bluuebunny/crossref_metadata_2025_split huggingface dataset:
A dynamic contact buckling analysis by the penalty finite element method
Authors: Kanto Y. , Yagawa G. 
Published: August 2005

AbstractThe present paper deals with the application of the finite element method to dynamic contact buckling problems. The penalty function method is applied to incorporate the contact conditions in the equation of motion and a trial‐and‐error method is employed to obtain the converged contact state. Numerical examples are analysed to show the effectiveness and the validity of the method, and it is applied to a dynamic buckling problem involving contact phenomena.
Explicit integration for three‐dimensional degenerated shell finite elements
Authors: Vlachoutsis Stefanos 
Published: August 2005

AbstractExplicit integration across the thickness for three‐dimensional degenerated shell finite elements is analysed. For this purpose a modifed formulation is proposed. The Jacobian matrix of the physical–parameter spaces transformation is decomposed into a product of ‘in‐middle‐surface’ and ‘out‐of‐middle‐surface’ terms. This enables an expansion to be carried out of the strain–displacement matrix into power series of the thickness variable. Explicit integration is then performed and the corresponding formulae of the stiffness and mass matrices are given. The possibility of ‘locking’ for thin structures is explained. The analysis is applied to homogeneous and multilayered structures. Numerical applications for linear problems are given in the last part of the paper.
A semi‐analytical method for time‐domain analyses of dam–reservoir interactions
Authors: Tsai Chong‐Shien , Lee George C. , Ketter Robert L. 
Published: August 2005

AbstractNon‐linear responses of dam–reservoir systems are not well understood, because of the lack of an exact time‐domain solution for the far field (extending to infinity) of the fluid. This paper presents a procedure for efficient time‐domain analyses. It is based on a semi‐analytical solution and is suitable for the determination of the interactive behaviour of dam–reservoir systems.In this formulation, the fluid domain is divided into a near (to the dam) field, which is finite, and a far field extending to infinity. Arbitrary shapes of the upstream face of the dam, and of the bottom of the reservoir floor in the near field, are presumed. Furthermore, the far field is assumed to have a constant depth. The irregular near field is modelled by using the finite element method. A time‐domain semi‐analytical solution is obtained for the far field. For a vertical dam subjected to earthquake and ramp loadings, numerical solutions obtained compared well with the piecewise exact form of the analytical solution.
Advanced development of time‐domain BEM for two‐dimensional scalar wave propagation
Authors: Israil A. S. M. , Banerjee P. K. 
Published: August 2005

AbstractAn improved formulation for solving 2D transient scalar wave propagation problems by the Boundary Element Method (BEM) is presented. The kernels presented are simpler and better behaved than those that have appeared in the published literature. An appropriate set of temporal shape functions for linear variation is used. For spatial variations isoparametric quadratic elements are used. All of these represent significant improvements over the present level of sophistication in the analysis of 2D transient scalar problems. The algorithm is implemented in a general purpose boundary element code known as GPBEST.
Application of the boundary element method to non‐linear diffusion with reaction problems
Authors: Ramachandran P. A. 
Published: August 2005

AbstractAn integral solution method based on the concept of the direct boundary element technique has been applied to develop a solution procedure for problems of diffusion with a non‐linear reaction in one dimension. The non‐linearity is handled by a process of quasi‐linearization over subintervals or elements in the main domain of integration. The weighting functions are defined for each subinterval such that the discretization is exact for the corresponding linear problem. This leads to a new powerful and simple method for the solution of this class of problems. A banded global matrix is obtained with both the concentration and its gradient as the unknown variables, and the problem is solved in an iterative manner. Illustrative results are presented for a test problem of diffusion with a second order reaction in an infinite slab, an infinite cylinder and spherical geometries. The accuracy of the method for situations with a sharp concentration gradient is demonstrated. The technique can also be used to numerically compute the solution in the boundary layer for fast reactions.
Finite element analysis of multiconductor printed‐circuit transmission‐line systems
Authors: Castillo Steven , Pantic Zorica , Mittra Raj 
Published: August 2005

AbstractIn this paper the finite element method (FEM) is used to analyse general, multiconductor transmission‐line systems of arbitrary cross‐section. The per‐unit‐length matrices of capacitance, inductance, conductance and resistance, which characterize a multiconductor transmission line, are obtained from the FEM analysis. Numerical results are presented and compared both with experimental results and other available data.
A truncated Newton–Lanczos method for overcoming limit and bifurcation points
Authors: Papadrakakis M. 
Published: August 2005

AbstractIn this study procedures for overcoming limit and bifurcation points in large‐scale structural analysis problems are described and evaluated. The methods are based on Newton's method for the outer iterations, while for the linearized problem in each iteration the preconditioned truncated Lanczos method is employed. Special care is placed upon line search routines for accelerating the convergence properties and enhancing the stability of the outer method. The proposed methodology retains all characteristics of an iterative method by avoiding the factorization of the current stiffness matrix. The necessary eigenvalue information is retained in the tridiagonal matrix of the Lanczos approach.
Flow through fissured porous media with deformable matrix
Authors: Valliappan S. , Khalili‐Naghadeh N. 
Published: August 2005

AbstractAn approach, which is based on the double porosity concept and takes into account pore deformation, has been presented to derive a set of coupled differential equations governing the behaviour of fissured porous media. This approach has resulted in a set of non‐linear (variable coefficient) differential equations. Various coefficients involved in the formulation have been explicitly defined in terms of measurable physical parameters. The finite element technique has been employed as the numerical tool for the solution of these equations. The results based on the proposed non‐linear formulation have been compared with those of previously presented linear (constant coefficient) formulations. It is found that, in relatively rigid formations, the linearity assumption is quite reasonable and can successfully model the behaviour of fissured porous media. However, in very deformable formations, the linearity assumption could lead to a significant level of error in the numerical solutions.
Two‐level domain decomposition preconditioning for the p‐version finite element method in three dimensions
Authors: Mandel Jan 
Published: August 2005

AbstractThis paper presents a flexible approach to domain decomposition preconditioning for problems expressed in terms of local stiffness matrices of subdomains. Evaluation of the preconditioner requires fully parallelizable local computations and the solution of a global auxiliary problem with few variables per subdomain. Convergence factors can be bounded using properties of the local stiffness matrices only. The method is applied to the p‐version finite element method for three‐dimensional elasticity. We treat each element as a subdomain and compute explicit convergence bounds.
Validation of structural computation codes in elastoviscoplasticity
Authors: Benallal A. , Chabrand P. , Ghazouane M. , Chaudonneret M. , Culié J. P. , Contesti E. , Gamha H. , Golinval J. C. , Turbat A. 
Published: August 2005

AbstractThis paper discusses various procedures for the implementation of viscoplastic constitutive equations in Finite Element Codes. The set of constitutive equations that has been used is described. Several kinds of implementation, using various numerical techniques, are proposed. Validations of these implementations and comparisons between them are investigated by means of a set of simple but comprehensive examples.
An alternating digital tree (ADT) algorithm for 3D geometric searching and intersection problems
Authors: Bonet Javier , Peraire Jaime 
Published: August 2005

AbstractA searching algorithm is presented for determining which members of a set of n points in an N dimensional space lie inside a prescribed space subregion. The algorithm is then extended to handle finite size objects as well as points. In this form it is capable of solving problems such as that of finding the objects from a given set which intersect with a prescribed object. The suitability of the algorithm is demonstrated for the problem of three dimensional unstructured mesh generation using the advancing front method.
Unconditionally stable algorithms for rigid body dynamics that exactly preserve energy and momentum
Authors: Simo J. C. , Wong K. K. 
Published: August 2005

AbstractWe show that, for rigid body dynamics, the mid‐point rule formulated in body co‐ordinates exactly conserves energy and the norm of the angular momentum for incremental force‐free motions, but fails to conserve the direction of the angular momentum vector. Further, we show that the mid‐point rule formulated in the spatial representation is, in general, physically and geometrically meaningless. An alternative algorithm is developed which exactly preserves energy, and the total spatial angular momentum in incremental force‐free motions. The implicit version of this algorithm is unconditionally stable and second order accurate. The explicit version conserves exactly angular momentum in incremental force‐free motions. Numerical simulations are presented which illustrate the excellent performance of the proposed procedure, even for incremental rotations over 65 degrees. The procedure is directly applicable to transient dynamic calculations of geometrically exact rods and shells.
A general methodological analysis for optimum design
Authors: Navarrina Fermin , Casteleiro Manuel 
Published: August 2005

AbstractGeneralized applications of modern numerical analysis methods—while digital computers experienced a fast development—produced a first revolution in design techniques, allowing one to perform computations considered unapproachable until that time. Introduction of Computer Aided Design (CAD) techniques—while high‐performance graphic peripherals experience a fast development—is actually producing a second revolution, by making easy and fast most routine design tasks. However, the introduction of Computer Aided OPTIMUM Design techniques has not yet produced the expected third revolution, in spite of the big amount of research and the interest of its potential applications. The authors think that this fact is due mainly to the dispersion of the optimum design research, and to the lack of a well established doctrine.In this paper we approach the design process from a general methodological perspective, suitable to be applied to a wide range of problems. The design process is organized in several related levels. This approach leads naturally to the concept of optimum design and to the statement of a general mathematical programming problem. The practical application of this methodology to any particular problem takes an efficient and modular form. First and second order sensitivity analysis techniques are introduced from the general formulation, and alternative techniques (adjoint state) of the direct differentiation method are discussed.DAO2, a powerful and versatile computer aided optimum design system by the Finite Element Method, has been developed by the authors1 according to this general methodology. The system can solve efficiently 2D and 3D structural fixed‐geometry and shape optimization problems. The power and viability of this methodology is illustrated by the solution to a structural optimization problem. The shape of the central section of an arch dam is optimized. A linear elastic structural FEM analysis is simultaneously performed for plane stress and for radial symmetry—while constraints are imposed for several load cases—taking into account the construction and loading stages. It should be emphasized that the same optimum design is reached in a small number of iterations starting from two significantly different initial designs.
A Treatment of wall boundaries for turbulent flows by the use of a transmission finite element method
Authors: Manouzi H. , Fortin M. 
Published: August 2005

AbstractA method to connect momentum Navier‐Stokes equations with the universal law of the wall using the finite element method is developed for turbulent wall flows. This method is based on a domain decomposition of the fluid into subdomains near a solid boundary where the law of the wall is valid. A transmission formulation is introduced to match these regions and a new class of boundary finite element is used. This finite element takes into account the near‐wall profile of the velocity and the transmission conditions. Computational results are presented for Poiseuille flow and flow over a backward‐facing step.
An investigation of a finite rotation four node assumed strain shell element
Authors: Parisch H. 
Published: August 2005

AbstractThe paper presents a shell formulation based on the ‘degenerated solid approach’. The theory employs covariant strains and performs explicit integration through the shell thickness. The rigid body motion is exactly represented. The consistent tangent stiffness matrix is evaluated for the four node quadrilateral. It is shown, in the final part, that this type of element, which distinguishes itself by a very simple and easily understandable theory, gives good answers for linear as well as non‐linear applications.
Non‐linear B‐stability and symmetry preserving return mapping algorithms for plasticity and viscoplasticity
Authors: Simo J. C. , Govindjee S. 
Published: August 2005

AbstractA class of second order accurate return mapping algorithms is presented which lead to symmetric algorithmic tangent moduli and contain the classical backward‐Euler return maps as a particular case. More importantly, it is shown that this class of return maps is contractive relative to the natural norm defined by the complementary Helmholz free energy function (B‐stability). Since the equations of classical plasticity and viscoplasticity are shown to be contractive relative to this natural norm, the requirement of B‐stability furnishes the appropriate notion of unconditionally stable algorithms for plasticity and viscoplasticity. The analysis that follows depends critically on the assumption of convexity. In particular, the models of plasticity and viscoplasticity considered obey the principle of maximum plastic dissipation. The proposed algorithms obey the discrete counterpart of this classical principle.
Convergence of the Newton‐Raphson algorithm in elastic‐plastic incremental analysis
Authors: Caddemi S. , Martin J. B. 
Published: August 2005

AbstractA spatially continuous, time discrete formulation of the loading of an elastic, perfectly plastic body governed by a von Mises yield condition is presented. It is assumed that incremental changes in strain occur along minimum work paths, which is equivalent to a backward difference implicit integration algorithm or the radial return method. This assumption permits the incremental problem to be formulated as a convex non‐linear programming problem. The classical Newton‐Raphson algorithm can be adopted to provide an iterative solution of the non‐linear programming problem. It is shown that if an elastic or secant predictor modulus is used, the algorithm converges monotonically. However, if a tangent predictor is used, a line search algorithm must be included to ensure convergence.
Mesh relaxation: A new technique for improving triangulations
Authors: Frey William H. , Field David A. 
Published: August 2005

AbstractGiven a list of points defining a domain boundary, a three‐stage process is often used to triangulate a domain. First, an appropriate distribution of interior points is generated. Next the points are connected to form triangles. And, finally, the connectivity data are used to reposition the interior points using the Laplacian smoothing technique, thereby usually improving the shapes of the shapes of the triangles. This paper describes a new techniques for mesh improvement—adjusting the connection structure during the second stage of this process. The new scheme, which we call mesh relaxation, consists of a procedure for iteratively making the mesh topology more regular by edge swapping. For each interior edge, a relaxation index is computed that depends on the degrees of its end points and adjacent points. Any edge for which this index exceed a prescribed threshold will be swapped, i.e. replaced by a new edge connecting the adjacent points of the original edge. After all edge swaps are completed, Laplacian smoothing is applied to the mesh. Example show that, when the mesh point density varies smoothly and due care is taken in the vicinity of the boundary, mesh relaxation can dramatically increase the regularity of the mesh and produce improve triangle shapes.
Material geometry optimization of involute structures using sensitivity derivatives with respect to global design variables
Authors: Hart Jonathan K. , Stanton Edward L. , Schmit Lucien A. 
Published: August 2005

AbstractA behaviour sensitivity analysis and optimization capability for involute structures has been developed and implemented via a test version of the P/COMPOSITE Module (which includes the CPATCHES finite element code for the analysis of 3‐D composites) in PATRAN. The user may obtain the sensitivity of the structural response with respect to a set of up to eight global material geometry variables that span the space of useful designs. The integrands of the sensitivity integrals are calculated in closed form and the same volume integration utilities that are employed throughout CPATCHES are used. This capability is restricted to problems in linear statics and a Cholesky equation solver is used. The behaviour sensitivity derivatives are validated by finite difference testing and through their successful application in severai involute optimization problems.
Thermal aspects of shear localization in microporous viscoplastic solids
Authors: Zavaliangos A. , Anand L. 
Published: August 2005

AbstractA set of phenomenological state variable constitutive equations for large deformations of isotropic, thermo‐elasto‐viscoplastic, porous materials is considered, and a new semi‐implicit, incrementally objective time‐integration procedure for these constitutive equations is developed. The constitutive equations and the time‐integration procedure are implemented in a finite element program, and used to study the shear band formation and ductile fracture initiation triggered by flow softening due to the combined effects of void growth and deformation heating, in a plane strain tension test.
Field‐consistency rules for a three‐noded shear flexible beam element under non‐uniform isoparametric mapping
Authors: Prathap G. , Naganarayana B. P. 
Published: August 2005

AbstractMost studies on the three‐noded quadratic Timoshenko beam element have been based on a 2‐point Gaussian integration rule for the shear energy or on the use of a smoothed substitute shape function or assumed shear strain field to improve its performance. However, if the mid‐node of the element is slightly displaced from the mid‐point position, the consistency requirements for the constrained shear strain field are more complex. This paper investigates this problem and the findings throw more light on consistency procedures demanded for distorted quadrilateral plate and shell elements. The optimal element which emerges from this study has bending and shear strain fields which have a linear variation over the element under non‐uniform mapping.
A thick–thin triangular plate element
Authors: Zhongnian Xu 
Published: August 2005

AbstractA simple and efficient triangular finite element is introduced for plate bending applications. The element is a three‐node triangular one with three basic degrees of freedom per node and two internal rotation degrees of freedom, using selective reduced integration. Numerical examples indicate that, despite its simplicity, the element is not only competitively accurate, but also useful as a thick‐thin triangular plate bending element. It is also pointed out that this element using selective reduced integration is in fact a mixed element.
Transient dynamic and damping analysis of laminated anisotropic plates using a refined plate theory
Authors: Pervez Tasneem , Zabaras Nicholas 
Published: August 2005

AbstractA refined model is presented for the linear transient dynamic and damping analysis of laminated anisotropic composite plates. Experimental measurements of specific damping capacity of unidirectional composite beams are used to predict the specific damping capacity of laminated composite plates in various modes of vibration. A finite element idealization is adopted, and the quadratic Lagrangian element is used together with selective/reduced integration. A viscous damping approximation is then employed to calculate the damped transient response of laminated plates. The effects of transverse shear deformation, symmetry condition, boundary conditions, anisotropy, aspect ratio, fibre orientation and the lamination scheme on specific damping capacity and damped transient response are investigated. Realistic examples illustrate the importance of these parameters. The present results agree very closely with experimental results available in the literature and can serve as a benchmark for future comparison by other investigators.
A new explicit variable time‐integration self‐starting methodology for computational structural dynamics
Authors: Tamma Kumar K. , D'Costa Joseph F. 
Published: August 2005

AbstractA new explicit variable time‐integration methodology and architecture which possesses self‐starting attributes, eliminates the need to involve acceleration computations, and which has improved accuracy characteristics in comparison to the traditional central‐difference‐type formulations customarily advocated is described for applicability to computational structural dynamics. To sharpen the focus of the present study, an explicit variable time‐integration architecture which is relatively simple, yet effective, is described. Unlike variable explicit time‐integration formulations adopted in the past, the present self‐starting variable time‐integration architecture and implementation aspects facilitate a simplified representation and a straightforward and effective approach for combining finite element meshes requiring different time steps in a single analysis. Numerical test cases are provided which demonstrate the applicability of the proposed formulations.