bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shape Optimization in Phosphate Production
Authors: Dietrich Nicolas , Marx Thomas , Pinnau René 
Published: November 2019

AbstractPhosphate as an industrial product is an essential ingredient in, e.g., agriculture and food industry. The production process is very energy consuming and takes place in high temperature melting furnaces. The costs of the productions are largely governed by the energy costs of the furnace and there is a high potential to save energy by increasing its energy efficiency. Naturally, the shape of the furnace has a high influence on its efficiency. In order to describe the temperature distribution within a furnace mathematically, a widely used model in the industry is the Rosseland approximation. We use this model and discuss the problem in the context of shape optimization.
Shape Optimization in High Temperature Processes
Authors: Marx Thomas , Dietrich Nicolas , Pinnau René 
Published: November 2019

AbstractHigh temperature processes have a wide field of applications in industrial processes, e.g., optimal design in glass cooling or shape optimization for melting furnaces. We consider here the SP1 approximation of the Radiative Heat Equation which includes reflecting boundary effects. This leads to a PDE‐constrained shape optimization problem, where the shape of the domain is the design variable.
Comparison of the mechanical properties of milk fouling and whey protein fouling
Authors: Liu Jintian , Wiese Hanna , Augustin Wolfgang , Scholl Stephan , Böl Markus 
Published: November 2019

AbstractThe formation of fouling deposit is a significant problem for the dairy industry. Many experimental analyses have been carried out to explore the cleaning process using whey protein solution as a surrogate material because the main fouling components in milk are whey proteins. In view of mechanical cleaning processes, the mechanical behaviour of milk and whey protein fouling is compared using indentation and relaxation experiments and material parameters of a visco‐hyperelastic model are determined using an inverse finite element method (FEM).
An Intrusive PCE Extension of the Contour Integral Method and its Application in Electrical Engineering
Authors: Frick Eduard , Dahl David , Seifert Christian , Lindner Marko , Schuster Christian 
Published: November 2019

AbstractFor the study of electromagnetic waves in a 2D environment, the Helmholtz equation can be reformulated in boundary integral form by the so‐called Contour Integral Method (CIM). The influence of uncertainty in the geometry is studied via Polynomial Chaos Expansion (PCE). A distinction is made between the so‐called intrusive and non‐intrusive PCE. Both methods are applied to the CIM and compared to each other and to Monte‐Carlo simulation (MC).
Riemannian Structure and Flows for Smooth Geometric Image Labeling
Authors: Savarino Fabrizio , Schnörr Christoph 
Published: November 2019

AbstractThe image labeling problem can be described as assigning to each pixel a single element from a finite set of predefined labels. Recently, a smooth geometric approach for inferring such label assignments was proposed by following the Riemannian gradient flow of a given objective function on the so‐called assignment manifold. Due to the specific Riemannian structure, this results in a coupled replicator dynamic incorporating local spatial geometric averages of lifted data‐dependent distances. However, in this framework an approximation of the flow is necessary in order to arrive at explicit formulas. We discuss preliminary results of an alternative model where lifting and averaging is decoupled in the objective function so as to stay closer to established approaches and at the same time preserve the ingredients of the original approach. As a consequence the resulting flow is explicitly given, without the need for any approximation, while still exploiting the underlying Riemannian structure.
Cluster‐based network model for drag reduction mechanisms of an actuated turbulent boundary layer
Authors: Fernex Daniel , Semaan Richard , Albers Marian , Meysonnat Pascal S. , Schröder Wolfgang , Ishar Rishabh , Kaiser Eurika , Noack Bernd R. 
Published: November 2019

AbstractWe introduce a novel data‐driven reduced‐order modeling approach, a Cluster‐Based Network Model (CBNM). Starting point is a set of time‐resolved snapshots associated with one or multiple control laws. These snapshots are coarse‐grained into dozens of centroids using k‐means++ clustering. The dynamics is modelled in a network between these centroids comprising the transition probability and corresponding transit time. The transition parameters depend on the control law. CBNM is successfully applied to an actuated turbulent boundary layer flow. The results show that CBNM is an attractive alternative to POD models as the model is human interpretable and dynamically robust by construction.
Dual‐energy extension of the uniform‐approximation approach
Authors: Schneider Patrick , Kienzler Reinhold 
Published: November 2019

AbstractIn the talk an extension of the uniform‐approximation approach, that relies on the truncation of the elastic energy after a certain power of a geometric scaling factor, towards an analogous truncation of the dual energy is proposed. On the one hand, this allows for a derivation of fully defined boundary value problems including compatible displacement boundary conditions. On the other hand, the extension enables us to provide an a priori error estimate for the systematic error of the arising approximative models with respect to the exact three‐dimensional solution.The approach is compared to the approach of a fixed kinematic assumption for the displacement field which is widely used in engineering. We show that the later approach leads in general to a more complex model for a comparable approximation accuracy so that the consistent approximation approach is to prefer.
Biomechanical simulations with dynamic muscle paths on NURBS surfaces
Authors: Penner Johann , Leyendecker Sigrid 
Published: November 2019

AbstractIn order to model the behaviour of muscles that work around the joints in musculoskeletal simulations, information about the muscle paths are needed. Typically, musculotendon paths, their lengths, and their force directions are modeled as the shortest connection wrapping around obstacles representing bones and adjacent tissue. In this work, the shortest path problem is described via constrained variational dynamics and is applied to a biomechanical example with muscle paths on non‐uniform rational B‐spline (NURBS) surfaces representing the wrapping obstacles. The results are compared with muscle paths from a G1‐continuous combination of geodesics [2,4,5].
Mesh adaptivity and error estimates applied to a regularized p‐Laplacian constrainted optimal control problem for multiple quantities of interest
Authors: Endtmayer Bernhard , Langer Ulrich , Neitzel Ira , Wick Thomas , Wollner Winnifried 
Published: November 2019

AbstractIn this work, we derive goal‐oriented error estimates and mesh adaptivity for multiple quantities of interest for optimal control problems with the regularized p‐Laplace equation as constraint. We apply the dual‐weighted residual method to the reduced formulation, and combine several quantities of interest. Finally, we present a numerical example with p = 10.
Simulation of subcritical crack propagation in hard metal microstructures
Authors: Wingender Dennis , Balzani Daniel 
Published: November 2019

AbstractIn order to investigate the wear mechanism in form of surface spalling in hard metals, their microstructures obtained by µCT‐scans are simulated using an extended eigenerosion framework. In order to directly exploit the voxel data from the scans, the microstructures are meshed with a voxel based algorithm which additionally leads to the generation of hanging nodes. In this contribution this simulation setup is described and numerical examples are provided, showing that the eigenerosion approach can suitably be combined with an efficient and automatized discretization using hanging nodes.
Finite‐strain thermo‐viscoplasticity for case‐hardening steels over a wide temperature range
Authors: Oppermann Philip , Denzer Ralf , Menzel Andreas 
Published: November 2019

AbstractThe aim of this work is the development of a thermodynamically consistent fully coupled finite‐strain thermo‐viscoplastic material model for metals. The model is based on a split of the free energy into a thermo‐elastic, a thermo‐plastic and a purely thermal part and covers nonlinear cold‐work hardening and thermal softening. Nonlinear temperature dependent effects are accounted for the elastic moduli, the plastic hardening moduli, the thermal expansion, the heat capacity and the heat conductivity. Furthermore, strain rate‐dependency of the current yield stress is realized using a temperature dependent nonlinear Perzyna‐type viscoplastic model based on an associative flow rule. The model and its parameters are fitted against experimental data for case hardening steel 16MnCr5 (1.7131).
Application of model order reduction to a finite element model of cryogenic turning
Authors: Becker Steven , Hotz Hendrik , Kirsch Benjamin , Aurich Jan C. , Müller Ralf 
Published: November 2019

AbstractMetastable austenitic steels offer the opportunity of a surface layer hardening integrated in the machining process. The hardening effect is achieved by a deformation induced austenite‐martensite phase transformation, for which high mechanical loads and low temperatures are necessary, typically below room temperature. These conditions can be accomplished during cryogenic turning, allowing a phase transformation in the surface layer of the workpiece. To study the austenite‐martensite transformation behavior, information about the temperatures in the contact zone between tool and workpiece during machining is necessary, which can hardly be measured. Therefore, FE simulations of the process are utilized to calculate the transient process temperatures. In this paper the idea of projection‐based model order reduction and its implementation into the finite element program FEAP are described, allowing a solution speed‐up while maintaining accuracy of the full‐order model.
The Cattaneo Model in the context of Thermoablation of Liver Tumors
Authors: Andres Matthias , Pinnau René 
Published: November 2019

AbstractLaser‐induced thermotherapy (LITT) is a medical treatment which attempts to destroy liver tumors by thermal ablation. Accurate simulation‐based predictions shall support the practitioner during the therapy. The heat transfer inside the liver is classically described by a nonlinear coupling of the bio‐heat equation and a radiative transfer model. In order to control the speed of heat propagation we consider an additional term for the second‐order time derivative of the solution and obtain a Cattaneo‐like model. For this model we investigate the problem of parameter identification in terms of PDE‐constrained optimization.
A bilinear identification‐modeling framework from time domain data
Authors: Karachalios Dimitrios S. , Gosea Ion Victor , Antoulas Athanasios C. 
Published: November 2019

AbstractAn ever‐increasing need for improving the accuracy includes more involved and detailed features, thus inevitably leading to larger‐scale dynamical systems [1]. To overcome this problem, efficient finite methods heavily rely on model reduction. One of the main approaches to model reduction of both linear and nonlinear systems is by means of interpolation. The Loewner framework is a direct data‐driven method able to identify and reduce models derived directly from measurements. For measured data in the frequency domain, the Loewner framework is well established in linear case [2] while it has already extended to nonlinear [6]. On the other hand in the case of time domain data, the Loewner framework was already applied for approximating linear models [3]. In this study, an algorithm which uses time domain data for nonlinear (bilinear) system reduction and identification is presented.
A CFD Model for Simulating the Electron Beam Welding of TRIP‐Matrix‐Composites
Authors: Borrmann Sebastian , Schwarze Rüdiger 
Published: November 2019

AbstractThe purpose of the presented model is the numerical simulation of the electron beam welding of metal matrix composites regarding heat transfer, phase change, and fluid and particle flow in the weld pool. The governing equations for the 3D, transient, incompressible heat and fluid flow are therefore extended by a phase change model and a heat source. Furthermore, Lagrangian particle tracking is used for the dispersed particle phase. The implementation of this model into OpenFOAM ensures reusability and expandability for further applications and refinements.
Analysis of Hertzian indentation fracture using a phase field approach
Authors: Strobl Michael , Seelig Thomas 
Published: November 2019

AbstractThe formation and further evolution of cracks caused by the compression of a stiff indenter onto the surface of an initially defect‐free brittle solid is a fascinating problem of fracture mechanics. Its prediction, however, is still a challenging task since crack nucleation is caused by a rather weak stress concentration in the contact near‐field. The present contribution focuses on phase field simulation of indentation fracture, including crack formation at some a priori unknown location outside of the contact region and the subsequent formation of a cone crack. While the phase field method, at first glance, appears to be a promising tool to simulate the current problem we elaborate critical issues and discuss essential modifications. Finally, the indentation fracture process is simulated showing the effect of varying indenter radii on crack initiation and the influence of Poisson's ratio on the angle of cone crack propagation in good agreement with experimental findings and other theoretical studies.
Spatially Regularized Geometric Assignment for Unsupervised Label Learning on Manifolds
Authors: Zern Artjom , Zisler Matthias , Petra Stefania , Schnörr Christoph 
Published: November 2019

AbstractWe introduce a smooth coupled system of Riemannian flows for simultaneously learning a dictionary of manifold‐valued prototypes and assigning these prototypes to the image data in a spatially coherent way. In particular, we detail a numerical update scheme for the evolution of prototypes on the Riemannian manifold of symmetric positive definite matrices. The scheme is applied to covariance descriptors are extracted from image data in order to demonstrate our approach.
A Computational Model for Biological Tissues Considering the Influence of Injury on Growth and Remodelling
Authors: Gierig Meike , Marino Michele , Wriggers Peter 
Published: November 2019

AbstractBiological tissues adapt to changed loading conditions through growth and remodelling (G&R) to reestablish a so‐called homeostatic state. On the other hand, loading conditions above their physiological limits, as during trauma or surgical procedures, cause injury and can initiate pathological G&R. Herein, a modelling approach for G&R influenced by injury is presented combining the theories of plasticity and homogenised constrained mixtures. The results show that injury has a significant impact on the G&R behaviour and thus on the accomplishment of homeostasis.
Comparing Abs‐Normal NLPs to MPECs
Authors: Hegerhorst-Schultchen Lisa C. , Kirches Christian , Steinbach Marc C. 
Published: November 2019

AbstractWe show that the class of unconstrained NLPs in abs‐normal form is a subclass of the class of MPECs and that the class of NLPs with general constraints in abs‐normal form is equivalent to the class of MPECs. Moreover, we compare constraint qualifications and stationarity concepts of these problem classes and observe close relations between them.
A Combined Homotopy‐Optimization Approach to Parameter Identification for Dynamical Systems
Authors: Schäfer Kai , Flaßkamp Kathrin , Fliege Jörg , Büskens Christof 
Published: November 2019

AbstractWhen applying the single shooting approach to solve nonlinear dynamic parameter identification problems, difficulties like undesired minima can occur. To circumvent this, we apply a homotopy continuation to find global minima. In contrast to the literature, we reduce the resulting series of optimization problems to a single one which leads us to the opportunity to compute homotopy paths in a more efficient way. We demonstrate our method with the help of a numerical example.
Mixed XFEM formulation for the simulation of heterogeneities including elasto‐plastic material behaviour
Authors: Löhnert Stefan 
Published: November 2019

AbstractMetal matrix composites often show large isochoric plastic deformations within the matrix material. For dominant plastic deformations this may lead to volumetric locking effects similar to locking in incompressible materials. Lower order mixed finite element formulations can alleviate this difficulty. Complex microstructures often require extensive effort to generate a mesh suitable for finite element simulations. The eXtended Finite Element Method may improve this situation by allowing for discontinuities in the displacement and/or strain field within any finite element. In this contribution a mixed XFEM formulation is presented combining the advantages of the XFEM and mixed FEM. The formulation is applied to small deformation elasto‐plasticity with linear isotropic and linear kinematic hardening. An example demonstrates its superior convergence behaviour compared to a standard XFEM formulation.
Thermo‐Chemo‐Mechanical Modeling of Cathode Particles in Lithium‐Ion Batteries
Authors: Nateghi Aref , Keip Marc-André 
Published: November 2019

AbstractLithium‐ion batteries are widely used in portable consumer electronics, power tools and electric vehicles. As the demand for Li‐ion batteries increases, a deeper understanding of the physical phenomena present in their operation becomes necessary. So far, there remain some obstacles to the wider use of Li‐ion batteries, e.g., capacity loss, self‐discharge and thermal runaway. These effects are mostly related to thermal phenomena in the battery. This underlines the importance of a deeper understanding of thermal effects in batteries. In this work, a four‐field formulation of the coupled problem of diffusion with stress generation and heat transfer in cathode particles of Li‐ion batteries is presented.
Comparison of the hybrid and multipoint‐flux method
Authors: Egger Herbert , Radu Bogdan 
Published: November 2019

AbstractWe compare two approaches for the efficient implementation of the mixed finite element method with applications for elliptic problems, like single phase flow, and hyperbolic problems, like the wave equations. We briefly explain the hybrid and the multipoint flux mixed finite element method (MFMFE) and conduct a comparison of the two methods in terms of efficiency.
Simulation of the flow behaviour of wood‐polymer composites in extrusion dies
Authors: Liese Fabian , Wünsch Olaf 
Published: November 2019

AbstractBy adding different fillers to polymers, both the mechanical and optical properties of the composite can be influenced. The addition of wood flour or fibers results in wood‐polymer composites (WPC), which are industrially processed into deckings by means of an extrusion process. As part of this project, the melt of high density polyethylen (HDPE) and fine wood flour is extruded into a square hollow profile.By means of thermo‐rheological measurements, the shear thinning behaviour as well as the solidification behaviour of WPC at various degrees of filling levels of the wood and different temperatures could be determined. At high fill levels of wood, removal by means of a crawler belt is no longer possible due to the low elongation, so that a partial solidification of the melt prior to exiting the extrusion die by cooling is necessary. In addition to solidification, wall slip effects in the area of cooling occur as a function of shear stress, which could also be measured and modeled using the Mooney method [1]. This contribution deals wih the numerical flow field calculations of such WPC in special extrusion dies. From the thermo‐rheological data a non‐linear viscous model is created. The aims of the numerical simulations with OpenFOAM are to reduce pressure loss and create a uniform velocity field at the outlet. Different parameters such as the mass flow of the melt and the temperatur of the cooling medium are varied.
A geometrically nonlinear micromorphic damage‐plasticity model
Authors: Brepols Tim , Wulfinghoff Stephan , Reese Stefanie 
Published: November 2019

AbstractThe present article is concerned with a novel gradient‐extended ‘two‐surface’ damage‐plasticity model for large deformations which is based on the micromorphic approach in the sense of Forest [4]. It is discussed how the additional partial differential equation for the micromorphic (i. e., ‘nonlocal’) damage variable – which typically needs to be solved in case of gradient‐extended material models – can be derived in a natural way on the basis of an extended form of the principle of virtual work by assuming additional ‘generalized’ stresses that act within the body. As was shown recently by the authors (see [3]), the model is able to suitably counteract the well‐known mesh‐dependence problem of conventional ‘local’ models involving damage.
Simulation of Calcium Waves in a Heart Cell on Modern Multi‐Core Parallel Computing Platforms
Authors: Barajas Carlos , Kopecz Stefan , Meister Andreas , Peercy Bradford E. , Gobbert Matthias K. 
Published: November 2019

AbstractScalability of parallel computer code is a concern in applications that rely on efficient simulations. We present a demonstration of weak scalability of a hybrid MPI+OpenMP code for the numerical solution of a system of seven coupled, non‐linear, time‐dependent reaction‐diffusion equations that model calcium induced calcium release in a heart cell. The results demonstrate that care needs to be taken in the implementation of the OpenMP pragmas to achieve weak scalability within a shared‐memory node and that MPI is capable to provide strong scalability across multiple nodes in a distributed‐memory cluster.
On the origin of passive rotation in rotational joints, and how to calculate it
Authors: Du Shucen , Schlattmann Josef , Schulz Stefan , Seibel Arthur 
Published: November 2019

AbstractIn this paper, a computation method for the output shaft's rotation of a passive rotational joint, especially of one that is deployed on a parallel mechanism, is investigated. As an alternative to typical geometric or screw theory methods, we propose a new approach that is based on the comparison between any passive rotational joint with a reference spherical joint. As examples, we apply our method to a universal joint and a novel double joint whose passive rotation is difficult to calculate with traditional methods.
Remarks on pure and simple shear
Authors: Voss Jendrik , Thiel Christian , Martin Robert J. , Neff Patrizio 
Published: November 2019

AbstractIn a 2012 article in the International Journal of Non‐Linear Mechanics, Destrade et al. showed that for nonlinear elastic materials satisfying Truesdell's so‐called empirical inequalities, the deformation corresponding to a Cauchy pure shear stress is not a simple shear. Similar results can be found in a 2011 article of L. A. Mihai and A. Goriely. We confirm their results under weakened assumptions and consider the case of a shear load, i.e. a Biot pure shear stress. In addition, conditions under which Cauchy pure shear stresses correspond to (idealized) pure shear stretch tensors are stated and a new notion of idealized finite simple shear is introduced, showing that for certain classes of nonlinear materials, the results by Destrade et al. can be simplified considerably.