bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laminate‐based modelling of microstructure and switching in ferroelectrics
Authors: Dusthakar Dinesh K , Menzel Andreas , Svendsen Bob 
Published: December 2014

AbstractThe purpose of the work is the thermodynamics‐based modelling of the polarisation and the deformation microstructure in the ferroelectric single crystal with the help of a laminate‐based approach. The incremental variational‐based rate‐dependent macroscopic model for dissipative ferroelectric material [1] and the laminate‐based microscopic model [2] established in the literature are taken as basis and shall be further extended to a single crystal laminate structure dependent on the loading frequency based on the coupled electromechanical framework taking the effect of polarisation into account. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards Phase Field Modeling of Ductile Fracture in Gradient‐Extended Elastic‐Plastic Solids
Authors: Aldakheel Fadi , Mauthe Steffen , Miehe Christian 
Published: December 2014

AbstractThe modeling of failure in ductile metals must account for complex phenomena at a micro‐scale as well as the final rupture at the macro‐scale. Within a top‐down viewpoint, this can be achieved by the combination of a micro‐structure‐informed elastic‐plastic model with a concept for the modeling of macroscopic crack discontinuities. In this context, it is important to account for material length scales and thermo‐mechanical coupling effects due to dissipative heating. This can be achieved by the construction of non‐standard, gradient‐enhanced models of plasticity with a full embedding into continuum thermodynamics [1,2]. The modeling of macroscopic cracks can be achieved in a convenient way by recently developed continuum phase field approaches to fracture based on regularized crack discontinuities. This avoids the use of complex discretization methods for crack discontinuities, and can account for complex crack patterns within a pure continuum formulation. Moreover, the phase field modeling of fracture is related to gradient theories of continuum damage mechanics, and fits nicely the structure of constitutive models for gradient plasticity. The main focus of this work is the extensions to gradient thermoplasticity and phase field formulation of ductile fracture, conceptually in line with the work [3]. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational aspects of three‐phase modelling using a suction dependent cap model
Authors: Gamnitzer Peter , Hofstetter Günter 
Published: December 2014

AbstractThis contribution is on computational aspects of the application of a suction dependent modified cap model for geomaterials, which was presented at the 84th GAMM annual meeting. The modified cap model features an elasto‐plastic material response and is formulated in terms of two independent stress variables, generalised effective stress and matric suction. It has a smooth, suction dependent yield surface. The cap model is usually used in the context of coupled three‐phase simulations. Thus, the computational aspects that will be discussed below comprise several levels: i) the stress projection level (at which a robust one equation projection scheme with improved start‐up procedure is applied), ii) the nonlinear system solution level (at which a line search is suggested to increase robustness) and iii) the linear system solution level (for which iterative solvers and preconditioners are discussed which have been found suitable for the problem under consideration). (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the simulation of soils under rapid cyclic loading conditions
Authors: Schenke Maik , Markert Bernd , Ehlers Wolfgang 
Published: December 2014

AbstractWhen simulating soils, which are subjected to dynamic loadings conditions, base on a convenient soil model, special attention has to be paid to the approximation of the real problem by a suitable initial‐boundary‐value problem (IBVP). In this regard, the semi‐infinite half‐space is split into a near‐field, which is, in general, the domain of interest, and a far‐field. However, truncating the half‐space at the near field, which is often sufficient in quasi‐static simulations, introduces artificial boundaries at which, in dynamic analysis, the incident waves are reflected back into the domain of interest. Several methods have been proposed in the literature to overcome this problem. The present contribution proceeds from a coupling approach, where the near and the far field are discretised with finite and infinite elements, respectively, and where additionally an energy‐absorbing layer is introduced at the interface. The aim of the present contribution is to perform a parametric study associated with a biphasic soil model based on the Theory of Porous Media (TPM). Therein, numerical simulations are carried out in order to judge the energy‐absorbing capabilities of the present far‐field treatment under different parametric conditions. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Macroscopic and mesoscopic modeling based on the concept of generalized stresses for cutting simulation
Authors: Cheng Chun , Mahnken Rolf , Uhlmann Eckart , Ivanov Ivan Mitkov 
Published: December 2014

AbstractBased on the concept of generalized stresses proposed by GURTIN [2] and FOREST et al. [1] macro‐ and meso‐scopic modelling are presented. For the macroscopic modelling we develop a multi‐mechanism model for strain rate and temperature dependent asymmetric plastic material behavior accompanied by phase transformation with consideration of the trip‐strain. Furthermore, we extend the multi‐mechanism model with the gradient of phase fraction, which is considered as an extra degree of freedom. For mesoscopic modelling a phase field model is implemented for describing phase transformations. For the scenario of a cutting process we have a martensite‐austenite‐martensite transformation. A generalized principle of virtual power is postulated involving generalized stresses and used to derive the constitutive equations for both approaches. Furthermore, parameters of the multi‐mechanism model related to visco‐plasticity with SD‐effect and the trip‐strain are identified for the material DIN 100Cr6. In the examples a cutting simulation for testing the multi‐mechanism model and a phase‐transformation simulation are shown. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A microscopically motivated continuum model for cellular materials
Authors: Diebels Stefan , Grammes Thilo , Goldschmidt Florian , Jung Anne 
Published: December 2014

AbstractCellular materials like metal foams exhibit localised deformation expressed in deformation bands under inelastic strain conditions. According to the compressible behaviour of metal foams, there is localised damage in crushing zones with a thickness of several pores. In the present contribution, a new phenomenological modelling approach has been developed, which allows the explicit consideration of micro structural effects. The model accounts for micro structural effects by a rheological model offering the possibility to reflect the macroscopic stress fluctuations. Connecting a micro structural size with the rheological spring model results in a modified elasticity law and allows the description of localisation effects. By introducing a rheological model, the constitutive equations still contain fundamental parameters, but these are motivated by the micro structure, whereas the continuum model is able to account for size effects. The model is experimentally validated and its microstructurally motivated parameters are experimentally identified in quasi‐static compression tests with unloading. Using digital image correlation (DIC), it was possible to connect the micro structural deformation to the global macroscopic stress‐strain behaviour. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison between a recursive method based on an inverse mechanical formulation and shape optimization for solving inverse form finding problems in isotropic elastoplasticity
Authors: Germain Sandrine , Landkammer Philipp , Steinmann Paul 
Published: December 2014

AbstractIn this paper we compare two methods, a recursive method based on an inverse mechanical formulation and a method based on a recursive shape optimization formulation, in order to solve inverse form finding problems in isotropic elastoplasticity. Both methods are succinctly presented and a numerical example is given. It was found that no difference could be found between the node coordinates on the undeformed configurations computed with both methods. However the convergence to the solution is faster with the recursive method based on an inverse mechanical formulation than with the method based on shape optimization. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase field modeling of domain evolution in ferroelectric materials in the context of size effects
Authors: Schrade David , Müller Ralf , Gross Dietmar 
Published: December 2014

AbstractPhase field modeling provides an efficient tool for the study of domain evolution in ferroelectric materials. Such models naturally introduce an inner length scale which represents the width of the interfaces between domains (domain walls). This inner length scale is of the order of a few unit cells, i.e. about 0.8 nm–2 nm. The focus of this contribution is on size effects in a) the switching behavior of ferroelectric thin films and b) the microstructure evolution in ferroelectric nanodots. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanical coupling of geometrically non‐coherent interfaces
Authors: Esmaeili Ali , Javili Ali , Steinmann Paul 
Published: December 2014

AbstractAn evacuated tube collector is composed of a vacuum glass tube forged to a metal tube creating an interface which undergoes thermomechanical cyclic loading. To numerically model such a thermomechanical and geometrically non‐coherent interface, a decohesion element with mixed‐mode capability, based on a normal‐shear decomposition of the displacement discontinuity vector is used, exploiting exponential traction‐separation laws. In addition to the classical strategies, interfacial elements are allowed to have an in‐plane stretch resistance by assuming a thermohyperelastic interface Helmholtz energy, a function of the rank‐deficient interface deformation gradient
$\overline{\bf F}$
and temperature
$\overline{\Theta}$
, as an extension of the surface/interface elasticity theory. The nonlinear governing equations are given and solved using the finite element method. The results are illustrated through a series of numerical examples for different material parameters. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermo‐mechanical modelling of cellular hybrid refractories
Authors: Jung Anne , Diebels Stefan 
Published: December 2014

AbstractRefractory materials are subjected to both quasi‐static and dynamic thermal loading (thermal shock) causing damage up to mechanical failure. Typical refractories are magnesia carbon bricks consisting of periclase (MgO) and carbon inclusions. Recently, a significant improvement of the thermo‐mechanical behaviour could be achieved by cellular hybrid composites made of periclase‐filled carbon foams. The present contribution focuses on MgO‐filled carbon foams and the investigation and optimisation of the structure‐property relationship with respect to a reduction of thermally induced stresses and damage. It is a transient as well as static, fully coupled thermo‐mechanical problem. According to the fact that, in general, refractories are brittle materials a linear elastic model, with a damage criterion was used. To optimise the structural morphology of the cellular refractories, the effect of micro structural changes has been determined. For the investigation of the thermal shock! behaviour, the results correlate very well with the experimentally motivated Hasselman relation. There is a significant size effect depending on the pore size. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Cyclic Thermomechanical Coupled Problem of Thermal Gradients in Friction Railway Disc Brakes
Authors: Lamjahdy Abdelkrim , Brunel Jean‐François , Lamure Benjamin , Dufrenoy Phillip , Weichert Dieter , Markert Bernd 
Published: December 2014

AbstractThe emergency braking distance of a TGV train at a speed of 320 km/h is almost 3000 m. Dry running brakes are reliable due to their predictable response to external stress and are thus used in such applications. The kinetic energy is dissipated proportionately into the brake disc and brake pad. This induced dissipation of energy and the high frequency of brake application cause high temperatures. These immense temperature changes could cause macroscopic cracks leading to failure of discs and accidents [1]. Generally, hot spotting describes the development of thermal localizations and can lead to early damage, early wear, pad performance loss, and squeal noise [2]. The aim of the present study is to improve a disc‐pad transient numerical model by use of a coupled thermomechanical method. It is based on full 3‐d thermomechanical calculations taking disc rotation into account. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A coupled multi‐component approach for bacterial methane oxidation in landfill cover layers
Authors: Sindern Andrea , Ricken Tim , Bluhm Joachim , Widmann Renatus , Denecke Martin , Gehrke Tobias 
Published: December 2014

AbstractMethane (CH4), which has a 25 times higher global warming potential than carbon dioxide (CO2), can be oxidated by methanotrophic bacteria into carbon dioxide and water. The biological oxidation of methane can be considered in the passive aftercare phase of landfills in order to reduce climate‐damaging methane emissions. Methanotrophic bacteria are situated within the landfill cover layer and convert the harmful methane emissions arising from the degradation of organic waste to the less harmful carbon dioxide. Hence, the passive aftercare of landfills in terms of methane oxidation layers is an efficient method to reduce contributions to the greenhouse effect.To model the coupled processes during phase transition from methane to carbon dioxide, the well‐known Theory of Porous Media (TPM) combined with the Mixture Theory has been used in order to develop a multi‐component Finite Element calculation concept, see [1, 3]. The thermodynamic consistent model analyzes the relevant gas productions of methane, carbon dioxide and oxygen. The model also accounts for the driving phenomena of production, diffusion and advection. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscoelastic modelling and experimental results of a dielectric electro‐active polymer diaphragm actuator
Authors: Gaida Philipp , Weinberg Kerstin , Jahr Andreas 
Published: December 2014

AbstractCommon actuating principles e.g. solenoids or piezo‐elements have mostly exploited their potential as electromechanical transducers. A new technology based on Dielectric Electro‐active Polymers (DEAPs) enables major progress in efficiency and functionality for actuators. In order to use the advantages of this new technology in a feasible application, a silicone based DEAP diaphragm actuator was tested experimentally. Here, the mechanical properties of the fundamental parts of the DEAP diaphragm actuator, namely the stressstrain behaviour of an equibiaxially pre‐stretched hyperelastic polymer and the mechanical response of a DEAP diaphragm actuator, were determined by appropriate test benches.The investigated DEAP diaphragm actuator consists of a dielectric, which corresponds to a thin elastic silicone film sandwiched between two compliant electrodes. Furthermore, DEAPs are pre‐stretched, actually up to five times their in‐plane dimensions, in order to improve their performance. In that context, the influence of the pre‐stretched state on the actuator performance was investigated. In addition, a viscoelastic finite‐element model of the electromechanical system has been developed and validated with the experimental results. The mechanical part of the DEAP diaphragm actuator was realized with an incompressible isotropic elastic model, whereas the electrical part was approximated with a circular parallel‐plate capacitor. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Algorithm of Exact Methods Obtaining of the Solution and Dynamical Flexibilities of Subsystem of the Mechatronic system
Authors: Buchacz Andrzej 
Published: December 2014

AbstractIn this paper the application of analysis of transverse vibrating subsystem of mechatronic systems by means of the exact were the main purposes of work to solve the task of assignment of frequency‐modal analysis and characteristics of mechatronic system. At first the problem of analysis in the form of the one differential equation of motion of mechanical subsystem or of the set of state equations of considered mechatronic model of object has been formulated and solved. Classic method to solve this problem have been used. The considered transverse vibrating mechanical subsystems of mechatronic system are a continuous beams with constant cross‐section, with free ends and/or clamped on one end. A ring transducer, which is the integral part of mechatronic system, extorted by harmonic force or voltage excitation, is assumed to be perfectly bonded to the beam surface. Parameters of the transducer have important influence on values of natural frequencies and on form of characteristics of considered mechatronic system. The poles of dynamical characteristic calculated by mathematical exact method and the Galerkin's method have approximately different or the same values; it is depended on the combination of boundary conditions of elementary beam. The results of the calculations were not only presented in mathematical form but also as a transients of examined dynamical characteristic which are function of frequency of assumed excitation. Practical implications of this work is to present the introduction to synthesis of considered class of mechanical and/or mechatronic beam‐systems with a constant changeable cross‐section. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Model reduction and dynamic iteration for coupled nonlinear systems
Authors: Kerler Johanna , Stykel Tatjana 
Published: December 2014

AbstractThe dynamical behavior of coupled systems is determined by different interconnected subsystems that are usually governed by entirely different physical laws and often act in different time and space scales. We discuss the simulation of coupled nonlinear systems using dynamic iteration combined with model order reduction. We also study the convergence of this approach and derive error estimates for approximate solutions. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective bulk moduli of materials containing stochastically distributed nano‐inhomogeneities with surface stresses
Authors: Nazarenko Lidiia , Bargmann Swantje 
Published: December 2014

AbstractIn the present contribution, a mathematical model for the investigation of the effective properties of a material with randomly distributed nano‐particles is proposed. The surface effect is introduced via Gurtin‐Murdoch equations describing properties of the matrix/nano‐particle interface. They are added to the system of stochastic differential equations formulated within the framework of linear elasticity. The homogenization problem is reduced to finding a statistically averaged solution of the system of stochastic differential equations. These equations are based on the fundamental equations of linear elasticity, which are coupled with surface/interface elasticity accounting for the presence of surface tension. Using Green's function this system is transformed to a system of statistically non‐linear integral equations. It is solved by the method of conditional moments. Closed‐form expressions are derived for the effective moduli of a composite consisting of a matrix with randomly distributed spherical inhomogeneities. The radius of the nano‐particles is included in the expression for the bulk moduli. As numerical examples, nano‐porous aluminum and nano‐porous gold are investigated assuming that only the influence of the interface effects on the effective bulk modulus is of interest. The dependence of the normalized bulk moduli of nano‐porous aluminum on the pore volume fraction (for certain radii of nano‐pores) are compared to and discussed in the context of other theoretical predictions. The effective Young's modulus of nano‐porous gold as a function of pore radius (for fixed void volume fraction) and the normalized Young's modulus vs. the pore volume fraction for different pore radii are analyzed. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An asymptotic approximation for a three dimensional linear elasticity problem with Robin boundary condition in a thick cylinder
Authors: Bare Zoufine , Orlik Julia 
Published: December 2014

AbstractThis contribution shows the asymptotic approximation of the displacements and shear stresses of a three dimensional (3D) linear elasticity boundary value problem in a thick beam with Robin boundary condition at an end. The analytic asymptotic approximation is compared to the numerical 3D Finite element solution. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Incremental Scheme to Homogenize Anisotropic Elastic Properties of Multi‐Phase Composites
Authors: Müller Viktor , Böhlke Thomas 
Published: December 2014

AbstractAn incremental homogenization scheme for the prediction of elastic properties of composites is reviewed. Similar to the differential scheme, the inclusions are included step‐by‐step. This approach accounts for high volume fractions of inclusion of different shape and elastic properties. A numerical example for a composite consisting of a polymeric matrix, glass fibers and voids is shown. The fiber distribution is chosen equivalently to a distribution in an injection molded short‐fiber reinforced composite. The volume fraction of the voids is varied. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A modified approximation of the exponential Cauchy‐Born rule for arbitrary shell‐like nanostructures
Authors: Findeisen Claudio , Wackerfuß Jens 
Published: December 2014

AbstractThe mechanical behaviour of shell‐like nanostructures, such as carbon nanotubes (CNT) can be described within the continuum mechanics by a generalisation of the Cauchy‐Born (CB) rule, introduced by Arroyo and Belytschko [1]. However, the finite element approximation presented in the literature requires the reference configuration to be planar. In case the configuration of interest is initially not planar, a preprocessing step is required that isometrically maps the planar reference configuration into the initial configuration. In order to calculate more complex structures, in this paper an extended finite element approximation is presented which is applicable to shell‐like atomic structures, whose reference configuration does not need to be planar and consequently the afore‐mentioned steps are no longer necessary. The accuracy of the proposed model is verified by two numerical examples. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)