bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transition from hyperelastic micromorphic to micropolar and microstrain continua
Authors: Leismann Thorben , Mahnken Rolf 
Published: October 2015

AbstractMicromorphic continua are equipped with additional degrees of freedom in comparison to the classical continuum, representing micro deformations of the material points of a body. They are also provided with a higher order gradient. Therefore, they are able to account for material size‐effects and to regularize the boundary value problem, when localization phenomena arise. Arbitrary micro deformations are allowed for in the micromorphic continuum, while the special cases micropolar continuum and microstrain continuum merely allow for micro rotation and micro strain, respectively. This paper is concerned with the transition from a micromorphic to a micropolar and a microstrain continuum. Three simple constitutive models are shown, which represent the three different continua. Additionally, the role of the micropolar and microstrain part in a micromorphic continuum is illustrated by a numerical example. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shape control of piezolaminated thin‐walled structures using nonlinear piezoelectric actuators
Authors: Mekala Narasimha Rao , Sachdeva Tarun , Schröder Kai‐Uwe 
Published: October 2015

AbstractIn the present paper a 2D‐shell finite element model is proposed to carry out static analysis of piezolaminated composite shells by incorporating nonlinear constitutive relations in order to describe the electromechanical coupling under strong electric fields. The present shell element has 5 mechanical DOFs and 3 electrical DOFs per node. The developed composite piezolaminated shell element is employed to study the static behavior and shaping of spherical antenna reflector laminated with piezo‐patches under both weak and strong electric fields. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling Dynamic Recrystallization in Polycrystalline Materials via Probability Distribution Functions
Authors: Nguyen Hai Van , Ebrahimzade Vahid , Hackl Klaus , Renner Jörg , Trinh Bach Tuyet 
Published: October 2015

AbstractA model of dynamic recrystallization in polycrystalline materials is investigated in this work. Within this model a probability distribution function representing a polycrystalline aggregate is introduced. This function characterizes the state of individual grains by grain size and dislocation density. By specifying free energy and dissipation within the polycrystalline aggregate an evolution equation for the probability density function is derived via a thermodynamic extremum principle. For distribution functions describing a state of dynamic equilibrium we obtain a partial differential equation in parameter space. To facilitate numerical treatment of this equation, the equation is further modified by introducing an appropriately rescaled variable. In this the source term is considered to account for nucleation of grains. Then the differential equation is solved by an implicit time‐integration scheme based on a marching algorithm [2]. From the obtained distribution function macroscopic quantities like average strain and stress can be calculated. Numerical results of the theory are subsequently presented. The model is compared to an existing implementation in Abaqus as well. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Martensitic transformations and damage: A combined phase field approach
Authors: Schmitt Regina , Kuhn Charlotte , Müller Ralf 
Published: October 2015

AbstractA combined continuum phase field model for martensitic transformations and damage is introduced. The present approach considers the eigenstrain within the martensitic phase which leads in the surrounding material to both tensile and compressive stresses. The damage model needs to account for an appropriate differentiation thereof, since compressive stresses should not promote fracture. Interactions between micro crack propagation and the formation of the martensitic phases are studied in two dimensions. In agreement with experimental observations, martensite forms at the crack tip and influences the crack formation. For the numerical implementation finite elements are used while for the transient terms an implicit time integration scheme is employed. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Continuum modeling of material interfaces and surfaces based on molecular statics computations
Authors: Sievers Christian , Mosler Jörn 
Published: October 2015

AbstractThe effective macroscopic properties of a broad variety of different materials are defined by the properties of the involved material interfaces and surfaces. However, in contrast to classical bulk materials, the mechanical properties of material interfaces can usually only be determined indirectly. For that purpose, two different approaches are presented which allow to compute macroscopic properties of material interfaces based on molecular statics computations. While the first of those is based on the principle of energy equivalence, the second one relies on the principle of stress equivalence. The advantages and disadvantages of both frameworks are analyzed. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parallel solution of volume‐coupled multi‐field problems using an Abaqus‐PANDAS software interface
Authors: Schenke Maik , Ehlers Wolfgang 
Published: October 2015

AbstractNumerical simulations have proven to be a powerful tool in several engineering disciplines, such as mechanical, civil and biomechanical engineering, and are thus widely used. However, the reliability of the simulations strongly relies on the governing material model. These models are usually developed in academic or industrial research projects and are implemented into dedicated software packages to proof their concepts. A transfer of these models from the research into a production‐related environment is often time consuming and prone to failures, and therefore a costly task.The present work introduces a general interface between the research code PANDAS, which is a dedicated multi‐field finite‐element solver based on a monolithic solution strategy, and the commercial finite‐element package Abaqus. The coupling is based on the user‐defined element subroutine (UEL) of Abaqus. This procedure, on the one hand, allows for a straight‐forward embedding of the PANDAS material models into Abaqus. On the other hand, it provides, in comparison to the native UEL subroutine of Abaqus, a user‐friendly programming environment for user‐defined material models with an extended number of degrees of freedom. Furthermore, the coupling also supports the parallel‐analysis capabilities for large‐scale problems on high‐performance computing clusters.The Abaqus‐PANDAS linkage can be applied to various coupled multi‐field problems. However, the present contribution addresses, in particular, volume‐coupled multi‐field problems as they arise when proceeding from the Theory of Porous Media (TPM) as a modelling framework. For instance, it can be used to model partially or fully saturated soils, or chemically or electro‐chemically driven swelling phenomena as they appear, for example, within hydrogels. Additionally, discontinuities, such as cracks, can be described for instance via phase‐field models or by the extended finite‐element method (XFEM). (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On electrostatic‐viscoelastic simulation of dielectric actuators
Authors: Schlögl Tristan , Leyendecker Sigrid 
Published: October 2015

AbstractDescribing and controlling the behaviour of dielectric elastomer actuated systems requires a suitable simulation model for the electro active polymers. This work is based on three dimensional finite elements to cover arbitrary actuator geometries. Maxwell's equations for electrostatics are coupled with the momentum balance by an electrostatic stress tensor. Time dependent quantities allow for a description of the deformation process depending on time. A potential energy function that is composed of Neo‐Hooke material behaviour, electric field energy and coupling terms covers the material properties. Viscoelastic effects are included and account for time dependent strains. A discrete version of Hamilton's principle leads to a structure preserving integration scheme for dielectric elastomers. The integration scheme is implemented in C++ and applied to examples. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Validation of a coupled FE‐model for the simulation of methane oxidation via thermal imaging
Authors: Thom Andrea , Ricken Tim , Bluhm Joachim , Widmann Renatus , Denecke Martin , Gehrke Tobias 
Published: October 2015

AbstractTo simulate the processes of methane oxidation in landfill cover layers, a new computational model was created. The purpose of the model is to allow a forecast on the performance of methanotrophic activity in landfill cover layers under changing environmental conditions. Therefore, a thermodynamic consistent model based on the well‐known Theory of Porous Media (TPM) combined with the mixture theory was developed, which analyzes the relevant gas productions of methane, oxygen and carbon dioxide. Diffusion, advection and conversion processes are considered as well as the energy production during methane oxidation. With the help of the thermal imaging technique a new experimental setup was developed in order to validate the coupled model in terms of the heat generation. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of ice under mechanical and thermal load
Authors: Urban Sten , Beitelschmidt Michael 
Published: October 2015

AbstractThe contact physics of the wheel‐rail contact of a railway vehicle under presence of water and ice at low temperatures is still not completely understood. For the investigation of the particular process in the contact zone a simulation is required, which is able to calculate the normal and tangential contact, the temperature field and the fluid‐structural interaction between wheel and rail at low temperatures under presence of snow and ice. For that purpose the behaviour of ice under wheel‐rail contact conditions is an important part. In this paper the thermal dynamic model of TSHIJOV [1], [3] for an adiabatic ice probe is updated by the new IAPWS equations of state for water [5] and ice phase Ih [4]. In a first approximation an ice specimen is loaded by specific wheel‐rail contact pressure distributions calculated by the half‐space formulation to clarify if phase transitions of ice can exist. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational Homogenization of Micromechanically Resolved Textile Materials
Authors: Mehnert Markus , Fillep Sebastian , Mergheim Julia , Steinmann Paul 
Published: October 2015

AbstractThis contribution deals with textile materials. On the macroscopic level textiles are characterized by a large area‐to‐thickness ratio, such that it is numerically efficient to treat the textile structure as a shell. To capture the contact behavior, fibers within a representative volume element are explicitly modeled by means of one dimensional beam elements on the microscopic level. A suitable, shell‐specific homogenization method is developed, which connects the homogeneous shell specific macro level to a fiber structured micro level. This contribution investigates the determination of the nonlinear constitutive behavior of textile materials. Selected examples for the macroscopic behavior of microscopic heterogeneous fiber structured materials are presented. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Clebsch transformation and its capabilities towards fluid and solid mechanics
Authors: Scholle Markus , Marner Florian 
Published: October 2015

AbstractIn fluid dynamics, Clebsch made use of the representation for the velocity field
$\vec u$
in terms of three potentials Φ, α, β in order to construct a first integral of the equations of motion in case of an inviscid flow with vortices. Apart from this, he received a self‐adjoint form of the equations allowing for deriving them from a variational formulation. In latter times the Clebsch transformation has been applied to different physical problems, for instance to baroclinic flow, Maxwell equations in classical electrodynamics [1], in Magnetohydrodynamics and even quantum theory within the context of a quantization of vortex tubes. Viscous flow, however, has not yet been formulated in terms of Clebsch variables to our best knowledge. It is the aim of this paper to demonstrate how Clebsch variables can be applied to viscous flow on the one hand, leading to a first integral of Navier‐Stokes equations as a first example. As a second example, solid mechanics is considered: by making use of an analogy between vortices in fluid flow on the one hand and dislocations in crystals on the other hand, a dynamic theory of dislocations can be established by using a certain modification of the Clebsch transformation. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient numerical method for fully‐resolved particle simulations on high‐performance computers
Authors: Schneiders Lennart , Grimmen Jerry H. , Meinke Matthias , Schröder Wolfgang 
Published: October 2015

AbstractA numerical method for fully‐resolved particle simulations on adaptively‐refined Cartesian meshes is presented. When the particle size is on the order of or smaller than the smallest scales of the carrier flow, fully resolving the particle surfaces on uniform Cartesian meshes results in a tremendous computational effort. This is circumvented by locally refining the mesh near the moving particle surfaces. A new dynamic load‐balancing strategy is described which enables the application of this approach to particulate turbulent flows on high‐performance computers. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Turbulent boundary layer on a plate. Reynolds analogy and new formulations of the temperature defect law
Authors: Vigdorovich Igor 
Published: October 2015

AbstractA consistent asymptotic theory describing hydrodynamic and thermal turbulent boundary layers on a flat plate in zero pressure gradient is developed. The fact that the flow depends on a limited number of governing parameters allows us to formulate algebraic closure conditions that relate the turbulent shear stress and turbulent heat flux to mean velocity and temperature gradients. As a result of an exact asymptotic solution of the boundary‐layer equations, the known laws of the wall for the velocity and temperature and the velocity and temperature defect laws as well as the expressions for the skin‐friction coefficient, Stanton number, and Reynolds‐analogy factor are obtained. The latter implies two new formulations for the temperature defect law one of which is completely similar to the velocity defect law and does not contain the Stanton number and the turbulent Prandtl number, and the other does not contain the skin‐friction coefficient. A heat‐transfer law is obtained that relates only thermal quantities. The theoretical conclusions agree well with experimental data. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Linear stability of a thin non‐isothermal droplet spreading on a rotating disk
Authors: Boettcher Konrad , Externbrink Timo 
Published: October 2015

AbstractPrevious works show that the linear stability of the contact line of an isothermal spreading droplet depends on the base state curvature of the free interface at the position of the unperturbed contact line [1]. Here the linear stability of a thin liquid droplet on a rotating disk is investigated, where the disk has a certain radial temperature profile and the ambient passive gas a constant temperature. It is shown that two different Marangoni effects influence the spreading beside centrifugal, gravitational, and capillary effects. The stability analysis prevails, that temperature gradients in the disk amplify some and damp other modes, while cooling the entire disk (or heating the gas) damps the growth rate of all modes and therefore seems to be an appropriate way to suppress the instability. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison of viscoelastic and empirical rheological models in context of squeeze flows
Authors: Descher Stefan , Wünsch Olaf 
Published: October 2015

AbstractThis work compares the behavior of a Giesekus and Carreau‐Yasuda fluid in a squeeze flow between two circular plates. In order to do this the Carreau‐Yasuda model is fitted to the shear viscosity curve of the Giesekus model and the squeeze stress is compared over the process time. The investigations are performed numerically with a 2.5 dimensional wedge model. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptation and Enhancement of Generalized Polynomial Chaos for Industrial Applications
Authors: Glaser Philipp , Kosmas Petridis , Heuveline Vincent 
Published: October 2015

AbstractThis contribution presents ideas, how to adapt stochastic elements to industrial applications and reduce the number of simulations in comparison to Monte Carlo. Especially when the mathematical model equations are not known and just an input/output interface is given. For this so called black box model which can be generated by many simulation tools the generalized polynomial chaos based on the idea of Wiener [1], and extended by Xiu and Karniadakis [2] is a suitable technique. One main advantage of this concept can be seen in the ability to produce functional representations of stochastic variability. This yields in a reduction of the simulation number compared to classical methods and can intensified by using a sparse grids approach [3]. Looking at industrial applications the concept can be applied to a huge amount of systems. For example, components including electronic drives, fuel injection valves, and mechanical parts. As an example of use, a simplified model of a DC drive with six uncertain parameters is taken into account. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polynomial chaos approach for tuned bladed rotors with geometric modification
Authors: Koebelé‐Cousquer Maxime , Proppe Carsten 
Published: October 2015

AbstractThe paper presents a polynomial chaos approach for direct appoximation of cyclic modes of a tuned bladed rotor with all blades having the same randomly modified geometry. In order to validate this approach, accuracy of the approximation is evaluated for a simple rotor and is compared with other approximation methods, where eigenfrequencies and eigenvectors are obtained using polynomial approximation of structural matrices. The results show the good accuracy of the polynomial chaos approach. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polynomial Chaos and the Heave Motion of a Cylinder in Random Seas
Authors: Kreuzer Edwin , Solowjow Eugen 
Published: October 2015

AbstractThe stochastic equation of motion for a heaving cylinder subject to irregular sea waves is solved numerically with the polynomial chaos framework. Thereby, the stochastic forcing is expressed by a truncated Karhunen‐Loève expansion and the hydrodynamic radiation is formulated as a state space model. We obtain the mean and the variance of the cylinder heave motion. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Virtual process design on combined quasi‐static and high‐speed forming
Authors: Rozgić Marco , Kiliclar Yalin , Stiemer Marcus , Reese Stefanie 
Published: October 2015

AbstractSheet metal forming processes play a key role in a vast number of manufacturing cycles. The pursuit of novel approaches and enhancements of process chains is limited by the tremendous cost of experimental investigations. Hence, virtual process design is a suitable tool to overcome this limitation and to investigate new aspects of the processes via computer aided design. This work focuses on the optimization of a class of triggering pulses utilized in combined quasi‐static and electromagnetic high‐speed forming that avoid reverse currents. As typical example double exponential pulses are treated. Non‐linear, constrained optimization exploiting a LSDYNA simulation of the forming process is used to determine parameters defining a triggering current pulse, yielding an enhanced forming result, in terms of sharper drawing radii. A more detailed discussion of the method is presented in [1]. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust Identification of Parametric Radiation Force Models via Impulse Response Fitting
Authors: Hatecke Hannes , Krüger Stefan 
Published: October 2015

AbstractThis paper presents a new identification method for obtaining parametric state‐space models for radiation force computation. These state‐space models can substitute the convolution integral in the equations of motion based on the impulse response function method. Thus, the method converts the integro‐differential equation to an ordinary differential equation which reduces the computational effort of radiation force computation significantly. The identification is performed in time‐domain which means that the retardation function is subject to fit. The method is verified by the application to a floating cylinder. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive FEM with goal‐oriented error estimation and an approximation of the dual problem for inelastic problems
Authors: Widany Kai‐Uwe , Mahnken Rolf 
Published: October 2015

AbstractAn approximation of the dual problem for goal‐oriented error estimation is derived, which preserves the numerical structure of the primal problem, usually found in standard finite element implementations for solid mechanics. For the error estimation we apply a higher‐order recovery procedure. An application to elasto‐plasticity is given. Numerical examples demonstrate the effectiveness of the procedure. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DAE‐formulation for optimal solutions of a multirate model
Authors: Pulch Roland , Kugelmann Bernd 
Published: October 2015

AbstractA dynamical system including frequency modulated signals can be transformed into multirate partial differential algebraic equations. Optimal solutions are determined by a necessary condition. A method of lines yields a semi‐discretisation in the case of initial‐boundary value problems. We show that the resulting system can be written in a standard formulation of differential algebraic equations. Hence appropriate time integration schemes are available for a numerical solution. We present results for a test example modelling the electric circuit of a ring oscillator. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiobjective optimal control of fluid mixing
Authors: Ober‐Blöbaum Sina , Padberg‐Gehle Kathrin 
Published: October 2015

AbstractIn this contribution an efficient numerical method to solve multiobjective optimal control problems of fluid flow mixing governed by the advection equation is presented. To obtain well‐mixed behavior for non‐diffusive processes, the multi‐scale mixing of measure introduced in [1] is used in the formulation of the multiobjective optimal control problem. For the approximation of the Pareto set we combine reference point methods with an adjoint based optimization approach. (© 2015 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)