bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fuzzy uncertainty in forward dynamics simulation using variational integrators
Authors: Eisentraudt Markus , Leyendecker Sigrid 
Published: December 2018

AbstractIn engineering applications, dynamic simulations are usually carried out with precisely defined input parameters. In this contribution, forward dynamics with epistemic parameter‐uncertainty is considered and α‐level discretisation in combination with α‐level optimisation is used to determine the output of the dynamical system – a fuzzy function. A new numerical method for an efficient realisation of α‐level optimisation in this context is developed, which combines forward dynamics steps and local optimisations. A variational integrator, which exhibits special structure preserving properties, is used as the underlying time integration scheme. However, the method can be combined with any time stepping scheme. In detail, an approximative description of the output as a function of the uncertain parameters is developed, which can be used to reduce the complexity of the developed algorithm.
Modeling and Simulation of Hysteresis Effects in Magnetorheological Elastomers
Authors: Kalina Karl A. , Brummund Jörg , Metsch Philipp , Kästner Markus 
Published: December 2018

AbstractHerein, a finite strain microscale model for magnetorheological elastomers with magnetically hard fillers is presented. Therein, the magnetic hysteresis of the particles are described by a phenomenological, thermodynamically consistent hysteresis model. To connect the microscopic fields to effective macroscopic quantities, a computational homogenization scheme is applied. Using the presented framework, the effective macroscopic magnetic as well as mechanical hystereses are calculated.
Simulation of anisotropic diffusion under large deformations in polymer blends
Authors: Voges Jannik , Juhre Daniel 
Published: December 2018

AbstractBlending polymers with different properties is a popular method to customize the behavior of a polymer material. For this, in some cases, the materials are mixed in molten form. At high temperatures, this usually yields a single phase, consisting of both the polymers. At lower temperatures, the blend often starts to decompose into two or more phases, which can yield a complex microstructure. One way to control this resulting structure, is to treat the cooling melt mechanically, whereby lamellar patterns are often observed. Performing computer simulations can help to understand the behavior of the mixture and thus help to be able to better control the microstructure of the polymer blends in the manufacturing process. This can improve the performance of the material.Following a well‐known approach, a phase‐field determines the material distribution in a domain, representing the microstructure of the polymer blend. Here, the Cahn‐Hilliard equation describes the evolution of the mentioned phase‐field, starting with a random initial distribution. The domain is strongly deformed to force a rearrangement of the structure while the blend is decomposing, thus a large deformation framework is considered, cf. [1]. The decomposition process is investigated, using simulations for different deformations and by comparing them to a simulation in the classical undeformed case. Anisotropic diffusion occurs in the deformed domains, which yields regular patterns.
Simulation of angioplasty using isogoemetric laminated composite shell elements
Authors: Roohbakhshan Farshad , Sauer Roger A. 
Published: December 2018

AbstractThe typical treatment for the opening of obstructed arteries or veins is balloon angioplasty. Different computational models, which usually use 3D finite solid elements to model the artery, have been introduced in the literature to analyze the angioplasty procedure. In this work, a laminated composite shell formulation derived from the Kirchhoff–Love shell theory is used to model the artery wall. The corresponding shell is formulated on the mid‐surface of the artery. As only the surface is discretized, the shell formulation is computationally less expensive than the common 3D solid elements, which require volumetric discretization.
Developing a model for the microscopic material behaviour of a tailored formed joining zone of an aluminium‐steel hybrid solid component
Authors: Baldrich Martina , Loehnert Stefan , Wriggers Peter 
Published: December 2018

AbstractTailored Forming is a complex process joining two materials before forming. Especially the joining zone of the hybrid solid component is a possible weakness. Hence, our goal is to predict and adjust the thermomechanical material behaviour of the joining zone during and after the tailored forming process. The hybrid solid components studied in this work are composed of the aluminium alloy EN AW‐6082 and the steel 20MnCr5. Metallurgical investigations on both materials show a polycrystalline microstructure. In the steel component, the two constituents ferrite and pearlite can be found with nearly the same volume fraction and randomly distributed grains. Furthermore, between the two bulk materials aluminium and steel, a thin layer of brittle intermetallic phases can be observed. In this work, the intermetallic phases are considered to behave purely thermoelastic, whereas the material model for aluminium, ferrite and pearlite represents thermoplastic material behaviour. We present the dislocation density based models for the thermoplastic materials formulated in a continuum mechanics framework. Thereby, different mechanisms of annihilation contributing to the evolution equation for the internal variables will be on focus.
A rate‐dependent damage model for prediction of high‐speed cracks
Authors: Butt Sahir , Meschke Günther 
Published: December 2018

AbstractExperiments [1] have shown that the energy release rate in high‐speed dynamic fracture processes strongly depends on the the macro crack propagation velocity. This dependence is due to the fact that the rate of the fracture surface creation is proportional to the energy flux into the crack. A crack propagating at high‐speed can create an order of magnitude larger fracture surface in form of micro‐branches than a low‐speed crack. To this end, a crack speed dependent damage model, which is based on the physics of micro‐branching, is presented and incorporated into peridynamic continuum theory. Numerical simulations are carried out on a plexiglas (PMMA) plate to show that the proposed model is capable of reproducing the physical phenomena observed in experiments.
Closed‐loop control of turbulent boundary layers using spanwise traveling surface waves
Authors: Albers Marian , Meysonnat Pascal S. , Schröder Wolfgang 
Published: December 2018

AbstractThe drag reduction technique of spanwise traveling surface waves in turbulent boundary layers is investigated in a closed‐loop control setup. The results show a dependence of the local skin friction on the spanwise coordinate and a successful application of the controller to determine the optimal amplitude.
A probabilistic white‐box model for PDE constrained inverse problems
Authors: Koschade Maximilian , Koutsourelakis Phaedon‐Stelios 
Published: December 2018

AbstractInstead of employing deterministic solvers in a black‐box fashion, we seek to address the inherent challenges of uncertainty quantification by restating the solution of a PDE as a problem of probabilistic inference. In doing so, state variables are treated as random fields, constrained or mutually entangled by underlying physical laws. The resulting fully probabilistic model expresses the PDE operator as prior knowledge and allows the solution of the PDE‐constrained inverse problem simply by introducing the observed data as an additional source of information. We demonstrate the proposed framework for the solution of PDE‐constrained inverse problems in a solid mechanics setting and employ adjoint‐free, second‐order methods to infer the joint posterior over the Hilbert space of displacement, stress and unknown material parameters. The method generalizes to nonlinear problems and higher‐order function spaces, while the Maximum‐A‐Posteriori estimate recovers the results obtained by the mixed Finite Element method derived from the Hellinger‐Reissner variational principle.
Coupling Structure in an Optimal Control Problem with PDEs and ODEs
Authors: Kimmerle Sven‐Joachim 
Published: December 2018

AbstractWe consider a general example for an optimal control problem subject to coupled differential equations (CDEs). As CDEs we define a coupled system of partial differential equations (PDEs) and ordinary differential equations (ODEs). All differential equations here represent a time evolution and are fully coupled. An averaging or evaluation operator, resp., is applied to PDE states entering into an ODE such that the ODE has no spatial dependency. Following a first‐optimize‐then‐discretize method, we derive the adjoint equations by means of the necessary first‐order optimality conditions. We prove that the coupling structure of the CDE problem in the adjoint system is reversed. This feature is observed and exploited in (continuous as well as discretized) optimal control problems in real‐world applications.
Experiments on wave propagation in soft materials
Authors: Aghayan Sam , Reppel Thomas , Bieler Sören , Weinberg Kerstin 
Published: December 2018

AbstractThe wave propagation in a group of soft resin based (3d printed) materials is investigated by using a Split Hopkinson Bar setup. The principal assumptions and the role of pulse shaping, as an approach to achieve constant strain rates and dispersion reduction, is discussed. The measured dynamic elastic modulus is presented and indicates that flexible resins have a dynamic elastic modulus of 20 to 40 MPa.
Pattern formation for a family of models with local/nonlocal interactions
Authors: Daneri Sara , Runa Eris 
Published: December 2018

AbstractWe establish pattern formation for a family of discrete and continuous functionals consisting of a perimeter term and a nonlocal term. In particular, we show that for both the continuous and discrete functionals the global minimizers are exact periodic stripes. One striking feature is that the minimizers are invariant under a smaller group of symmetries than the functional itself. In the literature this phenomenon is often referred to as symmetry breaking. In the continuous setting, to our knowledge this is the first example of a model with local/nonlocal terms in competition such that the functional is invariant under permutation of coordinates and the minimizers display a pattern formation which is one‐dimensional. Such behaviour for a smaller range of exponents in the discrete setting was already shown in [1].
Investigation of process parameter influences in single grain scratch simulations
Authors: Sridhar Praveen , Fares Driss , de Payrebrune Kristin M. 
Published: December 2018

AbstractLapping and grinding are manufacturing processes which can be seen as a sequence of many single grain scratches. During grinding, the grains perform an oriented movement, whereas during lapping, the grains lie loosely in the gap between the lapping wheel and the workpiece while moving in a completely disordered manner. The Institute of Applied Structural Mechanics conducts experimental investigations and simulations to better understand the complex process. The goal is to develop a physical force model of the grinding and lapping process, by which process predictions can be made. For this purpose, finite element (FE) scratch simulations with geometrically simplified grains are carried out and the qualitative dependencies, such as the influence of the grain geometry and infeed on the stresses are examined.
Optimal control simulations of two finger grasping
Authors: Phutane Uday , Roller Michael , Leyendecker Sigrid 
Published: December 2018

AbstractGrasping is a complex human action simulated here as an optimal control problem with a three‐dimensional rigid multibody model composed of two fingers along with the wrist and the forearm. The dynamics is described by a hybrid dynamical system with a given switching sequence (reaching or tree kinematic structure and grasping or closed loop contacts) and unknown switching times. The optimal control problem is solved using the direct transcription method DMOCC (discrete mechanics and optimal control), see [1], leading to a structure preserving approximation. An objective function such as the distance of contact points from the grasped object center of gravity or the sum of normal contact force is minimised subject to the discrete Euler‐Lagrange equations, boundary conditions and path constraints. The object dynamics is also taken into account.
Microstructure modelling using the scaled boundary finite element method
Authors: Birk Carolin , Tian Xinran 
Published: December 2018

AbstractAn automatic approach for the evaluation of effective material properties is presented. It is based on the scaled boundary finite element method (SBFEM). The SBFEM facilitates the use of structured meshes on highly heterogeneous domains. These meshes are obtained automatically from image data. Two examples illustrate the potential of the proposed methodology.
Deformation behaviour of small scale cp‐titanium specimen with large grains
Authors: Bischof Robert , Böhme Luisa , Kuhn Charlotte , Müller Ralf , Kerscher Eberhard 
Published: December 2018

AbstractTo describe the material behaviour of the microstructure of commercially pure (cp‐) titanium with the Finite Element (FE) Method, a crystal plastic material model is used. The anisotropic plastic deformation is considered by specifying the slip systems of the hexagonal‐closed‐packed (hcp) crystal structure. To circumvent the difficulties associated with possible non‐uniqueness of the set of active slip systems, a rate‐dependent formulation is used. Because of the volume preserving plastic deformation, locking effects can arise, which are dealt with by a modified F‐bar deformation gradient. To investigate the material behaviour of cp‐titanium small scale tensile test simulations are performed. Electronic backscatter diffraction (EBSD) investigations of the sample provides the specific grain orientations of the microstructure to perform realistic simulations.
On the Treatment of Plastic Deformation in the Particle Finite Element Method
Authors: Ye Xialong , Müller Ralf 
Published: December 2018

AbstractThe particle finite element method (PFEM) combines the benefits of discrete modeling techniques and approaches based on continuum mechanics. It provides a convenient tool to deal with the problem of large configurational change, such as metal cutting, in which nonlinear plasticity plays a key role [1]. In this article we introduce a phenomenological plasticity model with the help of a multiplicative decomposition of the deformation gradient and an intermediate local configuration into the PFEM framework. Numerical examples of cutting simulations are presented to show the performance of the formulation.
A brief history of logarithmic strain measures in nonlinear elasticity
Authors: Martin Robert J. , Münch Ingo , Eidel Bernhard , Neff Patrizio 
Published: December 2018

AbstractWe demonstrate that the notion of logarithmic strain tensors in nonlinear elasticity theory, which is commonly attributed to Heinrich Hencky, is actually due to the geologist G. F. Becker, who was the first to consider a fully three‐dimensional logarithmic stress response in an 1893 article.
Statistical Methods for Parameter Identification of Temperature Dependent Viscoelastic Models
Authors: Rosero‐Velásquez Hugo , Cottone Giulio , Colinas‐Armijo Natalia 
Published: December 2018

AbstractA fully fractional stochastic model for linear viscoelastic materials is proposed. Time dependent stress‐strain response for creep tests is described through Adaptive Links theory as a random process of successive micro‐stretching events due to disentanglements between groups of material fibers. The process is modeled by a Continuous Time Random Walk (CTRW) that tends in average to power‐law function, which corresponds to the creep kernel of the usual fractional model for viscoelasticity. Thermal effects are explained through changes in waiting time and jump compliance distribution parameters. Simulated CTRWs are compared with experimental results of specimens of epoxy resin. It was observed that simulated mean function approaches to measurements in long term during the creep phase. Additionally, parameter averages decrease for higher temperatures, representing more frequent jumps of fiber creep strain and faster development of creep process.
Analysis of Anisotropic Interaction Equations for Fingerprint Simulations
Authors: Kreusser Lisa Maria 
Published: December 2018

AbstractMotivated by the simulation of fingerprints we consider a class of interaction models with anisotropic, repulsive‐attractive interaction forces whose orientations depend on an underlying tensor field. This class of models can be regarded as a generalization of a gradient flow of a nonlocal interaction potential which has a local repulsion and a long‐range attraction structure. These anisotropic forces in our class of models cannot be derived from a potential and the underlying tensor field introduces an anisotropy leading to complex patterns which do not occur in isotropic models. This anisotropy is characterized by one parameter in the model. We study the resulting stationary solutions both analytically and numerically by considering the particle model and its continuum counterpart.
Identification of hyper‐ and viscoelastic properties of different flexible FDM printed specimens
Authors: Reppel Thomas , Weinberg Kerstin 
Published: December 2018

AbstractAdditive manufacturing, also known as 3D printing, has become a well‐established method in many different fields of fabrication. It is a preferred method to produce small series or even individual parts of components. The present work aims at the experimental identification of the hyper‐ and viscoelastic properties of two different kinds of highly flexible filaments for fused deposition modeling. A thermoplastic polyurethane TPU and a thermoplastic copolyester elastomer TPC. To this end, several uniaxial tensile tests, as well as relaxation experiments of printed specimens are performed. From the measured data we identify the parameters of different hyperelastic models. For the viscoelastic part we find the parameters of a Prony‐series with N elements of a generalized Maxwell‐model. We also consider a model based on generalized fractional elements [1,3,4].
Influence of the material parameter mapping from computed tomography data on the simulation of a bone‐implant system
Authors: Roland Michael , Tjardes Thorsten , Bouillon Bertil , Diebels Stefan 
Published: December 2018

AbstractIn this study, several mappings for material parameters based on computed tomography image data are tested with respect to their influence on the result of personalized finite element simulations (FEM). Therefore, a standard workflow was implemented including (1) segmentation of routinely acquired clinical tomogram data, (2) definition of several mappings from image–based Hounsfield units to elastic modulus using the apparent density and (3) patient–specific realistic boundary conditions acting during a normal step forward. This setup allows a comparison of simulation results with regard to the used material parameter mapping.
Mean field homogenization schemes for short fiber reinforced thermoplastics based on real microstructural information
Authors: Hessman Patrick Arthur , Welschinger Fabian , Hornberger Kurt 
Published: December 2018

AbstractThe effective elastic properties of a short glass fiber reinforced thermoplastic are estimated using different mean field homogenization schemes. The material's inherently complex microstructure is resolved by means of high resolution x‐ray tomography scans and utilizing a single fiber segmentation algorithm. This raw microstructural data is then directly considered in the models. Finally, the models are discussed and their estimates for the anisotropic effective stiffness tensor are compared to experimentally obtained direction‐dependent Young's moduli.
Bayesian inference for estimating model discrepancy of an electric motor
Authors: John David , Schick Michael , Heuveline Vincent 
Published: December 2018

AbstractUncertainty Quantification (UQ) is highly requested in computational modeling and simulation, especially in an industrial context. A main challenge is related to the fact that computational models are rarely able to represent the true physics perfectly and demonstrate a discrepancy compared to measurement data. Further, an accurate knowledge of considered model parameters is usually not available. E.g. fluctuations in manufacturing processes of hardware components introduce uncertainties which must be quantified in an appropriate way. Mathematically, such UQ tasks are posed as inverse problems, requiring efficient methods for their solution. We address this challenge by investigating the influence of model discrepancies onto the calibration of model parameters and further consider a Bayesian inference framework including an attempt to correct for model discrepancy by an additional term. A Markov Chain Monte Carlo (MCMC) method is utilized to approximate the posterior distribution. Synthetic measurement data from an electric motor model and an artificial model error are used to evaluate the framework. The application shows a promising perspective of the framework by good approximation of discrepancy and parameters.
Modeling, identification, and optimization of violin bridges
Authors: Marschke Sandra , Ring Wolfgang , Wohlmuth Barbara 
Published: December 2018

AbstractWe present the derivation and implementation of a mathematical model for the linear elastic structure of a violin bridge. In favour of getting highly accurate simulation results, special effort has been taken to reconstruct the computational geometry from a µ‐CT scan. After laying out our approach for this in detail, we also present first vibroacoustical analysis like solving the eigenvalue problem of elasticity for the orthotropic material law of the wooden bridge and simulation of its dynamical behaviour. We then conclude with explaining our ongoing work of identifiying material paramters by an inverse problem. With this project we are aiming to optimize a violin bridge regarding its material parameters and its shape.
Multi‐factors Optimization Design of Pin‐Fin Structure Using Respond Surface Method
Authors: Wang Xiang , Chen Min , Zhang Shunqi , Tate Derrick 
Published: December 2018

AbstractMost optimizations on pin fin heat sink only involve the relationship between single factor variable and performance. This study aims to find out the optimized solution for coupled effects of parameters based on RSM (Response Surface Methodology). Height and diameter of cylindrical pin‐fin are adopted as designed parameters, according to numerical simulation the interaction of different parameters are investigated and an optimized scheme is achieved.
Mesoscale Simulation of Shape Memory Alloy Film Damping
Authors: Ahmadi Shahabeddin , Jacob Kiran , Wendler Frank , Kohl Manfred 
Published: December 2018

AbstractThis paper presents a macroscale and mesoscale dynamic analysis of the forced vibration of a free‐standing bridge of superelastic shape memory alloy TiNiCuCo for novel miniature scale damping devices with ultra‐low fatigue properties. The effects of pre‐straining and excitation load are investigated in order to define an optimum operation point for a SMA bridge damper device. The analysis is performed under non‐isothermal conditions by taking into account the heat transfer and the rate‐dependence of release and absorption of latent heat.