bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the behaviour of a Newtonian liquid regarding the picture framing coating error
Authors: Sommer Oliver , Hehemann Sven , Wozniak Günter 
Published: December 2018

AbstractWe experimentally investigated the specific behaviour of Newtonian thin liquid layers at curved solid edges in a continuative investigation of the so‐called picture framing effect coating error. We used adapted laser‐induced fluorescence technique (LIF) to measure the layer thickness distribution for the examination of the underlying edge bead in a cross section. The main motivation is to find optimal combinations of influencing quantities to reduce the picture framing effect (edge beads) in order to achieve a homogeneous layer thickness distribution of the liquid coating on the surface of the substrate, especially at the edges. For this purpose, we varied the viscosity of the Newtonian liquid, the edge radii of curvature of the substrate and its orientation regarding the gravitational direction. The results, i.e. the edge bead dependencies on the tested parameters, are physically plausible. With these findings the picture framing effect as a whole is manipulable regarding a minimisation of the coating error.
Investigation of size effects due to material interfaces
Authors: Heitbreder Tim , Ottosen Niels Saabye , Ristinmaa Matti , Mosler Jörn 
Published: December 2018

AbstractThe thermodynamical consistent combination of classical non‐coherent cohesive zone models with surface elasticity theory is relatively new, cf. [1]. Relying on the variational structure of the underlying problem, a compact and direct derivation of the framework [1] is presented. By embedding the framework into the finite element method, the mechanical influence of interfaces within RVEs is investigated for different sizes. Thereby, a complex size effect combining the frequently observed “the smaller the stiffer" relation, but also the less often observed “the smaller the softer" relation is worked out. A combination of the both relations leads to a non‐monotonic size effect, that is influenced by the choice of the interface material parameter, see [2].
Study of model variants in a combined framework for multiplicative growth and remodeling in arterial walls
Authors: Zahn Anna , Balzani Daniel 
Published: December 2018

AbstractA combined framework for stress‐induced growth and fiber reorientation in arterial walls is presented. Assuming that the reduction of stress peaks and gradients in different loading situations is the main purpose of an effective adaptation process, a simplified study of model variants is performed on idealized arterial geometries.
Balancing Related Model Reduction with the MORLAB Toolbox
Authors: Benner Peter , Werner Steffen W. R. 
Published: December 2018

AbstractBalancing related model reduction methods are based on the idea of the balanced truncation method and can be used to preserve certain system properties like passivity or contractivity. The MORLAB toolbox provides efficient implementations for a big set of such methods. We will give an overview about the implemented methods and test some of these methods on a benchmark example.
A Data‐Driven Possibilistic Approach to the Identification of Uncertain Stability Lobe Diagrams
Authors: Hose Dominik , Hamann Dominik , Hanss Michael , Eberhard Peter 
Published: December 2018

AbstractIn this contribution, an alternative approach to classical regression analysis is explored which allows the identification of uncertain stability lobe diagrams for machining processes via a multi‐fidelity modeling approach.
Multi‐level preconditioning and eigenvector approximation for axisymmetric Maxwell eigenproblems
Authors: Kranjčević Marija , Arbenz Peter , Adelmann Andreas 
Published: December 2018

AbstractWe compute resonant modes in axisymmetric radio frequency cavities by solving a few generalized eigenvalue problems using the symmetric Jacobi–Davidson algorithm. In particular, we focus on the parallelization and the use of the multi‐level preconditioner for the correction equation. Additionally, we compute eigenvector approximations using the solutions of the problem on a coarser mesh and present the results on the problem of computing a few lowest modes of a real‐world cavity.
Development of a passive, wearable knee orthosis for the support of sit‐to‐stand movement with adaptive assistance moment
Authors: Ziegler Jakob , Parzer Herbert , Gattringer Hubert , Müller Andreas 
Published: December 2018

AbstractThe worldwide population aging and hence the higher risk of age‐related diseases facilitates interest in robotic devices for rehabilitation and movement assistance. A major factor of a persons functional independence is the ability to perform the movement task of standing up from a chair, also known as sit‐to‐stand (STS) movement. This work focuses on the development of a passive, wearable knee orthosis that supports the extension of the knee joint. As the knee flexes while sitting down a spring mechanism is loaded due to a cable wrapping around a deflection disc, thus generating a moment that assists standing up again. In order to prevent unintended knee extension this assistance moment should be minimized when the person is fully seated. To this end the geometry of the deflection disc, parametrized as B‐spline curve, is optimized in order to control the knee extension moment with respect to the knee angle. Initial tests with a first prototype show promising results.
A Virtual Element Method for Crack Propagation
Authors: Hussein Ali , Hudobivnik Blaž , Aldakheel Fadi , Wriggers Peter , Guidault Pierre‐Alain , Allix Olivier 
Published: December 2018

AbstractIn this contribution, a crack propagation within brittle materials is presented by means of a novel technique, the virtual element method (VEM) [1]. In comparison to FEM, VEM allows usage of arbitrary polygonal (2D) and polyhedral (3D) elements. Such a method can be extremely useful for simulation of crack propagation problems, which may be providing an alternative approach for XFEM and remeshing. Based on the stress intensity factor, calculated by the interaction integral, the direction of the crack propagation is predicted by using the maximum circumferential stress criterion. For domain discretization, we used arbitrary polygonal elements with arbitrary number of nodes. Without changing the element formulations, the crack path is constructed by splitting the elements in the direction of growth. Also, if the crack growth stops within the element, this can be easily accomplished. Finally, a numerical example is provided to demonstrate the performance of the model.
Coupled simulations involving light‐weight structures within turbulent flows: FSI strategy and non‐matching interface treatment for isogeometric b‐rep analysis
Authors: Wüchner Roland , Apostolatos Andreas , De Nayer Guillaume , Breuer Michael , Bletzinger Kai‐Uwe 
Published: December 2018

AbstractLightweight shell structures have gained significant popularity in the engineering design as they offer high load carrying capacity for low cost. While classical Finite Element models of such structures have been extensively used in practice, the shell formulations for Isogeometric Analysis (IGA), particularly for Kirchhoff‐Love shell structures [1], have demonstrated benefits arising from the smooth geometry description and the highly accurate solutions that are enabled. Moreover, the direct use of CAD‐models for the structural simulations is possible based e.g. on the Isogeometric B‐Rep Analysis (IBRA) [2]. Herein the application of IBRA to Fluid‐Structure Interaction (FSI) simulations of wind turbines is demonstrated, thus naturally extending IBRA to coupled multiphysics problems.
A probability‐box approach on uncertain correlation lengths by stochastic finite element method
Authors: Dannert Mona M. , Fau Amelie , Fleury Rodolfo M.N. , Broggi Matteo , Nackenhorst Udo , Beer Michael 
Published: December 2018

AbstractIn order to regard mixed aleatory and epistemically uncertain random fields within stochastic finite element method, a probability box approach using stochastic collocation method is introduced. The influence of an interval‐valued correlation length on the output is investigated.
A numerically robust anisotropic damage model
Authors: Fassin Marek , Eggersmann Robert , Wulfinghoff Stephan , Reese Stefanie 
Published: December 2018

AbstractThe present work deals with an elastic‐brittle anisotropic damage model utilizing a second order damage tensor. Artificial stiffening effects are excluded a priori by means of a specific choice of the elastic part of the free energy. Two strategies for the determination of the internal variables are investigated: (i) standard approach based on the evolution equations of the internal variables and (ii) use of a regularized dissipation potential (within the concept of generalized standard materials). The superior robustness of the latter approach is exemplarily shown with a convergence study of a uniaxial stretch test.
Analytical modelling of autofrettage processes – Historical approaches and new results
Authors: Rammerstorfer Franz G. , Bauer Stefan , Scheidl Jakob 
Published: December 2018

AbstractThere exist a number of classical analytical solutions for the calculation of the residual stresses produced by autofrettage. Historical solutions for thick‐walled tubes are based on assumptions, which are approximate in comparison with reality and limited in the range of applicability. New results for realistic boundary conditions reveal some unexpected phenomena.
Crack detection and parameter identification in finite and semi‐ infinite plane structures based on remote strain fields and the distributed dislocation technique
Authors: Boukellif Ramdane , Ricoeur Andreas 
Published: December 2018

AbstractA method for the detection of cracks in finite and semi‐infinite plane structures is presented. This allows both the identification of crack position parameters, such as length, location and angles with respect to a reference coordinate system and the calculation of stress intensity factors (SIFs). The method is based on strains measured at different locations on the surface of a structure and the application of the dislocation technique. Cracks and boundaries are modelled by continuous distributions of dislocation densities. This approach gives a set of singular integral equations with Cauchy kernels, which can be solved using Gauss‐Chebyshev numerical quadrature. Once knowing the dislocation densities, the strain at an arbitrary point can be calculated. The crack parameters as well as external loads are parameters which have to be determined by solving the inverse problem with a genetic algorithm. Once knowing loading and crack parameters, the SIFs can be calculated.
Flame propagation in arbitrarily shaped vessels
Authors: Gößnitzer Clemens , Steinrück Herbert 
Published: December 2018

AbstractA new method to capture the flame front in premixed, confined, low Mach number combustion using the flame‐sheet approximation is presented. Connected marker points represent the flame front along which a singular volumetric flux source is prescribed. Thus, the jump condition for the normal velocity is fulfilled. Application to two‐dimensional combustion in a channel with periodic boundary conditions shows good agreement to linear stability analysis of the perturbed flame front.
Prescribed Performance Adaptive Control of Uncertain Nonlinear Systems: State‐of‐the‐art and Open Issues
Authors: Rovithakis George A. 
Published: December 2018

AbstractPerformance in adaptive control designs for uncertain nonlinear systems, whose uncertainty is not purely parametric, was traditionally restricted to enforcing, besides stability, desirable behavior at steady‐state. In the literature, rigorous proofs have been provided guaranteeing tracking error convergence to residual sets, whose size depends on design parameters and some bounded though unknown terms. Therefore, even controllable, steady‐state accuracy was impossible to be a priori selected by any systematic procedure. Furthermore, transient performance such as maximum overshoot and convergence rate, was difficult to be established analytically even for known systems. The problem was approached via minimizing certain performance indices, which unfortunately were connected only indirectly with the actual system response. Hence, even though performance improvement is anticipated, no connection to a priori specified trajectory oriented metrics could be achieved. For classes of nonlinear systems Funnel Control has been proposed to provide solution. However, the problem remained largely unsolved for the case of adaptive closed‐loop uncertain systems. To fill in the gap, the Prescribed Performance Control (PPC) methodology was presented. This work is a review on PPC, highlighting on its main advantages and discussing on probably the most important open issues.
Parameter Optimization of a Reduced Model for Multi‐Contact Locomotion of Humanoid Robots
Authors: Seiwald Philipp , Leyerer Anian , Sygulla Felix , Rixen Daniel 
Published: December 2018

AbstractIn this study, we investigate a reduced model intended for approximating the complex multi‐body dynamics of our full‐sized humanoid robot LOLA. In particular, we compare various optimization algorithms to find an optimal set of model parameters. For rating parameter sets, we define a cost function which penalizes differences between the simulated motion of the full‐ and reduced model. Due to the complex motions of a walking humanoid robot, which includes cyclic opening and closing contacts, one is easily trapped in local minima. Thus the focus of this study lies on techniques for global optimization based on meta‐heuristics. We plan to use the reduced model for real‐time stability analysis during multi‐contact locomotion, i. e. walking with additional arm support.
Hygro‐thermo‐chemo‐mechanical modelling of shotcrete during tunnel advance
Authors: Gamnitzer Peter , Schreter Magdalena , Hofstetter Günter 
Published: December 2018

AbstractThis contribution deals with numerical modelling of drill‐and‐blast tunnelling. Special attention is paid to the modelling of a shotcrete layer supporting the surrounding rock after excavation. Due to an increasing load caused by further tunnel advance, and due to shrinkage caused by hydration which is restrained by the surrounding rock, the shotcrete is loaded in place at a very early age. Hence it is required to accurately model the evolution of its strength and stiffness. This is done using a fully coupled hygro‐thermo‐chemo‐mechanical multi‐phase model for the shotcrete. Creep of shotcrete is taken into account using a microprestress‐solidification approach. The constitutive model for the shotcrete is calibrated using experimental data obtained from laboratory tests reported in literature. The setup for the tunnelling simulation is completed assuming elastic‐plastic response for the surrounding rock and the additional steel anchors. The results of this contribution are considered to be a further step towards a more accurate modelling of excavation procedures in conventional drill‐and‐blast tunnelling.
Multilevel Monte Carlo Method for Stochastic Analysis of Fluid‐Structure Interaction
Authors: Kodakkal Anoop , Wüchner Roland , Bletzinger Kai‐Uwe 
Published: December 2018

AbstractAbstract: Uncertainty quantification for multi‐physics problems like fluid‐structure interaction (FSI) is challenging in terms of the required computational effort and complexity of physics involved. A Multilevel Monte Carlo (MLMC) approach for stochastic analysis of FSI problems is presented in the current study. An overall reduction in computational cost is achieved by variance reduction in MLMC method. The efficacy of MLMC algorithm for expensive problems like FSI is compared with classical Monte Carlo(MC) method and MLMC is found to achieve the required accuracy at a significantly reduced computational cost. An FSI benchmark test case with uncertain inputs is presented here. The possibility of uncertainty quantification for FSI systems with a plausible computational cost using MLMC is demonstrated.
Galerkin‐based mixed time finite elements for structural dynamics
Authors: Ströhle Timo , Betsch Peter , Schiebl Mark 
Published: December 2018

AbstractNumerically stable and accurate time integration methods are important in structural dynamics. We propose such a method based on a mixed variational formulation of the underlying semi‐discrete equations of motion. The newly developed scheme relies on a specific combination of the so‐called continuous Galerkin (cG(k)) method and the discontinuous Galerkin (dG(k)) method. We refer to [2] for an introduction of the original cG(k) and dG(k) methods for ODEs (see also [1]). The mixed approach relies on polynomial approximations of degree k on the level of each time finite element. In particular we make use of hierarchical interpolation polynomials. The present approach is closely related to Hellinger‐Reissner type mixed variational formulations for elastodynamics. The mixed method yields implicit time‐stepping schemes with order of accuracy equal to 2k for the displacements and velocities. In addition to that, the method is capable of conserving the energy in the case of conservative mechanical systems. Numerical examples are presented which highlight the numerical properties of the newly proposed mixed approach.
Scaled boundary isogeometric analysis of large deformations in solids
Authors: Chasapi Margarita , Klinkel Sven 
Published: December 2018

AbstractThe so‐called scaled boundary isogeometric analysis combines the advantages of the isogeometric analysis and the scaled boundary finite element method. Here, the parameterization of the solid follows the idea of the scaled boundary finite element method (SB‐FEM), where the boundary of the domain is scaled in respect to a specified scaling center inside the domain. In the framework of isogeometric analysis (IGA), the NURBS functions that describe the geometry also interpolate the unknown displacement field. Such a combined approach is advantageous for three‐dimensional solids, as a radial scaling parameter describes the interior of the solid and only the geometry of the boundary is required for the analysis. The motivation is therefore to fit the idea of the boundary representation modeling technique, which is the way solids are designed in CAD –namely only by their boundary surfaces. Our contribution introduces a formulation for geometrical nonlinear 2D problems. The derived formulation addresses hyperelastic material behavior for large deformations and plane strain conditions for the two‐dimensional domain. We solve the boundary value problem by applying the weak form of equilibrium in both radial scaling and circumferential direction of the boundary. Thereafter, the nonlinear deformation behavior requires a linearization and the application of the Newton‐Raphson iterative scheme. Finally, we study the performance of this approach on a numerical problem by comparison to the standard finite element method.
Hyperbolicity‐preserving stochastic Galerkin method for hyperbolic systems with uncertainties
Authors: Schneider Florian , Schlachter Louisa 
Published: December 2018

AbstractUncertainty Quantification through stochastic spectral methods is rising in popularity. We derive a modification of the classical stochastic Galerkin method that ensures the hyperbolicity of the underlying hyperbolic system of partial differential equations. The modification is done using a suitable linear scaling limiter, based on similar ideas in the context of kinetic moment models. We apply the resulting modified stochastic Galerkin method to the compressible Euler equations. Our numerical results show that it can compete with other UQ methods like the intrusive polynomial moment method while being computationally inexpensive and easy to implement.
Approximation of Periodic and Quasi‐Periodic Motions of a Rotor System with Visco‐elastic Seal Support by Using a Fourier‐Galerkin‐Method
Authors: Bäuerle Simon , Hetzler Hartmut 
Published: December 2018

AbstractIn this contribution a Fourier‐Galerkin method is used to calculate the periodic and quasi‐periodic motions of a rotor‐seal system. The system consists of a classical Laval‐rotor, a visco‐elastically supported rigid seal rigid and a turbulent fluid flow through the seal gap. The Fourier‐Galerkin method uses one‐ and two‐dimensional Fourier series to approximate steady‐state periodic solutions due to rotor mass unbalance and quasi‐periodic solutions due to unbalance and self‐excitation stemming from the seal fluid forces. The method is applied to continue solution‐branches of the rotor‐seal system which show periodic/ quasi‐periodic solutions, resonance, multiple Neimark‐Sacker bifurcations as well as synchronisation (Torus‐breakdown).
Constitutive modelling of sheet‐layered lamination stacks
Authors: Baloglu Maximilian Volkan , Willner Kai 
Published: December 2018

AbstractSheet‐layered lamination stacks found in electric motors as rotor and stator are a challenging task in structural mechanics due to their special design. The manufacturing process determines the nature of the microstructure resulting in the presence of bonding varnish or frictional contact between the individual metal sheets. For the latter case, a penalty method in normal and tangential direction can be used to capture the contact interactions of single plates. In combination with homogenization techniques, a transversely isotropic surrogate material model with a corresponding strain energy density can be identified. In this paper, the focus lies on the influence of the penalty parameters on the elastic quantities of the constitutive equation.
Implicit forming simulations for “Die‐Less‐Hydroforming”‐structures
Authors: Metzger Andreas , Ruff Daniel C. , Ummenhofer Thomas 
Published: December 2018

AbstractFEM forming simulations are often performed using an explicit solver, which usually requires time‐scaled and often mass‐scaled simulation approaches. Explicit simulation with the commercial software LS‐DYNA also provides very good results for the forming simulation of the innovative process of “"Die‐Less‐Hydroforming” when time‐scaling and relatively very strong mass‐scaling are used. Nevertheless, this paper presents an implicit forming simulation for “Die‐Less‐Hydroforming” using LS‐DYNA, which can be used on the one hand (in addition to costly experimental investigations) as comparison and verification of the explicit simulation. On the other hand, the simulation of the forming process, which in reality is quasi‐static, corresponds more precisely with regard to the mapping of its process time, since neither time‐scaling nor mass‐scaling are required when using the implicit solver in comparison to the calculation with the explicit solver.
Kirchhoff‐Love shell theory based on Tangential Differential Calculus
Authors: Schöllhammer Daniel , Fries Thomas‐Peter 
Published: December 2018

AbstractWe propose a parametrization‐free reformulation of the classical Kirchhoff‐Love shell equations in terms of tangential differential calculus. An advantage of our approach is that the surface may be defined implicitly, and the resulting shell equations and stress resultants lead to a more compact and intuitive implementation. Numerical tests are performed and it is confirmed that the obtained approach is equivalent to the classical formulation based on local coordinates.