bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural approach for thin‐walled beam‐columns with elastic‐plasticity
Authors: Conci Aura , Gattass Marcelo 
Published: August 2005

AbstractIn a realistic analysis of thin‐walled steel frames the warping of beam‐columns of open cross‐section must be considered. To model the behaviour of these structures up to collapse load, the plasticity of the material also has to be included in the analysis. This work presents the derivation of a new finite element for three‐dimensional non‐linear analysis of steel frames with bi‐symmetrical cross‐sections that models warping and elastic‐plasticity. The displacement field is described by the Principle of Sectorial Areas and is modelled with Hermitian functions. For the material non‐linearity the Incremental Plasticity Theory in a concentrated plasticity model has been used. The yield surfaces based on the natural stress resultants which include torsion and bimoment are used in the formulation of the element. The matrices of the proposed element are derived explicitly and implemented in a computer program which uses the Natural Approach. The implemented stress recovery process is insensitive to rigid‐body motions. The accuracy of the finite element and the efficiency of the implementation are illustrated through examples.
On the superconvergence of the Satisfying‐Babuska–Brezzi method
Authors: Franca Leopoldo P. 
Published: August 2005

AbstractA simple two‐point boundary value problem, written in a mixed form, is shown to have superconvergence characteristics using the Satisfying‐Babuska–Brezzi (SBB) method. Convergence and accuracy analyses reveal superior performance of the method compared to the usual Galerkin method.
Boundary elements in zoned media: Direct and indirect methods
Authors: Medina Daniel E. , Lean Meng H. , Liggett James A. 
Published: August 2005

AbstractSeveral formulations of the Boundary Element Method (BEM) are examined herein in the context of heterogeneous media. A strong singularity develops at re‐entrant interzonal corners and its effect is made more acute by large differences in the material properties. The effects of this singularity on the performance of the various BEM formulations are illustrated with examples. It is concluded that the direct BEM, either in the collocation or Galerkin formulations, is unable to give good results in zones of low conductivity. On the other hand the indirect BEM does not adequately reproduce the behaviour of the flow field near boundaries. A multi‐step version of the direct BEM is formulated to eliminate the difficulties introduced by the interzonal singularities.
Free‐vibration analysis of three‐dimensional solids by BEM
Authors: Wilson R. B. , Miller N. M. , Banerjee P. K. 
Published: August 2005

AbstractIn practical applications, it is often necessary to determine the natural frequencies and mode shapes of a solid, in addition to the static response under a variety of loading conditions. This paper discusses the calculation of natural frequencies and mode shapes of three‐dimensional solids using the boundary element method. The method developed is based on the use of particular integrals of the elastic equilibrium equations, and employs only real arithmetic. It represents an extension to three dimensions of work previously carried out for two‐dimensional problems in References 1 and 15. The method has been incorporated, for multiregion analysis, in the BEST3D (Boundary Element Solution Technology—Three Dimensional) computer program.Much of the work described in this paper was carried out under the support of National Aeronautics and Space Administration Contract NAS3–23697, ‘3D Inelastic Analysis Methods for Hot Section Components’. The program managers at the NASA‐Lewis Research Center are Dr C. C. Chamis and Mr Dale Hopkins. The program manager at Pratt & Whitney is Dr E. S. Todd
Results of the boundary element calculations are compared with analytical, finite element and experimental results.
A numerical technique for the solution of two dimensional elasticity problems
Authors: Tarazi Sami S. , Mandel James A. 
Published: August 2005

AbstractA numerical technique for the solution of two dimensional elasticity problems, referred to as The Method of Complex Finite Domains, is presented. The technique is based on assumed piecewise continuous fields of the Kolosov–Muskhelishvile complex potentials ϕ(z), Ψ(z). External loads and boundary conditions are modelled as continuous functions in terms of the functions' values at suitable quadrature points on the boundary. The method has a wide scope of applications because the structure of the complex potentials is known for many important regions and because of its flexiblity in modelling complex loads and boundary conditions. A numerical example that demonstrates the convergence and applicability of the method as well as the efficiency of the boundary load model is presented.
Partial hybrid stress element for transient analysis of thick laminated composite plates
Authors: Jing Hung‐Sying , Liao Ming‐Liang 
Published: August 2005

AbstractThe variationally consistent partial hybrid stress element proposed by the authors is extended to transient analysis of thick laminated composite plates in this paper. Through dividing six stress components into flexural (σx, σy, τxy, σz) and transverse shear (τxz, τyz) parts, the corresponding dynamic version of the modified Hellinger–Reissner principle is presented. By assuming stress parameters for transverse shear only, the partial hybrid stress element can be used to solve transient problems without any contradiction. The mass matrix derived is a simply consistent mass regardless of the assumed stress field. Comparisons are made with results available in the literature. Through thickness variations of all the six stress components for a dynamic version of Pagano's example are also presented for the first time. These results can serve as a reference source for future comparisons.
A mixed finite element for the analysis of large inelastic strains
Authors: Jetteur Ph. , Cescotto S. 
Published: August 2005

AbstractA 4‐node element with 1 integration point is developed for the analysis of elastoplastic large strains. It is based on the Hu‐Washizu principle and uses a co‐rotational formulation. Special care is taken to avoid spurious zero‐energy modes and incompressibility locking.This element successfully passes the large strain patch test. It proves to be accurate and computationally very cheap.
Geometrically non‐linear constant moment triangle which passes the von Kármán patch test
Authors: Morley L. S. D. 
Published: August 2005

AbstractA geometrically non‐linear constant moment triangular finite element is designed under Kirchhoff theory from a Hu–Washizu functional such that it passes the totality of von Kármán patch tests for constant strain and constant curvature. The non‐linear triangle has the same connection properties as in the linear theory where the constant strain triangle is superposed upon the displacement version of the constant moment triangle.
Non‐linear analysis of stiffened plates using super elements
Authors: Koko T. S. , Olson M. D. 
Published: August 2005

AbstractA new numerical technique for large deflection elasto‐plastic analysis of stiffened plates is presented. The method uses super finite elements which are macro elements having analytical as well as the usual finite element shape functions, specially designed so that only one plate element per bay and one beam element per span are needed. The large deflection theory by von Karman and the von Mises yield criterion and associated flow rule are employed. The governing equations are derived using the principle of virtual work, integrated numerically using Gauss quadrature and solved by Newton–Raphson iteration. Numerical solutions are presented for simple beams and plates, and plates stiffened in one or two mutually perpendicular directions. Good approximations are obtained with only one‐element representations of each plate bay or beam span with significant savings in computing time, costs and storage requirements as compared with using regular finite elements.
Experimental and finite element simulation methods for rate‐dependent metal forming processes
Authors: Shih Albert J. M. , Yang Henry T. Y. 
Published: August 2005

AbstractAn experimental procedure and a finite element simulation method for rate‐dependent metal forming processes are developed. The development includes the formulation of a tangential stiffness matrix for an axisymmetric solid finite element with four node, eight degree of freedom, quadrilateral cross‐section. The formulation includes the effects of elasticity, viscoplasticity, temperature, strain rate and large strains. The solution procedure is based on a Newton‐Raphson incremental‐iterative method which solves the non‐linear equilibrium equations and gives temperatures and incremental stresses and strains. Three examples are studied. In example 1, finite element simulation for the upsetting of a cylindrical workpiece between two perfectly rough dies is performed and the results are compared with alternative finite element solutions. In examples 2 and 3, both experimental and finite element studies are performed for the upsetting of a cylindrical billet and the forging of a ball, respectively. Annealed aluminium 1100 workpieces are used in both examples. For the finite element analysis, uniaxial compression tests are first performed to provide the material properties. The tests generate elastic moduli and two sets of stress‐strain curves (quasi‐static and constant strain rate), which are used to establish a rate‐dependent material model for input. For both examples 2 and 3, comparisons between the experimental and finite element simulation results for the forming force vs. die displacement relations and also for the deformed configurations show good agreement. The versatility of finite element methods allows for displaying detailed knowledge of the metal forming process, such as the distributions of temperature rise, yield stress, effective stress, plastic strain, plastic strain rate, forming forces and deformed configurations, etc. at any instance during the forming process.
An incompatible element for axisymmetric structure and its modification by hybrid method
Authors: Sze K. Y. , Chow C. L. 
Published: August 2005

AbstractThis paper introduces three four‐node quadrilateral axisymmetric elements. The first one is an incompatible element while the second one is a modification of the first element by an extended Hellinger‐Reissner principle. The second element is then simplified by incorporating the conceptual idea of free formulation and thus forms the third element. All of the three elements are found to be invariant, insensitive to nodal point numbering, free of locking for nearly incompressible material, able to pass the patch test and do not exhibit the false shear phenomenon. Numerical examples are given and satisfactory predictions are achieved.
Infinite boundary elements for dynamic problems of 3‐D half space
Authors: Chuhan Zhang , Chongmin Song , Pekau O. A. 
Published: August 2005

AbstractIn this paper, a new procedure for solving 3‐D dynamic problems of unbounded foundations in the frequency domain by using BEM is studied. For simulations of wave propagations due to far field effects, a type of infinite boundary element (IBEM) is presented for modelling a 3‐D regular or irregular half space. The wave type considered could be compressional, shear or a combination of the two. Through the analysis of the asymptotic behaviour of 3‐D fundamental solutions for elasto dynamics, a rather feasible technique for obtaining singular integral coefficients for dynamic problems has been developed. Through the analysis of the dynamic response for a 3‐D square foundation under a uniform load distribution, excellent accuracy has been achieved in agreement with previous numerical solutions. Another example–analysis of the dynamic compliance of a rigid square plate on a half space–has also shown very good results. The development of this infinite boundary element provides a powerful tool for dealing with 3‐D structure foundation interaction or wave propagation problems for irregular foundations such as arch dam canyons.
Fluid‐structure interaction analysis by the finite element method–a variational approach
Authors: Kock Ellen , Olson Lorraine 
Published: August 2005

AbstractWe have developed a finite element method for analysing non‐linear and linear fluid‐structure interaction problems by working directly from a variational indicator based on Hamilton's principle. We restrict our analyses to inviscid, irrotational and isentropic fluid flows. The variational indicator includes the fluid potential energy due to gravity, which is often ignored. This and the fact that we consider our domain to be variable provide us with the capability to model free surfaces.We demonstrate the effectiveness of both linear and non‐linear finite element formulations in analysing a variety of fluid‐structure interaction problems.
Solid elements with rotational degrees of freedom: Part 1—hexahedron elements
Authors: Yunus Shah M. , Pawlak Timothy P. , Cook Robert D. 
Published: August 2005

AbstractThis is the first of a two part paper on three‐dimensional finite elements with rotational degrees of freedom (DOF). Part I introduces an 8‐node solid hexahedron element having three translational and three rotational DOF per node. The corner rotations are introduced by transformation of the midside translational DOF of a 20‐node hexahedron element. The new element produces a much smaller effective band width of the global system equations than does the 20‐node hexahedron element having midside nodes.A small penalty stiffness is introduced to augment the usual element stiffness so that no spurious zero energy modes are present. The new element passes the patch test and demonstrates greatly improved performance over elements of identical shape but having only translational DOF at the corner nodes.
Automatic mesh generation and adaptation by using contours
Authors: Lo S. H. 
Published: August 2005

AbstractA general and efficient remeshing algorithm is presented for the discretization of arbitrary planar domains into triangular elements in consistency with the given node spacing function.The contour lines of the node spacing function at suitable calculated levels provide the natural lines of division of the problem domain into subregions, where finite element meshes of different element sizes are generated using the available general‐purpose mesh generators.1, 2Examples of remeshing for various node spacing functions are given to illustrate that high‐quality gradation meshes can be generated automatically without any user's intervention by this simple contour line method.
Shear‐flexible models for spatial buckling of thin‐walled curved beams
Authors: Saleeb A. F. , Gendy A. S. 
Published: August 2005

AbstractThe governing non‐linear finite element equations for the spatial stability analysis of curved beams, using a simple two‐noded model, are derived based on the incremental form of a mixed variational principle with independent discretization for its generalized strain field and the reference line displacements as well as cross‐sectional warping and bending/twisting rotations. The formulation is valid for both open‐and closed‐type thin‐walled sections, and this is accomplished by the use of a kinematic description based on a generalized beam theory in which shear deformation due to both flexural‐and warping‐torsional actions is accounted for. The effect of finite rotations in space is included, resulting in a second‐order accurate geometric stiffness matrix and ensuring that all significant instability modes can be predicted. Finally, the results obtained in a number of numerical simulations for lateral‐torsional bifurcation buckling of circular arches are presented to illustrate the model effectiveness and practical usefulness, and to provide explanations for the source of discrepancies noted in the results obtained in previous investigations.
Application of B‐spline approximation to symmetric buckling problems of truncated shallow spherical shells subjected to line loads
Authors: Gu Shuxian 
Published: August 2005

AbstractBy using cubic B‐spline approximations, reasonably accurate solutions are obtained for line‐loaded shallow spherical shells with a centre hole within a wide range of values of the geometrical parameter K (0 ≤ K ≤ 400, \documentclass{article}\pagestyle{empty}\begin{document}$ K = \sqrt {12(1 - v^2)} 2f/h $\end{document}, f = shell rise, h = shell thickness). It was found that the buckling loads Pc as well as the buckling threshold of the geometrical parameter Kc increase monotonically as the radius of the centre hole β increases if the hole edge is reinforced with a rigid ring and the outer edge of the shell is simply supported. However, the effect of the centre hole on Pc decreases rapidly as K increases and becomes negligible for K ≥ 45 and β ≤ 0.4.
Consideration of constraints within the finite element method by means of matrix operators
Authors: Mechnik Ralph‐Peter 
Published: August 2005

AbstractThe following paper describes the incorporation of different constraints into a finite element system by means of matrix operators in conjunction with consecutive corresponding transformations. Instead of increasing the number of equations‐as e.g. the Lagrange Multiplier Method10, 14 does‐the Matrix Operator Method yields a set of reduced magnitude which can be solved more efficiently. The method will be developed for two classes of constraints: (i) stiff coupling of previously known subdomains and (ii) contact problem between two bodies. The assembly rules to obtain the system matrices are deduced. An application is given by a three‐dimensional example of structural analysis in mechanical engineering.
Improved formulations of Qcs6 hybrid element for enhancing computational efficiency
Authors: Sze K. Y. , Chow C. L. , Chen Wanji 
Published: August 2005

AbstractThis article discusses two alternative methods of formulating the recently proposed quadrilateral plane element Qcs6, which is based on a generalized functional with multiple stress fields. The first method is derived by an extended Hu‐Washizu Principle with the presence of incompatible modes and enforcement of energy orthogonality, while the second one is established on a non‐conventional discrete local stress smoothing. Both methods can be applied to other structural element formulations with enhanced efficiency.
A new method for finite element transitional mesh generation
Authors: Chinnaswamy C. , Amadei B. , Illangasekare T. H. 
Published: August 2005

AbstractIn the preparation of finite element meshes, inclusion of transitional blocks is important in order to construct optimal meshes. In this paper, a new method is proposed which is capable of generating quaddominated arbitrary transitional meshes. These meshes are well graded and do not require any mesh smoothening algorithm. The inverse isoparametric mapping combined with an elimination procedure is used to construct transition zones. This new algorithm is described in detail and its efficiency is illustrated with appropriate examples.Different methods available for inverse isoparametric mapping are discussed with their merits and limitations. Many of the existing techniques for inverse isoparametric mapping require the calculation of some special coefficients which may vary with the element type. These techniques lose their clarity and efficiency in the case of three dimensional and higher order two dimensional elements. In this paper, a generalized iterative procedure is proposed to carry out the inverse isoparametric mapping. The computations in this approach are already part of every finite element program based on the isoparametric formulation. Hence implementation of the new algorithm is very simple and straightforward.
On the formulation of the acoustic boundary element eigenvalue problems
Authors: Ali1 Ashraf , Rajakumar C. , Yunus Shah M. 
Published: August 2005

AbstractAcoustic algebraic eigenvalue analysis by the Boundary Element Method (BEM) can be formulated by the Dual Reciprocity Method (DRM) of Nardini and Brebbia or by the Complementary Function‐Particular Integral Method (PIM) proposed by Ahmad and Banerjee. But both DRM and PIM require inversion of a matrix of size at least as large as the system matrices before the equations can be cast in the form of generalized eigensystem. This makes these methods inefficient for large problems of practical interest. In this paper, a rather simple technique is proposed which eliminates the need to invert any matrix in the process of setting up the algebraic eigenvalue problem, especially for the most important case where all the boundary walls are acoustically hard (∂P/∂n = 0). A few example problems having known analytical and experimental results are solved in order to demonstrate the validity of the new technique. It is also demonstrated that, unlike in elasticity, here the boundary element domain must be adequately zoned or an adequate number of internal points must be incorporated in order to solve truly 2‐D or 3‐D problems.
Non‐linear bending analysis of plates and shells by using a mixed spline boundary element and finite element method
Authors: Jianqiao Ye 
Published: August 2005

AbstractIn this paper, a mixed spline boundary element and finite element method is suggested to analyse non‐linear bending of plates and shells. Only the fundamental solutions for plates are required in order to establish the boundary integral equations. A quadratic rectangular spline element is adopted to deal with the membrane effects of plates and shells. Numerical examples show that the approach developed in this paper is very effective and especially promising for the non‐linear analysis of plates and shells.
Algorithms for draping fabrics on doubly‐curved surfaces
Authors: Van Der Weeën F. 
Published: August 2005

AbstractThree algorithms for draping biaxially woven fabrics on arbitrarily curved surfaces are presented and compared for numerical accuracy and computational expense. The first one minimizes the elastic energy in each fabric cell, while the two others are based on placing a net of interlocked and inextensible fibres on the surface along geodesic lines. A benchmark shows that the minimum energy technique performs the best and is also the most promising for further optimization in terms of numerical quadrature formulae.
The solution of large displacement frictionless contact problems using a sequence of linear complementarity problems
Authors: Björkman Gunnar 
Published: August 2005

AbstractA Newton method for solution of frictionless contact problems is presented. A finite element discretization is performed and the contact constraints are given as complementarity conditions. The resulting equations, which represent the equilibrium of the system, are formulated as a generalized equation. Generalized equations, from the discipline of Mathematical Programming, are a way of writing multi‐valued relations, such as complementarity conditions, in a way that is similar to ordinary equations. Newton's method is then used, in a straightforward way, to solve the present non‐linear generalized equation, resulting in a sequence of Linear Complementarity Problems (LCP's).