bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model order reduction for thermomechanical problems including radiation
Authors: Rother Stephan , Beitelschmidt Michael 
Published: March 2018

AbstractThermal field problems including heat exchange by radiation lead to nonlinear system equations with a high number of inputs and outputs as radiation heat fluxes correspond to the fourth power of the temperature and thermal loads are distributed over the whole surface. In an alternative approach presented here, radiation is defined as a part of the load vector. Thus, the system matrices are constant. Furthermore, loads changing synchronously during operation are grouped into one column of the input matrix and load vector snapshots are used to consider the radiation heat fluxes. Hence, the Krylov Subspace Method can be applied to significantly reduce the system dimension and the computation times allowing transient thermal parameter studies. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerische Simulation der Freispiegelströmung in einem Wasserrad
Authors: Schippke Hans‐Henning , Seidel Christian , Dinkler Dieter 
Published: March 2018

AbstractEs wird ein Berechnungsmodell für 2‐Fluid‐Strömungen mit drehendem Starrkörper vorgestellt, mit dem eine numerische Analyse der Strömungsvorgänge innerhalb von Schaufelwasserrädern möglich ist. Mit dem vorgestellten Berechnungsmodell erfolgt die erstmalige numerische Untersuchung der bei Schaufelwasserrädern auftretenden Strömungsvorgänge. Dabei werden die wesentlichen Punkte im Rahmen der numerischen Umsetzung eingehend diskutiert und die gewonnenen Ergebnisse anhand experimenteller Daten auf ihre physikalische Plausibilität hin überprüft. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A polarisation based approach to model strain dependent electrostatic pressure of dielectric elastomer actuators
Authors: Schlögl Tristan , Leyendecker Sigrid 
Published: March 2018

AbstractA wide‐spread lumped parameter model describing the electrostatic pressure is presented by Pelrine et. al. in 1998 [1]. In Pelrine's model, the electrostatic pressure is affected by the relative permittivity of the material, also known as dielectric constant. However, many researchers found that the dielectric constant of DEAs is not constant at all, but decreasing with increasing pre‐stretch of the material. In this work, an alternative modelling approach is presented, explaining the stretch dependent actuation pressure. It is shown that this new model fits experimental data found in literature quite well. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and simulation of electro‐chemomechanical behavior of ionic polymer‐metal composites within the framework of the Theory of Porous Media
Authors: Serdas Serdar , Bluhm Joachim , Schröder Jörg 
Published: March 2018

AbstractIonic polymer‐metal composites (IPMCs) serve as electro‐mechanical transducers for actuator and sensor applications, see [1]. Typically, they are sandwiched between two impermeable electrodes comprising the polymer network, the liquid, the fixed anions and the mobile cations. The actuation mechanism takes place by applying an electric potential (voltage) and the mobile cations move towards the cathode. Due to the relocation of the cations (electrostatic and ionic forces), a deformation of the IPMC can be observed. In contrast, the sensing mechanism is performed by applying a mechanical load yielding to a concentration redistribution and generating an electrical potential inside the IPMC. In Leichsenring [2], a parametric study has been carried out for the description of an IPMC. Therein, the Theory of Porous Media (TPM) was used, see [3], while the motion of the liquid and the cations were restricted. In the present contribution, the actuation and sensing behavior of an IPMC is presented within the framework of the TPM, see [5]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Large‐Deformation Phase‐Field Approach for the Modeling of Magneto‐Sensitive Elastomers
Authors: Sridhar Ashish , Keip Marc‐André , Miehe Christian 
Published: March 2018

AbstractMagneto‐sensitive materials show magneto‐mechanical coupled response and are thus of increasing interest in the recent age of smart functional materials. Ferromagnetic particles suspended in an elastomeric matrix show realignment under the influence of an external applied field, in turn causing large deformations of the substrate material. The magneto‐mechanical coupling in this case is governed by the magnetic properties of the inclusion and the mechancial properties of the matrix. The magnetic phenomenon in ferromagnetic materials is governed by the formation and evolution of domains on the micro scale. A better understanding of the behavior of these particles under the influence of an external applied field is required to accurately predict the behavior of such materials. In this context it is of particular importance to model the macro scopic magneto‐mechanically coupled behavior based on the micro‐magnetic domain evolution. The key aspect of this work is to develop a large‐deformation micro‐magnetic model that can accurately capture the microscopic response of such materials. Rigorous exploitation of appropriate rate‐type variational principles and consequent incremental variational principles directly give us field equations including the time evolution equation of the magnetization, which acts as the order parameter in our formulation. The theory presented here is the continuation of the work presented in [1, 7] for small deformations. A summary of magneto‐mechanical theories spanning over multiple scales has been presented in [4]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructural influence on macroscopic response regarding fluid flow through porous media applying TPM2‐Method
Authors: Bartel Florian , Ricken Tim , Schröder Jörg , Bluhm Joachim 
Published: March 2018

AbstractThanks to the advancements in the digital era we are able to capture naturally grown and artificially manufactured microstructures with various scanning devices like CT and MRT and can transfer the digital image data to finite element models. In addition, there has been a permanent improvement in the quality of additive reproduction technology. Looking at the biomedical industry producing organic parts, porous materials saturated with fluids play an important role. For this reason, we also have to develop appropriate simulation technology providing a description for porous materials regarding the underlying microstructure. This contribution presents a numerical experiment for the flow through a porous body with different underlying microstructures applying the TPM2‐Method. The different macroscopic behavior for the displacements, pressure distribution, and volumetric fluid flow for an isotropic and two differently orientated anisotropic microstructures are shown in section 3. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational inelasticity for loading conditions on multiple time scales by adaptive step size control
Authors: Gote Ajinkya , Eidel Bernhard 
Published: March 2018

AbstractThis contribution proposes an algorithm based on adaptive step size control for the simulation of inelastic solids and structures undergoing loading conditions at multiple time scales. Adaptivity in time integration of viscoelastic constitutive laws is directed by an refinement indicator which is constructed from integrators of different order, here a fourth‐order Runge‐Kutta (RK) method and linear Backward‐Euler. The key novel aspect is that by virtue of an recently established consistency condition the higher order methods, p ≥ 2, can achieve their full nominal order without fulfilling the weak form of balance of linear momentum in the RK stages, but only at the end of the time interval. A representative numerical example illustrates the performance of the present adaptive method and underpins the computational savings compared with uniform time step sizes. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison of mean field homogenization schemes for short fiber reinforced thermoplastics
Authors: Hessman Patrick Arthur , Hornberger Kurt 
Published: March 2018

AbstractDifferent mean field homogenization methods are applied to a short glass fiber reinforced polybutylene terephthalate. The different models' predictions for the anisotropic effective elastic properties are assessed and compared to experimental data from tensile tests. Additionally, the estimation of fiber stresses and the influence of the fiber length distribution is studied. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error‐controlled homogenization for a class of linear elastic composite problems
Authors: Ju Xiaozhe , Mahnken Rolf 
Published: March 2018

AbstractThe research field of model adaptivity is well established, aiming at adaptive selection of mathematical models from a well defined class of models (model hierarchy) to achieve a preset level of accuracy, see e.g. [4, 5]. The present work addresses its application to a class of linear elastic composite problems. In order to adaptively control both macro model and macro discretization errors, we present a coupled adaptive scheme, which is driven by a goal‐oriented error estimator based on duality techniques. For efficient computation of the dual solution, we make use of a patch‐based recovery technique proposed in [6]. As a possibility for model adaptivity, we propose a model hierarchy based on the classical bounding theories [2, 3], which is established in a natural and theoretically consistent manner, without combination of different methods using a priori knowledge. For illustration, a numerical example is presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An adaptive approach for modeling a fiber‐matrix composite with the FE2 method
Authors: Praster Maximilian , Klinkel Sven 
Published: March 2018

AbstractIn materials with a complicated microstructre [1], the macroscopic material behaviour is unknown. In this work a Fiber‐Matrix composite is considered with elasto‐plastic fibers. A homogenization of the microscale leads to the macroscopic material properties. In the present work, this is realized in the frame of a FE2 formulation. It combines two nested finite element simulations. On the macroscale, the boundary value problem is modelled by finite elements, at each integration point a second finite element simulation on the microscale is employed to calculate the stress response and the material tangent modulus. One huge disadvantage of the approach is the high computational effort. Certainly, an accompanying homogenization is not necessary if the material behaves linear elastic. This motivates the present approach to deal with an adaptive scheme. An indicator, which makes use of the different boundary conditions (BC) of the BVP on microscale, is suggested. The homogenization with the Dirichlet BC overestimates the material tangent modulus whereas the Neumann BC underestimates the modulus [2]. The idea for an adaptive modeling is to use both of the BCs during the loading process of the macrostructure. Starting initially with the Neumann BC leads to an overestimation of the displacement response and thus the strain state of the boundary value problem on the macroscale. An accompanying homogenization is performed after the strain reaches a limit strain. Dirichlet BCs are employed for the accompanying homogenization. Some numerical examples demonstrate the capability of the presented method. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of stress‐velocity LSFEMs for the incompressible Navier‐Stokes equations
Authors: Nisters Carina , Schwarz Alexander , Schröder Jörg 
Published: March 2018

AbstractIn this contribution three mixed least‐squares finite element methods (LSFEMs) for the incompressible Navier‐Stokes equations are investigated with respect to accuracy and efficiency. The well‐known stress‐velocity‐pressure formulation is the basis for two further div‐grad least‐squares formulations in terms of stresses and velocities (SV). Advantage of the SV formulations is a system with a smaller matrix size due to a reduction of the degrees of freedom. The least‐squares finite element formulations, which are investigated in this contribution, base on the incompressible stationary Navier‐Stokes equations. The first formulation under consideration is the stress‐velocity‐pressure formulation according to [1]. Secondly, an extended stress‐velocity formulation with an additional residual is derived based on the findings in [1] and [5]. The third formulation is a pressure reduced stress‐velocity formulation based on a condensation scheme. Therefore, the pressure is interpolated discontinuously, and eliminated on the discrete level without the need for any matrix inverting. The modified lid‐driven cavity boundary value problem, is investigated for the Reynolds number Re = 1000 for all three formulations. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and asymptotic investigation of a rotary wave in a cylindrical container
Authors: Steinrück Herbert , Maly Anton 
Published: March 2018

AbstractRotary gravity waves in a partially filled vertical cylindrical container excited by a rotating disc at the top of the cylinder are investigated. Analytical results for the growth rate of the waves are reported. Moreover, the development of the wave is shown in an experiment. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lamb wave resonance transmission through a system of deep notches in a plate‐like waveguide
Authors: Glushkov Evgeny , Glushkova Natalia , Eremin Artem , Lammering Rolf 
Published: March 2018

AbstractThe results of theoretical and experimental investigation into resonance phenomena accompanying guided wave propagation in a metallic plate with a finite regular system of rectangular deep notches are presented. While the expected intensification of wave blocking by a system of notches comparing to the case of a single defect is confirmed, the resonance transmission at the predicted frequencies within these forming stop bands is also observed. Noticeable motion localization in the waveguide area between the notches at these frequencies is visualized with experimental surface B‐scans. Their patterns coincide with the theoretical predictions obtained on the basis of a semi‐analytical computer model for the notched infinite plate. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generation of surface waves through friction: FEM investigation
Authors: Graf Matthias 
Published: March 2018

AbstractSliding friction between two bodies can generate elastic vibration. This study uses a finite‐element model comprising an elastic body sliding against a flat rigid surface with constant coefficient of friction. For the elastic body a structured topography is taken into account. The model shows traveling surface waves, which depend on the asperities of the sliding surface. It can be shown that the surface structure and its inertia are the cause for elastic waves in the contact region. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence of minimisers for nonlinear strain‐gradient elastoplasticity with finite or infinite cross‐hardening
Authors: Anguige Keith 
Published: March 2018

AbstractConsideration is given to the existence of minimisers for a family of variational models of finite‐strain single‐crystal elastoplasticity with infinite cross‐hardening. The non‐convex cross‐hardening condition on the plastic slip necessitates the use of special analytical tools, in particular the combination of the div‐curl Lemma with a slip‐exclusion Lemma of Conti & Ortiz [1], if one wishes to prove existence for physically reasonable parameters. A regularised model with a cross‐hardening matrix is also briefly discussed ‐ existence of minimisers for this model also follows by a div‐curl argument, at least if one goes over to the case of linearised elasticity. Moreover, in this case one can also prove that the regularised model Γ‐converges to the infinite‐cross‐hardening model as the hardening matrix becomes unboundedly large. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrothermal Description of Organic Semiconductor Devices by p(x)‐Laplace Thermistor Models
Authors: Fuhrmann Jürgen , Glitzky Annegret , Liero Matthias 
Published: March 2018

AbstractWe consider a p(x)‐Laplace thermistor model for electrothermal effects in organic semiconductor devices and propose a hybrid finite‐volume/finite‐element scheme which is combined with path‐following methods to find a numerical solution. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Material‐based process‐chain optimization in metal forming
Authors: Morand Lukas , Pagenkopf Jan , Helm Dirk 
Published: March 2018

AbstractThe characteristics of a manufacturing product are influenced by a variety of different factors, such as the material properties of the base product. The prediction of properties that give optimal results in metal forming applications is a complex task but of high interest for the manufacturer. To realize such a prediction scheme, the process chain is split up into individual process steps and for each of them an inverse modeling is required. The specific aim of this work is to present an approach for the inverse problem formulation of a process step and to solve it using methods of machine learning. Moreover, the challenges that often arise due to the ill‐posed nature of inverse problems will be discussed. The main focus is on the crystallographic texture of metals, which strongly affects the deformation behavior during a process step and highly influences the characteristics of the final product. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure‐exploiting polynomial chaos for uncertain optimal control problems with sparse derivative generation
Authors: Bergner Lilli , Kirches Christian 
Published: March 2018

AbstractWe present advances in structure‐exploiting non‐intrusive polynomial chaos methods for the numerical solution of nonlinear optimal control problems with parametric uncertainties. In particular, we make use of the special structure induced by the spectral projection to reuse model derivatives and exploit sparsity information leading to a fast automatic sensitivity generation. This greatly reduces the computational effort of Newton‐type methods for the solution of the resulting high‐dimensional surrogate problem. The results are complemented by a complexity comparison and a numerical case study. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Makroskopische Modelle zur Untersuchung der Dynamik von Schaumstrukturen
Authors: Kancheva Elena Vladimirova , Ams Alfons 
Published: March 2018

AbstractDie Dynamik offenporiger Schaumstrukturen wird diskutiert. Messungen realer Schaumstrukturen werden mit Computertomographen (CT) durchgeführt und anschließend über Korrelations‐ und Spektralanalyse statistisch ausgewertet. Für weißes Rauschen als Anregung des Modellschaums werden die Zeitlösungen und Autoleistungsdichtespektren berechnet und simuliert. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Comparison of Markov Chain Methods for Reliability Estimation
Authors: Proppe Carsten 
Published: March 2018

AbstractTwo Markov chain Monte Carlo simulation methods for reliability estimation, subset simulation and the moving particles algorithm, are compared based on theoretical arguments and test cases. The differences in the efficiency between both algorithms are rather small. They seem to be well suited for off‐the‐shelf reliability estimations, but with a different setting for the most important parameters (proposal density and initial sample size). (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hankel‐type norm of a random mass‐spring‐damper system
Authors: Pulch Roland 
Published: March 2018

AbstractWe consider linear dynamical systems including random variables for an uncertainty quantification. A quantity of interest is expanded into a series with orthogonal basis polynomials. We investigate a Hankel‐type norm of a truncated series. An approximation of this norm can be obtained by a quadrature formula, which implies a larger weakly coupled system. We present results of numerical computations using sparse grid quadratures in the case of a mass‐spring‐damper system. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topology and material orientation optimization based on evolution equations
Authors: Jantos Dustin Roman , Junker Philipp , Hackl Klaus 
Published: March 2018

AbstractMany modern high‐performance materials have inherent anisotropic elastic properties and its local material orientation can be considered to be an additional design variable for the topology optimization [1–3]. We extend our previous model for topology optimization with variational controlled growth [4–6] for linear elastic anisotropic materials, for which the material orientation is introduced as an additional design variable. We solve the optimization problem purely with the principles of thermodynamics by minimizing the Gibbs energy. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Notes on a novel finite element for anisotropy at large strains
Authors: Viebahn Nils , Schröder Jörg , Wriggers Peter , Balzani Daniel 
Published: March 2018

AbstractA locking phenomenon can be observed in the case of anisotropic elasticity, due to high stiffness in preferred directions. In this contribution we propose a formulation with the goal to overcome this locking problem. We apply a Simplified Kinematic for the Anisotropic part of the free‐energy by means of a constant approximation of the right Cauchy‐Green tensor. For the tested boundary value problem the SKA‐element performs excellent and behaves extremely robust. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards Riccati‐Feedback Control of Complex Flows with Moving Interfaces
Authors: Baran Björn , Benner Peter , Heiland Jan , Saak Jens 
Published: March 2018

AbstractProblems featuring moving interfaces appear in many applications. They can model solidification and melting of pure materials, crystal growth and other multi‐phase problems. The control of the moving interface enables to, for example, influence production processes and, thus, the product material quality.We consider the two‐phase Stefan problem that models a solid and a liquid phase separated by the moving interface. In the liquid phase, the heat distribution is characterized by a convection‐diffusion equation. The fluid flow in the liquid phase is described by the Navier–Stokes equations which introduces a differential algebraic structure to the system. The interface movement is coupled with the temperature through the Stefan condition, which adds additional algebraic constraints. Our formulation uses a sharp interface representation and we define a quadratic tracking‐type cost functional as a target of a control input.We compute an open loop optimal control for the Stefan problem using an adjoint system. For a feedback representation, we linearize the system about the trajectory defined by the open loop control. This results in a linear‐quadratic regulator problem, for which we formulate the differential Riccati equation with time varying coefficients. This Riccati equation defines the corresponding feedback gain.Further, we present the feedback formulation that takes into account the structure and the differential algebraic components of the problem. Also, we discuss how the complexities that come, for example, with mesh movements, can be handled in a feedback setting. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)