bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Modelling of Thermo‐Viscoplasticity of Case‐Hardening Steels Over a Wide Temperature Range
Authors: Oppermann Philip , Denzer Ralf , Menzel Andreas 
Published: March 2018

AbstractThe aim of this work is the development of a thermodynamically consistent fully coupled thermo‐viscoplastic material model for metals. The model is based on a split of the free energy into a thermo‐elastic, a thermo‐plastic and a purely thermal part and covers nonlinear cold‐work hardening and thermal softening. Nonlinear temperature dependent effects are accounted for the elastic moduli, the plastic hardening moduli, the thermal expansion, the heat capacity and the heat conductivity. Furthermore, strain rate‐dependency of the current yield stress is realized using a temperature dependent nonlinear Perzyna‐type viscoplastic model based on an associative flow rule. The model and its parameters are fitted against experimental data for case hardening steel 16MnCr5 (1.7131). (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and Simulation of the Thickness Dependence in Die Casting Structures
Authors: Martinez Page Maria Angeles , Ruf Matthias , Hartmann Stefan 
Published: March 2018

AbstractSeveral die casting materials show different mechanical responses for specimens with different thicknesses. This can be observed in the variation of parameters, such as the Young's modulus, the tensile strength or hardness of the material in specimens with different thicknesses. In order to model this effect, we have experimentally investigated a specimen of a zinc die casting alloy. We concentrate in the modeling of the porosity distribution and its influence on the mechanical response using Mori‐Tanaka proposal for incorporating porosity. The applicability of the model is shown with a simulation example. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanical Simulation of Friction Stir Welding of Aluminum Using an Adaptive Element‐Free Galerkin Method
Authors: Talebi Hossein , Frönd Martin , dos Santos Jorge F. , Klusemann Benjamin 
Published: March 2018

AbstractThe coupled themomechanical modeling of the friction stir welding (FSW) process is a challenging process when typical finite element methods are used. In this study we use a the Element Free Galerkin (EFG) method to model the material flow during the FSW process. We use a two‐way adaptive method (rh‐adaptive) during the coupled thermomechanical process to overcome potential numerical problems arising from the extensive mesh distortion and material deformation. We test the simulation strategy to simulate FSW of aluminum. The results show that the new simulation strategy can handle extreme plastic deformation of the metal efficiently. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface Wetting with Droplets: A Phase Field Approach
Authors: Diewald Felix , Kuhn Charlotte , Heier Michaela , Horsch Martin , Langenbach Kai , Hasse Hans , Müller Ralf 
Published: March 2018

AbstractIn order to be able to predict the static solution of three dimensional wetting scenarios, a free energy functional that is dependent on a continuous order parameter is formulated. This free energy functional can be linked to molecular dynamics (MD) simulations by input parameters. Static equilibrium configurations can be computed by minimizing the overall free energy using an evolution equation of Allen‐Cahn type. Details of the presented model are followed by illustrative examples that demonstrate the pertinency of the approach. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐Order Numerical Methods for Electromagnetic Induction
Authors: Gleim Tobias , Kuhl Detlef 
Published: March 2018

AbstractThe present paper establishes an axisymmetric benchmark model of a conducting loop, which implies an electromagnetic induction. Therein, the fully coupled MAXWELL equations are demonstrated in a monolithic solution strategy. This dynamic problem is solved with a high order finite element discretization using GALERKIN's method in space as well as in time. Furthermore, high order RUNGE‐KUTTA time integration methods are analyzed. Studies regarding an h error estimation and the order of convergence are examined. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FEM‐analysis of a multiferroic nanocomposite – comparison of experiment and numerical simulation
Authors: Lemke Veronica , Labusch Matthias , Schröder Jörg , Wende Heiko 
Published: March 2018

AbstractThe combination of electric and magnetic materials opens new possibilities in the field of sensor technologies and data storage [1]. These magneto‐electric (ME) materials have the property to change a physical ferroic quantity into another, i.e. a magnetic field can change the electric polarization and vice versa. The combination of multiple ferroic characteristics within materials is called multiferroic. Since magneto‐electric single‐phase materials are rare in nature and typically operate only at very low temperature, they are not favorable in technical applications. However, ME composites, consisting of ferroelectric and ferromagnetic phases, produce a strain‐induced magneto‐electric product property at room temperature [2]. In these composites, two different effects can be differentiated, the direct and the converse ME effect. The first one describes a polarization which is magnetically caused. In detail, a magnetic field is applied which produces a deformation of the magneto‐active phase which is transferred to the electro‐active phase and as a consequence this phase exhibits a polarization. Therefore, one can discover a strain‐induced polarization. The second effect to observe is a magnetization caused by an electric field. In our contribution, we focus on a (1‐3) composite, where cobalt ferrite nanopillars are embedded in a barium titanate matrix, see the experiments described in [3]. In the numerical simulations we compare the changes of the strain‐induced inplane polarizations of the ferroelectric matrix with experimental measurements. Furthermore, we analyze the magneto‐electric coupling coefficient. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A kinetic energy preserving DG scheme applied to mechanical FSI
Authors: Ortleb Sigrun 
Published: March 2018

AbstractIn the context of mechanical fluid‐structure interaction (FSI) comprising moving or deforming structures, fluid discretizations need to cope with time‐dependent fluid domains and resulting grid deformations in addition to the general challenges regarding e.g. boundary layers and turbulent phenomena. Recent approaches in the simulation of compressible turbulent flow are based on so‐called split forms of conservation laws to guarantee the preservation of secondary physical quantities such as kinetic energy. For the simulation of turbulent flows, this often leads to a better representation of the kinetic energy spectrum. Initially, kinetic energy preserving(KEP) DG schemes have been constructed on Gauss‐Legendre‐Lobatto(GLL) nodes containing the interval end points, however, KEP DG schemes based on the classical Gauss‐Legendre(GL) nodes are potentially more accurate and may be also more efficient than its GLL variant for certain applications. In this work, the KEP‐DG schemes both on GL and GLL nodes are applied to the classical moving piston test case via an ALE formulation on moving fluid grids showing a more accurate frequency representation of the structure displacement in case of GLL nodes. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐electro‐active polymers: material properties and structural effects
Authors: Rambausek Matthias , Keip Marc‐André 
Published: March 2018

AbstractThis contribution presents a constrained minimization formulation of incompressible finite‐strain magneto‐electro‐elasticity. We employ this formulation in multiscale (FE2) simulations where we analyze the effective magneto‐electric coupling properties of soft‐matter based magneto‐electric composites. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Heat Conduction in a Phase Field Model for Martensitic Transformation
Authors: Schmidt Simon , Müller Ralf 
Published: March 2018

AbstractWe study the martensitic transformation with a phase field model, where we consider the Bain transformation path in a small strain setting. For the order parameter, interpolating between an austenitic parent phase and martensitic phases, we use a Ginzburg‐Landau evolution equation, assuming a constant mobility. In [1], a temperature dependent separation potential is introduced. We use this potential to extend the model in [2], by considering a transient temperature field, where the temperature is introduced as an additional degree of freedom. This leads to a coupling of both the evolution equation of the order parameter and the mechanical field equations (in terms of thermal expansion) with the heat equation. The model is implemented in FEAP as a 4‐node element with bi‐linear shape functions. Numerical examples are given to illustrate the influence of the temperature on the evolution of the martensitic phase. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Consistent macroscopic tangent computation for FFT‐based computational homogenization at finite strains
Authors: Göküzüm Felix S. , Keip Marc‐André 
Published: March 2018

AbstractThe present work addresses the efficient computation of effective properties of periodic microstructures by the use of Fast Fourier Transforms. While effective quantities in terms of stresses and deformations can be computed from surface integrals along the boundary of an RVE, the computation of the associated moduli is not straight‐forward. The contribution of the present paper is thus the derivation and implementation of an algorithmically consistent macroscopic tangent operator that comprises the effective properties of the RVE. In contrast to finite‐difference based approaches, an exact solution for the macroscopic tangent is derived by means of the classical Lippmann‐Schwinger equation. The problem then reduces to the solution of a system of linear equations even for nonlinear material behaviour. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of discrete stress distribution for dry powder compaction using Discrete Element Method and weighted Voronoi tesselation
Authors: Rasche Stefan , Tahir Arshad , Könke Carsten 
Published: March 2018

AbstractPowder compaction of granular material plays a substantial role in the manufacturing process of ceramics industry and powder metallurgy industry. The compaction behaviour is ruled by granular flow and densification of deformable particles. Discrete element method (DEM) allows to investigate the powder compaction process numerically on the microscale by modeling the forces on the particle level and simulating the particle motion. Three‐dimensional data about particle size distribution and spatial structure of the particle packing can be extracted from micro‐computed tomography (µCT). An average stress tensor can be computed from DEM results, evaluating the contact forces and the distances from the particle center to the contact point with respect to an average cell volume. A weighted Voronoi tesselation of the polydisperse particle assembly is proposed for mapping a cell volume to each individual particle. With this approach all structural information of the particle system can be transferred from a discrete particle model to a heterogeneous volume model of micro‐structure. Discrete stress distributions for uniaxial powder compaction are presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hierarchical multiscale finite element approach for modelling the heat affected zone of welded joints
Authors: Wudtke Idna , Silani Mohammad , Kraus Matthias 
Published: March 2018

AbstractIn the present work a hierarchical multiscale approach, based on finite element method, is applied in order to characterize the heat affected zone (HAZ) of a welded joint with parent material S460M. The metallurgical constituents of particular regions of the HAZ was determined experimentally and, regarding the multiscale approach, a first‐order computational homogenization method was implemented. In this context, effective stress‐strain‐relations in particular spots of the HAZ are determined applying prescribed displacement boundary conditions. The obtained relations were considered in subsequent finite element calculations of butt‐welded joints under tensile loading, allowing a comparison of the numerical strain states to experimental results. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurements of partially lubricated contacts on different scales
Authors: Müller Michael , Ostermeyer Georg‐Peter 
Published: March 2018

AbstractThis paper focuses on experimental investigations for lubricated contacts with partially filled gaps. The measurements are performed on two different scales. A pin‐on‐disc test bench represents the microscopic scale whereas a novel test bench with asperities in the range of centimeters corresponds to a rather macroscopic scale. The results are compared and conclusions towards the tribological properties are drawn. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Euler‐Lagrange Simulations of Turbulent Two‐phase Flows with an Advanced Deterministic Bubble Coalescence Model
Authors: Hoppe Felix , Breuer Michael 
Published: March 2018

AbstractThe present paper is concerned with an advanced version of the deterministic coalescence model [1] and its application to turbulent bubble‐laden flows. The major drawback of this film drainage model – its incapability to handle large numbers of coalescence processes – is avoided by an a‐priori determination of a parametric relation for the transition time between the main drainage mechanisms. The comparison with experimental results yields a good overall agreement, while the application to a downward pipe flow demonstrates the ability of the model to efficiently handle large numbers of coalescence processes. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The lift on a small sphere in a linear shear flow near the interface of two immiscible fluids
Authors: Scheichl Stefan 
Published: March 2018

AbstractAnalytical expressions have been derived which predict, to lowest order, the inertial lift and the lateral migration velocity of a rigid sphere translating and rotating in a linear shear flow field near the flat interface of two immiscible fluids. This asymptotic analysis is primarily based on the assumption that the two Reynolds numbers defined by the gap width between the interface and the sphere, the shear rate and the translational slip velocity with which the spherical particle moves parallel to the interface are small. Furthermore, the radius of the sphere is assumed to be small compared to the gap width. To leading order in this creeping flow regime, the linear Stokes equations are obtained and a symmetry argument can be used to show that the Stokes solution does not predict any lift force. The transverse force experienced by the sphere and its migration velocity are due to the small but finite inertial terms in the Navier‐Stokes equations, which can be studied by perturbation techniques. By applying a Green's function approach and matched asymptotic methods, which also incorporate the effects of the outer Oseen‐like flow regime, the three components comprising the lift velocity have been calculated in closed form: the one induced by the shear rate only, the purely slip induced one and the one due to the interaction of the slip velocity with the shear flow field. The thus obtained expressions for the case of two immiscible fluids with arbitrary density and viscosity ratios extend the results that already exist in the literature for other flow configurations, such as an unbounded shear flow field [1] or a wall‐bounded one, where the wall lies either within the leading order Stokes region [2] or in the outer Oseen region [3]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tikhonov Functionals Incorporating Tolerances
Authors: Gralla Phil , Piotrowska‐Kurczewski Iwona , Maaß Peter 
Published: March 2018

AbstractTikhonov functionals are a well known method for solving inverse problems. They consist of a discrepancy and a penalty term. The first term evaluates the deviation of simulated data from measured data. We alternate this term by incorporating tolerances, which neglects small deviations from the data within a prescribed tolerance. This approach adapts ideas from support vector regression, which utilizes such a tolerance for identity operators and semi discrete problems. Furthermore, the application for inverse problems is motivated by applications where such tolerances naturally occur, e.g. application with multiple measurements. In this case instead of one measurement a confidence interval for the measurement can be used.In this work we provide an overview on the necessary analysis and alternation of Tikhonov functionals incorporating tolerances. In addition, an example of applications are shown and discussed. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some basic boundary value problems for plane theory of elasticity of porous Cosserat media with triple‐porosity
Authors: Gulua Bakur , Janjgava Roman 
Published: March 2018

AbstractThe static equilibrium of porous elastic materials with triple‐porosity is considered in the case of an elastic Cosserat medium. A two‐dimensional system of equations of plane deformation is written in the complex form and its general solution is represented by means of three analytic functions of a complex variable and three solutions of Helmholtz equations. The constructed general solution enables one to solve analytically a sufficiently wide class of plane boundary value problems of the elastic equilibrium of porous Cosserat media with triple‐porosity. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transient Modeling and Simulation of Gas Pipe Networks with Characteristic Diagram Models for Compressors
Authors: Huck Christoph , Tischendorf Caren 
Published: March 2018

AbstractOne challenge for the simulation and optimization of real gas pipe networks is the treatment of compressors. Their behavior is usually described by characteristic diagrams reflecting the connection of the volumetric flow and the enthalpy change or shaft torque. Such models are commonly used for an optimal control of compressors and compressor stations [4,7] using stationary models for the gas flow through the pipes. For transient simulations of gas networks, simplified compressor models have been studied in [1–3]. Here, we present a transient simulation of gas pipe networks with characteristic diagram models of compressors using a stable network formulation as (partial) differential‐algebraic system. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On approximation of finite‐energy sequences of Müller's functional with non‐standard 2‐well potential
Authors: Raguž Andrija 
Published: March 2018

AbstractWe present the basic results and conjectures regarding possibility of approximating finite‐energy sequences of Müller's functional (which was for the first time, and in its simplest form, studied in paper S. Müller: Singular perturbations as a selection criterion for periodic minimizing sequences, Calc. Var. Partial Differential Equations 1(2), 169–204 (1993)) by 1‐Lipschitz and 1‐periodic finite‐energy sequences. Our results extend known results in the case of simplest pinning term concerning the actual minimizers as small parameter epsilon tends to zero, whereby standard assumption on growth of 2‐well potential at infinity (which immediately yields equi‐coercivity) is replaced by non‐standard one. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fuzinsumo ‐ Fuzzy investigation with surrogate models
Authors: Oberleiter Thomas , Willner Kai 
Published: March 2018

AbstractIn this contribution, we investigate the accuracy of surrogate models for fuzzy systems. Within a virtual tolerance analysis, unknown uncertainties are considered by fuzzy numbers. These fuzzy numbers consist of higher‐dimensional intervals, where each interval is assigned a membership value. To reproduce fuzzy numbers correctly, a large number of system evaluations is needed. Instead of evaluating numerically expensive full systems, we employ surrogate models with radial basis functions. In order to find sufficiently accurate surrogate models with as few as possible sampling points, we investigate the influence of the sampling points on the respective fuzzy number intervals. As an example, we investigate the tilting of an X‐ray aperture, which shows different accuracy for different sampling strategies. The reference results for the nonlinear multi‐body system are calculated by a Matlab optimizer and are compared to the results of the surrogate models. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Greedy Subspace Method for Computing the ℒ∞‐Norm
Authors: Aliyev Nicat , Benner Peter , Mengi Emre , Schwerdtner Paul , Voigt Matthias 
Published: March 2018

AbstractWe consider the computation of the ℒ∞‐norm for a general class of ℒ∞‐functions and focus on the case where the function is represented in terms of large‐scale matrix‐valued factors. We propose a subspace projection method to obtain reduced approximations of this function by interpolation techniques. The ℒ∞‐norms are computed for the resulting reduced functions, then the subspaces are refined by means of the optimizer of the ℒ∞‐norm of the reduced function. In this way we obtain much better performance compared to existing methods. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of a family of flux‐correction methods as a remedy against overshoot in unsteady flow computation
Authors: Niessner Herbert 
Published: March 2018

AbstractStill Lax‐Wendroff schemes are occasionally used calculating one‐dimensional flow. Supplementary flux‐correction allows to reduce or even prevent unphysical overshoot occuring with discontinuous initial conditions. There is a whole family of variants [4] based on damping or smoothing with different stability limits, which will be considered here in more detail. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zeno phenomenon in hybrid dynamical systems
Authors: Dashkovskiy Sergey , Feketa Petro 
Published: March 2018

AbstractA way to prolong Zeno solutions to hybrid dynamical system beyond Zeno time is proposed. Additionally, we provide a new definition of asymptotic stability that is equipped with sufficient conditions for its verification. It allows to investigate long‐term behavior of the prolonged solutions to hybrid dynamical systems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of ship manoeuvring within the project GALILEOnautic
Authors: Roy Sylvain , Wernsing Heinrich , Büskens Christof 
Published: March 2018

AbstractThe goal of the project GALILEOnautic is to develop a system for autonomous navigation and optimal manoeuvring of cooperative ships within safety‐critical areas. In this context, many challenges arise in the field of optimization and optimal control. The research presented here addresses one of them, namely, the calculation of optimal trajectories and controls for a group of cooperative ships navigating within the limits of a harbour. The adopted approach is to embed all aspects of the problem into a single optimal control problem, whose objective is to minimize the time to destination of each ship as well as their overall energy consumption. Path constraints are applied to maintain the ships at a safe distance from each other and from the infrastructure of the harbour. A two‐ship scenario is implemented, for which optimal trajectories and controls are successfully computed. The numerical computation of this problem is performed using the software library WORHP, the official ESA NLP solver, and moreover the software TransWORHP, which transcribes optimal control problems into optimization problems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)