bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of free surfaces in 3‐D with the arbitrary Lagrange–Euler method
Authors: Szabo Peter , Hassager Ole 
Published: August 2005

AbstractThe arbitrary Lagrange–Euler (ALE) kinematic description has been implemented in a 3‐D transient finite element program so as to simulate multiple fluid flows with surfaces and interfaces of general shapes.The description of fluid interfaces includes continuity of velocity and a discontinuous tangential and normal stress appropriate for fluids of variable interfacial tension.The formulation is particularly relevant to the description of low and intermediate Reynolds number flow dominated by interfacial tension.
An orthogonal residual procedure for non‐linear finite element equations
Authors: Krenk Steen 
Published: August 2005

AbstractA general and robust solution procedure for non‐linear finite element equations with limit points is developed. At each equilibrium iteration the magnitude of the load is adjusted such that the residual force is orthogonal to the current displacement increment from the last equilibrium state. The method implements the physical condition that the orthogonal residual force will neither increase nor decrease the magnitude of the current displacement increment vector. The orthogonality condition is formulated directly in terms of conjugate variables and therefore does not contain any scaling parameters. Passage of load and displacement limit points is discussed as well as the relation to line search, minimum residual, and are‐length methods. The method is illustrated by two examples.
Large strain constitutive modelling and computation for isotropic, creep elastoplastic damage solids
Authors: Li Xikui 
Published: August 2005

AbstractA three‐dimensional fully coupled creep elastoplastic damage model at finite strain for isotropic non‐linear material is developed. The model is based on the thermodynamics of an irreversible process and the internal state variable theory. A hyperelastic form of stress–strain constitutive relation in conjunction with the multiplicative decomposition of the deformation gradient into elastic and inelastic parts is employed. The pressure‐dependent plasticity with strain hardening and the damage model with two damage internal variables are particularly considered. The rounding of stress–strain curves appearing in cycling loading is reproduced by introduction of the creep mechanism into the model. A numerical integration procedure for the coupled constitutive equations with three hierarchical phases is proposed. A consistent tangent matrix with consideration of the fully coupled effects at finite strain is derived. Numerical examples are tested to demonstrate the capability and performance of the present model at large strain.
A numerical study of mechanisms of accretion for rotating snow sleeves evolving on conductor rods
Authors: Poots G. , Skelton P. L. I. 
Published: August 2005

AbstractIt is the purpose of this paper to construct a mathematical/computational model for the accretion of snow on rotating snow sleeves attached to conductor rods, and to consider some of the limitations in the use of the assumption of perfect cylindrical‐sleeve growth, as currently employed to provide estimates of snow‐loading intensity.For purposes of illustration, three rotating snow accretion regimes are considered, in which the direction of the airflow is always taken as perpendicular to the axis of the conductor rod. Firstly, a horizontal conductor rod is free to rotate and is initially bare. Rotation of the system (conductor rod and accreted snow) is initiated by snow torque, due to eccentric snow loading on the windward side of the conductor, and is driven by aerodynamic torque generated by the windflow past the evolving, rotating, asymmetrical sleeve growth. Secondly, a vertical conductor rod is free to rotate and the bare rod is given an initial small angular velocity; the rotation of the accreting system is then driven by aerodynamic torque alone. Thirdly, a horizontal rod is fixed and is initially covered by an annulus of snow, supported by a thin layer of (unfrozen) water existing between the conductor and the snow sleeve. In this case, the rotation of the snow sleeve is due to the combined snow and aerodynamic torques and is now retarded by the viscous torque due to the rotating thin film of water.Asymptotic solutions obtained for small accretion time supplement numerical results derived from the computational models. Numerical results on these rotating non‐periodic snow accretion regimes are presented as a function of the wind speed, snow precipitation rate and diameter of the conductor rod.
Three‐dimensional parallel unstructured grid generation
Authors: Shostko Alexander , Löhner Rainald 
Published: August 2005

AbstractAn algorithm for the parallel generation of 3‐D unstructured grids is presented. The technique is an extension of the algorithm presented in Reference 21 for the 2‐D case. The method uses a background grid as the means to separate spatially different regions, enabling the concurrent, parallel generation of elements in different domains and interdomain regions. The parallel 3‐D grid generator was implemented and tested on the INTEL hypercube and Touchstone Delta parallel computers. The results obtained demonstrate the effectiveness of the algorithm developed. The methodology is applicable to the parallel implementation of a wide range of problems that are, in principle, scalar by nature, and do not lend themselves to SIMD parallelization.
Mesh partitioning for implicit computations via iterative domain decomposition: Impact and optimization of the subdomain aspect ratio
Authors: Farhat Charbel , Maman Nathan , Brown Gregory W. 
Published: August 2005

AbstractOptimal domain decomposition methods have emerged as powerful iterative algorithms for parallel implicit computations. Their key preprocessing step is mesh partitioning, where research has focused so far on the automatic generation of load‐balanced subdomains with minimum interface nodes. In this paper, we emphasize the importance of the subdomain aspect ratio as a mesh partitioning factor, and highlight its impact on the convergence rate of an optimal domain decomposition based iterative method. We also present a fast optimization algorithm for improving the aspect ratio of existing mesh partitions, and illustrate it with several examples from fluid dynamics and structural mechanics applications. For a stiffened shell problem decomposed by the optimal Recursive Spectral Bisection scheme and solved by the FETI method, this optimization algorithm is shown to improve the solution time by a factor equal to 1·54 and to restore numerical scalability.
Moving asymptotes and active set strategy for constrained optimization design in magnetostatic problems
Authors: Mahey P. , Saldanha R. R. , Coulomb J. L. 
Published: August 2005

AbstractIn this paper, we present an improvement of the optimization technique of the moving asymptotes applied to a class of magnetostatic design problem. Our approach includes, among other aspects, an active set strategy which turns possible to find feasible points during the iterative process. We present some numerical results obtained on real‐life case studies where the functions are computed by a complex finite‐element routine.
A parallelized Lattice‐Gas solver for transient Navier–Stokes‐flow: Implementation and simulation results
Authors: Krafczyk M. , Rank E. 
Published: August 2005

AbstractThe last decade has seen the development of Lattice‐Gas (LG) schemes as a complementary if not alternative method for the simulation of moderate Reynolds‐Number Navier–Stokes flow. After a short theoretical introduction we present a detailed discussion of implementation features for a specific 2D‐LG algorithm, which runs in parallel on a workstation‐cluster, discuss simulation results and compare one of them to experimental studies. Finally, we attempt to point out present problems and perspectives of these methods.
Assumed strain formulation for the four‐node quadrilateral with improved in‐plane bending behaviour
Authors: Stolarski Henryk K. , Chen Yung‐I 
Published: August 2005

AbstractA new assumed strain quadrilateral element with highly accurate in‐plane bending behaviour is presented for plane stress and plane strain analysis. The basic idea of the formulation consists in identification of various modes of deformation and then in proper modification of the strain field in some of these modes. In particular, the strain operator corresponding to the in‐plane bending modes is modified to simulate the strain field resulting from the assumptions usually made in structural mechanics. The modification of the strain field leads to the assumed strain operator on the element level. As a result, the so‐called shear and membrane locking phenomena are alleviated. The element exhibits remarkable success in bending‐ dominated problems even when severely distorted and high aspect ratio meshes are used. Another advantage of the present assumed strain element is that locking for nearly incompressible materials is also mitigated. While this assumed strain element passes the patch test only for the parallelogram shapes, the element provides convergent solutions as long as the initially general form of the element approaches a parallelogram shape with the refinement of the mesh.
Embedded representation of fracture in concrete with mixed finite elements
Authors: Lotfi Hamid R. , Shing P. Benson 
Published: August 2005

AbstractAs an alternative to the smeared and discrete crack representations, an embedded representation of fracture for finite element analysis of concrete structures is presented. The three‐field Hu–Washizu variational statement is extended to bodies with internal discontinuities. The extended variational statement is then utilized for formulating elements with a discontinuous displacement field. The new elements are capable of modelling different deformation modes of an internal discontinuity at the element level. The satisfactory performance of the embedded crack representation is verified by several case studies on concrete fracture.
High performance computational kernels for selected segments of a p finite element code
Authors: Barragy E. , Van De Geijn R. 
Published: August 2005

AbstractA high performance implementation is presented for three kernel routines commonly found in element‐byelement preconditioned conjugate gradient finite element codes. These routines include forming the element stiffness matrices and loading vectors, or in the case of a non‐linear problem, element residual vectors; and routines for applying element matrix–vector products. The present study considers tensor product elements of arbitrary mapping in 2‐D, although the generalization to triangular elements and serendipity elements is straightforward. The implementation presented is most appropriate for high p type finite element methods, where the element matrices are relatively large and dense. This results in a set of high performance kernels for superscalar architectures, which otherwise may be memory bandwidth limited. Performance studies are presented for a representative superscalar microprocessor, the Intel i860. As these types of microprocessors are at the heart of modern workstations as well as several parallel supercomputing systems, this work is relevant across a variety of platforms. The resulting kernels yield both high performance on a variety of sequential architectures as well as a high degree of code portability through the basic linear algebra subprograms mechanism.
Stable and time‐dissipative finite element methods for the incompressible Navier–Stokes equations in advection dominated flows
Authors: Simo J. C. , Armero F. , Taylor C. A. 
Published: August 2005

AbstractThis paper examines a new Galerkin method with scaled bubble functions which replicates the exact artificial diffusion methods in the case of 1‐D scalar advection–diffusion and that leads to non‐oscillatory solutions as the streamline upwinding algorithms for 2‐D scalar advection–diffusion and incompressible Navier–Stokes. This method retains the satisfaction of the Babuska–Brezzi condition and, thus, leads to optimal performance in the incompressible limit. This method, when, combined with the recently proposed linear unconditionally stable algorithms of Simo and Armero (1993), yields a method for solution of the incompressible Navier–Stokes equations ideal for either diffusive or advection‐dominated flows. Examples from scalar advection–diffusion and the solution of the incompressible Navier–Stokes equations are presented.
Out‐of‐core solver for large, multi‐zone boundary element matrices
Authors: Rigby R. H. , Aliabadi M. H. 
Published: August 2005

AbstractIn this paper an out‐of‐core solver is developed for a three‐dimensional elastostatic boundary element program. This program includes multi‐regions which enables a large model to be divided into a number of homogeneous sub‐models, each with their own material properties. The system matrix produced by multi‐regions is sparse, blocked and unsymmetric in character and so reduces disc space and solution time. The solver presented in this paper utilizes efficiently the structure of this matrix by holding only non‐zero parts of this matrix in a sequential, unformatted direct access file, reading in as much of the file as possible into the working space, performing Gauss elimination, then writing part of the matrix back to file. The maximum utilization of working space is particularly important on vector machines as vector activity is maximized whilst record read/write is minimized. The effect of multi‐regions on CPU is demonstrated on both the CONVEX and CRAY machines.
Reproducing kernel particle methods for structural dynamics
Authors: Liu Wing Kam , Jun Sukky , Li Shaofan , Adee Jonathan , Belytschko Ted 
Published: August 2005

AbstractThis paper explores a Reproducing Kernel Particle Method (RKPM) which incorporates several attractive features. The emphasis is away from classical mesh generated elements in favour of a mesh free system which only requires a set of nodes or particles in space. Using a Gaussian function or a cubic spline function, flexible window functions are implemented to provide refinement in the solution process. It also creates the ability to analyse a specific frequency range in dynamic problems reducing the computer time required. This advantage is achieved through an increase in the critical time step when the frequency range is low and a large window is used. The stability of the window function as well as the critical time step formula are investigated to provide insight into RKPMs. The predictions of the theories are confirmed through numerical experiments by performing reconstructions of given functions and solving elastic and elastic–plastic one‐dimensional (1‐D) bar problems for both small and large deformation as well as three 2‐D large deformation non‐linear elastic problems. Numerical and theoretical results show the proposed reproducing kernel interpolation functions satisfy the consistency conditions and the critical time step prediction; furthermore, the RKPM provides better stability than Smooth Particle Hydrodynamics (SPH) methods. In contrast with what has been reported in SPH literature, we do not find any tensile instability with RKPMs.
Asymptotic post‐buckling analysis of rectangular plates by HC finite elements
Authors: Lanzo Antonio D. , Garcea Giovanni , Casciaro Raffaele 
Published: August 2005

AbstractThe present paper extends the finite element perturbation approach already presented for pin‐jointed and framed structures15 to rectangular thin plates. Koiter's asymptotic strategy2 is coupled with a High‐Continuity finite element discretization of the plate.22 The consistency of the discrete model is discussed from the kinematical and numerical points of view and several numerical tests are reported. It appears that use of the HC elements makes the perturbation algorithm insensitive to the locking phenomenon occurring in the evaluation of the postbuckling behaviour. It also allows the use of very fine discretization meshes at low computational cost.
Analysis of symmetric domains in advanced applications with the boundary element method
Authors: Kaljević Igor , Saigal Sunil 
Published: August 2005

AbstractThe strategy in the boundary element method for the analysis of symmetric domains that does not require the modelling of contours corresponding to the axes of symmetry is investigated for a number of advanced applications. These applications include: treatment of domain loadings, two‐dimensional time domain transient elastodynamics, and the analysis of probabilistic problems in elastostatics with a random geometric configuration. Both symmetric as well as arbitrary loadings acting on the symmetric objects are considered. A number of case studies are presented to provide comparisons of computer memory and CPU time requirements for the analyses of the entire object versus the analyses of only the symmetric portion of the object. The numerical data presented clearly demonstrates the advantages of developing efficient symmetric formulations for advanced applications.
Singular boundary elements for the analysis of cracks in plane strain
Authors: Watson J. O. 
Published: August 2005

AbstractStraight and curved cracks are modelled by direct formulation boundary elements, of geometry defined by Hermitian cubic shape functions. Displacement and traction are interpolated by the Hermitian functions, supplemented by singular functions which multiply stress intensity factors corresponding to the dominant modes of crack opening in which displacement is proportional to the square root of distance r from the crack tip, and subdominant modes in which it is proportional to r1·5. The singular functions extend over many boundary elements on each crack face.A nodal collocation scheme is used, in which additional boundary integral equations are obtained by differentiation of the equation obtained from Betti's theorem. The hypersingular kernels of the equations so derived are integrated by consideration of trial displacement fields of subdomains lying to either side of the crack. Examples are shown of the analysis of buried and edge cracks, to demonstrate the effects of modelling subdominant modes and extending singular shape functions over many elements.
A conforming quadrilateral plate bending element revisited
Authors: Liu Ine‐Wei 
Published: August 2005

AbstractA new formulation of a 16‐degree‐of‐freedom conforming quadrilateral plate bending element using the Cartesian co‐ordinates is presented. The displacement function w is taken as a slight modification of bicubic polynomial in the Cartesian co‐ordinates. Use of this expression in the construction of finite element representations is expected to be useful specially for microcomputers. The simple stiffness matrix subroutine, coded in FORTRAN 77, for the general quadrilateral plate bending element is listed in the Appendix.
Wave envelope examples for progressive waves
Authors: Bettess Peter , Chadwick Edmund 
Published: August 2005

AbstractThe wave envelope method, due to Astley,1 is applied to some simple propagating wave problems governed by the Helmholtz equation and similar equations. It is shown that the method yields solutions which for some of the problems are exact and for the others are approximate and complex. In these cases however, when the number of elements is increased the trial function becomes a better approximation.
A plasticity model and algorithm for mode‐I cracking in concrete
Authors: Feenstra Peter H. , De Borst René 
Published: August 2005

AbstractA class of plasticity models which utilize Rankine's (principal stress) yield locus is formulated to simulate cracking in concrete and rock under monotonic loading conditions. The formulation encompasses isotropic and kinematic hardening/softening rules, and incremental (flow theory) as well as total (deformation theory) formats are considered. An Euler backward algorithm is used to integrate the stresses and internal variables over a finite loading step and an explicit expression is derived for a consistently linearized tangent stiffness matrix associated with the Euler backward scheme. Particular attention is paid to the corner regime, that is when the two major principal stresses become equal. A detailed comparison has been made of the proposed plasticity‐based crack formulations and the traditional fixed and rotating smeared‐crack models for a homogeneously stressed sample under a non‐proportional loading path. A comparison between the flow‐theory‐based plasticity crack models and experimental data has been made for a Single Edge Notched plain concrete specimen under mixed‐mode loading conditions.
Numerical methods for evaluation of service life of gear
Authors: Abers̆ek B. , Flas̆ker J. 
Published: August 2005

AbstractThe service life of mechanical parts, of which the gears are most important, is influenced to the greatest extent by defects occurring as cracks. In case of cracks the most important stage is the initiation and propagation of short fatigue cracks; further, the propagation of these crack up to their critical and/or permissible length also must be taken into account. As these are quite different areas we have introduced into calculations a completely new factor, i.e. the gear stress intensity factor Z. On the basis of the factor Z we have developed appropriate models, e.g. the programe STATFAG which ensures calculation of the service life of gears with and without cracks.
Automatic three‐dimensional finite element mesh generation via modified ray casting
Authors: Yeker Cengiz , Zeid Ibrahim 
Published: August 2005

AbstractThree‐dimensional (3‐D) finite element mesh generation has been the target of automation due to the complexities associated with generating and visualizing the mesh. A fully automatic 3‐D mesh generation method is developed. The method is capable of meshing CSG solid models. It is based on modifying the classical ray‐casting technique to meet the requirements of mesh generation. The modifications include the utilization of the element size in the casting process, the utilization of 3‐D space box enclosures, and the casting of ray segments (rays with finite length). The method begins by casting ray segments into the solid. Based on the intersections between the segments and the solid boundary, the solid is discretized into cells arranged in a structure. The cell structure stores neighbourhood relations between its cells. Each cell is meshed with valid finite elements. Mesh continuity between cells is achieved via the neighbourhood relations. The last step is to process the boundary elements to represent closely the boundary. The method has been tested and applied to a number of solid models. Sample examples are presented.
A novel finite element formulation for frictionless contact problems
Authors: Papadopoulos Panayiotis , Jones Reese E. , Solberg Jerome M. 
Published: August 2005

AbstractThis article advocates a new methodology for the finite element solution of contact problems involving bodies that may undergo finite motions and deformations. The analysis is based on a decomposition of the two‐body contact problem into two simultaneous sub‐problems, and results naturally in geometrically unbiased discretization of the contacting surfaces. A proposed two‐dimensional contact element is specifically designed to unconditionally allow for exact transmission of constant normal traction through interacting surfaces.
A linear programming formulation for incremental contact analysis
Authors: Šimunović Srdan , Saigal Sunil 
Published: August 2005

AbstractA novel algorithm for the analysis of contact problems in elasticity has been presented in this paper. The algorithm is based on the boundary element method and a direct approximation of the contact complementarity conditions using linear programming. An incremental loading scheme has been developed to ensure an accurate approximation of the deformation path that the object experiences during the process of contact. Several numerical examples have been analysed to illustrate the validity of the proposed formulations.