bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of Swelling Phenomena in Charged Hydrated Porous Media
Authors: Acartürk Ayhan , Ehlers Wolfgang , Abbas Ibrahim 
Published: December 2004

AbstractBiological tissues like articular cartilage and geomaterials like clay have a multicomponent microstructure. The charged solid is saturated by a viscous fluid, which itself is composed of several components: the liquid solvent and the dissolved ions, namely, water, anions and cations. These charged multiphase materials exhibit a swelling behaviour under varying chemical conditions.The model describing such materials combines electrochemical and mechanical effects like osmosis and electrostatics within a macroscopic formulation. Starting from the Theory of Porous Media (TPM), a four component model is presented, wherein all constituents are materially incompressible and mass exchanges are excluded. This isothermal model leads to a set of equations which consists of three primary variables: the solid displacement uS, the pore‐pressure p and the molar ion concentration cm, since the ion concentrations always depend on each other because of the electroneutrality condition.For the numerical treatment, the weak formulations of governing equations are implemented in the FE tool PANDAS, wherein Taylor‐Hood elements are used for the spatial discretization. Finally, a simulation of a 3‐d swelling experiment is shown. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of piezoelectric fiber distribution in composite smart materials
Authors: Bohn Niels , Gabbert Ulrich 
Published: December 2004

AbstractA new approach to obtain macroscopic properties of fiber‐matrix composite materials is given by the optimization of the fiber distribution for a given pair of materials. The optimization was carried out by Evolution Strategies using an interface to the finite‐element‐software ANSYS. To cover the effects of varied micro level parameters, a homogenization algorithm was included in the optimization process. Two applications verify the correct implementation of the software. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigation of microstructure evolution in metal forming processes
Authors: Bontcheva Nikolina , Petzov Georgi , Iankov Roumen 
Published: December 2004

AbstractGrain size evolution and phase transformation during metal forming processes is investigated numerically by means of the Finite element method. Appropriate microstructure models are involved into the FEM code MSC.MARC. Material characteristics obtained by means of own experiments are used. Hot closed die forging and rod rolling are considered. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Macroscopic finite element analyses of discretematerials based on directly evaluated micro‐macro transitions
Authors: Dettmar Joachim , Miehe Christian 
Published: December 2004

AbstractWe consider a homogenized macro‐continuum with locally attached microstructure of granules and derive specific micromacro transitions by a consistent transfer of discrete micro‐variables to field variables on a continuous macrostructure. Displacements and rotational constraints are imposed on the granules on the defined boundary frame of the microstructure. The constraints for linear displacements and uniform tractions on the surface yield upper and lower bound characteristics for periodic boundary conditions with regard to the aggregate stiffness. Secondly, we perform two‐scale analyses where we link simulations on the macro‐ and the microscales. Therein, coupled boundary‐value problems are solved on both scales. The macroscopic homogeneous problem is solved by a finite element method where the material model is implemented using the directly evaluated micro‐macro transitions on the basis of the discrete microstructures. Finally, a model problem is investigated to clarify the proposed method. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A unified approach for elasto‐plastic FEM simulations, incorporating adaptive spatial and time discretization
Authors: Eckert Steffen , Gross Dietmar 
Published: December 2004

AbstractIn FEM calculations the discretization should be chosen in a way, that further mesh refinement does not change the results. Otherwise the discretization error might yield unphysically stiff material behavior. If elasto‐plasticity is considered, a second type of error due to the time discretization of the evolution equations has to be taken into account. Due to the non‐linearity of the underlying initial boundary value problem, large time increments often result in non‐converging solutions during equilibrium iteration.In our approach the time integration error resulting from a second order BDF2 time integration method is calculated and utilized in an automatic step size control. In conjunction with a DAE‐treatment of the initial boundary value problem, it allows in the average considerably larger time steps compared to classical ‘elastic predictor – plastic corrector’ schemes. To reduce the discretization error, adaptive mesh‐refinement based on a Z2‐error‐estimator is performed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the numerical treatment of multiphasic flow processes in deformable porous media
Authors: Graf Tobias , Ehlers Wolfgang 
Published: December 2004

AbstractThe description of multiphasic flow processes and their interaction with a deformable solid skeleton plays an important role in a big field of engineering applications, as for example in the modelling of partially saturated soil or groundwater contamination. For a numerical simulation of such a material behaviour, a triphasic continuum mechanical model based on a multiphasic formulation embedded in the well‐founded framework of the Theory of Porous Media (TPM) is used. Therein, the single constituents are a materially incompressible elasto‐viscoplastic solid skeleton and materially compressible or incompressible pore‐fluids, e. g., water, oil or air. The numerical treatment is based on the weak formulations of the governing equations, where the primary variables are the displacement of the solid skeleton and the effective pressures or saturations of the pore‐fluids. An initial boundary‐value problem concerning an infiltration problem in a heterogeneous porous material is discussed in detail, where the resulting system of strongly coupled differential‐algebraic equations is solved by the FE tool PANDAS. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stress And Strain in a Yeast Cell Under High Hydrostatic Pressure
Authors: Hartmann Christoph , Delgado Antonio 
Published: December 2004

AbstractThe mechanical effects of the compression of a yeast cell (Saccharomyces cerevisiae) under high hydrostatic pressure (HHP) are modeled and simulated numerically. The deformation of the cell under pressure deviates strongly from isotropic volume reduction. In the cell wall, von‐Mises stress reaches the critical value upon failure at a pressure load between 415Mpa and 460MPa. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory and implementation of orthotropic materials in growing continua
Authors: Himpel Grieta , Kuhl Ellen , Menzel Andreas , Steinmann Paul 
Published: December 2004

AbstractMost biological tissues show a material behavior which is characterized through a pronounced anisotropy. In particular hard tissues such as bones or soft tissues as muscles are commonly modeled as either transversely isotropic or even orthotropic. In contrast to engineering materials, however, biological tissues possess the ability to adapt, e.g. their density, to the current loading situation. Based on a formulation for growth in isotropic continua, see for instance Kuhl, Menzel & Steinmann [3], and transversely isotropic continua as discussed e.g. in Himpel [2], we attend to a model for the functional adaption of orthotropic biomaterials. The material model has been implemented in a finite element code and is studied by means of a numerical example. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐Macro Modelling of Piezoelectric Fiber Composites
Authors: Kari Sreedhar , Berger Harald , Gabbert Ulrich 
Published: December 2004

AbstractThe present work deals with the numerical modeling of 1‐3 periodic composites made of piezoceramic (PZT) fibers embedded in a soft non‐piezoelectric matrix. We especially focus on predicting the effective co‐efficients of the periodic transversely isotropic piezoelectric fiber composites using representative volume element method (unit cell method). The results which are obtained from the FEM technique are compared with analytical homogenization method for different volume fractions. The effective co‐efficients are obtained for rectangular and hexagonal arrangement of unidirectional piezoelectric fiber composites. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large deformation frictional contact formulation based on a velocity description
Authors: Konyukhov Alexander , Schweizerhof Karl 
Published: December 2004

AbstractThe main idea of the velocity description is to describe kinematics of the contact in the specially defined local surface coordinate system which is related to the closest point projection procedure. All necessary operations for the description of the contact problems: kinematics, all differential operations etc. are considered from the geometrical point of view. While exploiting the differential geometry of the contact surfaces a consistent formulation for the contact problem, including friction is obtained. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strongly Coupled Analysis of Fluid‐Structure Interaction with Free Surface Flow
Authors: Kölke Andreas , Walhorn Elmar , Hübner Björn , Dinkler Dieter 
Published: December 2004

AbstractFor the numerical analysis of interactions of immiscible two‐fluid flows and lightweight elastic structures a discretization method based on stabilized space‐time finite elements is applied. The use of the level set method provides an implicitly given description of the evolving flow domains and useful geometrical information of the moving and topological changing fluid‐fluid interface. Due to the choice of a proper enriched basis within the partition of unity concept, the method is able to capture strong discontinuous solutions in space and time introduced by interfacial jump conditions and different material properties on each side of the moving interface. A numerical example demonstrates the ability of the method to handle complex free surface flow situations and their interplay with elastic bodies. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Piezoelectric Smart Lightweight Structures by the Finite Element Method for Acoustic Control
Authors: Lefèvre Jean , Gabbert Ulrich 
Published: December 2004

AbstractPiezoelectric patches are widely used as distributed actuators and sensors for active vibration control. Active control of sound in this way is mainly interesting in the low frequency range, where passive methods are less effective. To simulate such electromechanical‐acoustical systems a virtual overall model based on the FEM is presented in the paper. Different approaches for model reduction with respect to controller design purposes are discussed. As a simple test example the numerical model of an acoustic box is studied. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Numerical Approach to Mechanosensation of Bone Tissue based on a Micromechanical Analysis of a Single Osteon
Authors: Lenz Christian , Nackenhorst Udo 
Published: December 2004

AbstractThe subject of this work is to study the mechanosensation of bone tissue using a numerical approach. Therefore a finite element analysis of a single osteon was carried out. The calculated strains at the lacuna leads to a deeper insight into the mechanical conditions the osteocytes are exposed to. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An H‐matrix Type Preconditioner For Frictional Contact Problems
Authors: Abdelhakim Lotfi 
Published: December 2004

AbstractThe bilateral or unilateral contact problem with Coulomb friction between two elastic bodies is considered [1]. An algorithm is introduced to solve the resulting finite element system by a non‐overlapping domain decomposition method [2, 3]. The global problem is transformed to a independant local problems posed in each bodie and a problem posed on the contact surface (the interface problem). The solution is obtained by using a successive approximation method, in each step of this algorithm we solve two intermediate problems the first with prescribed tangential pressure and the second with prescribed normal pressure [8]. Our preconditioner construction is based on the application of the H‐matrix technique [6, 7] together with the representation of the H1/2 seminorm by a sum of partial seminorms [4]. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient finite element formulation based on the strong discontinuity approach for the modeling of material failure
Authors: Mosler J. , Bruhns O. T. 
Published: December 2004

AbstractA new finite element formulation based on the strong discontinuity approach is proposed. Following [1], localized inelastic deformations are represented as surfaces of discontinuous displacements within the respective finite element by applying the Enhanced Assumed Strain (EAS) concept. However, and in contrast to previous publications, the jump part of the displacement field is not condensed out at the element level by employing static condensation. Instead, the L2‐orthogonality condition is reformulated resulting in an equation which is formally identical to the necessary condition of yielding known from standard plasticity theory. Hence, it is possible to apply the return‐mapping algorithm to the numerical implementation. Only slight modifications of this by now classical algorithm are necessary. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast Numerical Simulation of 3D Steady‐State Hot Rolling Processes by Utilizing Diffpack and Deform
Authors: Obereder Andreas , Kainz Alexander 
Published: December 2004

AbstractIn hot rolling of steel a precise determination of strip spread, lateral flow, profile and flatness can be considered as key points to produce top quality strips satisfying the most demanding tolerances. Typical 3D‐effects like broadening and relative strip profile changes can only be predicted precisely by 3D‐numerical simulations. Commercial finite element packages, however, are very time consuming, especially when based on (updated) Lagrangian concepts and one is merely interested in the stationary process behaviour. Therefore, a fast quasi‐stationary description in Eulerian coordinates with deformationupdates via the streamline technique was developed and implemented numerically [1, 6]. The underlying rigid‐viscoplastic constitutive law for the strip or slab was implemented according to a non‐linear Newtonian fluid [2]. The solution of the free boundary value or contact problem including friction leads to a non‐linear variational inequality (cf. [3, 6]), which is solved iteratively in Eulerian coordinates. The self‐developed simulation code (written in C++, cf. [4]) can handle non‐linear plastic materials, contact and friction between the deformed work roll and the slab, including also grid adaptations. In this report simulation results for both edger and flat passes are presented. These results were calibrated with real mill process data and also validated against the commercial software package DEFORM [5] and yields satisfactory correspondence [6, 7]. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the simulation of a moving discontinuity by boundary element methods
Authors: Oberste‐Brandenburg Claus , Jovanović Lidija 
Published: December 2004

AbstractThe movement of a discontinuity in a continuum can usually be expressed in terms of the state in its direct vicinity. Thus, the knowledge of the local state around the discontinuity is vitally important in order to adequately describe its movement. Numerical schemes local to the discontinuity, as e.g. moving finite element methods, are appropriate approaches to describe its motion. However, for a large number of problems, the local state not only depends on measures of the discontinuity plane itself but also on measures related to the bulk behavior of the material, such as temperature or stress. For a complete description, the bulk behavior of the material has to be numerically modeled as well. In this contribution, the interface and its propagation is modeled explicitly by a two‐dimensional discretization of the interface. The same discretization is utilized to describe the behavior of the bulk material employing the boundary element method. As an example, the movement of a phase transition front in a single crystal is presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison between the material point method and the finite element method in view of extrusion problems
Authors: Schilling O. , Reese S. 
Published: December 2004

AbstractAn appropriate method for the simulation of continuous forming processes is the material point method (MPM) [1],[2] which combines the viewpoints of fluid dynamics and solid mechanics. The MPM and related methods [3] are derived from the particle‐in‐cell methods [4]. Bodies are discretised by Lagragian particles with pointwise mass distributions. The differential equations in their weak form are solved on temporary meshes built of standard finite elements. At the end of each time step the particle positions are updated and the mesh is replaced by a new mesh with a regular shape. The state variables at the nodes of the new mesh are extracted from the state variables at the particles by a transfer algorithm. When particles pass element boundaries, numerical difficulties might be observed. These are eliminated by a smooth approximation of nodal data from material point data. The modified MPM has been implemented together with the FEM in one programme because the similarities of the methods outbalance the differences. On the basis of numerical examples the results of both methods are compared. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New approach in Stochastic Finite Element Method
Authors: Sniady P. , Zielichowski‐Haber W. 
Published: December 2004

AbstractIn the paper, the new methodology for Stochastic Finite Element Method (SFEM) as the means to analyze structure in the probabilistic framework is presented. The concept of random influence vector is introduced and used to develop the universal formulas in the framework of SFEM that can work effectively for a wide variety of random loads. Furthermore, the derived formulas enable to separate the structural uncertain properties from random parameters of load resulting in the hybrid formulation of SFEM and to analyze the structure in probabilistic framework subject to any stochastic space load. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contour integration and “mixed–variables–technique” applied to an infinite plate on the halfspace
Authors: Trinks Carolin , Ruge Peter 
Published: December 2004

AbstractAn infinite plate on the halfspace is treated as a typical soil–structure interaction problem. Based on an analytical solution in the wavenumber– and frequency domain the dynamic flexibility is obtained using contour integration. The force–displacement relationship is transformed into the time domain by means of a rational approximation technique and the fractional calculus. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weakly coupled analysis of a blade in multiphase mixing vessel
Authors: Vesenjak Matej , Ren Zoran , Hriberšek Matjaž 
Published: December 2004

AbstractTwo or more physical systems frequently interact with each other, where the independent solution of one system is impossible without a simultaneous solution of the others. An obvious coupled system is that of a dynamic fluid‐structure interaction. [8] In this paper a computational analysis of the fluid‐structure interaction in a mixing vessel is presented. In mixing vessels the fluid can have a significant influence on the deformation of blades during mixing, depending on speed of mixing blades and fluid viscosity. For this purpose a computational weakly coupled analysis has been performed to determine the multiphase fluid influences on the mixing vessel structure. The multiphase fluid field in the mixing vessel was first analyzed with the computational fluid dynamics (CFD) code CFX. The results in the form of pressure were then applied to the blade model, which was the analysed with the structural code MSC.visualNastran forWindows, which is based on the finite element method (FEM). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FE‐formulation for plate and beam elements to simulate onset and propagation of discrete cracks in solid structures
Authors: Wackerfuß Jens , Gruttmann Friedrich 
Published: December 2004

AbstractThe aim of this paper is to present some numerical aspects related to the modeling both the formation and the propagation of discrete cracks in solid structures. The presented formulation corresponds to the concept of embedded discontinuities [1], and will be applied to a plate and to a beam element.The failure of solid structures is often triggered by a highly localized pattern of inelastic deformation in the form of narrow bands. Characteristic examples are shear bands in metals and soils, or localized bands of cracking in brittle materials, like concrete or rocks. A well known difficulty associated with classical (local, rate‐independent) continuum theories with strain softening attributes is that numerical solutions are found to lack invariance with respect to the choice of spatial discretization. For quasi‐static boundary problems, this mathematical inconsistency causes the loss of ellipticity for the governing equations (material instability). To regularize this inconsistency, several strategies have been applied. In the presented formulation, additional degrees of freedom are considered. Within the concept of embedded discontinuities, the regular displacements are enriched by discontinuities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of Yield‐line Geometries for Arbitrary Simply Supported Slabs
Authors: Wüst Jochen 
Published: December 2004

AbstractThe calculation of limit loads of slabs using the yield‐line theory requires the assumption of a kinematical collapse mechanism. In recent years several approaches concerning the optimization of predefined mechanisms have been introduced. Usually they contain semi‐automatic procedures which depend on user‐defined yield‐line predictions. This paper presents a systematic approach and a numerical procedure to find yield‐line predictions for arbitrary all‐side supported slabs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advanced Shell Element Formulations for Coupled Electromechanical Systems
Authors: Yang Fan , Lammering Rolf , Mesecke‐Rischmann Simone 
Published: December 2004

AbstractWith the significantly increasing applications of smart structures, piezoelectric material is widely used in branches of engineering sciences. Normally, the Finite Element Method is employed in the numerical analysis of these structures [2]. In this contribution, in order to avoid the locking effects and zero energy modes, the Assumed Natural Strain (ANS) Method [4] is implemented into four‐node piezoelectric shallow shell elements, by using the two‐field variational formulation in which displacements and electric potentials serve as independent variables and the three‐field variational formulation in which the dielectric displacement is taken as an independent variable additionally [3]. Moreover, a quadratic variation of the electric potential through the thickness direction is applied in the two‐field formulation. Numerical examples of piezoelectric sensors and actuators are presented, showing the behaviour of the shell elements by using different hybrid finite element formulations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)