bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat transfer in solid state laser systems: Applications of dynamic ADI methods
Authors: Gelinas R. J. , Doss S. K. , Murty S. S. , Trenholme J. B. 
Published: August 2005

AbstractThis article describes numerical modelling of heat transfer and thermoelasticity effects that are significant in thermo‐optical designs of solid state slab lasers capable of high average output power. The heat equation and equations of thermoelasticity are solved simultaneously to evaluate thermal stresses and microscopic deformations in isotropic and anisotropic laser host media. An efficient dynamic alternating‐direction implicit method has been developed and applied in this work to solve the steady state heat transfer and stress potential equations in two dimensions. Numerical results are presented for some problems that arise in baseline designs of experimental slab laser systems.
A global mapping method for improving the performance of quadratic elements
Authors: Nath B. , Potamitis S. G. 
Published: August 2005

AbstractA simple method is proposed in this paper for improving the performance (accuracy and convergence) of quadratic elements. In this the physical domain of the problem, as well as the constitutive relationships, are transformed globally by implementing a suitable co‐ordinate transformation, and the problem is then solved in the mapped (transformed) domain using finite elements of the mapped space following the processes of the conventional FEM.Results show that the method significantly improves the performance of quadratic elements in both two and three dimensions. The mathematical implications of mapping in this way indicate that the method can also be applied for improved performance to higher‐order elements if required.
An adaptive procedure for eigenvalue problems using the hierarchical finite element method
Authors: Friberg O. , Moller P. , Makovička D. , Wiberg N.‐E. 
Published: August 2005

AbstractAn adaptive procedure for the solution of the generalized linear eigenvalue problem within the hierarchical finite element method is described. The problem of finding for a given discretization, an upper limit eigenvalue that is accurate within a prescribed tolerance is especially studied. An error estimator is presented and a recomputational scheme for improved solutions is proposed. A numerical example is included.
Making curved interfaces straight in phase‐change problems
Authors: Storti Mario , Crivelli Luis A. , Idelsohn Sergio R. 
Published: August 2005

AbstractThis paper presents a method for straightening curved interfaces arising in phase‐change problems. The method works on isoparametric finite elements, performing a second transformation which maps the master element onto a new one in which the interface looks like a straight line. This allows using the current Gaussian integration technique for squares to evaluate the integrals over each phase. The method provides a better estimation of the contribution of latent heat effects to the residual vector, compared to those obtained by using the assumption that the interface is straight. Appropriate guidelines for solving the non‐linear system of equations arising in this kind of problem are also given. Several numerical examples are presented to show the performance of the method.
One‐dimensional calculations of two‐phase mixing flows
Authors: Thyagaraja A. , Fletcher D. F. , Cook I. 
Published: August 2005

AbstractA new algothm for the solution of two‐phase fluid flow problems is presented. The algorithm consisently ensures that the evolved volume fractions are all positive and sum to unity, even in the presence of large spatial and temporal gradients of volume fraction. The momentum equations are then solved using an iterative pressure correction method. Example calculations for buoyancy driven flows, with and without phase changes, are presented.
Mapped infinite elements in soil consolidation
Authors: Simoni L. , Schrefler B. A. 
Published: August 2005

AbstractThe problems of consolidation often involve unbounded continua. The most common solution is then achieved by limiting the studied area through the introduction, at finite distance, of a boundary on which adequate conditions on the field variables are imposed. In this paper mapped infinite elements are used to model the far‐field solution. Spatial discretization is hence performed on the basis of both finite and infinite elements. In two examples, solutions involving finite and infinite elements are compared with known analytical solutions and it is shown that an excellent agreement can be achieved by the use of mapped infinite elements.
Adaptive refinement for least‐squares finite elements with element‐by‐element conjugate gradient solution
Authors: Jiang B.‐N. , Carey G. F. 
Published: August 2005

AbstractAn error analysis and an adaptive refinement scheme are developed for use with a class of least‐squares finite element methods. The error indicators for the refinement procedure are based on element residuals which are calculated as part of the least‐squares method. The solution scheme used in the supporting numerical studies employs an elment‐by‐element conjugate gradient algorithm. Consequently, storage and computation are not influenced by nodal numbering.
A new efficient mixed formulation for thin shell finite element models
Authors: Rhiu J. J. , Lee S. W. 
Published: August 2005

AbstractA nine node shell element is developed by a new and more efficient mixed formulation. The new shell element formulation is based on the Hellinger–Reissner principle with independent strain and the concept of a degenerate solid shell. The new formulation is made more efficient in terms of computing time than the conventional mixed formulation by dividing the assumed strain fields into a lower order part and a higher order part. Numerical results demonstrate that the present nine node element is free of locking even for very thin plates and shells and is also kinematically stable. In fact the stiffness matrix associated with the higher order assumed strain plays the role of a stabilization matrix.
An improved discrete Kirchhoff quadrilateral thin‐plate bending element
Authors: Jeyachandrabose C. , Kirkhope J. , Meekisho L. 
Published: August 2005

AbstractBy combining discrete Kirchhoff theory with least‐squares smoothed shape functions, an improved quadrilateral thin‐plate bending element is derived. This element exhibits improved performance over an earlier DKQ element in predicting both displacements and stresses. Numerical examples are presented comparing the element with many other quadrilateral elements for standard test problems.
The front‐tracking scheme for the one‐dimensional freezing problem
Authors: Askar Hasan G. 
Published: August 2005

AbstractThe one‐dimensional freezing problem can be solved numerically for the temperature distribution accompanied by explicit reference to the position of the freezing front at each time interval. A new front‐tracking scheme provides accurate determination of the phase front, which is an essential requirement for the temperature distribution in the different phases of such problems. The front is made to coincide with a grid‐node throughout the analysis. The scheme uses a combination of the finite difference and the finite element methods for obtaining the solution of the freezing problems.
Substepping schemes for the numerical integration of elastoplastic stress–strain relations
Authors: Sloan S. W. 
Published: August 2005

AbstractThis paper describes two substepping schemes for integrating elastoplastic stress–strain relations. The schemes are designed for use in finite element plasticity calculations and solve for the stress increments assuming that the strain increments are known. Both methods are applicable to a general type of constitutive law and control the error in the integration process by adjusting the size of each substep automatically. The first method is based on the well‐known modified Euler scheme, whereas the second technique employs a high order Runge–Kutta formula. The procedures outlined do not require any form of stress correction to prevent drift from the yield surface. Their utility is illustrated by analysis of typical boundary value problems.
Triangular finite element for analysis of thick laminated plates
Authors: Chaudhuri Reaz A. , Seide Paul 
Published: August 2005

AbstractThe development of a general triangular C0 element, based on an assumed quadratic displacement potential energy approach, is presented for the analysis of arbitrarily laminated thick plates. The element formulation assumes transverse inextensibility and layerwise constant shear‐angle. Convergence of transverse displacement, moments and stresses, the effects of two different Gauss quadrature schemes and comparison of the present solutions with the available analytical/finite‐element results also form a part of the investigation. Furthermore, numerical results indicate close agreement between the LCST (layerwise constant shear‐angle theory) and the three‐dimensional elasticity theory with the length (or width) to thickness ratio as low as 4. Detailed comparison of the LCST‐based finite‐element solutions with those based on the CST (constant shear‐angle theory) and the CLT (classical lamination theory) clearly demonstrates the superiority of the former over the latter two, especially in the prediction of the distribution of the in‐plane displacements and stresses through the laminate thickness. This paper also introduces a new non‐dimensionalized parameter, Δθ*, which is shown to be a very useful measure for classification of the laminated plates and the suitability of different plate theories over various ranges of length‐to‐thickness ratio.
Numerical simulation of electrodeposition problems
Authors: Zamani N. G. , Chuang J. M. , Hsiung C. C. 
Published: August 2005

AbstractThe mathematical modelling of the electrodeposition phenomenon leads to a linear elliptic partial differential equation subject to non‐linear mixed boundary contitions. This is complicated further by the fact that the domain under consideration is evolving with time.Owing to the nature of the mathematical model, the boundary element method is a very efficient numerical technique for the solution of such problems. The authors report their numerical simulation of the above problem which also has applications in the cathodic protection systems for corrosion prevention.
A new approach for the hybrid element method
Authors: Chen Wanji , Cheung Y. K. 
Published: August 2005

AbstractA new functional which forms the basis of an improved hybrid element formulation is proposed. The variables for the functional include stresses, strains and displacements, and the displacements and stresses are further decomposed into two parts respectively. The proposed new formulation appears to be particularly suitable for improving conforming models.Based on this formulation, a new four‐node plane hybrid element Qcs6 can be developed, and the conforming element Q4 and the non‐conforming Wilson element Q and modified Wilson element Qm6 can also be derived directly by this hybrid approach. It should be noted that more accurate stresses can be obtained from this element which utilizes the concept of two stress components.
A theorem regarding the locking of tapered four‐noded membrane elements
Authors: Macneal Richard H. 
Published: August 2005

AbstractIt is shown that any four‐noded membrane element with two degrees of freedom per node will either lock in inplane bending or fail to pass a C0 patch test when the element's shape is an isosceles trapezoid. This result effectively closes out further effort to extend the linear strain capability of such elements beyond what has already been achieved for rectangular and parallelogram shapes.
An ‘upwind’ finite element method for electromagnetic field problems in moving media
Authors: Hahn Song‐Yop , Bigeon Jean , Sabonnadiere Jean‐Claude 
Published: August 2005

AbstractTime periodic finite element solutions for sinusoidally excited electromagnetic field problems in moving media are presented. Solutions by the Galerkin method contain spurious oscillations when the grid Peclet number is more than one. To suppress these osillations an upwind finite element method using two different time periodic test functions is introduced. One is multiplied to second and first order space derivative terms and the other to the time derivative term. Test functions are obtained from trial functions by adding or subtracting quadratic bias functions with appropriate scaling factors. Phase differences are considered between trial functions and bias functions. For simple interpretations of the phase differences complex scaling factors are used. The proposed method is developed to give nodally exact solutions for uniform grid spacing in one dimensional problems. Based on the one dimensional results a two dimensional upwinding scheme is also derived.
Composite mappings for planar mesh generation
Authors: Crawford R. H. , Waggenspack W. N. , Anderson D. C. , Bailey M. J. 
Published: August 2005

AbstractA new algorithm is presented for automatically grading meshes generated over planar triangular and quadrilateral regions using parametric mappings. Rational parametric bicubic Bézier polynomials are coupled with an element density function to concentrate elements around regions of high solution gradients.
Finite element simulation of long and short circular die extrusion experiments using integral models
Authors: Luo X.‐L. , Tanner R. I. 
Published: August 2005

AbstractA finite streamline element method for use with integral type constitutive equations in viscoelastic flow simulation, including thermal effects, is presented and some new results using this method in modelling the IUPAC extrusion experiments for low‐density polyethylene (LDPE), involving both long and short circular dies, are reported and discussed. It will be shown that the special streamline‐based elements provide a convenient way of particle tracking and strain tensor calculation. The extrusion calculation when using a relatively realistic KBKZ type integral model with multiple relaxation times is stable, and practically important Weissenberg numbers and swelling ratios have been reached without difficulty. The agreement with experimental swelling ratios is on the whole satisfactory. In order to make the model a good fit to the Trouton viscosity experimental data of the LDPE sample, a spectrum of elongational parameters has been introduced. The second normal stress term has also been added to the integral model to examine its effect on extrusion swelling. The non‐isothermal effects and the possibility of a wall slip near the die exit at high apparent shear rates are also discussed.
Analysis of stress and strain distributions in slab rolling using an elastic‐plastic finite‐element method
Authors: Liu C. , Hartley P. , Sturgess C. E. N. , Rowe G. W. 
Published: August 2005

AbstractThe cold rolling of rectangular section slabs is analysed for a range of width‐to‐height ratios (one to three) for which spread of the workpiece is appreciable. This necessitates the use of a three‐dimensional model. An elastic‐plastic finite‐element method is used to provide a complete description of the slab rolling process.The pressure distribution at the workpiece/roll interface is found to show the typical ‘friction‐hill’ observed in near‐plane‐strain experiments, but the pressure varies across the width of the interface. The shear‐stress distribution at the roll interface provides detailed information about the ‘neutral line’ which is usually assumed to occur where the shear stress changes direction. The 3‐D analysis shows clearly that there is a flow divide in both longitudinal and transverse directions.
Approximate methods for analysing the cold drawing of polymeric fibres and films
Authors: Neale K. W. , Tuḡcu P. 
Published: August 2005

AbstractApproximate methods for analysing steady‐state cold drawing processes in polymer forming are discussed. These methods are applied to both axisymmetric and plane‐strain drawing. The cold drawing process is associated with steady‐state neck propagation along the specimen. Modifications are introduced in the approximate steady‐state analysis which reflect the neck initiation and localization phases prior to steady‐state drawing. This is accomplished without resorting to an analysis of the entire load–deformation history of the process. Finite element results are also presented and compared with those of the proposed approximate analyses. These comparisons show the approximate analysis to be an extremely efficient and quite accurate computational scheme for the analysis of steady‐state cold drawing processes.
Analysis of bending effects in sheet forming operations
Authors: Wang Neng‐Ming , Tang Sing C. 
Published: August 2005

AbstractThe majority of work in numerical analyses of sheet metal forming operations is based on the simple membrane‐shell theory which neglects the effect of sheet bending. While useful information can be extracted from these analyses, especially for stretch‐dominated operations, the membrane theory is basically inadequate for analysing the draw‐type operations where sheet metal bends, slides and unbends over a draw radius.This paper presents axisymmetric and plane‐strain finite element analyses of stretch/draw of sheet metal over a die corner radius. Numerical solutions obtained from a total Lagrangian formulation of a finite‐strain thin shell theory are used to indicate the relative significance of including the bending effects in various simple forming operations. Comparisons of the calculated results with available experimental data are also given.
Thermal analysis of human body‐clothing‐environment system
Authors: Imre L. , Bitai A. , Horváth C. D. , Bánhidi L. , Pammer Z. 
Published: August 2005

AbstractFor the solution of thermal comfort problems a coupled model is presented consisting of the thermal model of the human body and of the clothing, with boundary conditions of the third kind.For thermal modelling the human body is divided into 16 parts according to the special character of the internal heat generation, of the blood vessel system and of the sweat secretion mechanism. Part models are connected by the flow paths of arteries and veins.Transport phenomena in the clothing are treated by a coupled heat and mass transfer model which permits various kinds of clothing for the different parts of the body.The equation system of the full model has been solved numerically by using time stepping schemes. As the results of the computations an approximative temperature field of the human body is produced.Calculated results have been compared with Experimental data.
A regular indirect boundary element method for thermal analysis
Authors: Wearing J. L. , Sheikh M. A. 
Published: August 2005

AbstractA Regular Indirect Boundary Element formulation is developed following a weighted residual approach. In this formulation, the fictitious source density, which appears in the integral equations of the method, is distributed on a surface which is exteriorly separated from the physical field boundary of the problem. This approach does not require the evaluation of singular integrals and produces undeteriorated solutions at geometric discontinuities. The formulation is presented here as applied to two dimensional and axisymmetric thermal problems. It includes a different subregioning scheme which treats each subregion, of a multidomain problem, separately, thereby eliminating the need for a sophisticated reduction scheme.
Solution accuracies of finite element reentry heat transfer and thermal stress analyses of space shuttle orbiter
Authors: Ko William L. 
Published: August 2005

AbstractAccuracies of solutions (structural temperatures and thermal stresses) obtained from different finite element thermal and structural models set up for the space shuttle orbiter are compared and discussed. For studying the effect of element size on the solution accuracies of finite element heat transfer and thermal stress analyses of the orbiter, five structural performance and resizing (SPAR) thermal models and five NASA structural analysis (NASTRAN) structural models were set up for the orbiter wing midspan bay 3. The structural temperature distribution over the wing skin (lower and upper) surface of one bay was dome shaped and induced more severe thermal stresses in the chordwise direction than in the spanwise direction. The induced thermal stresses were extremely sensitive to slight variation in structural temperature distributions. Both internal convention and internal radiation were found to have equal effects on the orbiter structural temperatures. Minimum degrees of element fineness required for thermal and structural models for the orbiter to yield satisfactory solutions were established. In transient heat transfer analysis most of the computation time was consumed in the time‐dependent temperature calculations and not in the radiation view‐factor computations.
Failure of mechanically loaded laminated composites subjected to intense localized heating
Authors: Gularte R. C. , Nemes J. A. , Stonesifer F. R. , Chang C. I. 
Published: August 2005

AbstractA numerical procedure is presented for predicting failure in laminated composites subjected to simultaneous intense localized heating and applied mechanical loads. The method consists of a non‐linear two‐dimensional, axisymmetric finite difference thermal analyser which considers the effects of surface ablation, radiation and convection losses and temperature dependent thermophysical properties. The thermal results are used in conjunction with a flat plate finite element code to predict the failure of laminated composites. Predictions based on the numerical analyses are compared with experimental results obtained from mechanically loaded graphite epoxy coupons spot‐irradiated at various intensities.
A comparative investigation on recurrence formulae in finite difference methods
Authors: Haberland Christoph , Lahrmann Andreas 
Published: August 2005

AbstractTo solve the transient heat‐conduction equation, the Pade‐approximation is introduced into the Finite Difference Method. But, if the time step is chosen too large relatively to the element size the Euler method (Pade (0,1) approximation) and the Crank–Nicolson solution (Pade (1,1)‐approximation) lead to significant oscillations. In contrast, the Full Implicit scheme (Pade (1,0)‐approximation) does not show this oscillatory behaviour, but is more inaccurate. Compared to these time stepping algorithms the presented Weighted Time Step method is seen to offer definite advantages.
Numerical simulation of forest fires
Authors: Richards Gwynfor D. 
Published: August 2005

AbstractThis paper reviews the work done to date on the numerical simulation of forest fires. A general model to predict forest fire spread under different conditions is presented and studied. The model is based on nth order reaction theory, and is sufficiently simple and flexible to conveniently deal with variations in wind velocity, forest properties, fire breaks and other phenomena of interest to the fire controller. The effects of changing various parameters in the equations are illustratd. Results for zero and constant wind velocity are given, together with the effect of abrupt wind changes and fire breaks.
Deformations and stresses in welding of shell structures
Authors: Lindgren Lars‐Erik , Karlsson Lennart 
Published: August 2005

AbstractThe simulation of welding of shell structures is investigated in this paper. In order to verify the implementation of the shell element adopted, two different problems were studied. In the first problem the butt‐welding of two plates was simulated. In the second problem the butt‐welding of a thin‐walled pipe was simulated. It is concluded from the analysis of the plate problem that the shell element is quite effective in the membrane state. The comparison between calculated values and experimental values for the residual stress field in the pipe shows that the shell element performs quite well in the analysis of a realistic problem.