bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hot Spots on Brake Disks – Model Reduction and Stability Discussion
Authors: Graf Matthias , Ostermeyer Georg‐Peter 
Published: November 2013

AbstractSliding friction results in heat generation. One design aim of brake systems is for the temperature field to rise homogeneously, but experiments have repeatedly shown a characteristic inhomogeneous temperature pattern on the disk, known as Hot Spots. This phenomenon is undesired, as it leads to noise, vibration, and material disruption. The uneven temperature distribution arises from what are known as “Thermoelastic Instabilities”. The solutions for temperature and displacements must be obtained in four dimensions: three spatial dimensions and one time dimension. The industrial design process requires massive parameter studies and a fast solution of the model. To develop such models, strategies which avoid discretization come into the focus. The presented model is based on the application of global Ansatz functions for the fields, which are scaled to fulfil boundary conditions. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Modeling of Cohesive Softening Effects in Thick Adhesive Layers
Authors: Kieser Florian , Klinkel Sven 
Published: November 2013

AbstractThis work is concerned with the material modeling of the inelastic behavior of bonding and debonding effects in adhesive layers. High‐strength adhesives are applied in building industries utilizing thick adhesive layers due to huge building elements and construction tolerances. Therefore a continuum approach is presented to describe the nonlinear material behavior. In the failure criterion two stress invariants are used, which involves the hydrostatic pressure as well as the deviator stress state. A non‐associated flowrule, which determines the evolution of the inelastic variables, is required to ensure the thermodynamical consistency of the model. Hardening and softening are included as well as the rate‐dependency of the adhesive. Furthermore the viscoplastic approach is used for regularization of the mesh dependency in case of material softening. The nonlinear material model is implemented in a finite element program. The material tangent modulus is incorporated to obtain quadratic convergence for the global equilibrium iteration. The identification of material parameters is discussed on the simulation of typical experiments for adhesive materials. As a drawback of the presented phenomenological material model, the large number of parameters involved in the constitutive description is discussed. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamically consistent modeling of yield surface distortion
Authors: Shi Baodong , Mosler Jörn 
Published: November 2013

AbstractFrom a macroscopic point of view, the deformation of most metals results in an evolution of the symmetry groups characterizing the isotropy of the considered materials. With respect to plastic deformation for instance, the shape of the macroscopic yield surface evolves during deformation. In the present paper, a novel constitutive framework capturing this evolution is proposed. This framework is based on the fundamentals of thermodynamics. Furthermore, it also shows a variational structure such that all state variables follow jointly from minimizing an incrementally defined energy functional. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application and evaluation of hyper‐ and hypoelastic‐based plasticity models in the FE simulation of metal forming processes
Authors: Brepols Tim , Vladimirov Ivaylo N. , Reese Stefanie 
Published: November 2013

AbstractMetal forming processes are usually accompanied by large plastic strains and rotations of the material elements which emphasizes the need for reliable finite strain elastoplasticity models in corresponding FE simulations. In this work, two specific finite strain hyper‐ and hypoelastic‐based plasticity models with combined nonlinear isotropic and kinematic hardening are presented and compared in numerical FE simulations. Although both models led to remarkably different results in a shear‐dominated single element deformation test, the structural simulation of a standard deep drawing process delivered nearly congruent results which suggests that both models are equally well‐suited for modeling metals in common forming processes. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Configurational Forces in Crystal Plasticity
Authors: Lohkamp Richard , Müller Ralf , Aurich Jan , Schneider Frank 
Published: November 2013

AbstractThe surface morphology of micro machined surfaces depends on the heterogeneous microstructure. A crystal plasticity model is used to describe the plastic deformation in cp‐titanium with its hcp crystal structure. Therefore the basal and prismatic slip systems are taken into account. Furthermore, self and latent hardening are considered. The rate dependency is motivated by a visco plastic evolution law. The cutting process of cp‐titanium is modeled within the concept of configurational forces for a standard dissipative media. This framework is implemented into the finite element method. An example illustrates the effects of the microstructure on plastic deformation and configurational forces. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the Homogenization on the Transient Behaviour of Size Distributed Polycrystals
Authors: Rieger Florian , Böhlke Thomas 
Published: November 2013

AbstractThe deformation in polycrystals is often heterogenous, e.g. due to grain size dependent hardening. In a semi‐analytical representative volume element (RVE), a log‐normal distributed grain size is assumed together with a grain size dependent local plastic behavior. The numerical results are well approximated by a simple analytical expression. The effect of the homogenization comparison stiffness on the transient behaviour is explained using a simplified localization equation. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of a viscoplastic material model on a combined quasi‐static‐electromagnetic forming process
Authors: Kiliclar Yalin , Demir O. Koray , Vladimirov Ivaylo N. , Kwiatkowski Lukas , Reese Stefanie , Tekkaya A. Erman 
Published: November 2013

AbstractThe prediction and simulation of material behavior by finite element methods has become indispensable. Furthermore, various phenomena in forming processes lead to highly differing results. In this work, we have investigated the process chain on a cross‐shaped cup in cooperation between the Institute of Applied Mechanics (IFAM) of the RWTH Aachen and the Institute of Forming Technology and Lightweight Construction (IUL) of the TU Dortmund.A viscoplastic material model based on the multiplicative decomposition of the deformation gradient in the context of hyperelasticity has been used [1,2]. The finite strain constitutive model combines nonlinear kinematic and isotropic hardening and is derived in a thermodynamically consistent setting. This anisotropic viscoplastic model is based on the multiplicative decomposition of the deformation gradient in the context of hyperelasticity. The kinematic hardening component represents a continuum extension of the classical rheological model of Armstrong‐Frederick kinematic hardening. The constitutive equations of the material model are integrated in an explicit manner and implemented as a user material subroutine in the commercial finite element package LS‐DYNA with the electromagnetical module. The aim of the work is to show the increasing formability of the sheet by combining quasi‐static deep drawing processes with high speed electromagnetic forming. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the influence of Spectral Elements for elastic wave propagation on the CFL‐Condition
Authors: Asmus Andreas , Lammering Rolf 
Published: November 2013

AbstractFor the simulation of the interaction of elastic waves in CFRP plates with inhomogeneities and defects the spectral finite element method (SEM) is under investigation. The SEM uses high‐order shape functions which are composed of Lagrange polynomials with nodes at the Gauss‐Lobatto quadrature (GLq) points. In this way we obtain a diagonal mass matrix which makes an explicit time scheme more efficient. The goal of this work is to investigate the effect of SEM on the CFL‐Condition. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A coupled chemo mechanical model for polymer degradation and erosion processes
Authors: Seydewitz Robert , Böl Markus 
Published: November 2013

AbstractIn nowadays polymer materials are used in a multitude of different applications. A promising class of smart materials are biodegradable polymers. The present work proposes a micromechanical motivated description of degradation. Since degradation leads finally to an eroding material both cases of erosion, namely bulk and surface erosion, are considered. Degradation is modelled in a strong coupled chemo mechanical framework for an arbitrary spatial motion problem. Deformations arising due to surface erosion are described as material motion. Finally, the modelling concept is embedded in a finite element method. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled chemomechanics and phase field modeling of failure in electrode materials of Li‐ion batteries
Authors: Dal Hüsnü , Miehe Christian 
Published: November 2013

AbstractWe propose a canonical finite strain theory for diffusion‐mechanics coupling for the intercalation induced stress generation in Li‐ion electrode particles. The intrinsic coupling arises from both mechanical pressure gradient‐induced diffusion of Li‐ion particles and diffusion induced swelling/shrinkage leading to mechanical stresses. In addition, we extend the finite strain theory for diffusion‐mechanics coupling to chemomechanical fracture of electrode particles by introducing a nonlocal crack phase field which replaces a sharp crack topology with a smooth diffuse interpolation between the intact and broken states of the material. We employ a semi‐implicit Galerkin‐type finite element method for the solution of resulting set of differential equations. In addition to the mechanical, chemical and crack phase field, we introduce the pressure as an independent field variable in order to reduce the smoothness requirements on the interpolation functions. We illustrate characteristic features of the proposed model by means of representative initial‐boundary value problems. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Modeling of Fluid‐Structure Interaction of Blood in a Vein by Simulating Conservation of Mass and Linear Momentum with the Finite Element Method in FEniCS
Authors: Lofink Paul , Müller Wolfgang H. 
Published: November 2013

AbstractIn medicine a fundamental understanding for blood flow in human arteries is significantly important. In socalled hemodynamics engineers all over the world simulate blood flows in healthy and diseased vessels. Scientific findings in this area help to improve cardiovascular assisting devices and to plan surgical operations. The difficulty with such simulations is the interaction of the blood flow with the elastic vessel wall, which deforms due to changing flow conditions. We will present a two‐dimensional model for blood flowing through an arterial vessel and investigate the balance of mass and the balance of linear momentum. We will adjust these balance equations appropriately and define time dependent boundary conditions. The necessary partial differential equations for the fluid‐structure interaction will be solved by using the finite element method in FEniCS [1]. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Influence of Incompressibility on the Microstructure of Dielectric Elastomers
Authors: Klassen Markus , Xu Bai‐Xiang , Müller Ralf 
Published: November 2013

AbstractDielectric elastomers (DE's) are considered in recent times for the development of so called smart actuators. This relatively soft material is deformed under the influence of an external electric field. It is an ideal candidate for application in which complex surface deformations are desired.To increase the deformation range the insertion of material inclusions seems to be a good alternative. In the current work a mixed three field formulation in proposed to handle the quasi incompressibility of DE's for numerical simulations. A numerical analysis is performed in which the mixed formulation is compared with a standard displacement formulation. The results show the importance of the consideration of the nearly incompressible behaviour for the case of heterogeneous DE's. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized boundary conditions and effective properties in cracked piezoelectric solids
Authors: Gellmann Roman , Ricoeur Andreas , Merkel Eugen , Wang Zhibin 
Published: November 2013

AbstractIn this paper we present two subjects of our actual research in the field. The first deals with the boundary conditions at the crack faces. The well known model by Hao and Shen gives opportunity to take the finite dielectric permeability of the crack into account, without having to solve the two‐ or three‐dimensional coupled boundary value problem of solid material and crack medium. This approach, however, is based on the assumption of the electric field being perpendicular to the crack faces. We investigate this problem for arbitrary poling and field directions based on a combined analytical‐numerical approach. The second focus of the paper is on the effective properties of piezoelectrics with cracks. Here, homogenization procedures are applied and extended towards coupled field problems including e.g. Maxwell stresses at internal boundaries and interfaces. Effective elastic, dielectric and piezoelectric constants exhibit interesting effects. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solution of Inverse Task of Mechatronic Systems by Means the Classical and Unclassical Methods of Modelling and Analysis
Authors: Buchacz Andrzej 
Published: November 2013

AbstractIn this paper the modelling by means of the different category graphs and analysis of vibrating subsystem of mechatronic systems by means of the exact and approximate methods have been presented. That approach was to nominate the relevance or irrelevance between the characteristics obtained by means of the exact method (only for the mechanical subsystem) and the approximate method. Such formulation concerns mostly the relevance of the natural frequencies‐poles of the characteristics both mechanical subsystems and mechatronic systems. Approximate solutions requiring all the conditions for vibrating mechanical and/or mechatronic systems have been finding and it may be introduction to synthesis of these systems, modeled by different category graphs. Research limitation is following, that torsional vibrating continuous mechanical subsystem and mechatronic systems are linear type. Presentation the introduction to synthesis of considered class of mechatronic bar‐systems with a constant changeable cross‐section is practical implications of this work. Originality of such formulation is focused on the use of the different category graphs for modelling and synthesising by different methods represented by graphs of vibrating bars to the synthesis of considered discrete‐continuous mechatronic systems. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical elements as implementation of active reduction of vibrations
Authors: Białas Katarzyna 
Published: November 2013

AbstractThe major aim of this study is to show how to carry out the process of structural and parametrical synthesis that is understood as a design method of the system with active suppression of vibrations. Active components are implemented as electric components. The other objective is to analyze how the active subsystem interacts with the overall investigated structure. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐isothermal gas flow in microchannel with equal wall temperatures
Authors: Milićev Snežana S. , Stevanović Nevena D. 
Published: November 2013

AbstractA non‐isothermal two‐dimensional compressible subsonic slip gas flows is analyzed in this paper. It is pressure‐driven steady flow in microchannels with variable cross section (convergent, divergent, and constant height channel). Since the flows correspond to microspaces, the rarefaction effect is taken in account. The obtained gas temperature profiles are non‐uniform. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Symmetric Boundary Conditions in the Context of Viscoelastic Fluid Flows
Authors: Al‐Baldawi Ammar , Alves Manuel A. , Wünsch Olaf 
Published: November 2013

AbstractIn order to reduce the numerical cost of three dimensional flow problems with geometrical symmetry, the use of symmetric boundary conditions is standard. For Newtonian fluid flow problems this approximation is usually appropriate, particularly when the Reynolds number is small. In the case of viscoelastic fluid flow simulations with stabilization techniques, such as the so‐called DEVSS and/or Log‐Conformation tensor methods, at high Deborah number flows this implementation is not straightforward, as in the Newtonian case. It is well known that viscoelastic models (e.g. Maxwellian models), show (purely) elastic flow instabilities when the Deborah number is increased above a critical value, even under creeping flow conditions. In this work we present numerical simulations with different stabilization techniques and different differential viscoelastic models at high Deborah number flows. As a test‐case, we compare the flow in a full two‐dimensional cross‐slot geometry to show the asymmetrical behavior of the viscoelastic fluid flow. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of higher interpolation orders in mixed LSFEM for the incompressible Navier‐Stokes equations
Authors: Serdas Serdar , Schwarz Alexander , Schröder Jörg , Turek Stefan , Ouazzi Abderrahim , Nickaeen Masoud 
Published: November 2013

AbstractThe focus of this contribution is the examination of the influence of different interpolation orders (especially for the pressure field) by solving the stationary incompressible Navier‐Stokes equations with least‐squares finite elements. We consider two different div‐grad first‐order systems which result in a three‐field formulation with stresses, velocitites and pressure, see e.g. SCHWARZ & SCHRÖDER [1] and BOCHEV & GUNZBURGER [2]. Additionally, a numerical example is presented to show the performance of the considered formulations. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Near‐separating, self‐similar turbulent boundary layer
Authors: Vigdorovich Igor 
Published: November 2013

AbstractThe self‐similar flow in a turbulent boundary layer, which is in a state close to separation as a result of the effect of adverse pressure gradient, is investigated. Such a boundary layer has a triple‐deck asymptotic structure. Between outer and near‐wall regions above the logarithmic sublayer, i. e. the constant‐stress layer, an intermediate region — the gradient sublayer — is formed, where the shear stress varies linearly due to adverse longitudinal pressure gradient. In the external part of the gradient sublayer, the velocity profile obeys the square‐root law. The velocity profile obtained from the solution for the outer region satisfies a slip condition on the wall. The slip value decreases as the similarity parameter $\Omega = \sqrt{- \delta^* U'/U}$ increases and vanishes at the value of Ω = 0.0911, which corresponds to separation, here δ* is the displacement thickness, and U and U′ are the free‐stream velocity and its derivative with respect to the longitudinal coordinate. In this case, the exponent m in the law specifying the free‐stream self‐similar velocity distribution increases, with separation occurring not at the minimal value of m = −1/3, which corresponds to the strongest adverse pressure gradient, but at the value m = 0.228. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Frequency Domain Waveform Inversion in a Tunnel Environment
Authors: Musayev Khayal , Hackl Klaus , Baitsch Matthias 
Published: November 2013

AbstractThe aim of the waveform inversion is to find an optimal model for the distribution of the elastic stiffness such that its response is consistent with the seismic data. In this study, a high‐order finite element method is being used to solve the forward problem in the frequency domain and a gradient‐based approach is followed to invert the model where an adjoint method eases the computational struggle by reducing the number of the required forward simulations significantly. Perfectly Matched Layers (PML) are implemented in order to absorb waves on the fictitious boundaries of the considered geometry. The model is inverted only over a limited number of frequencies. This reduces the number of the required forward simulations and the nonlinearity of the inverse problem. Every model is unique and has to be investigated before being inverted; appropriate boundary conditions, placement of the source and receiver locations, and an initial model close to the real model are crucial points to be considered separately and carefully. Applications to the reconnaissance problem in a tunnel environment are shown. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vortex Generation in a Liquid Metal Duct Flow near a Magnetic Dipole
Authors: Tympel Saskia , Boeck Thomas , Krasnov Dmitry , Schumacher Jörg 
Published: November 2013

AbstractThe generation of vortical structures by a strong magnetic dipole field in a liquid metal duct flow is studied by means of three‐dimensional direct numerical simulations. The dipole is considered as the paradigm for a magnetic obstacle which will deviate the streamlines due to Lorentz forces which act on the fluid elements. Our model uses the quasi‐static approximation applicable in the limit of small magnetic Reynolds numbers. The analysis covers the stationary flow regime at smaller flow Reynolds numbers Re as well as the fully time‐dependent regimes at higher values with a turbulent flow in the wake of the magnetic obstacle. We present a systematic study of these two basic flow regimes on Re and the Hartmann number Ha, a measure of the strength of the magnetic dipole field. Furthermore, three orientations of the dipole are compared, the streamwise, spanwise and wall‐normal ones. The most efficient generation of turbulence at a fixed distance above the duct occurs for the spanwise orientation in which we can observe the formation of Hartmann layers at the top plate. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lattice Boltzmann Constraints for Standard Optimization Problems
Authors: Linke T. , Büskens C. , Meier S. 
Published: November 2013

AbstractThis paper presents a simultaneous analysis and design (SAND) approach for the control of incompressible, stationary fluid problems ruled by the lattice Boltzmann equation. Therefore the discretized lattice Boltzmann fix point problem is used as constraint for the optimization problem. This allows for the use of standard non‐linear programming techniques.To validate the proposed method a topology optimization problem is solved with the NLP solver WORHP at moderate Reynolds numbers (Re< 1000) for a 2‐dimensional flow domain. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)