bluuebunny/crossref_metadata_2025_split huggingface dataset:
A finite element procedure for the stress analysis of tubular joint connections
Authors: Panagiotopoulos George D. 
Published: October 2005

AbstractAhmad's superparametric thick shell element with reduced integration, a transition element type having variable degrees‐of‐freedom per node and a three‐dimensional incompatible element have been used to calculate the stress distribution at the intersection region of T‐ and Y‐joint connections. To minimize the numerical effort, a transfinite blending function interpolation approach has been applied for the automatic mesh generation and the resulting system of linear equations has been solved using the front width method. Comparison of the computed solutions with some very carefully conducted experimental results has shown very good agreement.
Structural optimization: A new dual method using mixed variables
Authors: Fleury Claude , Braibant Vincent 
Published: October 2005

AbstractA new and powerful mathematical programming method is described, which is capable of solving a broad class of structural optimization problems. The method employs mixed direct/reciprocal design variables in order to get conservative, first‐order approximations to the objective function and to the constraints. By this approach the primary optimization problem is replaced with a sequence of explicit subproblems. Each subproblem being convex and separable, it can be efficiently solved by using a dual formulation. An attractive feature of the new method lies in its inherent tendency to generate a sequence of steadily improving feasible designs. Examples of application to real‐life aerospace structures are offered to demonstrate the power and generality of the approach presented.
An orthogonal decomposition approach to modal synthesis
Authors: Flashner H. 
Published: October 2005

AbstractModal synthesis is a method of formulating the equations of motion for complex vibratory systems. This approach has many advantages in modelling systems that consist of an assembly of linear dynamic elements whose modal characteristics are given. Presented in the paper is a procedure for synthesizing linear dynamic models into one dynamic description in a numerically stable way. This task is achieved by an orthogonal co‐ordinate transformation replacing the matrix inversions required when other procedures are used. The modal synthesis approach is formulated as a problem of finding the equations of motion for a linear system subject to a set of linear constraints. The numerical procedure to generate the equations of motion in terms of independent co‐ordinates is presented. The paper concludes with several examples that demonstrate the properties of the proposed method and its application to the modelling of vibratory systems.
An improved finite element for connecting adjacent laminae of two‐dimensional elements
Authors: Pack Steven C. , Mandel James A. 
Published: October 2005

AbstractA connector element for linking planes of two‐dimensional elements to enable approximate multiplane solutions to a class of three‐dimensional problems is developed. This connector element embodies the same displacement fields as assumed by the connected two‐dimensional isoparametric elements. A reduction from the general multiplane formulation to a dual plane model is shown to be appropriate for analysing bodies with uniformly spaced inclusions. Sample solutions are given, including cases with different continuity conditions in each plane.
Dynamic Lagrangian computations for solids, with variable nodal connectivity for severe distortions
Authors: Johnson Gordon R. , Stryk Robert A. , Dodd Jack G. 
Published: October 2005

AbstractThis paper presents an algorithm for dynamic Lagrangian computations for solids, in plane strain geometry, with variable nodal connectivity to allow for severe distortions. The nodes are somewhat analogous to flexible circular disks. When they move closer together than their equilibrium distance they generate compressive, repulsive forces. Conversely, when they move apart, they generate tensile, attractive forces. Material strength effects are also included. Because a node can only be affected by its ‘neighbour’ nodes, the approach has been designated the ‘NABOR’ approach. The key to this approach is that it is possible to have variable nodal connectivity—a node can acquire new neighbours, thus allowing all forms of distortion. The NABOR algorithm has been incorporated as an option into the explicit finite element code, EPIC‐2. By using both the NABOR grid and the EPIC‐2 finite element grid together, it is possible to perform Lagrangian computations for a wide range of problems.
Higher order Chebyshev basis functions for two‐point boundary value problems
Authors: Bamigbola O. M. , Ibiejugba M. A. , Onumanyi P. 
Published: October 2005

AbstractCubic basis functions in one dimension for the solution of two‐point boundary value problems are constructed based on the zeros of Chebyshev polynomials of the first kind. A general formula is derived for the construction of polynomial basis functions of degree r, where 1 ≤r < ∞. A Galerkin finite element method using the constructed basis functions for the cases r = 1, 2 and 3 is successfully applied to three different types of problem including a singular perturbation problem.
Hybrid finite element‐Monte Carlo method for coupled conduction and gas radiation enclosure heat transport
Authors: Kraus H. G. 
Published: October 2005

AbstractA hybrid two‐dimensional finite element‐Monte Carlo numerical solution method has been developed for solving complex transient non‐linear gas radiation enclosure problems. Solid conducting media are coupled to conducting gaseous or particulate participating media and both may be internally energy generating. Bilinear isoparametric elements are used, allowing geometrically complex enclosures with internal objects to be present. Radiative energy transport within the gaseous enclosures is accounted for using a Monte Carlo method which permits a broad range of complexities. Included here are: diffuse‐grey and specularly reflecting walls with temperature and spectrally dependent, and non‐homogeneous emissivities or absorptivities; absorbing/emitting gases with temperature and spectrally dependent, and non‐homogeneous emissivities or absorptivities; and isotropic or anisotropic scattering gases or particles. This method was verified by solving several standard steady state problems and comparing the solutions to those found using the conventional finite element, the P–N and the exchange factor methods. Solution times are comparable to those of the finite element method. A more complex transient problem solution is then given to demonstrate the versatility and power of the method.
Spline collocation in the flow of non‐Newtonian fluids
Authors: Doctor H. D. , Kalthia N. L. 
Published: October 2005

AbstractNatural convection flow of a non‐Newtonian fluid between two vertical infinite parallel flat plates forms the case study of the present work. Velocity profiles for the Prandtl–Eyring and Powell–Eyring fluid models are obtained through the method of spline collocation.The applicability and reliability of the techniques employed here are discussed in detail with a suggested error estimate and analysis. Accuracy in the successive iterations in the results is of the fourth order. To maintain this accuracy the help of a computer is not required for carrying out the calculation of velocity profiles. Thus the simplicity of the spline collocation technique is demonstrated in its application to flow problems.
Multilevel dynamic substructures
Authors: Leung A. Y. T. 
Published: October 2005

AbstractThe dynamic substructure method is extended to multilevel (recursive) substructures. The obvious distinction of the two approaches is that the stiffness and mass matrices before condensation are no longer frequency independent. The dynamic stiffness matrix at any substructure level is proved to be a function of the vibrating frequency in terms of some constant matrices which are derivable from the dynamic stiffness matrix at one lower substructure level. The method can accurately predict more modes than the number of degrees of freedom retained. The computational procedure, the generalized inverse iteration, the stationary principle of the system natural frequency and the generalized Rayleigh's quotient are derived for the frequency dependent matrices. Numerical examples are given to illustrate some engineering applications. A transcendental dynamic stiffness matrix can be transformed to a more convenient algebraic form by the present method.
Finite element/Newton method for the analysis of Czochralski crystal growth with diffuse‐grey radiative heat transfer
Authors: Bornside D. E. , Kinney T. A. , Brown R. A. , Kim George 
Published: October 2005

AbstractA quasi‐steady‐state, integrated system model describing high temperature heat transfer, solidification and the action of capillarity in the Czochralski crystal growth process is solved by a finite element/Newton method. The numerical analysis couples the calculation of the temperature field in all phases and the determination of the melt/crystal and melt/gas interfaces and the crystal radius free boundaries. The analysis includes conductive heat transfer in the melt, crystal, crucible, pedestal, heater and the surrounding insulation and diffuse‐grey radiation, which couples the heat transfer between surfaces, the crystal radius and the melt/gas free boundary through the view factors. Finite element approximations are used to reduce the entire problem to a coupled set of non‐linear algebraic equations. These are solved simultaneously by Newton's method with the Jacobian matrix computed by a combination of closed form expressions and finite difference approximations. Quadratic convergence of the Newton iteration is demonstrated along with a factor of four increase in computational efficiency over a successive iteration procedure that decouples the calculation of radiation from the rest of the heat transfer model.
Biharmonic analysis of rectilinear plates by the boundary element method
Authors: Camp C. V. , Gipson G. S. 
Published: October 2005

AbstractAn improved boundary element formulation (BEM) for two‐dimensional non‐homogeneous biharmonic analysis of rectilinear plates is presented. A boundary element formulation is developed from a coupled set of Poisson‐type boundary integral equations derived from the governing non‐homogeneous biharmonic equation. Emphasis is given to the development of exact expressions for the piecewise rectilinear boundary integration of the fundamental solution and its derivatives over several types of isoparametric elements. Incorporation of the explicit form of the integrations into the boundary element formulation improves the computational accuracy of the solution by substantially eliminating the error introduced by numerical quadrature, particularly those errors encountered near singularities. In addition, the single iterative nature of the exact calculations reduces the time necessary to compile the boundary system matrices and also provides a more rapid evaluation of internal point values than do formulations using regular numerical quadrature techniques. The evaluation of the domain integrations associated with biharmonic forms of the non‐homogeneous terms of the governing equation are transformed to an equivalent set of boundary integrals. Transformations of this type are introduced to avoid the difficulties of domain integration. The resulting set of boundary integrals describing the domain contribution is generally evaluated numerically; however, some exact expressions for several commonly encountered non‐homogeneous terms are used. Several numerical solutions of the deflection of rectilinear plates using the boundary element method (BEM) are presented and compared to existing numerical or exact solutions.
A finite element simulation of metal flow in moulds
Authors: Dhatt G. , Gao D. M. , Cheikh A. Ben 
Published: October 2005

AbstractNumerical tools for simulating the casting process are employed in an increasing manner by foundry engineers in order to understand and improve casting techniques. The correct simulation of metal flow and temperature profiles during filling is an important part of an overall numerical simulation kit which includes solidification and residual stress evaluations.In this study, we develop a two‐dimensional finite element model for studying metal flow and temperature fields during filling of mould cavities. A proper choice of turbulent/laminar model, correct tracking of metal free surface and evaluation of temperature to include metal‐air‐sand interaction are some of the essential features of the model.
Radiative ignition of fabrics and assemblies: Experiments and modelling
Authors: Durbetaki Pandeli , Tran Phuoc X. 
Published: October 2005

AbstractRadiative ignition studies wre carried out on vertical 2.54 cm circular fabric pairs, and single fabrics of 2.54 cm diameter and 15.2 × 15.2 cm. These fabrics were exposed to a time invariant radiative heat flux using the Large Ignition test Apparatus (LITA) and the Radiative Ignition Time Apparatus (RITA). A model has been developed which uses a quasi‐steady‐steady‐state approximation for the gas pahse. The transient effects and the thermal interaction between the plne‐parallel fabrics are accounted for through the variation of the fabric temperature with time. Ignition is considered to occur when the gas phase pyrolysate reaction rate is equal to the rate of pyrolysis. The predicted ignition times are compared with measured values and they show excellent agreement. Ignition times were found to depend strongly on heat flux, fabric size, interface spacing and oxygen concentration. IN the presence of a back fabric, the ignition time of the front fabrics decreases and this reduction is more pronounced at lower radiative heating intensities. Strong thermal interaction between the fabrics was also observed and it is expected that such interactions are responsible for the reduction of ignition time of the front fabric. No evidence of chemical interaciton has been observed.
Fixed grid techniques for phase change problems: A review
Authors: Voller V. R. , Swaminathan C. R. , Thomas B. G. 
Published: October 2005

AbstractThe aim of this paper is to categorize the major fixed grid formulations and solution methods for conduction controlled phase change problems. Using a two phase model of a solid/liquid phase change, the basic enthalpy equation is derived. Starting from this equation, a number of alternative formulations are obtained. All the formulations are reduced to a standard form. From this standard form, finite element and finite volume discretizations are developed. These discretizations are used as the basis for a number of fixed grid numerical solution techniques for solidification phase change systems. In particular, various apparent capacity and source based enthalpy methods are explored.
Application of the Trefftz method in plane elasticity problems
Authors: Jin W. G. , Cheung Y. K. , Zienkiewicz O. C. 
Published: October 2005

AbstractDirect and indirect approximations using sets of non‐singular, complete Trefftz functions, i.e. the complete systems of solutions, have been successfully applied to harmonic problems.1 In this paper, the procedure is applied to a more complex situation—plane elasticity problems.The examples show that the present method can avoid the difficulties relating to singular integration and has good accuracy compared with traditional boundary elements.
Viscous flow and transport with moving free and reactive surfaces
Authors: Murray Paul , Carey G. F. 
Published: October 2005

AbstractTransport of a chemical species through a viscous fluid with reaction at an interface is modelled by a quasi‐static process in which the transient behaviour is dominated by motion of the reactive surface. The reaction is accompanied by a molar volume change which leads to motion of the free surface. A decoupled stream function‐vorticity formulation is introduced in conjunction with a moving finite element method. This also permits convenient treatment of the free and reactive surface boundary conditions. The model is applied to the growth of oxide films on silicon surfaces and reveals the effect of surface curvature on film growth.
A numerical model for immiscible two‐phase fluid flow in a porous medium and its time domain solution
Authors: Li Xikui , Zienkiewicz O. C. , Xie Y. M. 
Published: October 2005

AbstractThe governing equations for the interaction of two immiscible fluids within a deforming porous medium are formulated on the basis of generalized Biot theory. The displacement of the solid skeleton, the pressure and saturation of wetting fluid are taken as primary unknowns of the model. The finite element method is applied to discretize the governing eqations in space. The time domain numerical solution to the coupled problem is achieved by using an unconditionally stable direct integration procedure. Examples are presented to illustrate the performance and capability of the approach.
Minimax multiobjective optimization in structural design
Authors: Tseng C. H. , Lu T. W. 
Published: October 2005

AbstractThe use of multiobjective optimization techniques, which may be regarded as a systematic sensitivity analysis, for the selection and modification of system parameters is presented. A minimax multiobjective optimization model for structural optimization is proposed. Three typical multiobjective optimization techniques—goal programming, compromise programming and the surrogate worth trade‐off method—are used to solve such a problem. The application of multiobjective optimization techniques to the selection of system parameters and large scale structural design optimization problems is the main purpose of this paper.
A study of heat transfer during flat rolling
Authors: Pietrzyk M. , Lenard J. G. 
Published: October 2005

AbstractTwo finite element thermal models of the flat rolling process are presented. The first gives a steady‐state convective‐diffusion solution in the centre plane and the other a non‐steady‐state solution in the plane perpendicular to the strip axis. To account for mechanical events the models use a rigid‐plastic finite element approach. The predictions of both models are compared with temperature measurements carried out in laboratory conditions during hot rolling of low carbon steel and cold rolling of aluminium. The models are also tested against temperature measurements in the seventh stand of a production type continuous hot strip mill. Conclusions are drawn regarding the adequacy of both two‐dimensional models for various kinds of flat rolling processes.
Adaptive FEM computation of forming processes—Application to porous and non‐porous materials
Authors: Zienkiewicz O. C. , Huang G. C. , Liu Y. C. 
Published: October 2005

AbstractThis paper presents the ‘flow formulation’ approach applicable to both compressible and incompressible forming analysis. Appropriate error estimates and adaptive remeshing schemes are described for updated co‐ordinate analysis. Several numerical examples are given. These are backward‐forward extrusion and thermally coupled extrusion of pore‐free materials, followed by cylinder upsetting, and tapered die extrusion of porous materials. The simulation of the deformation is shown as well as the distribution of effective strain and density at different time stages. The procedures are automatic and are incorporated in a general purpose code FEMMETA.
Finite element analysis of sheet metal forming problems using a selective viscous bending/membrane formulation
Authors: Oñate E. , de Saracibar C. Agelet 
Published: October 2005

AbstractIn this paper the possibilities of the viscous voided shell approach for deriving bending/membrane finite elements for sheet metal forming problems are presented. These elements can be selectively used for membrane or full bending analysis of some parts of the sheet according to the nature of the deformation. Numerical aspects of this approach are discussed and some examples of application are also given.
A numerical analysis of wrinkle formation tendencies in sheet metals
Authors: Neale K. W. , Tuǧcu P. 
Published: October 2005

AbstractA numerical analysis for the assessment of wrinkle formation tendencies in sheet metals is presented. A doubly‐curved thin shell element under biaxial plane stress states is considered, and the critical stress values for wrinkling are determined. The analysis is based on plastic bifurcation theory for the buckling of thin shells in short‐wavelength shallow modes. The effects of the various material and geometric parameters on wrinkling are investigated.
A new approach to the development of automatic quadrilateral mesh generation
Authors: Zhu J. Z. , Zienkiewicz O. C. , Hinton E. , Wu J. 
Published: October 2005

AbstractA methodology for the automatic mesh generation of quadrilateral elements is proposed. The methodology is based on the facts that (i) a region can always be subdivided entirely into quadrilaterals if the polygon which forms the boundary of the region has an even number of sides, (ii) a quadrilateral can be formed by two triangles which share a common side. By taking advantage of the techniques developed in an existing automatic triangular mesh generator, quadrilateral meshes can be generated according to the distribution of user specified element size over the domain of interest. In particular, an automatic quadrilateral mesh generator based on the advancing front technique for triangular mesh generation1 is described. Techniques to improve the quality of the generated quadrilateral meshes are introduced. The robustness and versatility of the mesh generator are demonstrated by a variety of examples.
Source field superposition analysis of two‐dimensional potential problems
Authors: Fenner R. T. 
Published: October 2005

AbstractThe source field superposition method for problems governed by Laplace's equation involves representing the potential field in a given solution domain as a superposition of fields generated by a number of sources. These sources are located outside the solution domain, and in the case of two‐dimensional singly‐connected finite domain problems can be uniformly distributed around the perimeter of a circle enclosing the physical domain. Some test problems are used to make detailed comparisons with the boundary element method. The results show that remarkable accuracy can be achieved, often to five or six significant figures, with very little computational effort relative to other numerical methods. In contrast to the boundary element method, however, geometric corners require no special treatment, and high aspect ratio of the solution domain is not a significant limitation.
An algorithm for three‐dimensional convection and diffusion with very different horizontal and vertical length scales
Authors: Lardner R. W. , Song Y. 
Published: October 2005

AbstractAn algorithm is developed and tested for the numerical solution of the three‐dimensional convection—diffusion equation appropriate for the marine environment, in which the horizontal and vertical scales differ by one or two orders of magnitude. The algorithm splits the horizontal and vertical parts of the process, treating the horizontal convection and diffusion explicitly and the vertical convection and diffusion by an implicit finite element method that is unconditionally stable. The overall stability conditions on the algorithm are discussed and its accuracy is verified through a number of test problems whose exact solutions are known.