bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructure evolution during rolling and annealing of mild steels
Authors: Bienger Pierre , Butz Alexander , Helm Dirk 
Published: November 2010

AbstractThe process chain for components made of sheet metals consists of different forming techniques like hot rolling, cold rolling, and deep drawing as well as heat treatment operations like annealing. For the design and optimization of the whole manufacturing process and the final component behavior, a correct representation of the material behavior and the application of appropriate numerical simulation techniques are required. For our first investigations, a ferritic mild steel DC04, which is a typical steel grade for automotive applications, is analyzed. Therefore, specimens are taken out of a real manufacturing process after hot and cold rolling and after annealing. These specimens are intensively investigated in order to study the texture evolution and the development of other material properties, like yield function during the process chain. In this paper different homogenization methods are used to simulate the texture evolution during cold rolling. The results are compared concerning accuracy and efficiency of the considered models. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructural changes of filled rubber‐like materials under cyclic loading
Authors: Dargazany Roozbeh , Itskov Mikhail , Liu Junwei 
Published: November 2010

AbstractThe concept of network decomposition has vastly been used in many micro‐mechanical models describing stress‐softening of rubber‐like materials in the first loading cycle as for example the Mullins‐effect. Nevertheless, this concept highly simplifies the rubber matrix by decomposing it into two parallel networks that have no interactions with each other.In order to take into account the interactions between these networks some further extensions to the network decomposition concept seem necessary. To this end, a third network is introduced and the concept of rubber cell is proposed and developed. Using this concept, the influence of the filler network on elasticity of the two networks can be predicted by considering the cell as a RVE. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a model of viscoelasticity with internal state variables
Authors: Peters Johanna , von Estorff Otto , Achenbach Manfred , Lion Alexander 
Published: November 2010

AbstractIn classical theories of viscoelasticity, time‐dependent effects are accounted for only with respect to the mechanical properties. However, glass‐forming materials such as polymers, for example, also show viscoelastic effects in their thermal properties as can be seen from measurements of the coefficient of thermal expansion or the heat capacity. In this contribution, a model is presented that is able to describe effects associated with the glass transition in the mechanical as well as the thermal properties in one consistent approach. To this end, the state space known from equilibrium thermodynamics is enlarged by internal state variables. These variables are to describe the deviation from equilibrium, hence allowing for a description of viscoelastic effects. Closed form expressions for the complex modulus as well as the compliance, the complex heat capacity at constant stress as well as at constant strain, and the complex coefficient of thermal expansion as well as the thermal modulus are derived and discussed. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formulation and Numerical Implementation of Ferroelectrics at Large Strains
Authors: Rosato Daniele , Miehe Christian 
Published: November 2010

AbstractIn recent years, an increasing interest has been shown in functional materials such as ferroelectric polymers. For such materials, viscous effects and electric polarizations cause hysteresis phenomena accompanied with possibly large remanent strains and rotations. Ferroelectric polymers have many attractive characteristics. They are light, inexpensive, fracture tolerant, and pliable. Furthermore, they can be manufactured into almost any conceivable shape and their properties can be tailored to suit a broad range of requirements. In this work, continuous and discrete variational formulations are exploited for the treatment of the non‐linear dissipative response of ferroelectric polymers under electrical loading. The point of departure is a general internal variable formulation that determines the hysteretic response of this class of materials in terms of an energy storage and a rate‐dependent dissipation function. The ferroelectric constitutive assumptions, which account for specific problems arising in the geometric nonlinear setting, are discussed. With regard to the choice of the internal variables, a critical factor is the kinematic assumptions. Here, we propose the multiplicative decomposition of the local deformation gradient into reversible and remanent parts, where the latter is characterized by a metric tensor. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of bainitic phase transformation
Authors: Schneidt Andreas , Mahnken Rolf 
Published: November 2010

AbstractIn this work, we present a macroscopic material model for simulation of austenite to bainite and of austenite to martensite transformations accompanied by transformation‐induced plasticity (TRIP), which is an important phenomenon in metal forming processes. In order to account for the incubation time the model considers nucleation of the bainite phase. When this quantity attains a barrier term, growth of bainite volume fraction is started. The model formulation allows for individual evolutions of upper and lower bainite. Furthermore, the numerical implementation of the constitutive equations into a finite element program is described. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FEM simulation of oxidation induced stresses in a simplified thermal barrier coating system
Authors: Seiler Philipp , Bäker Martin , Rösler Joachim 
Published: November 2010

AbstractTo study the behaviour of the complex failure mechanisms in thermal barrier coatings, a simplified model system is used to reduce the number of system parameters. The artificial system consists of a bond‐coat material (fast creeping Fecralloy or slow creeping MA956) as the substrate with a Y2O3 partially stabilized plasma sprayed zircon oxide TBC on top and a TGO between the two layers. A FEM simulation was developed to calculate the stress distribution inside the coating system. The simulation permits the identification of compression and tension areas which are established by the growth of the oxide layer and the stresses which occur during the heating and cooling processes. Full thermal cycles, including heating from RT to 1000°C, dwelling for 2 hours and cooling to RT, were simulated.The stress distributions provide an insight into the possible failure mechanisms in the coating and allow to draw conclusions for optimizing real thermal barrier coating systems. It is shown that the failure mechanism depends on the creep properties of the bond‐coat. Therefore, optimizing the creep properties may adjust lifetime of the whole coating system. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of shear band formation in elastic material by energy relaxation
Authors: Trinh Bach Tuyet , Hackl Klaus 
Published: November 2010

AbstractFollowing up the previous work, [1], a new approach to the problem of shear localization is proposed, based on energy minimization principles associated with micro‐structure developments. In this approach, two different material models are included. They represent the behaviour of material at very small strain and very large strain, respectively. Herein, shear bands are treated as the micro‐shearing of rank‐one laminates. The thickness of a shear band represented by its volume fraction is assumed to tend to zero while the strain inside the shear band tends to infinity. The existence of shear bands in the structure leads to an ill‐posed problem which can be solved by means of energy relaxation. The performance of the proposed energy relaxation is demonstrated through numerical simulation of a tension test under plane strain conditions. The presented numerical simulation shows that there is no mesh‐dependence. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Multiphasic Model Describing the CO2 Injection Problem
Authors: Komarova Irina , Ehlers Wolfgang 
Published: November 2010

AbstractAccording to the annual data, the portion of ejected carbon dioxide (CO2) into the atmosphere is much higher in comparison to other greenhouse gases. Therefore, the development of various scenarios in order to reduce the CO2 concentration in the atmosphere is nowadays a challenge and a relevant subject in research. The current investigation is dedicated to the modelling of a CO2 injection into a water‐saturated aquifer as the most capable reservoir, where its upward migration is blocked by a dense cap‐rock layer. The major part of the study is focused on two specific processes taking place in the stored reservoir: the phase transfer phenomenon of the supercritical CO2 which occurs under changeable surrounding conditions and the sequestration‐driven deformation of the solid skeleton acting under the pressure of the pumped CO2. For the numerical simulations within a continuum‐mechanical framework, a multiphasic model based on the Theory of Porous Media is introduced. Moreover, the main principles of developing a constitutive equation for the mass production term for the mass balance equation are discussed here. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application for generating characteristics of free and bonded systems
Authors: Buchacz Andrzej , Wrobel Andrzej 
Published: November 2010

AbstractThe present paper is the continuation of earlier publications with stack of piezoelectric plates. This work is an author's idea of application for generating characteristics of piezoelectric systems. The presented program, called Piezo3D, allows for generation a single piezoelectric plate graphs as well as complex, free and bonded systems. An additional advantage is the ability to obtain the 3D graphs, in which the characteristics of the test graph can be based not only on frequency, but also on other parameters such as the thickness of the plate. The application is written in the numerical software "Matlab". (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of heterogeneous dielectric elastomer actuators
Authors: Müller Ralf , Xu Bai‐Xiang , Gross Dietmar , Lyschik Mathias 
Published: November 2010

AbstractDielectric elastomer actuators, consisting of an elastomer film sandwiched between two compliant electrodes, are of increasing interests in application. Due to the nonlinearity, the nature of large deformation and the coupling of different physical fields, numerical investigations based on reasonable models are necessary. In the present work, the modeling and the numerical simulation of deformable dielectrics are discussed in a coupled electro‐mechanical framework. It shows how the Maxwell stress contributions can be implemented efficiently into a finite element method. For the purpose of improving the efficiency of the actuators, strategies to increase the electro‐mechanical coupling by a modified microstructure are discussed. The idea of introducing ceramic inclusions in soft elastomer is proposed, which can at the same time make use of the high relative dielectric constants of the ceramics and the large deformation of the soft elastomer. Numerical results confirm the improvement of the performance efficiency. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the number of grains in a polycrystal on the prediction of texture during rolling by using the Taylor approach
Authors: Jöchen Katja , Böhlke Thomas 
Published: November 2010

AbstractThe estimation of the texture in a sheet metal induced by rolling is an important issue for the accurate description of forming operations as, e.g., deep drawing. In this paper, we discuss the influence of the number of grains in the polycrystal on the prediction of the pole figures as well as on the α and β fiber in the orientation distribution function. For this study, we use the Taylor model as homogenization method where it is assumed that the macroscopic deformation of the polycrystal is identically transferred to each single crystal. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Dirichlet boundary conditions in second‐order FE2‐schemes
Authors: Sehlhorst Hans‐Georg , Düster Alexander , Jänicke Ralf , Diebels Stefan 
Published: November 2010

AbstractIn recent years FE2‐methods have become quite popular since they allow for accurate modeling of materials with inherent microstructures like, for example, foams, biological tissues, or cement paste. In FE2‐schemes of first‐order usually standard continua are applied on both, the micro‐ and the macroscale, whereas in FE2‐schemes of second‐order at least on the macroscale an extended continuum theory is considered. In both cases the scales are coupled by projection and homogenization rules. Due to the extended kinematics, second‐order schemes can capture higher‐order effects like, for example, size effects. In this contribution we discuss the projection of extended deformation modes when applying high‐order finite elements with hierarchic shape functions to discretize the microstructure. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wavelet‐based Methods for Multirate PDAEs
Authors: Winkler Renate 
Published: November 2010

AbstractWe present an adaptive envelope method for the transient simulation of problems with widely separated time scales. Typical applications are circuits where a periodic carrier signal is modulated by a slower signal. The presented method is specifically designed to work even in the case of steep gradients due to digital‐like signal structures. Using different independent variables for the slow and the fast time scales the original system is transformed to a hyperbolic multi‐rate differential‐algebraic system, from which the solution of the original system can be reconstructed. After discretising the slow time scale a periodic boundary value problems in the fast time scale has to be solved for each slow time step. These are solved by wavelet collocation using piecewise linear ansatz‐functions. To adapt the grid the solution is represented in terms of a hierarchical set of biorthogonal wavelets to detect the areas with rapidly changing solutions and to coarse or refine the grid. The performance of the method is illustrated by a circuit example. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation der Zeitabhängigkeit von Selbstorganisationsprozessen in gefüllten Gummiwerkstoffen
Authors: Ihlemann Jörn , Wulf Hans 
Published: November 2010

AbstractGefüllte Gummiwerkstoffe zeigen in mechanischen Belastungsversuchen ein sehr komplexes Verhalten. Dies gilt insbesondere auch für die Geschwindigkeitsabhängigkeit des Materialverhaltens. Die SOLP‐Theorie erklärt diese Ergebnisse mit einem auf molekularer Ebene ablaufenden, auf dem Zerfall und der Rekombination physikalischer Bindungen beruhenden Selbstorganisationsprozess. Der Überprüfung dieser Hypothese dient ein Simulationsprogramm, welches den Selbstorganisationsprozess nachbildet. Zunächst wird das dem Programm zugrunde liegende Modell vorgestellt. Im Anschluss daran werden Ergebnisse der Simulationen mit Messungen verglichen. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Variational Homogenization Approach to Electromechanical Hystereses Caused by Domain Wall Movement
Authors: Zäh Dominic , Rosato Daniele , Miehe Christian 
Published: November 2010

AbstractIn recent years, increasing interest in so‐called smart materials such as ferroelectric polymers and ceramics has been shown. Those materials are used in various actuators, sensors, and also in medical devices. In this paper, we outline a micro‐macro approach to the modeling of macroscopic hystereses which directly takes into account the microstructural evolution of electrically poled domains. To this end, an incremental variational formulation for a gradient‐type phase field model is developed and exploited for the simulation of electromechanically coupled problems. The formulation determines the hysteretic response of the material in terms of an energy‐enthalpy and a dissipation function which both depend on the microscopic remanent polarization treated as an order parameter. The gradient‐type balance law for the phase field can be considered as a generalization of Biot's equation for standard dissipative materials and may be related to the classical Ginzburg‐Landau equation. Furthermore, the variational formulation serves as natural starting point for a compact and symmetric finite element implementation of the coupled micromechanical problem covering the displacement, the electric potential, and the microscopic polarization vector. For this three‐field scenario we develop a variational‐based homogenization method which determines the overall macroscopic hysteretic properties of a polycrystalline aggregate. The proposed computational method can be used as a numerical laboratory for the improvement of microstructural properties. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localized Roll‐Solutions in the Ekman‐Couette‐System
Authors: Withalm Martin , Hoffmann Norbert P. 
Published: November 2010

AbstractIn the Ekman‐Couette‐System, where the usual Couette‐System is additionally rotated about its normal axis, localized single roll solutions have been known for some time. By varying different system parameters, a new localized solution emerging by saddle‐node bifurcations from these known solutions has now been found. This new solution is of the same localized nature like the old solution but with an additional roll. Further bifurcations lead then to an increasing number of rolls, still localized. This behavior is kind of analogous to the so called ‘homoclinic snaking’ which has recently been investigated in conjunction with the Swift‐Hohenberg equation and binary fluid convection. It might link the unstable localized single roll solutions with stable multi roll solutions or even with stable periodic roll solutions, which has to be shown yet. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Peculiarities of the surface and guided waves propagation in heterogeneous composites with nematic coatings
Authors: Zakharov Dmitry , Kaptsov Alexandr 
Published: November 2010

AbstractUsing the effective low frequency model of nematic medium we study the phase speeds and attenuations of the quasi‐Rayleigh and Love waves in composite made of elastic core with the peripheral coating, as well as the fundamental S0 and A0 Lamb modes in heterogeneous plates. The analytical and numerical analysis revealed two types of unusual resonance effects disturbing wave propagation. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of wall conductivity on turbulent channel flow under spanwise magnetic field
Authors: Krasnov Dmitry , Parepalli Prarthana , Zikanov Oleg , Boeck Thomas 
Published: November 2010

AbstractThe effect of wall conductivity on turbulence in electrically conducting fluid in the presence of a constant magnetic field is considered. A channel flow with a spanwise magnetic field is analyzed using high‐resolution direct numerical simulations performed for the case of low magnetic Reynolds number. It is found that the effect of suppression of wall‐normal momentum transfer and reduction of wall friction identified earlier for the flow with perfectly insulating walls is enhanced if the walls are electrically conducting. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Optimization of the Full Radiative Heat Transfer System
Authors: End Thomas 
Published: November 2010

AbstractSolving the full radiative heat transfer equation, moderately discretized in space, time, frequency and direction, results in a tremendously huge system of equations. A common approach to avoid this problem is to use moment methods neglecting the directional dependence on radiation. Our approach, however, is to solve the full radiative heat transfer system with all dependencies and to optimize the heat distribution and the radiative flux, respectively, for a desired temperature function or desired radiative flux function. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pivot Tightening for the Interval Cholesky Method
Authors: Garloff Jürgen 
Published: November 2010

AbstractThe performance of the Cholesky decomposition in interval arithmetic is considered. In order to avoid the algorithm breaking down due to an interval pivot containing zero, a method is presented by which such a pivot can be tightened. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
hp‐Adaptivity in Two and Three Space‐Dimensions
Authors: Bürg Markus , Dörfler Willy 
Published: November 2010

AbstractWe present an hp‐adaptive refinement strategy for two and three space‐dimensions, which is based on the strategy presented in [2], and a convergence result for this strategy is stated. Then the refinement strategy is applied to some two‐ and three‐dimensional model problems. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis and Application of the Rational B‐Spline Finite Element Method in 2D
Authors: Klassen Markus , Müller Ralf , Mergheim Julia , Fischer Paul , Steinmann Paul 
Published: November 2010

AbstractNon‐Uniform Rational B‐Splines (NURBS) are basis functions used in CAD software to describe exact geometric models. The implementation of these basis functions in the context of the Finite Element Analysis (FEA) is known as isogeometric analysis. The concept and definition of NURBS is briefly presented here. Since these functions are implemented as shape functions for the isogeometric analysis, the refinement strategies are discussed. The example of an infinite plate with circular hole serves as a benchmark. Finally, isogeometric analysis is applied to gradient elasticity since NURBS functions are of higher continuity and this is required in gradient elasticity. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Verification Tools for Reduced Derivatives Computed by a First‐Optimize‐Then‐Discretize Approach for Optimal Control Problems
Authors: Clever Debora 
Published: November 2010

AbstractWe give an overview about several verification tools to study consistency between discrete optimization problem and discrete derivatives when using independent discretization schemes for state and adjoint systems within the context of optimal control problems. We present strategies that detect impreciseness within a considered quantity without any additional effort. They are therefore a suitable tool to control the grid refinement within a multilevel setting. More detailed tools are useful to verify the problem implementation and to analyze the quantities discretization error order. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A State‐Space Implementation of Anti‐Causal Iterative Learning Control
Authors: Becker Urs , Damm Tobias 
Published: November 2010

AbstractIterative learning control is used to find input signals which match a previously generated output trajectory by repetitively correcting the inputs through the tracking errors. Using causal learning operators this only works up to a relative degree of one. We overcome this restriction with an anti‐causal approach following [1] and show a practical implementation in the state‐space with some examples. We also motivate the method as useful to determine inputs for simulations and test‐rigs. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)