bluuebunny/crossref_metadata_2025_split huggingface dataset:
An explicit update formula for implicit time integration within finite strain viscoelasticity
Authors: Shutov Alexey , Landgraf Ralf , Ihlemann Jörn 
Published: November 2013

AbstractIn this paper a model of finite strain viscoelasticity and its numerical integration is considered. The mechanical behaviour can be represented by the one‐dimensional rheological model of Maxwell fluid which consists of an elastic spring (Hooke body) and a viscous dashpot (Newton body) connected in series. The constitutive model is formulated within the framework of nonlinear continuum mechanics and is based on the decomposition of the deformation gradient into elastic and inelastic parts. The elastic part of the model is defined by a Neo‐Hookean hyperelastic relation between elastic strains and stresses. Furthermore, an incompressible flow rule for the description of viscous flow is assumed. The numerical integration of the inelastic flow rule is accomplished using the implicit integration scheme of Euler‐backward method. To this end, Shutov et al. (2013) recently proposed a new closed form solution for the corresponding time stepping algorithm. The algorithm retains all favourable characteristics of the Euler‐backward method. Moreover, no local iterative procedure is required which results in a highly efficient implicit time stepping scheme. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stress Integration of the Hoek‐Brown Material Model Using Incremental Plasticity Theory
Authors: Rakic Dragan , Zivkovic Miroslav , Milovanovic Vladimir 
Published: November 2013

AbstractThis paper presents the formulation of the stress integration procedure for the Hoek‐Brown (HB) material model with non‐associative yielding condition by using the incremental plasticity method. Main idea of this method is to reach the solution by calculating the plastic matrix according to the method of incremental plasticity (used for elastic constitutive matrix corrections), and with the use of the total strain increment. Computational procedure is implemented within the PAK program package. Results of this procedure were compared with the solutions obtained by other program that contains this material model. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical modelling of finite strain magneto‐viscoelastic deformations
Authors: Saxena Prashant , Hossain Mokarram , Steinmann Paul 
Published: November 2013

AbstractLarge strain magneto‐viscoelastic deformations in the presence of a finite magnetic field are modelled in this paper. Internal dissipation mechanisms are proposed using a multiplicative decomposition of the deformation gradient and an additive decomposition of the magnetic induction. Using thermodynamically consistent constitutive and evolution laws, numerical results showing stress relaxation and magnetic field evolution are presented to illustrate the theory. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Complex‐Step Derivative Approximation Schemes for the Robust Calculation of Numerical Constitutive Tangent Moduli
Authors: Tanaka Masato , Fujikawa Masaki , Balzani Daniel , Schröder Jörg 
Published: November 2013

AbstractMany material models lead to complicated formulations of the exact consistent tangent modulus tensor and therefore its derivation and implementation might be elaborate. In this case numerical approximations of the moduli can provide an alternative in particular for scientific development purposes. Here, a robust numerical approximation of the tangent modulus tensor that can be implemented within FE‐software is proposed using an innovative numerical derivative scheme. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon‐dioxide storage and phase transitions: on the numerical modelling of injection and leakage
Authors: Häberle Kai , Ehlers Wolfgang 
Published: November 2013

AbstractThe injection of supercritical CO2 into deep saline aquifers is regarded as one possible alternative to lessen the impact of emitted CO2 on the greenhouse effect. During injection, a great variety of thermodynamical and mechanical changes of both the fluid phases and the porous solid matrix can be expected. The prediction of these processes is crucial to prevent from critical incidents during CO2 injection, such as leakage of CO2 or contamination of drinking water.For simulation purpose, a macroscopic, fully coupled description of multi‐phasic flow inside a deformable porous medium based on the Theory of Porous Media (TPM) is generated. Appropriate constitutive relations are applied to account for changes in the fluid properties of both the saline water and CO2 during injection and leakage. Furthermore, an elasto‐plastic description of solid deformations of the porous matrix is included.The model is tested based on a benchmark problem. Therein, the leakage of CO2 through an abandoned well after injection is investigated. The fully coupled approach between fluid flow and solid deformation allows additional results to be gained from the simulation. Quantification of the leakage rate through the abandoned well and localisation of phase‐change events are addressed to calibrate the presented model. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Finite Deformation Microsphere Model for Magneto‐Visco‐Elastic Response in Magnetorheological Elastomers
Authors: Ethiraj Gautam , Zäh Dominic , Miehe Christian 
Published: November 2013

AbstractIn this work we present a novel approach to the modeling of magnetorheological elastomers (MREs) for finite deformations. Keeping in mind the composite nature at the microscale, we employ the microsphere model as an effective tool to capture the constitutive response of the material. The microsphere model has been successfully applied to the modelling of rubber‐like materials. Here, we extend this approach by taking into account the effect of the magnetic dipole‐dipole interactions on the orientation of the polymer chains. Thus, the presented microsphere model is directly motivated by considering the underlying phenomena at the microscale level. Finally the material model is embedded in a finite element framework and the results of a boundary value problems is presented. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equations of Motion of Robotic System With Piezo‐Modified Viscoelastic and Magnetorheological Elements of Fractional Order
Authors: Cajić Milan , Lazarević Mihailo 
Published: November 2013

AbstractIn this communication, the Rodriguez method is proposed for modeling dynamics of the robotic system, where Lagrange's equations of second kind of rigid bodies system in covariant form are used. Discrete hybrid elements with so called piezo‐modified Kelvin‐Voight (PKV) and magnetorheological (MRD) type of viscoelastic models with fractional order derivatives are introduced in to the system of motion equations by means of generalized forces. The results obtained are illustrated by numerical examples. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element simulation for material accumulation and welding processes including a free melt surface
Authors: Jahn Mischa , Luttmann Andreas , Schmidt Alfred 
Published: November 2013

AbstractA modeling and simulation approach for problems with solid‐liquid‐solid phase transitions and a free surface, feasible for material accumulation processes based on laser‐based free form heading and welding processes for joining different metallic materials is presented. Both named processes are modeled within the framework of continuum mechanics by coupling the Stefan problem with the Navier‐Stokes equations including a free capillary surface. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An analytical solution for the mechanically coupled diffusion problem in thin‐film electrodes
Authors: Stein Peter , Zhao Ying , Xu Baixiang 
Published: November 2013

AbstractThis paper presents a quasi‐static solution for the mechanically coupled diffusion problem in a Lithium‐ion battery thin film electrode during charge. The concentration field and the stresses are calculated under the assumption of a constant flux. The influence of the electrode's stiffness, its thickness, and of the current density on the results are discussed. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A monolithic finite element discretization for coupled Darcy‐Stokes flow
Authors: Braack Malte , Nafa Kamel 
Published: November 2013

AbstractWe consider a Stokes system and a Darcy system in a porous media, mutually coupled together by the the well‐known Beaver‐Joseph‐Saffman interface conditions. Standard approaches use different finite elements in the two parts in order to account for the different stability properties of the two equation systems. In contrast to this, we use standard equal‐order finite elements in both parts. Stability is obtained by adding local projection terms (LPS) to the Galerkin formulation. We formulate the scheme and give an a priori estimate. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polycrystal vs. Classical Continuum Models for Structures
Authors: Prygorniev Oleksandr , Naumenko Konstantin , Altenbach Holm 
Published: November 2013

AbstractIn this work a comparison of polycrystal and classical continuum models illustrated by examples of full structures is investigated. The general idea is to represent the averaged distribution of displacement, stress and strain fields for statistically randomized realizations of discrete structures. A technique for averaging fields in the FEM program ABAQUS is proposed and implemented. To improve the computation efficiency mesh dependence was investigated. Results of simulation are given for a rectangular plate and for the Kirsch's problem for both examples elastic as well as inelastic material behavior. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The hp‐d version of the finite cell method with local enrichment for multiscale problems
Authors: Joulaian Meysam , Düster Alexander 
Published: November 2013

AbstractThe finite cell method is extended to enable the computation of solids consisting of heterogeneous materials. The approach is based on a domain decomposition utilizing the hp‐d method. Our results reveal that the proposed method improves the accuracy of the finite cell method significantly. It also paves the way for combining the finite cell method with other approaches like partition of unity based methods which can be of interest in many cases, such as dealing with composites and numerical homogenization. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A crystal plasticity framework based on the Continuum Dislocation Dynamics theory: relaxation of an idealized micropillar
Authors: Monavari Mehran , Schmitt Severin , Sandfeld Stefan 
Published: November 2013

AbstractThe motion and interaction of dislocation lines are the physical basis of the plastic deformation of metals. Although ‘discrete dislocation dynamic’ (DDD) simulations are able to predict the kinematics of dislocation microstructure (i.e. the motion of dislocations in a given velocity field) and therefore the plastic behavior of crystals in small length scales, the computational cost makes DDD less feasible for systems larger than a few micro meters. To overcome this problem, the Continuum Dislocation Dynamics (CDD) theory was developed. CDD describes the kinematics of dislocation microstructure based on statistical averages of internal properties of dislocation systems. In this paper we present a crystal plasticity framework based on the CDD theory. It consists of two separate parts: a classical 3D elastic boundary value problem and the evolution of dislocation microstructure within slip planes according to the CDD constitutional equations. We demonstrate the evolution of dislocation density in a micropillar with a single slip plane. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical experiments for the appropriate representative volume element size selection on thin texturized metals under mechanical loads
Authors: Montalvo‐Urquizo Jonathan , Ungermann Mischa 
Published: November 2013

AbstractIn this work, we analyze a strategy for the selection of the adequate RVE size for elastic problems on thin sheets with strong texture. The selection strategy includes the construction of the geometric descriptor as periodic tesselation of the sheets and the stochastic assignment of stiffness matrices for the different material grains inside the RVE. The procedure is illustrated with an example on DC01 steel sheets with thickness 50 µm. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Designing Statistically Similar RVEs for 3D Dual Phase Steel Microstructures
Authors: Scheunemann Lisa , Balzani Daniel , Brands Dominik , Schröder Jörg 
Published: November 2013

AbstractThis contribution presents a method for the construction of three‐dimensional Statistically Similar Representative Volume Elements (SSRVEs) for dual phase steels (DP steels). From such kind of advanced high strength steels, enhanced material properties are observed, which originate in the interaction of the individual constituents of the material on the microscale. Our aim is to directly incorporate the microstructure in the material modeling, which can be accomplished by applying i. e. the FE2 method. A RVE representing the real material is used in the microscopic boundary value problem, which is solved at each macroscopic integration point. Since such RVEs usually exhibit a high complexity due to the underlying real microstructure, high computational costs are a drawback of the approach. We replace this RVE with a SSRVE, which has a lower complexity but which is still able to represent the mechanical behavior of the RVE and thus of the real microstructure. Virtual experiments show the performance of the method. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Variational Approach to Dynamic Recrystallization Using Probability Distributions
Authors: Nguyen Hai Van , Hackl Klaus , Renner Jörg 
Published: November 2013

AbstractWe investigate a model of dynamic recrystallization in polycrystalline materials. A probability distribution function is introduced to characterize the state of individual grains by grain size and dislocation density. Specifying free energy and dissipation within the polycrystalline aggregate we are able to derive an evolution equation for the probability density function via a thermodynamic extremum principle. Once the distribution function is known macroscopic quantities like average strain and stress can be calculated. For distribution functions which are constant in time, describing a state of dynamic equilibrium, we obtain a partial differential equation in parameter space which we solve using a marching algorithm. Numerical results are presented and their physical interpretation is given. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A model for fluid flow in non‐fully filled tribological interfaces – Part 2: Simulations
Authors: Müller Michael , Bubser Florian , Ostermeyer G.‐P. 
Published: November 2013

AbstractThe paper presents simulation results of an algorithm for non‐fully filled gaps, as it was introduced in part one of this work. The model considers the roughness of two solid surfaces moving relative to each other in reference to its effect on the fluid displacement. Due to the lack of fluid in the gap, the area where a hydrodynamic pressure can build up is rather small. However approaching asperities can build up local pressure. The non‐linear effect of the filling ratio on the pressure build‐up and the fluid flow is shown using a simplified topography of two ellipsoidal asperities. Depending on the filling ratio the fluid is squished out of the decreasing gap volume between the two asperities. So the amount of solid to solid contact is reduced by the fluid flow. The paper also discusses the behaviour of a multi asperity contact by means of two Gaussian height distributed surfaces sliding over each other. It is discussed how the starved regime influences the local pressure distribution and the gap geometry. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the Free‐Surface Flow in Partially Filled Extruders
Authors: Lübke Martin , Wünsch Olaf 
Published: November 2013

AbstractIn this work we present the free‐surface flow of high viscous Newtonian liquids in a simplified extruder model, namely the flat‐plate model. Due to high density and viscosity ratios, a free‐surface approach based on the volume of fluid method is used. The material distribution for different degree of fillings and the resulting power consumption is investigated. In addition, the obtained power characteristic is compared against analytical consideration and numerical simulation of a fully filled case. The investigation shows that the power characteristic of a partially filled extruder can be estimated by a fully filled computation. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical investigation on the dynamic stall of a vertical axis wind turbine
Authors: Frunzulica Florin , Dumitrescu Horia , Dumitrache Alexandru 
Published: November 2013

AbstractIn the last years, for home user, the wind turbine with vertical axis (VAWT) began to be more attractive due benefits in exploitation. In terms of aerodynamics, when the wind speed approaches the speed of operation (low value of tip speed ratio ‐TSR) the blade airfoil exceeds the critical angle of incidence for static conditions. Angle of incidence varies quickly across blade and the blade works in dynamic stall condition. The goal of the present work is to investigate the two‐dimensional dynamic stall phenomenon around the NACA 0012 airfoil at relatively low Reynolds. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Utilizing CFD‐Simulations to Assess Flow‐Induced Vibrations of Slender Beams in Cross‐Flow
Authors: Strecha Johannes , Steinrück Herbert 
Published: November 2013

AbstractFlow‐induced vibrations of a slender U‐beam in cross‐flow are assessed, using the proprietary CFD‐solver ANSYS‐CFX. The U‐beam has two degrees of freedom: heaving motion and rotation. The flow‐ and motion‐governing equations are solved together, using an iterative coupling method. We find, that using this iterative coupling does not ensure a valid long‐time behaviour of the solution. The results of free vibration simulations would allow investigation of the excitation mechanisms. But for determining possibility of large amplitude vibrations, methods relying on forced motion are deemed more promising. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discrete Adjoint based Sensitivity Analysis for Optimal Active Flow Control of High‐Lift Configurations
Authors: Nemili Anil , Özkaya Emre , Gauger Nicolas 
Published: November 2013

AbstractBlowing and suction type of active flow control techniques can be used to delay the flow separation on the flap and to enhance the aerodynamic performance of high‐lift configurations. Effective separation control and maximum enhancement in the mean lift coefficient are achieved by finding the optimal actuation parameters. The optimal set of actuation parameters can be obtained by combining the gradient based algorithms with discrete adjoints. In the present work, an unsteady discrete adjoint incompressible RANS solver is developed for the optimal active separation control. The adjoint solver is applied to the test case of active flow control on the flap of a 2D high‐lift configuration. Sensitivity gradients are presented to demonstrate the accuracy of unsteady adjoint RANS solver. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Convergence of a finite difference method for the time‐fractional diffusion equation with concentrated capacity
Authors: Delić Aleksandra 
Published: November 2013

AbstractWe investigate the convergence of difference scheme for the time‐fractional differential equation with fractional derivative of an order $\alpha\in(0,1)$ with the coefficient at the time derivative containing Dirac delta distribution. Convergence order of $O(\tau^{2-\alpha}+h^2)$ is proved. A numerical example demonstrates the theoretical results. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tensile‐bending coupling in the limitting 1D beam equations resulting from the frictional contact
Authors: Bare Zoufine , Orlik Julia 
Published: November 2013

AbstractThe asymptotic dimension reduction for beam contact problems without friction leads to decoupled ODE systems in the longitudinal variable, see [4]. This decoupling is due to the fact that friction is not taken into account. In this work we extend [2] by an alternative scaling of the tensile force in the 3D formulation that permits us to reduce the dimension of a contact problem with friction in tensile direction, too. The tension and the bending component in the direction of the contact normal are coupled due to the friction. The coupling of the displacement components is illustrated by a numerical example. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approximation rate and invertibility for some singular integral operators
Authors: Vasilyev Alexander , Vasilyev Vladimir 
Published: November 2013

AbstractWe consider discrete analogues of multi‐dimensional singular integrals and integral operators in a half‐space in square integrable and Hölder spaces with weight, and invertibility of discrete operators, and give the approximation rate for discrete operators. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Galerkin Approach for Solving Matrix Equations with Hierarchical Matrices
Authors: Boysen Dirk , Börm Steffen 
Published: November 2013

AbstractWe consider a new approach for computing solutions of certain matrix equations, for example AXA = C, AX + XB = C or AX = I. This approach is based on a variational formulation in the matrix space, employing the Frobenius inner product. Using the space of ℋ2‐matrices as trial space leads to a sparse linear system that can be solved by iterative methods to compute an approximate solution of the underlying matrix equation. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Acceleration of Kaczmarz Projection Algorithm
Authors: Pomparău Ioana 
Published: November 2013

AbstractIn the paper [1], a direct version of the classical Kaczmarz algorithm was proposed, which gives us in only one iteration a solution of an arbitrary consistent system of linear equations. Unfortunately, as any direct method applied to large sparse matrices, this algorithm is based on some modifications of the system matrix sparsity structure such that a big fill‐in appears. In order to overcome this difficulty, in the present paper we propose a modified version of this direct Kaczmarz algorithm in which the transformations applied to the system matrix try to conserve the initial sparsity structure. This transformations are done via clustering using Jaccard and Hamming distances. The modified Kaczmarz algorithm is no more a direct method, but we obtain an acceleration of convergence with respect to the classical Kaczmarz algorithm. Numerical experiments which ilustrate the efficiency of our algorithm are also presented. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
LQR control for a Diesel engine's air system
Authors: Kemper Anna , Wöbbekind Mitja , Büskens Christof , Schollmeyer Michael 
Published: November 2013

AbstractDue to more and more restrictive emission standards, the air system of Diesel engines has evolved into a complex system with several coupled actuating and controlled variables. In this paper, a linear‐quadratic regulator (LQR) is used as a model‐based, multivariable, optimal control of the air system. This technique is validated by results of an on‐board test. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)