bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural modifications simulated by virtual distortions
Authors: Holnicki‐Szulc Jan , Gierlinski Jacek T. 
Published: November 2005

AbstractA numerical strategy for the simulation of structural modifications by virtual distortions is proposed. Two cases of structural modification are considered: the first concerns modifications of material distribution, and the second modifications of local constitutive relations (e.g. unilateral constraints for stresses or deformations). A formaulation of the fundamental equations of the simulation method is presented. These equations are applicable to the general structural modification problem of a truss‐like structure. Then numerical algorithms which refer to particular applications, such as progressive collapse analysis or the analysis of structures with gaps, are discussed.The versatility of the method is illustrated with a number of examples, and the computational advantages of structural modification by the virtual distortion method are discussed.
Finite element solution of two‐dimensional inverse elastic problems using spatial smoothing
Authors: Schnur D. S. , Zabaras Nicholas 
Published: November 2005

AbstractA finite element method (FEM) is presented for calculating the surface tractions on a body from internal measurements of displacement at discrete sensor locations. The solution algorithm employs a sensitivity analysis which minimizes the difference between the calculated and measured displacements at each sensor location. Spatial regularization is one technique employed to stabilize the minimization process by imposing various degrees of smoothness on the solution. It also allows the problem to be solved with fewer sensors than traction boundary nodes. As an alternative to spatial regularization, a method based on ‘keynodes’ is introduced which assumes that each component of the boundary traction distribution can be described by a polynomial of specified order. The methods are applied to several two‐dimensional examples including a rolling contact problem. The effects of parameters such as the number of sensors, the location of the sensors and the error in the sensor displacements are discussed.
A new approach to boundary modelling for finite difference applications in solid mechanics
Authors: Dow John O. , Jones Michael S. , Harwood Shawn A. 
Published: November 2005

AbstractProcedures for extending the useful scope of the finite difference method in solid mechanics applications are presented. The improvements centre around the introduction of the physical nature of the deformations into the equations used to formulate the approximate solution. This is accomplished by evaluating the coefficients of Taylor series expansions for the displacement approximations in terms of rigid body motions, strains and derivatives of strains. This procedure is demonstrated with plane stress applications. The ability to interpret the derivative approximations physically allows the fictitious nodes typical of the finite difference method to be rationally incorporated into the model as a means of enforcing traction boundary conditions. An example problem is solved using both regular and irregular meshes. The displacements and stresses compare well with finite element solutions.
Generalized axisymmetric elastodynamic analysis by boundary element method
Authors: Wang Hui‐Ching , Banerjee Prasanta K. 
Published: November 2005

AbstractThe boundary element formulation for three‐dimensional problems of steady state (periodic) dynamic analysis has been cast into the generalized axisymmetric form by expressing the boundary tractions and displacements in terms of a Fourier series expansion. The resulting formulation has been developed for the dynamic analysis of axisymmetric geometries subjected to non‐axisymmetric loading. The analysis has been implemented in a large general purpose analysis capable of analysing both finite as well as semi‐infinite domains and a series of examples has been shown to demonstrate the versatility of the implementation.
Natural approach for geometric non‐linear analysis of thin‐walled frames
Authors: Conci Aura , Gattass Marcelo 
Published: November 2005

AbstractA new stiffness matrix for geometrically non‐linear analysis of three‐dimensional beam‐columns with bisymmetrical, thin‐walled, I‐type cross‐sections is presented. The displacement field is described in terms of natural and rigid‐body displacements and both Cartesian and natural matrices are derived. A novelty of the resulting method is the use of this dual description in all aspects of the analysis including the computer implementation. A companion paper1 that introduces the plastic behaviour of the material also justifies the need for this dual approach as a means to separate nodal forces from stress resultants in the cross‐section of the 3D beam‐column element. The current development uses the updated Lagrangian formulation and corrections in the element matrix are made to properly consider the behaviour under finite rotation. It is shown that accuracy and convergence of the solution process can be improved if the natural matrices derived here are used in a new force recovery process that is insensitive to rigid‐body displacements.
A higher‐order triangular plate bending element revisited
Authors: Dasgupta Suman , Sengupta Dipak 
Published: November 2005

AbstractA new formulation of an eighteen‐degrees‐of‐freedom higher‐order triangular plate bending element using triangular area co‐ordinates is presented. The displacement function w is taken as the complete fifth‐order polynomial in area co‐ordinates. The normal slope along an edge of the triangle is constrained to vary cubically. The twenty‐one constants are expressed explicity in terms of eighteen degrees of freedom. The element stiffness matrix is expressed as a product of component matrices for which explicit expressions are developed and presented. No numerical inversion or integration is necessary. The formulation is expected to be useful specially for microcomputers.
Consistency aspects of out‐of‐plane bending, torsion and shear in a quadratic curved beam element
Authors: Naganarayana B. P. , Prathap G. 
Published: November 2005

AbstractCurved beams in civil engineering applications call for out‐of‐plane bending and torsion under the action of out‐of‐plane transverse shear loads. The design of a quadratic displacement curved beam element capable of representing shear deformation as in the Timoshenko beam theory requires special attention to the manner in which the shear strain is represented. Field‐inconsistent representations of the out‐of‐plane transverse shear strain will result in a loss of efficiency and introduce spurious oscillations in the bending moment, torsional moment and shear force. The optimal field‐consistent assumed strain interpolation for shear is derived and it is demonstrated to posses very high accuracy which is free from spurious force and moment oscillations.
The graphical representation of FE temperature field calculation results
Authors: Stelzer J. F. 
Published: November 2005

AbstractAfter having finished the FE computer run and determined the temperature vector of a heat conducting body the question arises how to present these results in an easily understood way. The only tool to manage this task satisfactorily is the application of graphics. This paper reflects the due historical roots and gives an overlook of the relevant developments. Recently, there have been special advantages concerning finite element results presentations of temperature fields. This concerns the temperature field colouring, which can be considered as an indirect method of contouring, and the direct method of contouring, which means finding and connecting points of equal temperature. In the 3‐D case these features are to be combined with hidden surface or hidden line removal techniques to give easily perceptible pictures. Sometimes, not just the temperatures but the heat fluxes attract the main interest. An adequate method is the drawing of heat flux arrows. This is taken into account, too. With 2‐D problems, the presentations of temperature distributions by mountains is popular.
The dual reciprocity boundary element method for spontaneous ignition
Authors: Partridge Paul W. , Wrobel Luiz C. 
Published: November 2005

AbstractThis paper studies the non‐linear heat conduction problem of spontaneous ignition of a reactive solid by using the dual reciprocity formulation of the boundary element method. First, critical values of the Frank‐Kamenetskii parameter δ are computed for some common geometrical shapes. Then, transient analyses are carried out for values of δ below and above δc, producing the expected behaviour, with ignition occurring for δ > δc.
Curved Mindlin beam and axi‐symmetric shell elements—A new approach
Authors: Day R. A. , Potts D. M. 
Published: November 2005

AbstractTwo sets of strain definitions for analysis of curved Mindlin beams and axi‐symmetric shells are examined. Their conventional finite element implementations are shown to be unsuitable. The parameter used as a nodal degree of freedom in the first conventional method to describe the cross section rotation is in general a discontinuous function and has no clear physical meaning. The second conventional method has relied on an incorrect differentiation for its successful use in finite element analysis. A new approach which overcomes these problems is presented. Examples are given to illustrate the incorrect results that can be obtained from the two conventional methods and to show that the new approach provides accurate solutions to general curved beam and axi‐symmetric shell problems.
Superconvergence recovery technique and a posteriori error estimators
Authors: Zhu J. Z. , Zienkiewicz O. C. 
Published: November 2005

AbstractA new superconvergence recovery technique for finite element solutions is presented and discussed for one dimensional problems. By using the recovery technique a posteriori error estimators in both energy norm and maximum norm are presented for finite elements of any order. The relation between the postprocessing and residual types of energy norm error estimators has also been demonstrated.
Petrov‐Galerkin finite element model for compressible flows
Authors: Brueckner Frank P. , Heinrich Juan C. 
Published: November 2005

AbstractA Petrov‐Galerkin method for the solution of the compressible Euler and Navier‐Stokes equations is presented. It is based on the introduction of an anisotropic blancing diffusion in the direction of the local direction of propagation of the scalar variables. The local direction in which the anisotropic diffusion is introduced is uniquely determined, and the magnitude of the balancing diffusion is automatically calculated locally using a criterion that is optimal for one‐dimensional transport equations.The algorithm has been implemented using four‐noded bilinear elements with forward Euler and second‐order Runge‐Kutta methods of integration in time. Several applications are presented and show the stability and approximation properties of the method.
Trust region methods for structural optimization using exact second order sensitivity
Authors: Sunar M. , Belegundu A. D. 
Published: November 2005

AbstractThe performance of multiplier algorithms for structural optimization has been significantly improved by using trust regions. The trust regions are constructed using analytical second order sensitivity, and within this region, the augmented Lagrangian ϕ is minimized subject to bounds. Evaluation of first and second derivatives of ϕ by the adjoint method does not require derivations of individual (implicit) constraint functions, which makes the method economical. Eight test problems are considered and a vast improvement over previously used multiplier algorithms has been noted. Also, the algorithm is robust with respect to scaling, input parameters and starting designs.
Direct evaluation of singular integrals in elastoplastic analysis by the boundary element method
Authors: Lu Shan , Ye T. Q. 
Published: November 2005

AbstractThis paper presents a new method for the direct and accurate evaluation of strongly singular integrals in the sense of Cauchy principal values and weakly singular integrals over quadratic boundary elements in three‐dimensional stress analysis and quadratic internal cells in two‐dimensional elastoplastic analysis by the boundary element method. A quadratic triangle polar co‐ordinate transformation technique is applied to reduce the order of singularity of the singular integrals. Next, a form of Stokes' theorem is introduced in order to remove the singularity in the Cauchy principal value integrals; therefore, the evaluation of these integrals can be carried out by standard Gaussian quadrature. Numerical examples of 2‐D elastoplastic problems and a 3‐D elastic problem show the effectiveness and efficiency of the method.
The finite element solution of elliptical systems on a data parallel computer
Authors: Hutchinson Scott , Hensel Edward , Castillo Steven , Dalton Kim 
Published: November 2005

AbstractA study is conducted of the finite element solution of elliptic partial differential equations on a data parallel computer. A nodal assembly technique is introduced which maps a single node to a single processor. The system of equations is first assembled and then solved in parallel using a conjugate gradient algorithm for unsymmetric, non‐positive definite systems. Using this technique and a massively parallel machine, problems in excess of 100k nodes are solved.Results of electromagnetic scattering, governed by the 2‐d scalar Helmholtz equation, are presented for both an infinite cylinder and an airfoil cross‐section. Solutions are demonstrated for a wide range of object sizes. A summary of performance data is given for a set of test problems.
A hierarchical approach to automatic finite element mesh generation
Authors: Yuen M. M. F. , Tan S. T. , Hung K. Y. 
Published: November 2005

AbstractA point‐based two‐stage hierarchical method for automatic finite element mesh generation from a solid model is presented.Given the solid model of a component and the required nodal density distribution, nodes are generated according to the hierarchy—vertex, edge, face and solid. At the vertices, nodes are established naturally. Nodes on the edges, faces and inside the solid model are generated by recursive subdivision. The nodes are then connected to form a valid and well‐conditioned finite element mesh of tetrahedron elements using modified Delaunay Triangulation. Checks are conducted to ensure the compatibility of geometry and topology between the solid model and the mesh.
A numerical approach for determining weight functions in fracture mechanics
Authors: Beghini M. , Bertini L. , Vitale E. 
Published: November 2005

AbstractThe paper deals with the development of a numerical method for determining Weight Functions in two‐dimensional problems. After a short review of some recent numerical techniques an original approach is presented. The method is based on Finite Element calculations with coarse meshes and on the knowledge of some values of the Stress Intensity Factor for one reference loading condition. The validity of the method is demonstrated for a theoretical case and its accuracy and suitability are discussed with reference to practical applications.
An adaptive finite element method for transient compressible flows with moving boundaries
Authors: Probert E. J. , Hassan O. , Morgan K. , Peraire J. 
Published: November 2005

AbstractA description is given of an adaptive finite element method for the simulation of two dimensional compressible flows with moving boundaries. The method is implemented on an unstructured triangular grid and the mesh adaptation is achieved by local grid regeneration, using an error estimation procedure coupled to an automatic triangular mesh generator. Two numerical examples are included to illustrate the numerical performance of the method.
Finite element analysis of heat transfer and flow problems using adaptive remeshing including application to solidification problems
Authors: Lewis R. W. , Huang H. C. , Usmani A. S. , Cross J. T. 
Published: November 2005

AbstractAn error estimation technique for adaptive finite element analysis of heat conduction problems is described. The performance of this technique is demonstrated using a two‐dimensional steady‐state linear benchmark problem with a known analytical solution. A transient non‐linear heat conduction problem involving solidification is then solved as a typical practical application. Some preliminary investigations for error indicators in flow problems are presented.
Paving: A new approach to automated quadrilateral mesh generation
Authors: Blacker Ted D. , Stephenson Michael B. 
Published: November 2005

AbstractThis paper presents a new mesh generation technique, paving, which meshes arbitrary 2‐D geometries with an all‐quadrilateral mesh. Paving allows varying element size distributions on the boundary as well as the interior of a region. The generated mesh is well formed (i.e. nearly square elements, elements perpendicular to boundaries, etc.) and geometrically pleasing (i.e. mesh contours tend to follow geometric contours of the boundary). In this paper we describe the theory behind this algorithmic/heuristic technique, evaluate the performance of the approach and present examples of automatically generated meshes.
Bounds on eigenvalues of finite element systems
Authors: Lin Jerry I. 
Published: November 2005

AbstractBounds on eigenvalues of various finite element systems are analysed by using an element eigenvalue theorem together with the Global Eigenvalue Theorem. Both two dimensional continuum dynamics and heat conduction problems are considered. These bounds provide stable time steps for explict time integration schemes. A reduced eigenproblem at element quadrature point level, with all zero eigenvalues suppressed, is also presented in this paper. The simplified eigenproblem results in simple formulas for calculating the eigenvalues.
The Lanczos algorithm applied to unsymmetric generalized eigenvalue problem
Authors: Rajakumar C. , Rogers C. R. 
Published: November 2005

AbstractApplication of the two‐sided Lanczos recursion to the unsymmetric generalized eigenvalue problem is presented. The system matrices are real and unsymmetric. Therefore, the recursions are performed in real arithmetic and complex arithmetic is employed in the QR algorithm used to extract the eigenvalues of the transformed tridiagonal matrix. The biorthonormal transformation of the unsymmetric generalized eigenvalue problem is considered in detail with appropriate proofs presented in Appendices. Issues relating to the computer implementation of the unsymmetric generalized eigenvalue problem are discussed. The example problems solved demonstrate the working of the algorithm in extracting the complex and/or real eignevalues of an unsymmetric system of matrices. Also, the algorithm is applied to extract a few of the eigenvalues of a large fluid‐structure interaction problem, and the results are compared with the eigenfrequencies extracted by an unsymmetric subspace iteration procedure presented in the literature.
A boundary integral equation method for an inverse problem related to crack detection
Authors: Nishimura N. , Kobayashi S. 
Published: November 2005

AbstractThis paper discusses an application of a boundary integral equation method (BIEM) to an inverse problem of determining the shape and the location of cracks by boundary measurements. Suppose that a given body contains an interior crack, the shape and the location of which are unknown. On the exterior boundary of this body one carries out measurements which are interpreted mathematically as prescribing Dirichlet data and measuring the corresponding Neumann data, or vice versa, for a field governed by Laplace's equation. The inverse problem considered here attempts to determine the geometry of the crack from these experimental data. We propose to solve this problem by minimizing the error of a certain boundary integral equation (BIE). The process of this minimization, however, is shown to require solutions of certain are proposed. Several 2D and 3D numerical examples are given in order to test the performance of the present method.
Dynamics of flexible multibody systems using cartesian co‐ordinates and large displacement theory
Authors: Avello Alejo , de Jalón Javier García , Bayo Eduardo 
Published: November 2005

AbstractA formulation for the dynamic analysis of flexible systems, composed of slender bodies that can be accurately modelled by beams is presented in this paper. A new set of state variables, composed of Cartesian co‐ordinates of points and unit vectors, is introduced to define the beam with respect to an inertial frame. A non‐linear Timoshenko beam finite element capable of handling finite displacements with small linear elastic strains is developed. This allows relative displacements between material points of a single beam to be arbitrarily large. Since deformations are not explicit variables, there is no need to define a moving reference frame attached to each flexible body. Instead, deformations are obtained through a displacement‐deformation relation based on finite‐displacement beam theory. The differential equations of motion are obtained using the Lagrange equations. A symmetric, constant and sparse mass matrix is obtained in the inertial frame. Constraints are introduced with a penalty formulation and the resulting set of ordinary differential equations is integrated with Newmark's family of methods. The whole formulation is extremely simple and the results demonstrate the capabilities and efficiency of the proposed method for dynamic simulation, even when relative displacements are finite in a single beam or coupling effects are significant.
Modelling and control of flexible robots
Authors: Chedmail P. , Aoustin Y. , Chevallereau Ch. 
Published: November 2005

AbstractThe object of this paper is to present a study on the modelling and control of flexible robots by using a knowledge based control design approach. We first develop an appropriate model of such a mechanical system in the case of open loop robot structures. We use a total Lagrangian formulation. After discretization, the degrees of freedom are the joint variables and the elastic degrees of freedom of each link. The elastic motions are referred to the rigid configuration of the considered link. The control law is obtained by using a non‐linear decoupling technique which is applied to the joint variables. A second control loop performs an active damping of the elastic motions: it is based on the linearized model and uses the LQR method. This approach has been experimented with a two flexible links robot. The results demonstrate its feasibility. Further developments mainly concern theoretical aspects on the robustness of these control laws, the identification of the model parameters and the choice of other appropriate modelling techniques.
Direct determination of periodic solutions of the dynamical equations of flexible mechanisms and manipulators
Authors: Meijaard J. P. 
Published: November 2005

AbstractA method based on finite elements, characterized by generalized strains as functions of the nodal co‐ordinates, is the basis for the computer program SPACAR for the kinematic and dynamic analysis of flexible multibody systems. This program allows also the evaluation of the linearized dynamical equations, which makes possible the implementation of a method for the direct determination of stationary and periodic solutions and of a continuation method for these solutions if some parameter is varied. As an illustration, these methods are applied to a Duffing equation, a double pendulum and a slider‐crank mechanism with an elastic connecting rod.