bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of the move limits for the sequential linear programming method
Authors: Chen Ting‐Yu 
Published: August 2005

AbstractThe sequential linear programming (SLP) method is one of the easiest optimization techniques used to treat non‐linear optimization problems. The successful application of the method is based on the proper choice of the move limits, which are unfortunately uncertain in the SLP algorithm. To enhance the efficiency and reliability of the SLP algorithm, six methods are proposed to calculate the move limits. The first three methods use the constraint equations to compute the minimum variations needed from the current design point to reach the constraint boundaries. The fourth method incorporates the cost function information as well as the constraints to figure out the move limits. The last two methods form a quadratic programming (QP) subproblem and solve for the change of the quadratic cost function. The move limits used in SLP are then computed from the estimated change of the linear cost function from the QP solution. Four numerical examples are employed to demonstrate the solution process by the methods proposed. The advantages and disadvantages of these methods are discussed.
A non‐recursive Lagrangian solution of the non‐causal inverse dynamics of flexible multibody systems: The planar case
Authors: Ledesma Ragnar , Bayo Eduardo 
Published: August 2005

AbstractA technique is presented for solving the inverse dynamics of flexible planar multibody systems. This technique yields the non‐causal joint efforts (inverse dynamics) as well as the internal states (inverse kinematics) that produce a prescribed nominal trajectory of the end effector. A non‐recursive Lagrangian approach is used in formulating the equations of motion as well as in solving the inverse dynamics equations. Contrary to the recursive method previously presented, the proposed method solves the inverse problem in a systematic and direct manner for both open‐chain as well as closed‐chain configurations. Numerical simulation shows that the proposed procedure provides an excellent tracking of the desired end effector trajectory.
Adaptive and hierarchical modelling of fatigue crack propagation
Authors: Fish Jacob , Nath Aditya 
Published: August 2005

AbstractA methodology is developed to simulate adaptively and hierarchically fatigue crack growth in structural components. Cracks are modelled, by overlaying portions of the finite element mesh free of cracks with a discontinuous finite element field containing unconstrained double nodes along the discontinuity. Crack propagation is simulated by advancing the crack front in the superimposed mesh only keeping the underlying mesh fixed. Adaptivity in time and space domain together with the hierarchical nature of the method ensure both economical and reliable simulation of crack propagation. Numerical results of fatigue crack growth in the attachment lug were found to be, in good agreement with the experimental data.
A parallel row‐oriented sparse solution method for finite element structural analysis
Authors: Law Kincho H. , Mackay David R. 
Published: August 2005

AbstractThis paper describes a parallel implementation of LDLT factorization on a distributed‐memory parallel computer. Specifically, the parallel LDLT factorization procedure is based on a row‐oriented sparse storage scheme. In addition, a strategy is proposed for the parallel solution of a triangular system of equations. The strategy is to compute the inverses of the dense principal diagonal block submatrices of the factor L, stored in a row‐oriented structure. Experimental results for a number of finite element models are presented to illustrate the effectiveness of the parallel solution schemes.
Non‐linear co‐ordinate transformation of finite part integrals in two‐dimensional boundary element analysis
Authors: Hildenbrand J. , Kuhn G. 
Published: August 2005

AbstractThis paper describes a method for the numerical computation of hypersingular integrals as they appear in the boundary element analysis. The proposed method is based on the finite part concept and allows for arbitrary curved boundary elements. Owing to the unknown transformation properties of finite part integrals undergoing a non‐linear co‐ordinate transformation, the definition formula of finite part integrals is applied prior to the transformation into the usual element co‐ordinate system. The resulting integrals are regular and may be evaluated by standard Gaussian quadrature rules. The method is described in detail for the boundary integrals of two‐dimensional linear elastostatics. Numerical examples are inclcded for this type of problem, but the method may easily be adapted to other two‐dimensional problems.
Crack length measurements with a potential drop method: A finite element simulation
Authors: Ke Y. , Ståhle P. 
Published: August 2005

AbstractA potential drop method, as used for estimations of crack lengths during three‐point‐beind experiments, is studied. The mechanical state is calculated using a finite element method. The deformed body obtained is used for a subsequent calculation of the electrostatic state. Calculations are performed for both two‐ and three‐dimensional models. The material is assumed to be elastic, linearly hardening plastic and electrostatically linear. Large deformations are considered. Further, the non‐linearity caused by the load, depending on the contact area between the cylinder on which the load is applied and the specimen, is considered. The increased contact area did not influence the mechanical state very much but had a direct impact on the electrostatic state. The changes in the potential drop recordings due to deformation and electrical current passing through the load cylinder were shown to be considerable. The study explains, at least partly, the experimental observations. A more reliable registration of crack growth initiation is the main outcome of the analysis.
Some useful renumbering strategies for unstructured grids
Authors: Löhner Rainald 
Published: August 2005

AbstractSeveral renumbering strategies for unstructured grids are discussed. They lead to a minimization of eache‐misses and an optimal grouping of elements for different computer platforms, from superscalar workstations to multiprocessor register‐to‐register vector machines. Timings for a typical computational fluid dynamics (CFD) code that employs these renumbering strategies indicate that CPU requirements may be halved by applying them. The renumbering strategies discussed are all of linear time complexity, making them ideally suited for applications requiring frequent mesh changes. Furthermore, these renumbering strategies are not only valid for element‐based codes but carry over to edge‐based or face‐based field solvers.
Numerical design of thin‐walled structural members on account of their strength
Authors: Kalamkarov Alexander L. , Kolpakov Alexander G. 
Published: August 2005

AbstractThe numerical design and optimization problems for the reinforced thin‐walled structural members on account of a local strength criterion are considered. Two types of the elements of construction are analysed in detail: wafer plates and honeycomb‐like shells. The optimal design concerns the following factors: the values of the effective stiffness moduli; the minimization of the weight; the ability to sustain the required ultimate strains. The computations are based on the application of the general homogenized shell model. The effective computational algorithm for a global minimum search for the function of several variables under the restrictions and the computer software are developed and applied. The asymptotically correct results for the effective stiffness moduli and the local stress distributions, which are available in the framework of the general homogenized shell model, ensure that the gain of optimization will not be overlapped by modelling errors. The effectiveness and advantages of the developed approach is illustrated by several numerical examples. The optimal design computational algorithm is extended to the case of fatigue failure analysis.
Pathologies associated with the numerical analysis of hyper‐anisotropic materials
Authors: šimáček Pavel , Kaliakin Victor N. , Pipes R. Byron 
Published: August 2005

AbstractThe rise in popularity of composite materials has brought to light the necessity of analysing materials exhibiting the kinematic constraint of directional inextensibility. Numerical phenomena associated with the analysis of such hyperanisotropic materials are described herein. The phenomena include: element locking dependent on fibre orientation, spurious tension modes and difficulties associated with elements possessing large material parameter ratios. To facilitate the present description, these phenomena are compared to, and contrasted with the well‐documented problems associated with the analysis of incompressible or nearly incompressible media. Based on the results of eigenvalue analyses, elements satisfying the Babuška‐Brezzi condition for incompressible media are found to perform rather poorly when analysing hyperanisotropic materials. These findings are supported by the results of a simple example.
Effects of element distortions on the performance of isoparametric elements
Authors: Lee Nam‐Sua , Bathe Klaus‐Jurgen 
Published: August 2005

AbstractWe discuss the effects of element distortions on the performance of displacement‐based isoparametric quadrilateral finite elements. Suitable example problems for both the Lagrangian and the serendipity types of elements are used to show numerically the effects of element distortions. The effects of angular and curved‐edge distortions are evaluated analytically in terms of the abilities of the elements to represent exactly various polynomial displacement fields. We then solve a plane stress problem adaptively to demonstrate the effect of element distortions on the accuracy of the stress distribution. The conclusion is that the Lagrangian elements are not affected by angular distortions and are therefore the more reliable elements for general use.
An efficient numerical method for modelling initiation and propagation of cracks along material interfaces
Authors: Beer G. 
Published: August 2005

AbstractA numerical method, based on the multiregion concept in the boundary element method, is presented for modelling crack propagation. The advantage of the method is that the non‐linear iterations only involve interface degrees of freedom and that the propagation of cracks is modelled by disconnecting degrees of freedom and no remeshing is necessary.
p‐version least‐squares finite element formulation of Burgers' equation
Authors: Winterscheidt Daniel , Surana Karan S. 
Published: August 2005

AbstractA p‐version least‐squares finite element formulation for non‐linear problems is presented and applied to the steady‐state, one‐dimensional Burgers' equation. The second‐order equation is recast as a set of first‐order equations which permit the use of C0 elements. The primary and auxiliary variables are approximated using equal‐order p‐version hierarchical approximation functions. The system of non‐linear simultaneous algebraic equations resulting from the least‐squares process is solved using Newton's method with a line search. The use of ‘exact’ and ‘reduced’ quadrature rules is investigated and the results are compared. The formulation is found to produce excellent results when the ‘exact’ integration rule is used. The combination of least‐squares finite element formulation and p‐version works extremely well for Burgers' equation and appears to have great potential in fluid dynamics problems.
Higher‐order MITC general shell elements
Authors: Bucalem Miguel Luiz , Bathe Klaus‐Jüen 
Published: August 2005

AbstractTwo mixed‐interpolated general shell finite elements for non‐linear analysis‐a 9‐node element and a 16‐node element‐are presented. The elements are based on the Mixed Interpolation of Tensorial Components (MITC) approach in which the covariant strain component fields for the in‐plane and shear actions are interpolated and tied to the also interpolated displacement field. Both the 9‐node element, referred to as the MITC9 element, and the 16‐node element, referred to as the MITC16 element, are tested numerically and found to have high predictive capabilities.
Flow past a cylinder with and without an appurtenance
Authors: Tamaddon‐Jahromi H. R. , Townsend P. , Webster M. F. 
Published: August 2005

AbstractThis paper constitutes a numerical study of flow around a cylinder for cases with and without an appurtenance, and throughout a range of Reynolds numbers. This is achieved by solving the two‐dimensional evolutionary Navier‐Stokes equations using a pressure‐velocity finite element method. The particular form of scheme employed is a combination of Taylor‐Galerkin and pressure‐correction methods. This scheme delivers second‐order accuracy in time and introduces three fractional stages within each time‐step. One of the practical applications of this work is the prediction of flows around gas and oil platforms at sea, and of concern to off‐shore engineers are the effects of adding a sacrificial anode to the cylindrical legs of a platform. Such an appurtenance added to the basic cylindrical shape induces different drag forces on the legs depending on the angle of attack of the motion of the sea relative to the appurtenance location. Unidirectional and oscillatory flow solutions are reported, concentrating on flow patterns and forces experienced on the body surface, and the vortex shedding process.
Modelling edge effects with the C0 plate bending elements: Part 2. The performance of the reformulated four‐node element
Authors: Briassoulis D. 
Published: August 2005

AbstractThe reformulated four‐node element has exhibited an excellent behaviour in static finite element analyses being free of shear and machine locking problems and of zero energy modes and modelling accurately relatively thick plates. In the present paper, the element under consideration is shown to exhibit an analogous excellent performance in modelling highly demanding boundary layer plate bending problems.
Application of the hybrid zone/Monte Carlo method to 3‐D curvilinear grids in radiative heat transfer
Authors: Haidekker A. , Charette A. , Kocaefe Y. S. 
Published: August 2005

AbstractThe zone method is applied to non‐orthogonal curvilinear grids for the computation of radiative heat transfer. The interchange areas are calculated by the Monte Carlo technique which has been fitted with a generalized ray tracing procedure. The method is applied to two complex three‐dimensional (3‐D) cases where in homogeneities are present in the radiation space (non‐uniform gas properties and/or shadowing effects), and the gas is taken as gray. For comparison purposes, the same examples are worked out with the discrete transfer method. Very small discrepancies are found between the two methods for the surface heat fluxes, but the gas volumetric radiative sources are much more sensitive to inhomogeneities in the gas phase, resulting in higher discrepancies for these terms. The method can be readily extended to incorporate real gases and scattering effects.
Generalized mixed finite element model for pre‐ and post‐quasistatic buckling response of thin‐walled framed structures
Authors: Gendy A. S. , Saleeb A. F. 
Published: August 2005

AbstractAdopting an updated Lagrangian approach, the general framework for the fully non‐linear analysis of thin‐walled framed structures is developed using a simple, two‐node, C0‐model (HMB2). The governing equations are derived based on a consistent linearization of an incremental mixed variational principle of modified Hellinger/Reissner type with independent assumptions for displacement and strain fields. All coupled significant modes of deformations, i.e. stretching, bending, shear, torsion and warping, are accounted for in the generalized‐beam theory employed. Emphasis is placed on devising effective solution procedures to deal with finite rotations in space, particularly with regard to their effect on the derivations of load‐correction matrices corresponding to configuration‐dependent externally applied forces/moments. The effectiveness and practical usefulness of present model are demonstrated through a number of test problems involving beam assemblages undergoing large displacements and rotations in space.
Dynamic analysis of structures with unilateral constraints: Numerical integration and reduction of structural equations
Authors: Barauskas Rimantas 
Published: August 2005

AbstractStructural dynamic equations with unilateral constraints upon the displacements, velocities and accelerations are employed in order to represent vibrating elastic structures with normal, oblique impact and friction interaction points.For obtaining a numerical integration scheme the Lagrange multipliers and a minimum work approach are employed at each time step. The algorithm is presented as an extension of the generalized Newmark scheme. It seems to retain the asymptotic features of the original one.The reduction of the number of dynamic degrees of freedom of the unilaterally constrained structures is carried out by representing the equations of motion in modal co‐ordinates of the unconstrained structure and truncating the dynamic contributions of higher modes.The presented techniques have been verified by investigating free longitudinal vibroimpact motion laws of an elastic vibroconverter and free longitudinal and bending vibration of a vibroconverter interacting with a moving rigid body by oblique impact and friction forces.
Numerical flow modelling in a locally refined grid
Authors: De Lange H. C. , De Goey L. P. H. 
Published: August 2005

AbstractAn algorithm is presented to model two‐dimensional, non‐isothermal, low Mach number flows with a local steep density gradient. The algorithm uses an adaptive, locally refined, non‐staggered grid and has been developed, especially for modelling laminar flames. The governing equations, based on a stream‐function–vorticity formulation, are presented and discretized using hybrid finite differences. A (isothermal) test problem is presented to compare the accuracy of the results of the solver presented in this paper, with the results of algorithms found in the literature. However, this test problem proves to be not well suited for the application of a locally refined grid, since it does not contain a local steep gradient. For this reason an additional test problem is constructed that clearly shows the advantages of the locally refined grid as compared to a uniform grid with respect to both the calculation time as well as the number of grid nodes needed. Furthermore, a laminar premixed flame is modelled with simple chemistry to show that the algorithm, presented in this paper, converges to a stabilized flame when an adaptive grid technique is used.
Analysis of sheet metal forming operations by a stress resultant constitutive law
Authors: Chou C. H. , Pan J. , Tang S. C. 
Published: August 2005

AbstractSheet metal forming is simulated by finite element methods using a stress resultant constitutive law in this paper. A Lagrangian description of axisymmetric and plane‐strain shell deformation is first reviewed. Then a stress resultant constitutive law in rate form is presented, where the effect of thickness reduction due to large plastic deformation is considered. A finite element formulation in terms of stress resultants and their work‐conjugate generalized strain rates is derived based on the virtual work principle. A hemispherical punch stretching operation and a plane‐strain draw operation are simulated by a finite element program based on the finite element formulation. The results of these finite element simulations are in good‐agreement with those using the through‐the‐thickness integration method. The results of the hemispherical punch stretching simulation suggest that the coupling term of moments and membrane forces of the modified Ilyushin yield function should be eliminated to avoid numerical instability under stretching‐dominated conditions for this rate‐independent plasticity formulation. Further, the results suggest that the hardening rule in a power‐law form based on the small‐strain approach must be modified to take account for finite deformation effects of combined stretching and bending. Under the plane‐strain draw operation, the sheet experiences a large amount of bending before the final stretching. The simulation based on the stress resultant constitutive law can produce this essential aspect of deformation pattern as that of the through‐the‐thickness integration method, whereas a simulation based on a membrane theory cannot. In conclusion, the results of these simulations indicate that a finite element program based on the stress resultant constitutive law can simulate sheet‐forming processes with much shorter computational time than that based on the through‐the‐thickness integration method.
Exterior stable domain segmentation integral equation method for scattering problems
Authors: Zeng Xiaogang , Bielak Jacobo 
Published: August 2005

AbstractThis paper is concerned with the development of an exterior domain segmentation method for the solution of two‐ or three‐dimensional time‐harmonic scattering problems in acoustic media. This method, based on a variational localized, symmetric, boundary integral equation formulation leads, upon discretization, to a sparse system of algebraic equations whose solution requires only O(N) multiplications, where N is the number of unknown nodal pressures on the scatterer surface. The new procedure is analogous to the one developed recently1 except that in the present formulation we avoid completely the use of the hypersingular operator, thereby reducing the computational complexity. Numerical experiments for a rigid circular cylindrical scatterer subjected to a plane incident wave serve to assess its accuracy for normalized wave numbers, ka, ranging from 0 to 30, both directly on the scatterer and in the far field, and to confirm that, contrary to standard boundary integral equation formulations, the present procedure is valid for critical frequencies.
On the membrane locking of h–p finite elements in a cylindrical shell problem
Authors: Leino Yrjö , Pitkäranta Juhani 
Published: August 2005

AbstractWe study the performance of high‐order h–p finite clement schemes in approximating the nearly inexlensional deformation state of a thin cylindrical shell roof with both ends free. Severe locking is demonstrated for both quadratic and cubic elements, and even for higher order if the grid is not aligned with the axis of the cylinder.Carefully designed selective reduced integration is shown to improve the accuracy of the finite element approximation at low and moderately high orders. However, so far this technique seems to work well only on aligned grids.