bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finite‐element‐based simulation of multi‐physics materials
Authors: Schenke Maik , Ehlers Wolfgang 
Published: March 2018

AbstractFrom a micro‐structural point of view, many natural or engineered materials can be assigned to the class of multi‐physics materials. Therein, their macroscopic observed behaviour is governed by different micro‐structural physical phenomena. For instance, when electro‐active polymers (EAP) are subjected to an electric field, the resulting chemical and electrical imbalances trigger micro‐structural diffusion processes, which re‐establish the equilibrium state, thereby causing macroscopic deformations. Further examples for these materials are partially or fully saturated porous media (e. g. foams, soils, filters, fibre‐reinforced plastics), chemical‐ or electrical‐active materials (e. g. hydrogels, lithium‐ion batteries, fuel cells) or biological tissues (e. g. bone, cartilage). Addressing the simulation of multi‐physics materials, which often exhibit a complex and heterogeneous micro‐structure, it is convenient to proceed from a macroscopic modelling approach. In this regard, the aforementioned materials can be described exploiting the macroscopic Theory of Porous Media (TPM) as a suitable modelling framework, see, e. g. [1,2].The material models, which are usually developed during either academic or industrial research projects, are often implemented into self‐developed programme codes to scrutinise the advancements and but also the limitations of the material models. However, when addressing industrial application scenarios, these codes often lack the necessary functionality, for instance, in terms of modelling features to build complex initial‐boundary‐value problems (IBVP) and user interaction, such as a convenient graphical user interface (GUI). A general coupling allows to overcome these shortcomings. In particular, on the one hand, it provides a straight‐forward transfer of the outcome of research projects, namely, the comprehensive material‐model library of PANDAS into an simulation environment relevant for industrial applications. On the other hand, it gives access, in comparison to the native user‐element subroutines, to a convenient environment for the description user‐defined volume‐coupled multi‐field materials. In this connection, the present contribution exemplarily describes a co‐simulation approach between the commercial finite‐element (FE) package LS‐DYNA and the actual stand‐alone coupled FE‐based solver PANDAS. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Variational Homogenization Approach on Large Strain Micro‐Electro‐Mechanics
Authors: Vallicotti Daniel , Sridhar Ashish , Keip Marc‐André 
Published: March 2018

AbstractFunctional materials have received a lot of attention in recent years. Composite materials of soft polymers with embedded ferroelectric particles are advantageous due to the large deformations possible in such materials. Phenomenological modeling of associated electromechanical coupling phenomena has been extensively covered. However, complex multi‐scale interactions based on a microscopic electric domain evolution and its effect on the overall macroscopic response is of utter importance for the understanding of the underlying physical phenomena. This necessitates the use of multi‐scale approaches such as computational homogenization to reliably predict and in turn enhance the overall material response. We propose a variational framework for micro‐electro‐mechanical response at large deformations embedded into a scale‐bridging scenario by using homogenization techniques in order to define the macroscopic overall response of electro‐active materials. Starting point is a rate‐type saddle‐point variational principle on the microscale yielding the Euler‐Lagrange equations and a Ginzburg‐Landau‐type evolution equation for the polarization order parameter. A challenge is to link the gradient‐type continuum description of the microstructure to a local electro‐mechanical macro‐continuum. This is achieved by exploiting a generalized Hill‐Mandel macro‐homogeneity condition, yielding periodic boundary conditions at the faces of the microstructure. Numerical examples demonstrate the capabilities of the framework and show the effect of particle interactions based on evolving electric domains on the overall macroscopic response. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diffusion induced void nucleation in SnPb solder joints
Authors: Werner Marek , Weinberg Kerstin 
Published: March 2018

AbstractTowards a simple and robust model for void‐based fatigue prediction, we investigate the interaction of voids with its surrounding by using a multi‐field method. We couple the concentration fields of tin c1 and lead c2 with an additional field c3, where the latter is assigned with a void field. The interaction potential manifests three stable states. Two are obtained by experimental results of tin‐lead (SnPb) and the void stable state is postulated by construction. The logarithmic form of the thermodynamically consistent configurational entropy is approximated within this study by a fourth order polynom. It has been shown that the interfacial energy coefficient is independent of void's size, but rather depends numerically on the mesh size, which is used in the model presented here. Both governing equations follows a Cahn‐Hilliard‐type equation to mimic the microstructural changes. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transformation strains for bainitic variant evolution in steel
Authors: Ehlenbröker Ulrich , Petersmann Manuel , Antretter Thomas , Mahnken Rolf 
Published: March 2018

AbstractIn our work, we supplement a thermodynamically consistent multi‐scale model for the bainitic phase transformation in a low alloy steel, which takes into account the mechanisms of elasto‐viscoplasticity, phase transformations and heat conduction as well as the poly‐crystalline structure of steel. In order to obtain realistic simulation results, the microscopic conversion procedures for the austenite‐to‐bainite transformation have to be described in an appropriate way. To this end, the transformation strains for the crystallographic variants have been adjusted. For calculation of transformation strains a theory for the formation of dislocated martensite, more precisely a hierarchical packet‐block structure, is used. The calculated transformation strains are used in a simulation of bainite phase transformation in a polycrystalline RVE. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale Rubber Friction Analysis on Rough and Flexible Surfaces
Authors: Hartung Felix , Kaliske Michael 
Published: March 2018

AbstractIn this work, a multiscale homogenization approach is introduced to provide friction features between rubber and rough contact partners. Different length scales of the rough surface are considered by using a decomposition of the height difference correlation (HDCF) or the power spectral density function (PSDF) in several sinusoidal waves to accumulate the micro‐ and mesoscopic friction into a macroscopic friction coefficient. By using the finite element method (FEM), the sensitivity of the influencing factors for instance slip velocity and contact pressure may be investigated for rigid and flexible surfaces in the two‐ and the three‐dimensional case. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of a DC electric field on the von Kármán vortex street in the wake of a confined cylinder
Authors: Scholz Mathias , Hardt Steffen , Barz Dominik P. J. 
Published: March 2018

AbstractWe investigate the influence of a DC electric field on the flow around and in the wake of a confined cylinder by means of numerical simulations. Our results indicate that even very small electrical perturbations have significant impact on the settling time of the lift coefficient. Moreover, the oscillations of the lift coefficient of pure pressure‐driven and pressure‐driven flow with induced electrical field are in anti‐phase. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigating Asymptotic Suction Boundary Layers using a One‐Dimensional Stochastic Turbulence Model
Authors: Fragner Moritz M. , Schmidt Heiko 
Published: March 2018

AbstractThe one‐dimensional turbulence model (ODT) is applied to study turbulent asymptotic suction boundary layers for a Reynolds number of Re = u∞/v0 = 333, where u∞ and v0 are the free stream and suction velocity, respectively. In here we will demonstrate that a large eddy suppression mechanism may reduce the influence of ODT model parameters, such as the viscous cut‐off parameter Z. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectral Analysis of Large Scale Structures in Fully Developed Turbulent Pipe Flow
Authors: Zanoun El‐Sayed , Öngüner Emir , Shahirpour Amir , Merbold Sebastian , Egbers Christoph 
Published: March 2018

AbstractThe present work focuses on spectral analysis of the streamwise velocity fluctuations obtained, utilizing the Cottbus Large Pipe (CoLaPipe) test facility for R+ ≤ 3500, where R+ is the Reynolds number based on the wall friction velocity, uτ, and the pipe radius, R. Measurements of the streamwise spectra have been conducted using a single hot‐wire probe. Few runs have been also performed using Particle Image Velocimetry (PIV) as a structure visualization evidence and for spatial correlation purposes. The spectral analysis is being carried out to reveal few insights into pipe flow structure, allowing to follow the foot prints of such structures as well as providing estimates of their energy contents. The cumulative energy is examined as a function of the streamwise wavelength, describing the most energetic motions found in spectral data at various wall normal locations. For the current Reynolds number range, the Very Large Scale Motions (VLSM) and the Large Scale Motions (LSM) were evident as localized peaks in pre‐multiplied spectra, having mean wavelengths approximately of 12R, and 3R, respectively. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Slow viscous flow near a superhydrophobic surface with trapped gas bubbles
Authors: Ageev Aleksei , Golubkina Irina , Osiptsov Alexander 
Published: March 2018

AbstractThe Boundary Element Method (BEM) is used to solve the problem of Stokes flow of a viscous fluid over a periodic striped texture of a superhydrophobic surface (SHS), partially filled with frictionless gas bubbles. The shape of the bubble surfaces and the position of the meniscus pinning points relative to the cavity walls are taken into account in the study. Two kinds of flows important for practical applications are considered: a pressure‐driven flow in a thin channel with a bottom superhydrophobic wall and a shear‐driven flow over a periodic texture. We study the flow pattern in the fluid over a single cavity containing a bubble with a curved phase interface shifted into the cavity. A parametric numerical study of the averaged slip length of the SHS is performed as a function of the geometric parameters of the texture. It is shown that the curvature of the phase interface and/or its shift into the cavity both result in the decrease in the average slip length. It is demonstrated that the BEM can be an efficient tool for studying Stokes flows over textured superhydrophobic surfaces with different geometries of microcavities and phase interfaces. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thin liquid droplet on top of a rotating non‐isothermal liquid layer
Authors: Boettcher Konrad , Bothe Mike 
Published: March 2018

AbstractWafers are usually coated by using spin‐coating, where centrifugal forces are used to spread a droplet on the rotating wafer. This flow is unstable to the fingering instability, where several segments of the wetting front spread faster than the average, resulting in several fingers. The liquid flows via the existing fingers while the area in between does not get coated. A precise experimental investigation is problematic, as the droplet has to be placed quite exactly in the center of the rotation. Replacing the wafer by a second liquid should lead to a parabolic‐shaped free interface and the droplet should center itself due to gravity. Here, we derive a model for the free interfaces of a thin droplet on top of a rotating liquid by taking gravity, centrifugal forces, friction, (thermo‐)capillary and line forces into account. Additionally, this setup is the simplest example of multiple coating, where several free interfaces and contact lines influence each other. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic wave radiation and scattering in heterogeneous soil using the scaled boundary finite element method
Authors: Birk Carolin , Gravenkamp Hauke , Bazyar Mohammad Hossein 
Published: March 2018

AbstractA time‐domain approach for the simulation of elastic waves in heterogeneous soil domains is presented. It is based on modelling both near and far field by the scaled boundary finite element method (SBFEM). The SBFEM facilitates the use of a structured mesh in the near field region without the need to circumvent hanging nodes. The quadtree mesh is obtained automatically from image data. Radiation damping in the far field is modelled accurately by means of a displacement unit‐impulse‐response‐based formulation. An example analysis of wave radiation by an alluvial basin illustrates the potential of the proposed methodology. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of the piston geometry to generate a desired stress wave shape
Authors: Burgert Jens , Seemann Wolfgang , Hartenbach Felix 
Published: March 2018

AbstractImpacting rods are used in various devices in practical life but also for scientific experiments. The challenge in modeling is the collision between the impacting rods which leads to a sudden velocity jump at the contact zone. Thus, the non‐smooth problem is difficult to calculate with commercial FE programs.In this contribution, an approach to calculate 1D impact problems is presented. The geometries of the impacting rods are approximated with piecewise constant cross sections. On a constant segment, the solution of the wave problem is known by the D'Alembert solution and at each change of cross section the incoming wave is partly reflected and partly transmitted which is considered by transition conditions. This results in a multitude of transmissions and reflections that are all contributing to the final shape of the stress in the rods. Finally, the approach is applied in the field of rock drilling and the stress shape of the impacting rods is presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stationary single waves in turbulent open‐channel flow
Authors: Müllner Markus , Schneider Wilhelm 
Published: March 2018

AbstractSteady two‐dimensional turbulent open‐channel flow is considered. Stationary single‐wave solutions are investigated. The fully‐developed oncoming flow is slightly supercritical. The Reynolds number is very large. The analysis is kept free of turbulence modelling. As stationary solitary waves cannot exist in turbulent flow for a plane bottom with constant roughness [1], two particular perturbations of the conditions at the channel bottom are examined: 1) We revisit the case [1] where the friction coefficient locally differs slightly by a constant from the reference value upstream; 2) An unevenness of very small height in the channel bottom (bump, ramp) is admitted, with the bottom roughness taken constant. An analogy between these cases is presented. In both cases, three stationary solutions for the surface elevation are found: A stable and an unstable solitary wave, respectively, and a single wave of a second kind with smaller amplitude. For the latter, an analysis for weak dissipation yields a uniformly valid solution that is in good agreement with the numerical results for various parameters. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid computational aeroacoustics based on compressible flow data at low Mach numbers
Authors: Schoder Stefan , Toth Florian , Kaltenbacher Manfred 
Published: March 2018

AbstractIn some practical applications (e.g. cavity with a lip), even at low Mach numbers, acoustic feedback mechanisms excite flow structures. The compressible flow simulation cannot distinguish between a pure fluid dynamic part and acoustic phenomena. With this in mind, we propose a workflow based on Helmholtz‐Hodge decomposition, to extract pure source terms of the compressible flow simulation, to model the sound radiation. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wave Propagation in a beam with random material properties
Authors: Zimmermann Eugen , Eremin Artem , Lammering Rolf 
Published: March 2018

AbstractModern composite materials, e.g., carbon fibre reinforced plastics (CFRP), exhibit a complex micro structure due to their fabrication process. The latter, being usually omitted in mechanical models through the homogenization of elastic properties, has a strong influence on the propagation of ultrasonic guided waves [1, 2]. Though it is possible to model the wave phenomena deterministically, taking into account a realistic distribution of fibres and polymer matrix, it is desirable to develop an improved model for the finite element analysis (FEM), which consider the stochastic properties in a more general way. In the current work, an approach for the simulation of waves in a isotropic beam with random material properties is presented. For the numerical computations with the FEM the Young's modulus was discretized by the Karhunen‐Loève Expansion (KLE). Numerical investigations on the excited and propagating guided waves are presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structured deformations and applications
Authors: Morandotti Marco 
Published: March 2018

AbstractThe scope of this contribution is to present an overview of the theory of structured deformations of continua and two applications, all of which involve using this rather new formulation of mechanics problems in contexts that are different from one another, thus showing the power and versatility of the theory. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metropolis‐Hastings Importance Sampling Estimator
Authors: Rudolf Daniel , Sprungk Björn 
Published: March 2018

AbstractBased on the proposed states of the Metropolis‐Hastings (MH) algorithm we construct a MH Importance Sampling estimator for the approximation of expectations. The new approximation scheme is asymptotically correct and numerical experiments indicate that it can outperform the classical MH Markov chain Monte Carlo estimator. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Objective Functions for the Shape Optimization of Temperature Control Channels in High‐Pressure Die Casting
Authors: Frings Markus , Behr Marek , Elgeti Stefanie 
Published: March 2018

AbstractIn high‐pressure die casting, the quality of the produced cast parts highly depends on the die quality. One die component are temperature control channels. The state‐of‐the art approach for the temperature control channels are boreholes drilled from the sides into the die that are afterwards formed into a closed flow channel by inserting plugs.Since additive manufacturing methods are available to manufacture the dies, an obvious step is to construct more advanced temperature control channels. The shape of these free‐form channels can be obtained by numerical optimization.To find the optimal shape of the channels, appropriate objective functions are required. This contribution is focused on such objective functions. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of topology and shape by combining phase field modeling and discrete stochastic algorithms
Authors: Keller Alexander , Münch Ingo , Wagner Werner 
Published: March 2018

AbstractWe propose a concept for the comprehensive optimization of load bearing structures. The main idea is to decompose the optimization task. First, we use a phase field model to evolve the topology as basic design. The parameters of this process are the filling level of the design domain and the tendency to nucleate more or less holes. Second, we use an interface to set up a subsequent structural model, where cross‐sections and positions of nodes are simultaneous optimization parameters of a metaheuristic optimization method. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exploration of Internal Response Sensitivities of Materially Nonlinear Structures
Authors: Liedmann Jan , Barthold Franz‐Joseph 
Published: March 2018

AbstractIn this paper the idea of design exploration in the context of structural design sensitivity analysis considering elastoplastic material behaviour is outlined. Sensitivity information involves the influence of history dependent material behaviour and is obtained analytically by means of a variational approach. Applying singular value decomposition (SVD) to response sensitivities provides deep insight into sensitivity information and can be used to identify design changes with major influence on structural response. With this additional information, it is possible to refine an optimisation problem and reduce its complexity. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Open‐source tool‐chain for optimal input design for dynamical systems
Authors: Mayr Simon , Grabmair Gernot 
Published: March 2018

AbstractIn this paper we present a free tool for semi‐automated matching of virtual and real prototypes in a wide range of industrial applications. Within the introduction we would like to explain the motivation behind the development of our tool. After a short description of the basic principles of input design for dynamical systems, we are focusing on the individual steps of the tool‐chain, implemented in our software. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometrically nonlinear crystal plasticity implemented into a discontinuous Galerkin element formulation
Authors: Alipour Atefeh , Wulfinghoff Stephan , Bayat Hamid Reza , Reese Stefanie 
Published: March 2018

AbstractSingle crystal viscoplasticity, with a regularization technique for the power law, is presented and implemented into a discontinuous Galerkin (DG) framework. Although single crystal plasticity has been extensively studied, its examination with the regularization method in combination with a DG formulation leads to a numerically efficient and robust model. The performance of the DG framework in crystal viscoplasticity is shown by an example. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adjoint based topology optimization of conjugate heat transfer systems
Authors: Goeke Stephan , Wünsch Olaf 
Published: March 2018

AbstractThis paper presents a topology optimization method for coupled thermal problems. Heat transfer linked with the forced convection flow inside cooling channels is investigated using a conjugate model. This model includes both the full Navier‐Stokes equations for the fluid medium and the energy equations for both fluid and solid. In this present work, the adjoint method is extended to such conjugate heat transfer (CHT) systems to optimize their performance by the use of gradient based methods. This performance is usually a compromise between an increase in heat flux or temperature distribution at a surface and maintaining a low pressure loss within the system. To exemplify the method a uniform temperature distribution is chosen and evaluated numerically. For implementation the open source CFD Software OpenFOAM is used. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Motion planning problem with obstacle avoidance for step‐2 bracket‐generating systems
Authors: Grushkovskaya Victoria , Zuyev Alexander 
Published: March 2018

AbstractThis paper considers the obstacle avoidance problem for control‐linear systems satisfying the Hörmander condition with the first‐order Lie brackets. To solve the problem under consideration, we use a family of oscillating periodic control functions with state‐dependent coefficients. The proposed approach is shown to be applicable for different shapes of obstacles and various potential functions generating collision‐free paths. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)