bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards variational constitutive updates for finite strain plasticity models based on non‐associative evolution equations
Authors: Mosler Jörn 
Published: March 2010

AbstractIn this contribution, first steps towards variational constitutive updates for finite strain plasticity theory based on non‐associative evolution equations are presented. These schemes allow to compute the unknown state variables such as the plastic part of the deformation gradient, together with the deformation mapping, by means of a fully variational minimization principle. Therefore, standard optimization algorithms can be applied to the numerical implementation leading to a very robust and efficient numerical implementation. Particularly, for highly non‐linear, singular or nearly ill‐posed physical models like that corresponding to crystal plasticity showing a large number of possible active slip planes, this is a significant advantage compared to standard constitutive updates such as the by now classical return‐mapping algorithm. While variational constitutive updates have been successfully derived for associative plasticity models, their extension to more complex constitutive laws, particularly to those featuring non‐associative evolution equations, is highly challenging. In the present contribution, a certain class of non‐associative finite strain plasticity models is discussed and recast into a variationally consistent format. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The conservation energy principle in description of stable and unstable states for aluminium
Authors: Wegner T. , Kurpisz D. 
Published: March 2010

AbstractIn the paper the physical model based on the energy conservation principle is proposed. On the basis of this principle the division of energy on volumetric and deviatory parts is presented. In this model a concept of energy division is recognised as important. Using the strain energy density function we can formulate criteria of the material equilibrium stability. Considerations are carried out for aluminium. All assumptions are based on uniaxial tension test supported by transverse deformation measurements. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and Simulation of Curing Processes of Epoxy Resin
Authors: Yagimli Bülent , Lion Alexander 
Published: March 2010

AbstractDuring the curing reaction, the adhesive changes its thermomechanical material behaviour from a viscous fluid to a viscoelastic solid. This phase transition is an exothermal chemical reaction which is accompanied by thermal expansion, chemical shrinkage and changes in temperature. In this work the numerical simulation of the curing process will be presented. The material model for the implementation is presented in [1]. For the implementation of the material model the consistent tangent operator has been derived. In the presentation, experimental data and simulation are shown. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromechanical Modeling of Woven Fiber Composites for the Construction of Effective Anisotropic Polyconvex Energies
Authors: Ebbing Vera , Schröder Jörg , Neff Patrizio , Gruttmann Friedrich 
Published: March 2010

AbstractIn computer simulations where constitutive equations are considered polyconvex energies can preferably be used because the existence of minimizers is then automatically guaranteed. In this work we investigate the capability to simulate woven fiber composites using polyconvex energies. A virtual experiment of the microstructure of the considered composite is performed and the results are used for the specification of an effective macroscopic anisotropic polyconvex model. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On The Formulatio and Numerical Implementation of Dissipative Electro‐Mechanics at Large Strains
Authors: Rosato Daniele , Miehe Christian 
Published: March 2010

AbstractIn the last year an increasing interest in functional materials such as ferroelectric polymers and ceramics has been shown. For those materials viscous effects or electric polarizations cause hysteresis phenomena accompanied with possibly large remanent strains. This paper outlines aspects of the formulation and numerical implementation of dissipative electro‐mechanics at large strains. In the first part, we focus on the geometric nature of dissipative electro‐mechanics. In a second part, we discuss constitutive assumptions which account for specific problems arising in the geometric nonlinear setting. This concerns the definition of objective energy storage and dissipation functions with suitable symmetries and (weak) convexity properties. With regard to the choice of the internal variables entering these functions, a critical point are kinematic assumptions. Here, we investigate the multiplicative decomposition of the local deformation gradient into reversible and remanent parts as well as the introduction of a remanent metric. In a third part, we summarize details of the constitutive updates as well as the finite element formulations, both on the basis of compact incremental variational principles. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Configurational–Force–Based Adaptive Methods in Nonlocal Gradient‐Type Inelastic Solids
Authors: Welschinger Fabian , Miehe Christian 
Published: March 2010

AbstractWe propose a configurational‐force‐based framework for h‐adaptive finite element discretizations of solids with nonlocal, gradient‐type constitutive response. Typical applications are related to gradient‐type damage mechanics, strain gradient plasticity and regularized brittle fracture. On the theoretical side, we outline a general incremental variational framework for the multifield problem of gradient‐type dissipative solids, where generalized internal variable fields account for the current state of evolving microstructures. The Euler equations of the multifield variational principle define the macroscopic balance of momentum along with balance‐type evolution equations for the generalized internal variables in the physical space as well as the balance of configurational forces in the material space. We propose a staggered computational scheme for satisfying those balances in both the physical as well as the material space. The coupled micro‐ and macro‐structural balances of momentum and internal variables provide a solution in the physical space for a given finite element mesh. The balance in the material space is then used to provide an indicator for the quality of the finite element mesh and accounts for a subsequent h‐type mesh refinement. Such a configurational‐force‐based approach provides in a natural and unified format mesh refinement indicators for a broad class of complex nonlocal problems. This framework is applied to damage‐type regularized brittle fracture. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of viscoelastic material behaviour close to the glass transition temperature
Authors: Johlitz Michael , Diebels Stefan , Lion Alexander , Possart Wulff 
Published: March 2010

AbstractIn this contribution we investigate the mechanical behaviour of polyurethane over a range of different but constant temperatures from the glass to the viscoelastic state. Therefore uniaxial tension tests are performed on dogbone specimens under different isothermal conditions. In this manner an experimental data set is provided. As a theoretical basis we present the well known thermomechanically coupled one dimensional linear viscoelastic material model which is able to display the experimentally observed material behaviour. For this we adopt temperature dependent relaxation times. The introduced model parameters are identified via a standard parameter identification tool. Finally, the experimental results are compared with the ones of simulations of the identified model parameters. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A finite element model for laminated piezoelectric shell structures
Authors: Legner Dieter , Klinkel Sven , Wagner Werner 
Published: March 2010

AbstractThin piezoelectric laminates are used for a wide range of technical applications. A four‐node piezoelectric shell element is presented to analyse such structures effectively. In case of bending dominated problems incompatible approximation functions of the electrical and mechanical fields cause incorrect results. In order to overcome this problem the finite element formulation is based on a mixed variational principle implying six independent fields: displacements, electric potential, strains, electric field, mechanical stresses and dielectric displacements. This allows for an interpolation of the strains and the electric field in thickness direction independent of the bilinear interpolation functions. A piecewise quadratic approach for the shear strains in thickness direction and the corresponding electric field is proposed for arbitrarily layered shells. Regarding coupling of electrical and mechanical fields this yields to an appropriate balance of the approximation functions. Numerical examples show more precise results in contrast to standard elements with lowest order interpolation functions. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic finite deformation viscoelasticity and energy‐consistent time integration
Authors: Müller Melanie , Groß Michael , Betsch Peter 
Published: March 2010

AbstractIn the present work we deal with the conserving integration of viscoelastic bodies undergoing finite deformations.Isotropic viscoelastic materials can be described by using a symmetric viscous internal variable ${\cal C}_i$ for measuring the inelastic strains, and the right Cauchy‐Green tensor $\cal C$ as measure of the total strain (see Reese & Govindjee [1]). Then, by using the unsymmetric product tensor ${\cal C} {\cal C}_i^{-1}$, the purely elastic strains enter the isotropic free energy function. Alternatively, the i application of the symmetric right stretch tensor ${\cal U}_i$ as internal variable allows to define a symmetric elastic strain tensor ${\cal C}_e$ which enters the free energy (see also Miehe [2]). These two different approaches lead to different evolution equations for the viscous internal variable.In this lecture, both evolution equations are discretised by an ordinary midpoint rule at each Gauss point of a standard nonlinear displacement‐based finite element in space. For discretising the semidiscrete Hamilton's equations of motion in time, we use numerical time integrators which preserve the fundamental conservation laws of the underlying system. In particular, we make use of a modified midpoint rule according to the discrete gradient method, proposed in Gonzalez [3]. Numerical examples demonstrate the difference between both formulations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermo‐mechanical behaviour of X‐ray masks in micro system technology
Authors: Körner Claudia , Seemann Wolfgang 
Published: March 2010

AbstractIn the field of micro system technology, the fabrication of micro structure components is on the cusp to industrial production due to economical competition and the necessity to innovate technology. Regarding the X‐Ray lithography process (LIGA), an X‐Ray radiation passes through a mask in form of a membrane with extremely high intensive synchrotron radiation. This leads to locally high temperatures and thus to an inhomogeneous and unsteady deformation in the mask and in the resist. Though, necessary for the production process, this concentration of energy is contradictory to the demand of quality. The goal of this paper is to present a first simplified model of the exposure step in a finite‐element program in order to get a tool providing an optimization of the temperature rise. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanically coupled modeling and simulation of aluminum alloys during hot forming processes
Authors: Parvizian Farhad , Kayser Tobias , Svendsen Bob 
Published: March 2010

AbstractThe aim of this work is thermomechanically coupled simulation and modeling of material behavior and microstructural evolutions during metal forming processes such as extrusion. The material model is implemented as an UMAT in the Finite Element (FE) software ABAQUS. The microstructre parameters such as subgrain size, misorientation and dislocation density are considered as internal state variables. Some of the results of the applied model are presented. The simulation results are in good agreement with experimental observations. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamic Modelling of Defect Migration in Ferroelectric Materials
Authors: Goy Oliver , Mueller Ralf , Gross Dietmar 
Published: March 2010

AbstractMotivated by the phenomenon of electric fatigue, point defects and their interaction in ferroelectric material are studied with a focus on the tendency of clustering. The underlying continuum model takes into account the full anisotropic electromechanical material properties. Isotropic and anisotropic defect descriptions and their influence on defect interaction will be compared. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proof of Positive Definiteness of FI and Extended Finite Element Tearing and Interconnecting XFETI
Authors: Sadeq Obaid Abdulrahman , Reese Stefanie 
Published: March 2010

AbstractWe propose a mathematical theorem to prove the positive definiteness of the term FI used in Finite Element Tearing and Interconnecting introduced by Farhat [1]. Furthermore, we introduce a new idea to extend FETI to include non‐self adjoint operators emerging from, for example, elastoplastic large deformation, non‐associative plasticity or when coupling BEM and FEM [2]. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Freezing and thawing processes in porous media – Experiment and Simulation
Authors: Bluhm Joachim , Ricken Tim , Bloßfeld Wolfgang Moritz 
Published: March 2010

AbstractIn this paper, a ternary macroscopic model has been presented with respect to the simulation of freeze‐thaw cycles in liquid filled porous media. Regarding the detection of energetic effects during the phase transition a modified ansatz for the supply term of mass was discussed. The illustrated results of the example show that the simplified model is capable to predict experimental observations. Especially, the influence of the heat of fusion could be realized in an efficient manner. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrical Aspects of the Incorporation of Free Space in Magnetomechanics at Finite Strains
Authors: Kiefer Björn , Rosato Daniele , Miehe Christian 
Published: March 2010

AbstractThis paper addresses the modeling of finite magnetoelasticity with a particular focus on the incorporation of free space energy storage and magnetic body forces. First, a coordinate‐invariant formulation of an extended Neo‐Hookean model with magnetostrictive coupling is presented. Then, a finite element model for finite magnetomechanics based on a variational stationarity principle is formulated. The influence of magnetic body forces is studied in an exemplary boundary value problem. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The discrete‐continuous model of the one‐dimension vibrating mechatronic system
Authors: Buchacz Andrzej , Płaczek Marek 
Published: March 2010

AbstractThis work presents the analysis of the flexural vibrating one‐dimension mechatronic system – the cantilever beam and the piezoelectric transducer bonded with the beam's surface by means of a connection layer. The external RC circuit is adjoined to the transducer's clamps. Dynamic equations of motion of the considered mechatronic system were written down using discrete – continuous mathematical model, taking into consideration the influence of the connection layer and the external electric circuit. The dynamic flexibility of the mechatronic system was assigned on the basis of the approximate Galerkin's method. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the Chain‐Like Non‐Linear Multi‐Degree‐of‐Freedom Systems Constant Parameters under Dynamical Complex Loads
Authors: Bocian M. , Jamroziak K. , Kulisiewicz M. 
Published: March 2010

AbstractA determination of mechanical properties of the real material systems under dynamical excitations is a very complex problem. The real system can be described by continuous model as well as a discrete model with a finite number of degree‐of‐freedom. Some mechanical systems like beams, rods, strings, tow‐lines etc. have so‐called chain‐like configuration and may be treated as the dynamical one‐dimensional cascade systems. In this paper, an identification method of internal interaction force, which can be arbitrary selected in discrete chain‐like non‐linear system, is presented. The method was tested on example of a two‐mass system in which the interaction forces were modeled by spring‐damper elements in a non‐parallel arrangement. In experiment some non‐sinusoidal complex loads were applied. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A reformulation of the Jiles‐Atherton hysteresis model for ferromagnetic/ferroelectric components
Authors: Müller Andreas 
Published: March 2010

AbstractThe original Jiles‐Atherton model for modeling hysteresis in ferroelectric media relates the magnetization, or likewise the magnetic polarization, and the magnetic field strength. Since discrete dimensional electromechanical systems are usually modeled using the flux formulation the Jiles‐Atherton model is not applicable in its original form. In this contribution a reformulation in terms of the magnetic flux density is presented. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of self‐activating temperature influence on cracks initiation in GRP laminates
Authors: Katunin Andrzej , Moczulski Wojciech 
Published: March 2010

AbstractThe paper deals with problems of fatigue processes of GRP laminates under the influence of cyclic loads. An important aspect which takes place in laminate fatigue with polymer matrix is self‐activating temperature generated by friction. As it has been shown in previous authors' research, the phenomenon has significant influence on laminate behavior, also, when self‐activating temperature comes to glass‐transition temperature, which begins transition from elastic to viscoelastic material model. After passing over of this temperature the stiffness decreasing is supervised, that can lead to more quick propagation of faults (especially delaminations) and decreasing of life cycle of composite laminate element. The aim of the presented paper is simulation research of fatigue processes with taking into consideration self‐activating temperature and rheology of material. In the research four cases are analyzed, in which layers rotation, self‐activating temperature increasing and changes of rheological model were taken into consideration. As the research shows, the self‐activating temperature has significant influence on fatigue processes, because it can cause transition of the rheological model of the material. In the future research an experimental verification of the model is planned. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the calculation of crack face opening displacements in fiber reinforced composites under plane loading
Authors: Richter Mike , Bayer Daniela 
Published: March 2010

AbstractThis paper concerns with the calculation of the crack face opening displacement in fiber reinforced composites using analytical, semi‐analytical and numerical approaches. Crack bridging is one of the most characteristic effects of fibers on the material behavior of the composite. Knowing the crack face opening displacement the additional strain due to cracks can be calculated and used in homogenization procedures. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Ghost Forces in 3D Quasicontinuum Model
Authors: Shan Wenzhe , Nackenhorst Udo 
Published: March 2010

AbstractIn this contribution, we propose an intuitive explanation for the artificial effect, named as ghost force, that arises in the coupling region of a multiscale method, known as Quasicontinuum method, and introduce a simple technique that can be used to reduce this ghost force. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromechanical material models for polymer composites through advanced numerical simulation techniques
Authors: Al Kassem G. , Weichert D. 
Published: March 2010

AbstractThe paper deals with the determination of macroscopic material properties of polymer composites by meso‐mechanical numerical modeling. Focus is laid on the methodology how to build up appropriate representative volume elements (RVE) to describe the microstructure of spherical‐particles and fibers reinforced composites and how to apply appropriate 3D boundary conditions. The work includes the comparison of the effective material parameters calculated through numerical homogenization of our FE‐models with existing analytical formulations as well as with experimental data. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Obtaining Cosserat material parameters by homogenization of a Cauchy continuum
Authors: Branke Dominik , Brummund J. , Haasemann G. , Ulbricht V. 
Published: March 2010

AbstractAn increasing importance of composites with sandwich architecture and fibre‐reinforced components is recognizable especially in aerospace and light weight industry. Due to the inner structure such materials often exhibit a complex behavior. If the ratio of micro‐ and macroscopic length scales, l and L, violates the condition l/L ≪ 1, a higher order continuum should be used to describe the macroscopic material behavior correctly. The numerical simulation requires reliable material constants, for which the experimental determination is laborious and sometimes impossible. Alternatively homogenization methods can be used for the numerical identification of overall material parameters. A short introduction to the linear Cosserat theory is followed by an extended homogenization procedure to derive the macroscopic material constants of a linear Cosserat continuum. The parameters obtained with a heterogeneous cell are used to simulate different bending load cases. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bounds for the Elastic Properties of Pyrolytic Carbon
Authors: Böhlke Thomas , Langhoff Tom‐Alexander , Piat R. 
Published: March 2010

AbstractThe elastic properties of heterogeneous materials without defects depend on both the constitutive properties of the constituents and the microstructural characteristics. In this paper the first‐order bounds of aggregates of domains with hexagonal material symmetry are determined in terms of tensorial texture coefficients. The predictive capability of these bounds is compared to higher‐order bounds for pyrolytic carbon. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical homogenisation strategy for micromorphic continua
Authors: Jänicke Ralf , Diebels Stefan 
Published: March 2010

AbstractIn this contribution, we apply a numerical homogenisation scheme for micromorphic continua replacing constitutive equations on the macroscale by a microscopic boundary value problem. The aim of this procedure is to describe the influence of the microtopology on the effective behaviour of microstructured materials such as biological tissues as well as polymer or metal foams. On the one hand, that allows for avoiding the numerically expensive calculation of a fully resolved microstructure. On the other hand there is no need to identify additional material parameters which are in general hard to interpret from the physical point of view. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)