bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bouc hysteresis without an elastic restoring force under white noise excitation using the beta distribution
Authors: Kasess Christian H. , Waubke Holger 
Published: November 2019

AbstractThe Bouc model comprises three coupled first‐order differential equations which describe the behavior of hysteretic materials. Closure methods have been shown to yield good approximations of the probability density of the state variables under white noise excitation. Previously, a new closure approach for hysteretic softening behavior was introduced, utilizing the beta distribution together with a non‐linear mapping using the inverse hyperbolic tangent. This allows to properly model the finite support of the distribution of the hysteretic force. In the current work, this beta closure approach was applied to single‐degree‐of‐freedom‐systems under stationary white noise excitation lacking, however, an elastic restoring force. Thus, no stationary state is reached. Although the results show a good agreement with Monte‐Carlo simulations there are still deviations in certain higher order moments of the displacement and the velocity depending on the noise strength.
Continuum‐mechanical modelling of apoptosis
Authors: Schröder Patrick , Wagner Arndt , Stöhr Daniela , Rehm Markus , Ehlers Wolfgang 
Published: November 2019

AbstractIn cancer cells, the administration of drugs, such as TRAIL, can induce a mode of cell death (apoptosis). This applied reagent shifts the cell's internal inhibition and activation reactions towards the activation of caspases, triggering the cell death. In this contribution, a macroscopic model in the framework of the well‐known Theory of Porous Media is introduced to model the apoptosis reaction for lung‐cancer metastases located in brain tissue. Therein, the density‐production terms describe the apoptosis via a set of ordinary differential equations. The model is adapted to apoptosis experiments, measuring the survival rate of lung‐cancer cells in dependency of the TRAIL concentration. Thereby, the model is compared to a reduced model version using a constitutive logarithmic apoptosis function within the production terms.
On the analysis of crack‐closure behaviour using the phase‐field method together with the novel concept of Representative Crack Elements
Authors: Storm Johannes , Supriatna Dennie , Kaliske Michael 
Published: November 2019

AbstractFor the analysis of crack closure behaviour and the determination of forces transferred across the crack, several stress‐based splits are used for the phase‐field method so far. Steinke and Kaliske [1] proposed a kinematic analysis of the crack‐closure behaviour for isotropic linear‐elastic material behaviour, which overcomes some important issues of the previous splits (volumetric‐deviatoric and spectral split). The paper presents a novel approach for the phase‐field method, which adopts the idea of a kinematic crack analysis. Therefore, an underlying representative model of a discrete crack is coupled to the phase‐field model in order to determine the degraded and the crack‐closure behaviour. Finally, a closed form solution of the approach is presented for linear elasticity and results for thermo‐elasticity are shown. The model is validated by showing self‐consistency and the results are compared to those from the previously mentioned splits.
On higher‐order interface models
Authors: Heitbreder Tim , Mosler Jörn 
Published: November 2019

AbstractInterface models are well established and frequently applied in material science. Classical non‐coherent interface models such as cohesive zone models are described by a Helmholtz energy depending on the displacement jump. The extension to thermodynamically consistent combination of classical non‐coherent cohesive zone models with surface elasticity is still relatively new, cf. [1] and [2]. These models depend on the displacement jump as well as on the surface deformation gradient. In this contribution the impact of higher‐order surface gradients is investigated.
A stochastic material model to describe continuous mode conversion
Authors: Zimmermann Eugen , Lammering Rolf , Eremin Artem 
Published: November 2019

AbstractDeterministic material models are not able to comprehensively describe phenomena observed in experiments. The continuous mode conversion (CMC) of propagating waves in carbon fiber reinforced plastic (CFRP) plates is an example of this. The mechanism is similar to the conversion in the presence of defects. If a symmetrical mode while propagating through a plate‐like structure encounters a damage, which is non‐symmetric with respect to the waveguide thickness, the symmetrical mode converts into an asymmetric mode at the obstacle. The conversion is usually bounded to the location of the obstacle. In contrast, the CMC occurs even in damage free CFRP structures and manifests itself in conversion taking place permanently or continuously. The reason for this phenomenon is the irregular distribution of fiber and matrix material. With the extension to the stochastic context, it is possible to work out an enhanced material model which is able to reproduce the observed wave behaviour.
Efficient assembly of linearized equations in nonlinear homogenization
Authors: Kunc Oliver , Fritzen Felix 
Published: November 2019

AbstractA novel deformation gradient‐based Reduced Basis homogenization method is compared to the well‐established displacement‐based approach in the geometrically nonlinear context. Algorithmic complexity, the intrusiveness, and the simplicity of the each approach are addressed. It is found that the novel method is advantageous in most respects, especially in returning good approximations of the macroscopic tangent stiffness.
Methods for Finding the Offset in Robust Subspace Fitting
Authors: Lellmann Jan , Neumayer Sebastian , Nimmer Max , Steidl Gabriele 
Published: November 2019

AbstractWe propose a method for finding the offset in robust PCA which differs from the often used geometric median and arises in a natural way from maximizing the log‐likelihood estimator of a heavy‐tailed Student's t‐distribution. Proof‐of‐concept numerical comparisons with other algorithms show the very good behavior of our approach.
Modeling the actuation and sensing behavior of an IPMC within the framework of the Theory of Porous Media
Authors: Bluhm Joachim , Serdas Serdar , Schröder Jörg 
Published: November 2019

AbstractElectroactive polymers (EAPs) are considered as smart materials. Therein, a differentiation between an electric and an ionic EAP will be made. In this contribution, in particular the ionic polymer‐metal composites (IPMCs) are investigated which belong to the class of the ionic EAPs. These kind of materials act as an actuator and a sensor in variety of applications. The actuation application is given by applying an electrical voltage to the electrodes which instantaneously leads to the relocation of the mobile cations towards the cathode. The sensor application is performed by loading the IPMC mechanically which generates an electrical field. For the prediction of the behavior of this material, the theoretical framework of electrodynamics in combination with the Theory of Porous Media has been taken into account, see [1–3]. A numerical example for the 2D sensing behavior is investigated.
On the Dynamics of a Prestressed Sliding Wedge Damper
Authors: Aramendiz Jimmy , Fidlin Alexander , Baranowski Eugen 
Published: November 2019

AbstractThis paper presents a prestressed sliding wedge damper as an effective alternative for the reduction of vibration amplitudes. Due to the system's non‐smooth and non‐linear characteristics, it offers advantages over conventional linear dampers, e.g an amplitude adaptive behavior. First, the equations of motion which describe the system's characteristics are derived. Second, an analytical model based on a modal coordinate transformation and averaging methods is proposed. A numerical model, which uses an elasto‐plastic contact model is set up, in order to fully model the systems behavior. An analysis of the dampers characteristics shows that it is a pseudo‐viscous damper realized via dry friction. The analytical and numerical results are compared and show a reasonable agreement, as within asymptotic methods. This work presents the first investigations into prestress influence on such a damper and offers insight into future theoretical, numerical, and experimental analysis.
On different geometric approaches to the dynamics of finite‐dimensional mechanical systems
Authors: Eugster Simon R. , Capobianco Giuseppe , Winandy Tom 
Published: November 2019

AbstractThe language of differential geometry allows a coordinate‐free representation of physical quantities. This led to the development of several geometric theories for the description of finite‐dimensional mechanical systems. These approaches differ in the mathematical concepts they invoke and in the classes of mechanical systems they can describe. This short note aims to give an overview on the following three popular approaches, all of which are limited to time‐independent mechanical systems. While in the first approach, the motion of the mechanical system is considered as a curve in the system's configuration manifold, in the latter two, the corresponding motions are interpreted as curves in the tangent or the cotangent bundle of the configuration manifold.
Virtual testing of additively manufactured grid structures
Authors: Gebhardt Ulrike , Gärtner Roland , Berner Matthias , Holtzhausen Stefan , Hufenbach Julia Kristin , Kühn Uta , Kästner Markus 
Published: November 2019

AbstractAdditive manufacturing lifts the restrictions of classical manufacturing methods and enables us to produce lattice structures within otherwise massive bulk material to increase the lightweight potential of technical components. In this contribution we present a multiscale approach to characterise additively manufactured lattice structures. Tensile tests provide the properties of the bulk material and are input for a homogenisation scheme and a detailed numerical model to perform virtual experiments. The virtual experiments are compared to actual experiments on test specimen to validate the modelling approach.Process parameters strongly influence the overall mechanical behaviour of additively manufactured lattice structures and are cause for macroscopic deviations of the geometry. Those deviations can be additional material at the struts or an inner porosity of the structure. They are identified, quantified and a first numerical analysis of their influence is presented.
Robust Feedback Control of Nonlinear PDEs by Polynomial Approximation of the Hamilton‐Jacobi‐Isaacs Equation
Authors: Kalise Dante , Kundu Sudeep , Kunisch Karl 
Published: November 2019

AbstractWe present a computational method for the synthesis of optimal robust feedback laws for nonlinear dynamics based on the solution of a nonlinear Hamilton‐Jacobi‐Isaacs equation. This equation is approximated with an iterative method involving the solution of high‐dimensional linear PDEs, for which we use of a Galerkin method with global polynomial ansatz functions. The method is applied for controlling dynamics arising from a pseudospectral discretization of nonlinear parabolic PDEs.
Influence of friction on the locomotion of soft robots
Authors: de Payrebrune Kristin M. 
Published: November 2019

AbstractThe recent interest in soft robots results from their adaptability, versatility and flexibility, which is very advantageous for new applications in human‐robot interaction, health care or field exploration. Many feasibility studies have already demonstrated the versatility of soft robots to grip irregular objects, walk on uneven surfaces, or interact with humans. Further research on mathematical models of these continuously deformable robots is ongoing to predict their performance in real life and operational situations. In particular, the models should be able to describe nonlinear material properties, contact situations and the dynamic behavior of the soft robot in action, which is a major challenge.In this paper, basic measurements of the friction behavior of a fabricated pneu‐net bending actuator are performed in different actuation phases. In order to analyze the dependence on the momentary actuation, the coefficient of friction is related to the applied pressure, which shows a nonlinear characteristic. The results are used in the Euler's Elastica model of the soft bending actuator to describe the overall deformation according to the contact conditions more precisely.
Applying the FROSch Overlapping Schwarz Preconditioner to Dislocation Mechanics in Deal.II
Authors: Heinlein Alexander , Rheinbach Oliver , Röver Friederike , Sandfeld Stefan , Steinberger Dominik 
Published: November 2019

AbstractParallel computational results for problems in dislocation mechanics are presented using the deal.II adaptive finite element software and the Fast and Robust Overlapping Schwarz (FROSch) Preconditioner.
Parameter identification of strain rate dependent hardening for sheet metals
Authors: Söhngen Benjamin , Willner Kai 
Published: November 2019

AbstractIn this contribution we examine the influence of strain rate on the isotropic hardening of two sheet metals. The nominal strain rates vary between 0.0005 s−1 and 20 s−1 and the full field deformation is captured with the help of digital image correlation (DIC) technique. For modelling the strain rate dependent behaviour, we introduce a rate dependent part in the definition of the hardening stress, distinguishing between approaches that incorporate the rate dependency in an additive or multiplicative manner. The hardening laws are thereby embedded in a large strain plasticity framework based on the logarithmic strain space. The material parameters are identified both in a “direct” fashion, where the gap between constitutive equation and measured stress‐strain curve is minimized and inverse, by using the finite element method (FEM) to generate force‐displacement curves and the virtual fields method, which compares internal and external virtual work.
A New C0‐Continuous FE‐Formulation for Finite Gradient Elasticity
Authors: Riesselmann Johannes , Ketteler Jonas , Schedensack Mira , Balzani Daniel 
Published: November 2019

AbstractThree field mixed C0‐continuous gradient elasticity finite element formulations contain both displacement and displacement gradients as solution variables. In this contribution a new formulation is proposed, in which the displacements are not part of the problem anymore, but only displacement gradients, leading to a reduced number of variables to be discretized. In numerical examples the proposed formulations are compared to finite strain adaptations of existing mixed three field approaches for small strains and unveil favorable computing time. For the 3D case a further reduction of variables through a penalty formulation is investigated.
SH wave generated Lamb wave in a plate with a localized region of material nonlinearity
Authors: Wang Yanzheng , Chen Weiqiu , Zhang Chuanzeng 
Published: November 2019

AbstractHigher harmonics are sensitive to micro‐defects, which can be utilized in the development of nonlinear ultrasonic techniques (NLUTs). Thus, the higher harmonic generation by material nonlinearity has attracted considerable attention. However, few works have been done on the elastic wave propagation in a finite structure with a localized region of material nonlinearity. The propagation of the SH wave in a plate with a localized region of quadratic material nonlinearity is investigated in this paper. The nonlinear governing equations are reduced to a set of linear equations at different orders by using the perturbation method. The incident plane SH wave satisfies the zero‐order equations. The elastic waves generated by the nonlinear material region can be obtained by solving the first‐order equations, whose inhomogeneous terms can be regarded as the equivalent body forces and surface tractions. In the first‐order approximation, only the Lamb wave can be generated by the interaction of the SH wave with a region of quadratic material nonlinearity. In this paper, the analytical solution for the generated backward Lamb wave is obtained, whose amplitude varies with a material‐dependent constant linearly and with the length of the nonlinear region in the form of a sine function.
A study on nanoparticle transport in a micro blood vessel
Authors: Bavandi Mahrokh , Wünsch Olaf 
Published: November 2019

AbstractThis study focuses on the simulation of a nanoparticle loaded blood flow in a micro‐channel. The Euler‐Euler approach is used to describe the multi component behavior of blood. Nanoparticles are modeled by a concentration equation. The influence of the magnetic field gradient on particle transport is investigated for different Reynolds numbers.
On the influence of strain hardening on a rising bubble
Authors: Descher Stefan , Wünsch Olaf 
Published: November 2019

AbstractThis work deals deals with a constitutive approach that enables the independent modelling of shear and elongation behaviour. Studies are performed for a rising air bubble in a closed tank to investigate the influence of strain hardening on the shape of the bubble. It is shown that the occurrence of a cusp at the rear pole, which is well known to form in polymeric liquids, can be related to strain hardening only.
Effect of crystallographic orientation in modelling of anisotropic plasticity with an analytical yield function
Authors: Neuhaus Selina , Srivastava Kinshuk , Scholl Sebastian , Diebels Stefan 
Published: November 2019

AbstractThe mechanical properties of thermomechanical rolled low alloyed (TM) steels highly depend on their microstructure, which is formed during the production processes of the metal plate. Additionally, an elastic‐plastic anisotropy is encountered in these materials due to the texture of the ferritic grains. Hence, the material exhibits different stress‐strain curves in rolling direction (RD), normal direction (ND) and transverse direction (TD).The aim of the present work is to include plastic anisotropy of the body‐centered cubic, ferritic phase in an already existing microstructure‐based model for the elasto‐plastic deformation of TM steels and thereby, to widen the scope of such a model to a broader range of materials. The following contribution discusses the results of simulations on single crystals and bicrystals by using an analytical yield function in order to accomplish a deeper understanding of the behaviour and applicability of an analytical, anisotropic yield function on grain level to describe anisotropically deforming metals.
A fuzzy uncertainty model for analytical and numerical homogenization of transversely fiber reinforced plastics
Authors: Caylak Ismail , Penner Eduard , Mahnken Rolf 
Published: November 2019

AbstractThis work is directed to aleatoric and epistemic uncertainties in the framework of mean‐field and numerical homogenization, in order to determine the overall effective properties of transversely linear elastic fiber reinforced composite (FRC) which are taken into account by stochastic and fuzzy analysis. The stochastic part of material parameters is expanded with the multivariate polynomial chaos expansion, where for epistemic uncertainties the polynomial chaos coefficients are defined as design variables modeled as fuzzy sets. In this work, the combination of both types of uncertainty are treated with fuzzy‐random variables. Then, the fuzzy response for each selected α‐level is obtained from the minimum and maximum values of the quantity of interest (QoI). However, the QoI becomes a fuzzy‐random variable and depends on the design variables as well as the random variables. In order to avoid stochastic optimizations, so‐called surrogate QoIs are used, which can be described by ordinary and central moments. The representative example deals with a fuzzy‐random analysis of a unidirectional boron/aluminum FRC to demonstrate the versatility of the proposed formulation.
Reconstruction of Non‐Stationary Signals by the Generalized Prony Method
Authors: Keller Ingeborg , Plonka Gerlind , Stampfer Kilian 
Published: November 2019

AbstractWe derive a method for the reconstruction of non‐stationary signals with structured phase functions using only a small number of signal measurements. Our approach employs generalized shift operators as well as the generalized Prony method. Our goal is to reconstruct a variety of sparse signal models using a small number of signal measurements.
Variational Integrators and Fluid‐Structure‐Interaction at Low Reynolds‐Number
Authors: Kern Dominik , Groß Michael 
Published: November 2019

AbstractFor the special case of incompressible and highly viscous fluids, the interaction with a rigid body can be collected in a damping matrix, relating the velocities and angular velocities of the body with the fluid force and torque. This damping matrix (a.k.a. viscous resistance matrix) depends exclusively on the geometry and needs to be computed only once. We consider a rigid body moving in an unbound fluid. The generalized dissipative forces from the fluid onto the body enter the time discretization via the discrete D'Alembert Principle. As generally large rotations may occur, we chose quaternions for a singularity‐free description of the body orientation. The corresponding holonomic constraint of a unit quaternion is enforced on the position and momentum level by the RATTLE algorithm. The problem of Stokes drag on a sedimenting particle serves as an example.
Detailed simulations for flamelet modelling of SOx formation from coal
Authors: Wen Xu , Stein Oliver T. , Debiagi Paulo , Scholtissek Arne , Kronenburg Andreas , Kempf Andreas M. , Hasse Christian 
Published: November 2019

AbstractThis paper reports on recent progress in the modelling of pulverised coal flames. A brief review of current research on fully‐resolved and Euler‐Lagrange simulations in the context of flamelet modelling of pulverised coal combustion is given first. This is followed by more recent results from the flamelet modelling of SOx formation due to fuel‐S in pulverised coal flames.
On the approximation of surface elasticity theory by means of phase‐field theory
Authors: Lammen Henning , Mosler Jörn 
Published: November 2019

AbstractWithin surface elasticity theory originally proposed by Gurtin and co‐workers ( [1]), effects associated with surface tension are naturally captured. In this paper, surface elasticity theory is approximated by means of phase field theory, cf. [4] and [5]. The resulting approximation is employed in order to analyze the size effects induced by the coupling of bulk and surface energies. For that purpose, the phase field framework is compared to the underlying sharp interface model proposed in [2].
Low rank surrogates for fuzzy‐stochastic partial differential equations
Authors: Gruhlke Robert , Eigel Martin , Moser Dieter , Grasedyck Lars 
Published: November 2019

AbstractWe consider a particular fuzzy‐stochastic PDE depending on the interaction of probabilistic and non‐probabilistic (via fuzzy arithmetic in terms of possibility theory) influences. Such a combination is beneficial in an engineering context, where aleatoric and epistemic uncertainties appear simultaneously. The fuzzy‐stochastic dependence is described in a high‐dimensional parameter space, thus easily leading to an exponential complexity in practical computations. To alleviate this severe obstacle, a compressed low‐rank approximation in form of Hierarchical Tucker representation of the desired parametric quantity of interest is derived. The performance of the proposed model order reduction approach is demonstrated.