dannenhoffer John F. 
Published: November 2005

AbstractIn recent years, numerical analysts have increasingly turned to adaptive‐grid techniques to efficiently obtain highly‐accurate solutions to partial‐differential equations. This paper presents a comparison of two distinct grid‐adaptation approaches, grid‐point redistribution and grid‐embedding, applied to two‐dimensional, steady, inviscid, shocked flows. Grid redistribution is accomplished through a control function approach applied to the elliptic‐grid generator while the embedding approach consists of a fixed global grid and an automatically chosen number of irregularly shaped, embedded regions. For both techniques, the Euler flow equations are integrated to steady state using Ni's Lax‐Wendroff‐type integrator to predict the flow fields about a variety of isolated airfoil configurations. The application of a common integration scheme as well as a common adaptive control function leads to a direct comparison of the effectiveness of the two adaptation approaches for the types of problems tested.
Shape reconstruction and volume meshing for complex solids
Authors: Baker Timothy J. 
Published: November 2005

AbstractThe reconstruction of a solid surface from a series of cross‐sections and the generation of a volume mesh that conforms with a prescribed surface are issues that arise in numerous applications. We describe an approach to both these problems that is based on the generation of a tetrahedral mesh which automatically captures a triangulation of the surface points. A simple algorithm for introducing a set of interior points permits a simple partition of the volume mesh into two disjoint sets of tetrahedra such that one set determines the interior of the solid while the second determines the exterior.
Multi‐domain two‐ and three‐dimensional thermoelasticity by BEM
Authors: Deb A. , Banerjee P. K. 
Published: November 2005

AbstractA computationally advantageous multi‐domain boundary element formulation is presented for uncoupled thermoelastic analysis of two‐ and three‐dimensional isotropic media. Particular integrals capable of representing exactly a quadratic temperature distribution in both two and three dimensions are employed. These particular integrals are derived using an orderly approach. When temperature data are provided at discrete points, the best fit quadratic distribution is generated in the least square error sense which, together with a multi‐domain approach, makes it possible to represent an arbitrary temperature distribution within acceptable bounds. Numerical examples are given to show the efficiency and effectiveness of the present formulation, which is now incorporated in a general purpose boundary element code named GPBEST.
Efficient and accurate four‐node quadrilateral C0 plate bending element based on assumed strain fields
Authors: Shi Guangyu , Voyiadjis George Z. 
Published: November 2005

AbstractBased on the assumed element strain fields and the interrelated displacement‐rotation interpolations, a four‐node (12 dof) quadrilateral C0 finite element, designated as QCCP‐2, for the analysis of thick/thin plates is developed in this paper. The four‐node C0 plate element presented here possesses a linear bending strain field, and the element stiffness matrices are given explicitly. Therefore, the present four‐node C0 plate element is more efficient and accurate than the existing four‐node C0 plate elements where the constant strain stiffness matrices are obtained by numerical integration. By the use of the interrelated displacement‐rotation interpolations, QCCP‐2 is capable of automatically satisfying the Kirchhoff assumption for the case of thin plates. Consequently, QCCP‐2 is not only free of shear locking, but also free from the numerical ill‐conditioning. Furthermore, QCCP‐2 passes the patch test of thin plates. The four‐node quadrilateral C0 elements presented here can automatically reduce to the corresponding three‐node triangular elements. Several numerical examples are given to demonstrate the efficiency and accuracy of the C0 plate bending element QCCP‐2.