bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical study of adhesive and cohesive failure of structured interfaces
Authors: Hirsch Franz , Kästner Markus 
Published: March 2018

AbstractIn this contribution, a numerical study is presented, which addresses the failure behaviour of structured interfaces within a computational homogenisation scheme. Different local phenomena, e.g. the surface roughness and different local failure types like cohesive failure of the polymer and adhesive failure of the local interface and their effects on the overall interface characteristics are investigated. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mean and full field homogenization of artificial long fiber reinforced thermoset polymers
Authors: Kehrer Loredana , Pinter Pascal , Böhlke Thomas 
Published: March 2018

AbstractBased on two artificial microstructures representing a long fiber reinforced thermoset material, the effective linear elastic material properties are calculated by both a mean and a full field homogenization method. Concerning the mean field method, the effective elastic material properties are approximated using the homogenization scheme by Mori and Tanaka, formulated explicitly in terms of orientation averages. This allows to use orienation tensors of 2nd and 4th order describing the orientation information on the micro level. The full field method is based on the fast Fourier transformation (FFT), for which the effective material properties are determined by volume averaging. The comparison between both methods show good agreements, the deviations are in the range between 2% and 12%. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational sensitivity analysis of physical reaction forces and application to multiscale problems
Authors: Kijanski Wojciech , Barthold Franz‐Joseph 
Published: March 2018

AbstractNowadays profitability and efficiency of practical and industrial applications and therefore of material design is becoming a more important issue. Due to different well‐known and established approaches for analysis and simulation of complex heterogeneous materials on multiple scales based on numerical homogenisation techniques, development and production of high performance materials (using 3d printers for example) and as a consequence optimisation and design of materials is reality. The objective is to find optimal structures with optimal material distribution under given constraints related to posed problems and tailoring applications to their special requirements. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effective shear modulus for an n‐layered composite sphere
Authors: Lenz Peter , Dammann Christian , Mahnken Rolf 
Published: March 2018

AbstractThis work presents the derivation of the effective shear modulus for a heterogeneous material composed of multi‐layered composite spheres embedded in a linear elastic matrix. It is based on the composite spheres model known from the literature. In contrast to previous publications the effective shear modulus is obtained by equating the results of two models: In the first model, a heterogeneous sphere is embedded in an equivalent homogeneous material, whereas in the second model, the heterogeneous sphere is replaced by an equivalent homogeneous sphere. In the context of both, a shear stress approach and a shear deformation approach, this results into an overdetermined system of equations which is solved with the least squares method. In a numerical study our results are compared to effective moduli and bounds from the literature. Furthermore, a convincing agreement with experimental data for glass microspheres embedded in a polyester matrix is demonstrated. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation and validation of a solidification experiment using a continuum mechanical two‐phase/‐scale model
Authors: Moj Lukas , Ricken Tim , Foppe Manuel , Deike Rüdiger 
Published: March 2018

AbstractA numerical simulation of a solidification experiment is presented. The experimental setup consists of an empty screwed up mould, which is filled up with molten steel and cools down due to atmospheric conditions. During the cooling process, the temperature at the centre as well as the shrinkage at the narrow side, respectively, have been recorded. The simulation has been run via the software ANSYS modified by specific provided programmer interfaces, the User Programmable Features (UPFs). All required temperature dependent material parameters have been provided by ThyssenKrupp Steel Europe. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effective thermal conductivity of carbon nanotube composites
Authors: Nagaraj Manish , Timothy Jithender J. , Meschke Günther 
Published: March 2018

AbstractThe effective thermal conductivity of Carbon Nanotube (CNT)‐polymer composites has been estimated using analytical and computational models. The analytical approach is based on the Cascade Continuum Micromechanics (CCM) model formulated within the framework of mean‐field homogenization and the computational approach is based on numerical homogenization of the composite microstructure using image based Voxel‐FEM (Finite Element Method). Comparison of the analytical and computational model predictions with experimental data show that the interfacial thermal resistance is overestimated by the analytical model as a consequence of not taking into account the CNT fiber tortuosity (curviness). (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomagnetic convection under alternating magnetic fields
Authors: Szabo Peter S. B. , Lee Yeaw‐Chu , Früh Wolf‐Gerrit 
Published: March 2018

AbstractThermomagnetic convection within a square cavity filled with a magnetic fluid was studied under alternating magnetic field. The aim was to explore the response of the magnetic fluid towards alternating magnetic fields. A set of frequencies for the sinusoidal variation of the magnetic field intensity was used to study the heat transfer characteristics across the problem geometry. The effect on heat transfer was quantified by an averaged Nusselt number. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CFD studies on the surge detection of a radial compressor flow by analyzing the unsteady secondary flow field
Authors: Bamberg Stephan , Schnitzer Jakob , Weber Manuel , Rusche Stefan , Eißler Werner 
Published: March 2018

AbstractThe objective of this investigation is the development of a reliable methodology allowing the accurate prediction of compressor surge. In this context a centrifugal compressor used in a commercial application with five main and five splitter blades, installed in regular passenger vehicles, is numerically analyzed. For this purpose a CFD analysis is conducted. The steady‐state and unsteady secondary flow field is analyzed and studied by a frequency analysis to detect critical oscillations. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluating flame turbulence scale in diffusion combustion of diesel fuels
Authors: Loboda Egor , Matvienko Oleg , Agafontsev Mikhail , Reyno Vladimir 
Published: March 2018

AbstractThis paper presents results of mathematical simulations of dynamic flame behavior that occurs in burning diesel fuel, as well as experimental data on turbulent flame eddies provided by infrared thermography. The comparison of the simulated and experimental data documents a good match between the parameters of flame thermodynamics and the combustible gas flow in a turbulent eddy. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigations of bubbles rising in water
Authors: Höffmann Ann Kathrin , Ehrhard Peter 
Published: March 2018

AbstractThe hydrodynamics of rising air bubbles in water filled bubble columns are examined using a transient numerical model following the Euler‐Euler method. In this particular case the bubble‐size distribution is assumed to be mono‐disperse and the influence of this assumption on the specific mass‐transfer area is discussed. Additionally, the influence of the bubble size is discussed with regard to the mass‐transfer area, the air volume‐fraction, and the axial air velocity profile. To validate the numerical model, experimental results from tomographic measurements at the Helmholtz‐Zentrum Dresden‐Rossendorf (HZDR) are used. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On transcritical states in viscous flow passing the edge of a horizontal plate
Authors: Scheichl Bernhard , Bowles Robert I. 
Published: March 2018

AbstractThis contribution puts forward some recent advances in the rigorous (asymptotic) theory of gravity‐ (and capillarity‐)driven shallow flow of a viscous liquid past a horizontal plate, originating in jet impingement oblique to it. Hence, our concern is twofold: with steady developed flow over the distance from the jet centre to the trailing edge of the plate, referred to as a pronounced hydraulic jump blurred by viscous diffusion; with the predominantly inviscid transcritical limit arising near the edge due to scale reduction given an intrinsic expansive singularity taking place there. In the latter situation envisaged briefly, condensing nonlinear inertial effects, weak time dependence, and (very) weak streamline curvature as the essential ingredients into a distinguished limit demonstrates the generation of a weak (transcritical) hydraulic jump by a plate‐mounted obstacle. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Prediction of Aerodynamic Noise Generated from an Aircraft in Low Mach Number Flight
Authors: Rašuo Boško , Jazarević Vladimir 
Published: March 2018

AbstractThe paper describes numerical prediction of aerodynamic noise generated from an Aircraft. Simulation of turbulent flow is done solving the incompressible Navier‐Stokes equation, where turbulence is modeled applying the orthogonal subgrid scale (OSGS) method with dynamical subscales. Because of comparison, the same simulation is done using the LES (Large Eddy simulation). It is shown how simulation of turbulent flow affects the prediction of acoustic sources calculated using Lighthill's analogy. Translation from the time to frequency domain is done through DFT (Direct Fourier Transform), which gives smaller usage of memory. Acoustic sources are used in the inhomogeneous Helmholtz equation to simulate pressure wave propagation in the domain. It is shown that OSGS with dynamical subscales gives better representation of the spectrum. Overall, better prediction of energy transfer across large and small eddies will give better allocation and presentation of acoustics sources. These sources will change wave propagation of the pressure in the acoustic field. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical investigation of vortex roll‐up processes using different wingtip shapes
Authors: Uhl Anna , Dufhaus Sebastian , Hörnschemeyer Ralf , Stumpf Eike 
Published: March 2018

AbstractVortex roll‐up processes of different generic wingtip shapes are investigated using the DLR TAU flow solver in combination with a Reynolds Stress Model. In contrast to a non‐rounded layout an elliptical rounding of the wingtip planform leads to multiple vortices at the wingtip and results in an axial velocity deficit in the vortex core further downstream. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of a Likelihood Function based on a Global Sensitivity Analysis
Authors: Glaser Philipp , Kosmas Petridis , Schick Michael , Heuveline Vincent 
Published: March 2018

AbstractIn future the model quality will have an increasing priority in the industrial context and suitable techniques and methods to quantify them have to be developed. In this paper we want to focus on the challenge of selecting the most informative measurement data for a time‐dependent simulation model to infer parameter distributions. Sobol indices are used to give a estimate about the global sensitivity of those parameters and they are illustrated for the given benchmark problem. In this context the gained knowledge on the parameters is used to define a Likelihood function for the Bayes' rule. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SmartFarm – Data based optimization for optimal energy management
Authors: Jung Francesca , Büskens Christof , Lachmann Malin 
Published: March 2018

AbstractIn the project SmartFarm we develop a method that automatically decides which renewable energies are profitable to use at the farm for the next hours. To this means optimization methods are used on various levels. Initially, all necessary data is measured on a demonstration object. This data forms the basis for data based learning methods for the modelling of the consumers (e.g. milk cooling), the producers (e.g. solar plant) and the energy storage systems (e.g. battery storage device). In this paper we will focus on the data based models of the producers and energy storage systems. Optimization methods are used to identify optimal parameters for a general ansatz function, which is derived from a Taylor approximation.We develop all models with real data of the demonstration object and verify them with this data as well. Numerical results and the further course of action will be discussed in the paper. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modification of TLS algorithm for solving ℱ2 linear data fitting problems
Authors: Hnětynková Iveta , Plešinger Martin , Žáková Jana 
Published: March 2018

AbstractIt has been proved that the classical TLS algorithm fails to construct a TLS solution of linear data fitting problems AX ≈ B that belong to the class ℱ2. It will be shown how to modify this algorithm in order to reach a TLS solution. Such solution is not necessarily the minimum 2‐norm or Frobenius norm one. A few ideas how to decrease its norm are briefly discussed. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time Domain BEM Based on Generalised Convolution Quadrature
Authors: Diao Hanzhi 
Published: March 2018

AbstractWe present the application of the generalised convolution quadrature (gCQ) technique to the time domain boundary element method (BEM) which solves the retarded potential boundary integral equation (RPBIE). Our result allows to employ the multi‐stage Runge‐Kutta method as the time stepping scheme for the generalised convolution quadrature which is used in the time domain BEM for acoustic problems in either a bounded three‐dimensional domain or in its unbounded exterior. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Ritz‐Galerkin Discretization of PDEs with Variable Coefficients in arbitrary Dimensions using Sparse Grids
Authors: Hartmann Rainer , Pflaum Christoph 
Published: March 2018

AbstractSparse grids can be used to discretize elliptic differential equations of second order on a d‐dimensional cube. Using the Ritz‐Galerkin discretization, one obtains a linear equation system with 𝒪 (N (log N)d−1) unknowns. The corresponding discretization error is 𝒪 (N−1 (log N)d−1) in the H1‐norm. A major difficulty in using this sparse grid discretization is the complexity of the related stiffness matrix. To reduce the complexity of the sparse grid discretization matrix, we apply prewavelets and a discretization with semi‐orthogonality. Furthermore, a recursive algorithm is used, which performs a matrix vector multiplication with the stiffness matrix by 𝒪 (N (log N)d−1) operations. Simulation results up to level 10 are presented for a 6‐dimensional Helmholtz problem with variable coefficients. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a digital approximation for pseudo‐differential operators
Authors: Vasilyev Alexander , Vasilyev Vladimir 
Published: March 2018

AbstractWe introduce a concept of a discrete pseudo‐differential operator using general ideas of the theory and would like to show correlations between continuous and discrete cases. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parameter Identification in Stochastic Differential Equations to Model the Degradation of Metal Films
Authors: Pedretscher Barbara , Kaltenbacher Barbara , Bluder Olivia 
Published: March 2018

AbstractIn automotive industry, reliability analysis of smart power semiconductor devices is mandatory for safety reasons. To reliably forecast the lifetime of devices, a mathematical description of the material degradation due to applied stress is required. In this work, the degradation process of a metal film of interest under thermo‐mechanical stress is studied. Therefore, a bi‐layer test structure (metal film on substrate) is used. Degradation refers to the formation, growth and coalescence of voids, initializing cracks that propagate through the metal film. Since the film's elastic‐plastic deformation is triggered by random diffusional activities with drift, stochastic differential equations (SDEs) are used to model the evolution of the microstructural heterogeneity in the metallization.The choice of an efficient numerical method to estimate the unknown parameters of the inverse problem is complex due to ill‐posedness and rare measurements. To address these challenges, an approach by Dunker and Hohage of 2014 is followed, where parameter identification in SDE models is performed on basis of the Kolmogorov forward (Fokker‐Planck) equation [1]. The mentioned approach has to be adapted to our application. Firstly, a stochastically consistent cost functional is defined, taking into account the different type of measurements and secondly, instead of estimating a function, a finite set of model parameters has to be recovered. For efficient computational optimization an adjoint approach is used to calculate the gradient of the cost functional. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of a Filter‐ and a Model Predictive Control Based Motion Cueing Algorithm
Authors: Ellensohn Felix , Schwienbacher Markus , Venrooij Joost , Rixen Daniel 
Published: March 2018

AbstractMotion Cueing Algorithms (MCA) include control strategies to take into account the motion‐based driving simulator's restrictions concerning workspace limits and dynamic boundaries. A typical 6‐DoF simulator consists of a motion system which exhibits three translational and rotational degrees of freedom. Its actuators are capable of realizing accelerations, velocities and positions in a limited range. Based on these facts MCAs aim to generating realistic simulations of the driving motion (such as a driving manoeuvre) in order to immerse persons in virtual environments provided by the simulator. Filter‐based, classical MCAs belong to the most applied algorithms and mainly consist of linear transfer functions. Whereas, Model Predictive Control (MPC) algorithms rest upon a reduced model of the technical system's dynamics and, optionally, a model of the human motion perception system. An optimization problem subject to the restrictions of the motion system predicts the control variables over a time horizon. This paper addresses the strengths and weaknesses of the two stated approaches with focus on Motion Cueing errors. These errors describe discrepancies between the motion that is to be simulated (e.g. a driving manoeuvre) and the motion that is eventually provided by the combination of the MCA and the motion simulator. On basis of the results, it gives an outlook why optimization based algorithms have a higher potential to improve driving simulation. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two Degree‐Of‐Freedom Online Compensation of a Piezoelectric Micro‐Positioning Unit
Authors: Schindlbeck Christopher , Pape Christian , Reithmeier Eduard 
Published: March 2018

AbstractDue to their almost unlimited resolution and fast dynamics, piezoelectric actuators are a common choice for mechatronic systems targeting positioning tasks with high demands on precision. However, these piezoelectric actuators inherently suffer from nonlinear characteristics (mainly hysteresis and creep effects) which need to be addressed by appropriate control strategies. The operator‐based modified Prandtl‐Ishlinksii (mPI) approach does not only model hysteresis effects with asymmetries and creep effects but also provides an analytical solution for its inverse model. Online feedforward compensation of the aforementioned nonlinear effects can be realized by using the inverse model and additional weight adaptation. In this paper, online compensation via the mPI model is applied to a commercial micro‐positioning unit driven by piezoelectric actuators with more than one degree of freedom (DOF). For validation of the proposed approach, two coupled trajectories in the X‐Y plane are utilized. Subsequent tracking error analysis validates the efficacy of the stated approach. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Edge‐wise funnel synchronization
Authors: Trenn Stephan 
Published: March 2018

AbstractRecently, it was suggested in [Shim & Trenn 2015] to use the idea of funnel control in the context of synchronization of multi‐agent systems. In that approach each agent is able to measure the difference of its own state and the average state of its neighbours and this synchronization error is used in a typical funnel gain feedback law, see e.g. [Ilchmann & Ryan 2008]. Instead of considering one error signal for each node of the coupling graph (corresponding to an agent) it is also possible to consider one error signal for each edge of the graph. In contrast to the node‐wise approach this edgewise funnel synchronization approach results (at least in simulations) in a predictable consensus trajectory. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the transformation formulas of the Hankel‐norm approximation
Authors: Benner Peter , Werner Steffen W. R. 
Published: March 2018

AbstractThe Hankel‐norm approximation of a linear time‐invariant system is a method of model reduction which yields the best approximation in the Hankel semi‐norm. For the application of the method to systems with a non‐singular descriptor matrix E we generalize the transformation formulas. The resulting formulas provide additional degrees of freedom which can be used to avoid undesired numerical operations or a resulting ill‐conditioned system. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Construction of a Lyapunov functional for a class of controlled population balance models
Authors: Zuyev Alexander , Kienle Achim , Benner Peter 
Published: March 2018

AbstractIn this paper, we consider a class of controlled population balance equations describing granulation processes in chemical engineering. Such a control system admits an equilibrium which is not asymptotically stable in general. In order to stabilize this equilibrium, we consider the perturbed system and introduce a Lyapunov functional candidate as a weighted L2‐norm. It is shown that the weight function for this construction may be defined in terms of solutions to a certain differential inequality. We present a solution of this differential inequality in a particular case and discuss possible extensions of this approach for multidimensional hyperbolic systems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new method for network redesign via rank one updates
Authors: Gernandt Hannes , Krauße Dominik , Sommer Ralf , Trunk Carsten 
Published: March 2018

AbstractWe present a method to place the eigenvalues of an electrical network towards a prescribed set of complex numbers by inserting an additional capacitance into the network. For the proof, we use recent results on rank one perturbations of regular matrix pencils. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new bound for the distance to singularity of a regular matrix pencil
Authors: Berger Thomas , Gernandt Hannes , Trunk Carsten , Winkler Henrik , Wojtylak Michał 
Published: March 2018

AbstractFor regular matrix pencils 𝒜(s) = sE − A the distance to the nearest singular pencil in the Frobenius norm of the coefficients is called the distance to singularity. We derive a new lower bound for this distance by using the spectral theory of tridiagonal Toeplitz matrices. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)