bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation model for anisotropic fibrous materials
Authors: Ask Anna , Ristinmaa Matti 
Published: February 2009

AbstractPaper and paper–based materials such as cardboard are used in a wide variety of applications and in the development of new applications such as boxes an accurate simulation model is of major importance. Industrially made paper material typically has an orthotropic fibrous structure, due to the manufacturing process, where the fibers tend to align in the direction of motion in the machine. In this work a plasticity–based material model allowing for finite strains is developed. The model is suitable for materials with an anisotropic fibrous structure such as paper. The general framework is based on separate mappings describing the deformations of the continuum and the substructure and a multiplicative split of these mappings into elastic and plastic parts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of two different models to account for induced flow anisotropy during complex loading processes
Authors: Barthel Clemens , Svendsen Bob , Levkovitch Vladislav , Wang Jian 
Published: February 2009

AbstractSome metals exhibit an increase of the yield stress after orthogonal strain path changes, i.e. so–called cross hardening. Two approaches are discussed in this work which are capable of taking that effect into account in an appropriate manner. The first approach is closely related to that of Teodosiu and Hu. The second model considers besides the movement of the center of the yield surface and its proportional expansion also the change of its shape and is able to describe the induced anisotropic behavior with regard to complicated loading histories. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A micro‐macro approach to the failure of rubber‐like materials
Authors: Dal Hüsnü , Kaliske Michael 
Published: February 2009

AbstractRubbery polymers are modelled with hyperelastic constitutive laws by which the material can be stretched indefinitely or up to a certain locking stretch value. However, no material can sustain indefinite stretch and store infinite energy. Failure occurs after a threshold value for stress and/or energy is attained. Within this context, an approach for failure analysis of rubber–like materials based on the constitutive description of material is presented. The model is based on a hyperelastic material law representing the energy stored in rubber network due to the chain conformations connected in series to an interatomic bond potential representing the energy stored in the polymer chain due to the interatomic displacement. For the representation of the micro–macro transition in terms of non–affine kinematics, micro–sphere model is utilized. Morse potential is used for the description of the interatomic bond, which describes the energetic contribution to rubber–like materials and governs the failure of the polymer chain. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the constitutive inequalities and acceleration waves in micropolar media
Authors: Altenbach Holm , Eremeyev Victor A. 
Published: February 2009

AbstractAcceleration waves in nonlinear thermoelastic micropolar media are considered. We establish the kinematic and dynamic compatibility relations for a singular surface of order 2 in the media. An analogy to the Fresnel–Hadamard–Duhem theorem and an expression for the acoustic tensor are derived. The condition for acceleration wave's propagation is formulated as an algebraic spectral problem. It is shown that the condition coincides with the strong ellipticity of equilibrium equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exploitation of Configurational Forces in Extended Nonlocal Continua with Microstructure
Authors: Frankenreiter Ilona , Zimmermann Dominik , Miehe Christian 
Published: February 2009

AbstractWe investigate aspects of the application of configurational forces in extended nonlocal continua with microstructure. Focussing on multifield approaches to gradient–type inelastic solids, the coupled problem is governed by the macroscopic deformation field, while nonlocal inelastic effects on the microstructure are described by a family of order parameter fields. The dual macro– and micro–field equations are derived within an incremental variational framework. Using an incremental principle, due to the variation with respect to the material position, an additional balance in the material space appears with the dual macro–micro–balances in the physical space. In view of the numerical implementation of this coupled problem by a finite element method, the incremental variational framework is recast into a discrete format in terms of discrete macro– and micro–physical nodal forces and configurational nodal forces. Applying a staggered solution scheme, the configurational branch is used as a postprocessing procedure with all the ingredients known from the solution of the coupled macro–micro–problem. The procedure is implemented for a nonlocal, viscous damage model. The consequences with regard to the configurational nodal forces are assessed by means of a numerical example. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and theoretical investigation on the microstructure of aluminum alloys during extrusion
Authors: Kayser Tobias , Parvizian Farhad , Svendsen Bob 
Published: February 2009

AbstractThe purpose of this work is the investigation of the material behavior of aluminum alloys during extrusion and cooling. In particular, the alloys of the 6000 series (Al–Mg–Si) and 7000 series (Al–Zn–Mg) are relevant here. Under the corresponding conditions, their behavior is controlled mainly by dynamic recovery during the extrusion and static recrystallization during cooling. For the development of a suitable material model EBSD measurements are done on different parts of an extruded Al6060 specimen. For this sample a microstructure picture is generated and a statistical analysis is performed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aspects of a direct homogenization procedure for electro‐mechanically coupled problems
Authors: Keip Marc‐André , Schröder Jörg 
Published: February 2009

AbstractThe aim of this work is to discuss a micro–macro homogenization procedure for electro–mechanically coupled problems. In this context a two–scale homogenization ansatz for ferroelectric ceramics based on an FE2‐approach is presented. The microscopic discretization of the heterogeneous structure of the polycrystalline material allows for the incorporation of microscopic effects, which are necessary to determine the corresponding overall macroscopic material response. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Eulerian Rate Model for Pseudoelastic NiTi Shape Memory Alloys
Authors: Luig Patrick , Bruhns Otto 
Published: February 2009

AbstractA phenomenological material model for the pseudoelastic material behavior of polycrystalline NiTi is presented. It is consistently derived within the Eulerian framework using the Kirchhoff stress (weighted Cauchy stress) and the stretching tensor. Deformation–like variables such as elastic or inelastic strains are omitted. The model is based on a non–convex Helmholtz free energy function for the phases austenite and martensite, which is formulated in terms of the Kirchhoff stress, temperature, mass fraction of martensite, and a tensorial internal variable accounting for the average orientation of the martensite variants. Evolution equations for the mass fraction of martensite as well as for the average orientation of the martensite variants are derived, taking into account the restrictions imposed by thermodynamics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A higher gradient theory for solid mixtures
Authors: Müller W.H. , Brandmair A. 
Published: February 2009

AbstractDuring use the microstructure of solders will change over time. To enable us to determine the lifetime and reliability of these materials, a theory to predict such changes is needed. In this paper two kinds of changes are considered: The forming of intermetallic compounds due to chemical reactions of two components and spinodal decomposition of a binary alloy followed by coarsening. A theoretical approach is presented and evaluated numerically. For this purpose, an extended diffusion equation is needed and derived within the framework of undisputed concepts of the entropy principle. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Amplitude‐ and temperature effects of filler‐reinforced rubber: Experiments and Modelling
Authors: Rendek Martin , Lion Alexander 
Published: February 2009

AbstractRubber–like materials exhibit special mechanical properties in a wide range of technical applications. To achieve a desired behaviour of the end product, the materials are reinforced with active fillers like carbon black. In the focus of this paper are selected cyclic–monofrequent experiments with constant strain amplitudes. Special attention will be focused to the excitation with small dynamic amplitudes. The amplitude dependence of the storage and loss moduli is known as the Payne–effect. We study the amplitude– and temperature dependence of storage and loss modulus as well as dissipation effects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory and Numerics of Rate‐Dependent Incremental Variational Formulations in Ferroelectricity
Authors: Rosato Daniele , Miehe Christian 
Published: February 2009

AbstractThis paper is concerned with macroscopic continuous and discrete variational formulations for domain switching effects at small strains, which occur in ferroelectric ceramics. The developed new three–dimensional model is thermodynamically–consistent and determined by two scalar–valued functions: the energy storage function (Helmholtz free energy) and the dissipation function, which is in particular rate–dependent. The constitutive model successfully reproduces the ferroelastic and the ferroelectric hysteresis as well as the butterfly hysteresis for ferroelectric ceramics. The rate–dependent character of the dissipation function allows us also to reproduce the experimentally observed rate dependency of the above mentioned hysteresis phenomena. An important aspect is the numerical implementation of the coupled problem. The discretization of the two–field problem appears, as a consequence of the proposed incremental variational principle, in a symmetric format. The performance of the proposed methods is demonstrated by means of a benchmark problem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modellierung der Umwandlungsplastizität und Viskoplastizität niedrig legierter Stähle
Authors: Schneidt Andreas , Mahnken Rolf 
Published: February 2009

AbstractBei dem Hybridumformprozess zur Einstellung gradierter Strukturen werden Kalt– und Warmumformung kombiniert. Dabei ist die gleichzeitige Umformung erwärmter und nicht erwärmter Bereiche eine verfahrensspezifische Besonderheit des Prozesses. Durch die Einstellung eines vordefinierten Temperaturprofils werden Werkstücke mit gradierten und somit flexiblen Werkstoffeigenschaften erreicht. Aufgrund der simultan auftretenden kalten und erwärmten Bereiche während des Hybridumformprozesses herrschen in dem Bauteil verschiedene Gefügezustände vor. Es treten sowohl weiche perlitische und ferritische als auch harte martensitische und bainitische Gefüge auf. Der Schwerpunkt unserer Arbeit wird auf die Austenit—Martensit Umwandlung gelegt. Für die numerische Simulation wird ein makroskopisches viskoplastisches Materialmodell mit Berücksichtigung der Umwandlungsplastizität (TRIP) präsentiert. Auf der Basis experimenteller Daten wird das Materialmodell kalibriert. Aufgrund fehlender Experimente wird ein numerisches Homogenisierungsverfahren eingesetzt, um das Fließverhalten des Mischgefüges zu berücksichtigen. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plane constrained shear of single crystal strip with one and two active slip systems
Authors: Le Khanh Chau , Sembiring Pramio 
Published: February 2009

AbstractThe plane constrained shear problems of a single crystal strip with one and two active slip systems are considered within the continuum dislocation theory. Analytical solutions are found for single slip and symmetric double slip systems which exhibit the energetic and dissipative thresholds for dislocation nucleation, the Bauschinger translational work hardening and the size effect. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary value problems in the theory of binary mixtures of thermoelastic solids
Authors: Svanadze Merab 
Published: February 2009

AbstractIn this paper the diffusion model of the linear theory of thermoelasticity of binary mixtures is considered. The basic properties of wave numbers of the longitudinal and transverse plane waves are established. The interior boundary value problem (BVP) of steady vibration of binary mixtures of thermoelastic solids is formulated. The existence theorems of eigenfrequencies of the BVP of steady vibrations are proved. The connection between plane waves and existence of eigenfrequencies is established. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of shear localization in elastic material by means of energy relaxation
Authors: Trinh Bach Tuyet , Hackl Klaus 
Published: February 2009

AbstractA new approach to the problem of shear localization is proposed. It is based on the energy minimization principle associated with micro–structure developments and the micro–shearing of a rank–one laminate which is aligned to shear band. The thickness of the shear band represented by the volume fraction is assumed to tend to zero. The non–convex energy due to the formation of the shear band is solved by energy relaxation in order to ensure that the problem is well–posed. An application of the proposed formulation to isotropic linear elastic material is presented. The capability of the proposed energy relaxation is demonstrated through numerical simulation of a plane strain tension. The numerical results demonstrate that there is no mesh–dependence. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromechanical Generalization of the Mises‐Hill Anisotropy Yield Criterion
Authors: Tsotsova R. , Böhlke T. 
Published: February 2009

AbstractThis paper proposes a new micromechanically motivated yield criterion expressed in terms of the leading tensorial texture coefficient of the crystallite orientation distribution function. The central finding is that although only a 4th–order anisotropy tensor occurs in the expression for the yield locus, the ansatz provides significantly better results in comparison to the quadratic Hill condition. The improvement is due to cubic and quartic tensorial contributions in terms of the stress direction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational Formulations and FE Active‐Set Strategies for Rate‐Independent Nonlocal Material Response
Authors: Welschinger Fabian , Miehe Christian 
Published: February 2009

AbstractWe propose a variational framework for the description of rate–independent nonlocal materials with microstructure and outline details of its numerical implementation. On the theoretical side, we focus on a multifield approach to microstructural dissipative mechanisms. To this end, the current state of the evolving microstructure is described by global fields of microscopic order parameters and their gradients, which together with the macroscopic deformation field define the multifield character of the problem under consideration. Focussing on rate–independent standard dissipative materials, the constitutive response is governed by an energy storage and a non–smooth dissipation function. For this scenario, we outline an incremental variational framework whose Euler equations define the macroscopic equilibrium along with the non–smooth global evolution of the order parameters. The formulation features fully–coupled macroscopic and microscopic field equations and associated boundary conditions. The key difficulty on the numerical side is the implementation of the global non–smooth evolution of the order parameters. Here, we outline a new active set strategy for the global finite element discretization of the multifield problem, where inequality constraints on the microscopic fields are taken into account by active nodal sets. An important consequence of the proposed variational approach is the symmetry of the coupled algebraic system. The proposed setting is specified for model problems of isotropic damage mechanics and crystal plasticity. The applicability of the proposed approach to nonlocal solids is highlighted by means of representative numerical examples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ermittlung (der Temperaturabhängigkeit) materialspezifischer Kennwerte von Miniaturproben aus Lotgut mittels Nanoindentation
Authors: Müller Wolfgang H. , Worrack Holger , Sterthaus Jens , Wilden Johannes 
Published: February 2009

AbstractFür die zuverlässige Herstellung und den Gebrauch immer kleiner werdender Geräte und Strukturen ist die Kenntnis der zugehörigen Werkstoffeigenschaften unerlässlich. Deren Ermittlung muss an Miniaturproben durchgeführt werden, da die gebräuchlichen, auf Standardproben beruhenden Verfahren keine verlässlichen Aussagen über das Materialverhalten im µm–Bereich geben. Aus diesem Grund wird hier die Ermittlung lokaler Parameter von Werkstoffen in Bauteilen in Anlehnung an die Untersuchung bleifreier Lotwerkstoffe mit Hilfe der sog. Nanoindentation beschrieben. Das Verfahren dient in erster Linie der Bestimmung von Standardwerkstoffkennwerten wie dem Elastizitätsmodul, der Fließgrenze und der Härte. Des Weiteren ist die Nanoindentation in der Lage, über den Ansatz der i nversen Methode ein vollständiges Spannungs–Dehnungs–Diagramm zu ermitteln, welches in dieser Arbeit mit dem Ergebnis eines herkömmlichen Zugversuchs verglichen wird. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison of the flow around a flexible and a non‐flexible airfoil for flapping wing propulsion
Authors: Bansmer S. , Unger R. , Kähler C. , Haupt M. , Radespiel R. , Horst P. 
Published: February 2009

AbstractThe flow around flapping airfoils is evaluated using the Stereoscopic Particle Image Velocimetry (PIV) technique. Resulting from the measurements is the distribution of the turbulent shear stress. This serves as an indicator for the position of transition from laminar to turbulent flow. The distributions were compared for both a flapping non–flexible airfoil and a flexible airfoil. It was determined that there are differences between the flow around the flexible and the non–flexible airfoils. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nuclear solitary waves
Authors: Chen X.‐N. , Maschek W. 
Published: February 2009

AbstractThis paper gives an overview of our recent work on the fission solitary wave reactor concept. In order to gain an insight into this problem a simple but appropriate model, namely a one–group diffusion equation coupled with simplified burn–up equations of e.g. the common U238–Pu239 conversion chain is studied. It is shown that this coupled system is analytically solvable in its one–dimensional case and a permanent plane solitary wave exists in a fertile medium, e.g. natural uranium. This wave mechanism could realize a nuclear reactor, which possess a constant reactivity and, more importantly, improves significantly the utilization of nuclear fuel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Finite Element Algorithm for Electromechanical Contact Problems
Authors: Weißenfels C. , Wriggers P. 
Published: February 2009

AbstractIn the last hundred years a lot of work is done in describing and measuring the influence of the pressure on the resistance and wear in electrical contacts. But up to now there exists a lack of knowledge in predicting and optimizing the behavior of electrical contacts with numerical simulation tools considering the pressure dependency. The present work provides a new constitutive model for the contact interface in the case of current flow and a new friction law including electrical wear phenomena. Additionally numerical investigations are made to compare the numerical results with experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Point defect interaction in tranversally isotropic ferroelectrics
Authors: Goy Oliver , Mueller Ralf 
Published: February 2009

AbstractFunctional materials, especially ferroelectrics are used in many devices like actuators, sensors and electronic devices. Due to high amounts of mechanical and electrical load cycles, fatigue phenomena may occur. This so called electric fatigue causes a decrease of the electromechanical coupling capability. It is assumed, that the ability to switch polarisation states, which is the reason for the ferroelectric effect, is decreased in the presence of point defects. These defects are ionic and electronic charge carriers, which can interact with each other, with microstructural elements in the bulk and with interfaces. Accumulation of defects can primarily lead to degradation, because of the loss of polarisation switchability.The interaction of defects in the bulk is simulated to get a better understanding of the defect accumulation processes. A model based on configurational forces can be used to obtain thermodynamic consistent kinetic laws. The material used is transversally isotropic and modelled with linear electromechanical coupling. The focus is on the influence of this material anisotropy on the defect interaction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stable long‐term simulation of dynamically loaded elastomers
Authors: Groß Michael , Betsch Peter 
Published: February 2009

AbstractA well–known problem in long–term simulations of flexible solid bodies is the restriction to small time steps of standard time integrators in order to obtain a stable simulation. One approach is to achieve exact energy conservation while simulating a nonlinear elastic body (see Reference [1] and the references therein). Additionally, total linear and total angular momentum is conserved for a free motion. This approach leads to a qualitatively improved solution, because the approximated time evolution exactly fulfills the same physical laws as the exact time evolution. Incorporating energy dissipation, the energy conserving time integration is extended to an energy consistent time integration. It turned out that such an energy consistent time integration is also of great advantage when computing finite motions of flexible solid bodies with material dissipation (see References [2,3]). This paper points out that an energy consistent time discretisation is also advantageous for dynamic finite deformation thermoviscoelasticity under dynamic loads. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled Problems of Dynamics in Materially Incompressible Saturated Porous Media
Authors: Heider Yousef , Markert Bernd , Ehlers Wolfgang 
Published: February 2009

AbstractThe mechanical behavior of saturated porous materials is largely governed by the interaction between the solid skeleton and the pore fluid. This interaction is particularly strong in dynamic problems and leads to numerical challenges especially in the case of incompressible constituents. In fact, the permeability plays a significant role in this coupling and influences the choice of a proper time integration scheme. Proceeding from the macroscopic Theory of Porous Media (TPM) within the isothermal and geometrical linear regime, the governing balance equations of the dynamic binary solid–fluid model are the solid and fluid momentum balances, and the overall volume balance of the biphasic mixture. This set of coupled partial differential equations (PDEs) is solved within the framework of the mixed Finite Element Method (FEM) applying two different time solution methods, viz., a monolithic implicit and a splitted implicit–explicit scheme. The time stepping algorithms are implemented into the FE program PANDAS and a Scilab FE routine and compared on a one–dimensional wave propagation example. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)