bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Heat Transfer Properties for the FE Simulation of Cryogenic Turning
Authors: Becker Steven , Hotz Hendrik , Kirsch Benjamin , Aurich Jan C. , v. Harbou Erik , Müller Ralf 
Published: March 2018

AbstractIn order to shorten the process chain in manufacturing and thus to optimize the manufacturing time, current researches investigate the possibility of combining two process steps, turning and hardening.During cryogenic turning of metastable austenitic steel, deformation induced hardening in the surface layer of the workpiece can be achieved by applying high passive forces onto the workpiece [1]. This leads to an increase in the wear resistance [2] as well as the fatigue strength [3]. For the employed austenite‐martensite phase transformation it is necessary to maintain low process temperatures, typically below room temperature. Thus, cryogenic cooling has to be applied to counteract the heat, generated during machining [4].For a better understanding of the influence of different cutting and cooling parameters on the temperature field during cryogenic turning, and thus martensite formation, knowledge of the exact temperature distribution in the workpiece and the workpiece surface temperature in the contact zone is essential. Since in situ measurements of the latter are hardly possible, an inverse determination via transient finite element simulation is performed [5].In order to model cryogenic turning, material properties, thermal loads and heat transfer coefficients defining convective heat transfer, have to be determined first. These model parameters are investigated independently in stand‐alone experiments, applying only one thermal load at a time. The magnitudes of these values are obtained by iteratively modifying the initial values in the model until correspondence with measured temperature data from the experiment is achieved.The present finite element approach only takes thermal loads into account and is performed in the finite element program FEAP (Finite Element Analysis Program) with an Eulerian mesh, which requires special consideration of the rigid body rotation of the workpiece. The Eulerian treatment results in an unsymmetrical system matrix, and a special stabilisation is required to avoid numerical oscillations in the time integration scheme [5]. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust implementation of multi‐slip crystal plasticity for micro machining simulations based on Fischer‐Burmeister complementary functions
Authors: Bischof Robert , Schneider Frank , Müller Christopher , Kuhn Charlotte , Aurich Jan C. , Müller Ralf 
Published: March 2018

AbstractAs opposed to macro scale machining processes, the crystalline structure of commercially pure (cp) titanium plays an important role in micro machining processes. Finite element simulations of micro machining processes involve several challenges, since the workpiece material undergoes large deformations during chip formation and eventually material separation needs to be modeled. A robust implementation of the finite deformation multi‐slip crystal plasticity model describing the material response is the basis of such simulations. One challenge is the determination of the active set of plastic slip systems. Standard explicit predictor‐corrector formulations based on the Karush‐Kuhn‐Tucker (KKT) conditions often fail. In order to circumvent the explicit determination of the set of active slip systems, the KKT conditions can be replaced by a system of Fischer‐Burmeister complementary functions. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An ignored source in the foundations of continuum physics “Die Allgemeinen Ansätze der Mechanik der Kontinua” by E. Hellinger
Authors: Eugster Simon R. , l'Isola Francesco 
Published: March 2018

AbstractIn 1913, Ernst Hellinger finished his remarkable article DIE ALLGEMEINEN ANSÄTZE DER MECHANIK DER KONTINUA, which appeared in German language in the “Encyklopädie der mathematischen Wissenschaften mit Einschluss ihrer Anwendungen”. Following his predecessors J.‐L. Lagrange, G. Piola and the Cosserat brothers, Hellinger presents in this paper a nonlinear field theory of continuum physics entirely based on a variational principle “the principle of virtual displacements”. Even though Hellinger focuses on the fundamentals of continuum mechanics, he presents within the very same variational framework the physics of optics, electrodynamics, thermodynamics and the theory of relativity. Accordingly, Hellinger's paper can be understood as a contribution to continuum physics in general. However, due to the establishment of English as the upcoming scientific language and due to the refusal of a variational formulation of continuum mechanics in the subsequent period, Hellinger's contribution to the foundations of continuum physics has been ignored for decades and has almost fallen into oblivion. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Affine Micro‐Sphere Model for Strain‐Induced Crystallization in Rubbery Polymers
Authors: Nateghi Aref , Keip Marc‐André , Miehe Christian 
Published: March 2018

AbstractNatural rubber crystallizes under stretch and its amorphous structure becomes semi‐crystalline. Tensile strength, fatigue life and crack growth resistance of rubber increases with crystallization. Crystallization leads to a hysteresis in the stress‐stretch diagram of rubber, see [1]. Recently, computational modeling of strain‐induced crystallization has drawn the attention of researchers, see [2, 3] and [4]. In this work, we propose a micromechanically motivated material model for strain‐induced crystallization in rubbers. To this end, we construct a microscopic model for a single crystallizing polymer chain based on non‐Gaussian chain statistics. A thermodynamically consistent evolution framework for crystallization in the chain level is proposed. The chain model is then integrated into the affine micro‐sphere model. Finally, numerical results obtained by the model are compared to experimental data. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of inelastic material parameters using component‐oriented specimen with design of experiments
Authors: Nostitz Niklas , Hendrik Kröger Nils , Ihlemann Jörn 
Published: March 2018

AbstractFor the simulation of the mechanical behaviour of components, an appropriate material model and a good experimental data base to identify the material parameters are needed. Due to the fact that the typically used standard test specimen do not include any inhomogeneous effects, an alternative component‐oriented specimen is introduced. To improve the identification, a design of experiments strategy is employed. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biomaterial spider silk: Potential candidate for airbag fabric material
Authors: Prajapati Kaushik Govindbhai , Patil Sandeep P. , Carmai Julaluk , Koetniyom Saiprasit , Markert Bernd 
Published: March 2018

AbstractIn the present work, the mechanical properties of spider silk are assigned to the airbag fabric material. Finite element simulations were performed on the airbag model in order to study its benefits over the traditional fabric material. We designed the airbag model with spider silk material and performed impact analysis. Finally, the obtained results are compared with the standard airbag test. Our analysis pave the way towards the new promising material for airbags. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of PLLA near glass transition temperatures
Authors: Raza Syed Hasan , Klusemann Benjamin 
Published: March 2018

AbstractThe treatment for Coronary Heart Diseases – caused by the deposition of plaque on arterial walls – which has been the deployment of a metal stent in the blocked artery, poses serious complications in the form of accumulation of blood clots due to the permanent and rigid nature of metals. Meanwhile, Bioresorbable Vascular Scaffolds (BVSs) – made up of poly l‐lactide (PLLA) – are transient implants offering support to the artery for 6–9 months and leaving no trace behind once dissolved after 2 years. PLLA, however, has lower strength compared to metals and thus requires a higher thickness to make it useful for transplants. Thermal annealing, which can alter the microstructure of PLLA to make it thinner and stronger, is a good solution for this problem. In order to implement thermal annealing, experimentation and simulations are required to study the behaviour of the microstructure during the process. In general, its behaviour below glass transition temperature and at short time‐scale is glassy, while above glass transition temperature and at long time scale is rubbery. With constitutive models available for other polymers, such as polyethylene terephthalate (PET), it is intended to develop a constitutive model for PLLA accordingly. In this regard, the Buckley model is implemented. The model allows studying the behaviour in PLLA at the temperatures of interest during thermal annealing. Numerical results will be presented and compared for neat PLLA samples for different strain rates and temperatures. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite Element Approximation of Fluid‐Structure Interaction with Coupled Wave Propagation
Authors: Ebna Hai Bhuiyan Shameem Mahmood , Bause Markus 
Published: March 2018

AbstractIn this contribution, a concept of coupling the fluid‐structure interaction (FSI) with an ultrasonic wave propagation is proposed. It is referred to as the extended Fluid‐Structure Interaction (eXFSI) problem. The eXFSI is a one‐directional coupling of typical FSI problem with an ultrasonic wave propagation in fluid‐solid and their interaction (WpFSI). Notably, the WpFSI is a strongly coupled problem of acoustic and elastic wave equations and automatically adopts the boundary conditions from the FSI problem at each time step. To the best of our knowledge, such a model is novel in the literature. The principal aim we pursue is to explore and develop concept of the efficient numerical solution of the eXFSI problem. The solution of the eXFSI and WpFSI models constitute an important part of on‐live and off‐live structural health monitoring (SHM) systems design for composite material and lightweight structures. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermo‐mechanical modeling of turbine blades taking into account structural defects
Authors: Kunin Artsem Boris , Loehnert Stefan , Wriggers Peter 
Published: March 2018

AbstractIn turbine blades of aero‐engines typical defects are cracks due to high mechanical and thermal loads. The extended finite element method (XFEM) is used for simulations of fracture mechanics problems with cracks. Discontinuities in the displacement and temperature field are allowed and the crack opening displacement and crack tip stress field are reproduced accurately. Since crack closure and non‐physical penetration of the crack surfaces may occur under certain load conditions, it becomes necessary to enforce the non‐penetration condition for crack surfaces. This contact formulation is assumed to be frictionless. The node‐to‐segment approach proposed in [3] is extended to ten‐node tetrahedral elements with quadratic shape functions. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Description of the Damage and Healing Behavior of an Extrinsic and Autonomous Self‐Healing Anisotropic Material
Authors: Specht Steffen , Bluhm Joachim , Schröder Jörg 
Published: March 2018

AbstractIn this contribution, the damage and healing behavior of a fiber reinforced polymeric composite will be investigated. Therefore, the considered Helmholtz free energy function for the polymeric matrix material consists of two parts, an isotropic part for the description of the isotropic polymer and an anisotropic part for the reinforcement. As theoretical framework, the Theory of Porous Media is used, where internal interactions (phase transitions, temperature exchange, ...) can be described by so‐called production terms. At the end a numerical example of an anisotropic self‐healing polymer is presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromorphic homogenisation and its application to a model of ductile damage
Authors: Hütter Geralf 
Published: March 2018

AbstractHeuristic gradient extensions of classical damage models are established to overcome their spurious mesh dependency. In contrast, an extension of Gurson's model of ductile damage towards the microdilatational theory is presented through a straight‐forward homogenization. FEM simulations prove the regularization capabilities of the model. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contact Mechanics in Computational Homogenization
Authors: Leichner Alexander , Andrä Heiko , Simeon Bernd 
Published: March 2018

AbstractConcerning homogenization, we consider in this contribution periodic boundary‐interface value problems (BIVP) within representative volume elements (RVE), which contain porous materials consisting of possibly many separate objects. For instance, these RVEs are available from micro scans in voxel resolution. However, the occurrence of contact between deformable, solid objects requires advanced techniques of methods solving common elasticity problems. With regard to that, we will demonstrate the treatment of contact between each of those by means of an implicit boundary description, used for both surface reconstruction and contact detection. Furthermore, a new technique for solving contact problems is introduced which can be easily integrated as material law routine into so called fast solvers [1], performing on Cartesian grids and exploiting the fast Fourier transform (FFT). In the end, we will present numerical results for a standard problem from contact mechanics, obtained by this new approach. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interaction boundary layer theory applied to a benchmark flow problem
Authors: Braun Stefan 
Published: March 2018

AbstractConsider planar, incompressible laminar high Reynolds number (Re) flow between two parallel plates: fluid is removed through the permeable upper wall in order to generate adverse pressure gradient conditions in mean flow direction. As a consequence of relatively weak suction, the boundary layer at the impermeable lower wall is forced to separate locally. The corresponding reverse flow region (separation bubble) is known to react very sensitively to perturbations of any kind and typically undergoes rapid transition to the turbulent flow state. The present paper briefly summarizes the current status of the corresponding asymptotic flow description in the limit as Re → ∞. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of crystallization processes in viscoelastic polymer melt flows
Authors: Descher Stefan , Wünsch Olaf 
Published: March 2018

AbstractA simplified model for plate extrusion is presented. Calculations for the exponential form of the Phan‐Thien Tannner fluid combined with a nonisothermal crystallization model are performed. A Study for the Deborah‐ and Péclet‐number is carried out to investigate if stress is transported in regions of crystallization. It is shown that for the presented model, this is only the case for regions close to walls. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Attractors for the motion of finite‐size particles in a two‐sided lid‐driven cavity
Authors: Wu Haotian , Romanò Francesco , Kuhlmann Hendrik C. 
Published: March 2018

AbstractParticle trajectories in an incompressible cavity flow are investigated experimentally. The flow is driven by two facing walls moving with same speed in opposite directions. When the flow is steady and three‐dimensional, finite‐size and neutrally‐buoyant particles are rapidly attracted to periodic orbits. Three‐dimensional particle tracking is used to reconstruct single particle trajectories. Experimental results are presented and compared with numerical simulations. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Steady transonic dense gas flow past two‐dimensional compression/expansion ramps
Authors: Kluwick Alfred , Cox Ted 
Published: March 2018

AbstractThe dynamic behaviour of compressible fluids depends crucially on the curvature of isentropes in the pressure/specific volume diagram. Most conveniently this curvature is expressed in form of a non‐dimensional quantity Γ now commonly referred to as the fundamental derivative of gasdynamics, Thompson [5]. Bethe‐Zel'dovich‐Thompson (BZT) fluids have the distinguishing property that they exhibit embedded regions in the general neighbourhood of the thermodynamic critical point where Γ is negative in contrast to classical gases of low molecular complexity including perfect gases where Γ is strictly positive.The behaviour of steady transonic flows of such fluids is essentially governed by two non‐dimensional parameters: (Γ) and its derivative with respect to the density at constant entropy (Λ), Cramer and Fry [2], Kluwick [4]. The resulting response to external forcing is surprisingly rich in nonclassical phenomena such as rarefaction shocks, sonic shocks, split shocks, etc. and is studied in detail for the canonical problem of two‐dimensional flow past compression/expansion ramps. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An infinite mapping layer for deep water waves
Authors: Toth Florian , Schoder Stefan , Kaltenbacher Manfred 
Published: March 2018

AbstractIn order to accurately and efficiently model the propagation of surface gravity waves in infinitely deep domains, we introduce an infinite mapping layer which transforms the unbounded physical domain into a bounded computational domain by means of a mapping function. The method was implemented in the framework of the finite element method, where it can be straightforwardly combined with a perfectly matched layer to model unbounded domains in horizontal direction. Finally, the application of the method is demonstrated by a simple 3D example. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modal analysis of wingtip vortices by means of Proper Orthogonal Decomposition
Authors: Dufhaus Sebastian , Brautmeier Sarina , Uhl Anna , Hörnschemeyer Ralf , Stumpf Eike 
Published: March 2018

AbstractThis paper discusses the influence of different wingtip geometries on the first eigenmodes of wingtip vortices. With the use of Proper Orthogonal Decomposition (POD) of a turbulent velocity field, a modal decomposition of coherent structures, high energetic eigenmodes are determined. Based on the results found by Fabre et al. [1], these eigenmodes may be a key factor for the stability analysis. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of chemotactical biofilm growth in evolving microstructures
Authors: Schulz Raphael 
Published: March 2018

AbstractThe work is concerned with the growth of biofilms made by chemotactical bacteria within a two‐dimensional saturated porous media. The increase of a biomass on the surface of the solid matrix changes the porosity and impede the flow through the pores. By formal periodic homogenization an averaged model describing the process via Darcy's law and upscaled transport equations with effective coefficients given by the evolving microstructure at the pore‐scale was derived in [3]. Based on the assumption of uniform evolve of the underlying pore geometry and slight self‐diffusivity of the bacteria, solvability in a weak sense global in time or at least up to a possible clogging phenomenon can be shown. Furthermore, by assuming sufficient regularity on the data we prove boundedness of the solution. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control in Autonomous Driving
Authors: Cobus Andreas , Rick Matthias , Sommer Laura , Backfisch Niels , Probst Alexander , Echim Mitja , Büskens Christof 
Published: March 2018

AbstractAutonomous driving is no longer a subject of science fiction. Instead it has become a field of highly topical developments and has already reached numerous milestones. The Audi Autonomous Driving Cup provides a stage for students to participate in this development process. This competition, carried out in Germany, Austria and Switzerland, provides miniature vehicles of normed hardware to the participants which have the task of implementing algorithms for autonomous handling of problems such as lane tracking, obstacle detection, adaptive cruise control, overtaking, turning as well as entering and exiting parking spaces. To present the concept of optimal control based on a single track model in combination with image processing methods we focus in this paper on the parking manoeuvre only. Thereby we show that optimization and control techniques can play a key role in the design of autonomous vehicles. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Direct Computation of the Byrnes‐Isidori Normal Form
Authors: Röbenack Klaus 
Published: March 2018

AbstractIf an input‐affine single‐input single‐output control system has a well‐defined relative degree, there exists a (local) change of coordinates transforming the system into the Byrnes‐Isidori normal form. By this transformation, the system is decomposed into two subsystems. The first subsystem can be linearized by feedback, and the second subsystem does not directly depend on the input. To achieve this structure, the last components of the transformation have to fulfill a partial differential equation. Practically, the appropriate choice of these coordinates is usually left to the (experienced) user. In this note, the author suggests a direct calculation based on the computation of flows of certain vector fields. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Project scheduling under uncertainty and resource constraints
Authors: Hartmann Veronika , Lahmer Tom , Smarsly Kay 
Published: March 2018

AbstractThis paper proposes a method to improve the reliability of construction schedules by optimizing schedule robustness of construction projects. The schedule robustness is measured by a criterion evaluating the impact of deviations from the initial schedule on the makespan, which arise during the realization phase of a construction project. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Equilibrium of a Coupled ODE‐PDE Problem for Surface Nanobubbles
Authors: Kimmerle Sven‐Joachim , Sverdrup Knut , Berg Peter 
Published: March 2018

AbstractWe consider a mathematical model for surface nanobubbles arising from hydrogen electrolysis in polymer electrolyte membrane (PEM) electrolyzers. Experimental advances in recent years indicated longer lifetimes of surface nanobubbles than may be explained by classical theories. Contrary to [5], we state a full model of an evolving single surface nanobubble yielding a coupled system consisting of a partial differential equation (PDE) for the hydrogen concentration in water and an ordinary differential equation (ODE) for the radius evolution. In the special case of dynamic equilibrium conditions, we prove the well‐posedness of this steady state problem by a fixed‐point strategy, assuming an acute‐angled contact angle, and that the corresponding algorithm allows for its numerical simulation. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)