bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of a magnetic pendulum in the presence of an oscillating conducting plate
Authors: Boeck Thomas , Sanjari Seyed Loghman , Becker Tatiana 
Published: January 2021

AbstractA pendulum with an attached permanent magnet moving near a conductor is a typical experiment for the demonstration of electromagnetic braking. When the conductor itself moves, it can transfer energy to the pendulum. We study a simple but exact analytical model where the conductor is a horizontally unbounded flat plate. For this geometry, eddy currents and induced Lorentz force due to the motion of a magnetic dipole are known analytically in the quasistatic limit. A vertical oscillation of such a horizontal plate located beneath the magnet is considered. In this setup, the vertical position of the pendulum is an equilibrium point when the magnetic moment of the magnet is perpendicular to its plane of motion. Depending on the strength of the magnetic dipole moment, the frequency and amplitude of the plate as well as the distance between plate and magnet, the plate oscillation can destabilize the equilibrium. The stability limits for weak electromagnetic coupling are computed analytically using the harmonic balancing method. For stronger coupling, the stability limits are obtained numerically using Floquet analysis. Chaotic motions with finite amplitudes are also found.
Study of Exploiting Coarse‐Grained Parallelism in Block‐Oriented Numerical Linear Algebra Routines
Authors: Kroiz Gerson C. , Bardakoff Alexandre , Blattner Timothy , Keyrouz Walid 
Published: January 2021

AbstractWe have developed streaming implementations of two numerical linear algebra operations that further exploit the block decomposition strategies commonly used in these operations to obtain performance. The implementations formulate algorithms as data flow graphs and use coarse‐grained parallelism to (1) emit a block in the result matrix as soon as it becomes available and (2) compute on multiple blocks in parallel. This streaming design benefits data flow graphs consisting of multiple linear algebra operations as it removes synchronization points between successive operations: a result block from an operation can be used immediately in an algorithm's successor operations without waiting for the full result from the first operation. Early comparisons with OpenBLAS functions on CPUs show comparable performance for computing with large dense matrices and an earliest arrival time of a result block that is up to 50x smaller than the time needed for a full result. More thorough studies can show the impact of such implementations on the performance of systems by chaining multiple linear algebra operations.
A multi‐scale fatigue‐damage model for fiber‐reinforced polymers
Authors: Magino Nicola , Köbler Jonathan , Andrä Heiko , Schneider Matti , Welschinger Fabian 
Published: January 2021

AbstractExperimental studies of Chebbi et al. [1] on fatigue loading of fiber‐reinforced polymers have shown that there is a phase of stable stiffness decrease prior to growing fatigue cracks. Modeling this stiffness degradation is an essential step in understanding fatigue effects of these materials.The constitutive behavior of short‐fiber reinforced polymers depends on numerous factors, such as fiber‐volume content, the aspect ratio of the fibers, the fiber‐orientation tensor and the loading direction. Accounting for these influence factors on a purely experimental basis is very time and resource demanding.As a remedy, we follow a multi‐scale approach for simulating the fatigue‐damage evolution in short‐fiber reinforced polymers. Using a simple damage model for the polymer matrix, the model inherently accounts for the influence of the fiber micro‐structure through homogenization. We show that the stiffness degradation predicted by this model is of anisotropic nature and depends strongly on loading direction and fiber‐orientation tensor.Due to its specific structure, the model permits a straightforward model‐order‐reduction strategy and can be efficiently employed for component‐scale simulations, see Köbler et al. [3].
Buckling analysis of elastically clamped laminated plates using third‐order shear deformation theory
Authors: Schreiber Philip , Mittelstedt Christian , Beerhorst Matthias 
Published: January 2021

AbstractThis paper considers the buckling of transverse shear‐deformable orthotropic laminated plates under uniaxial compression, which is modeled with the third‐order shear deformation theory (TSDT). The consideration of transverse shear deformation is relevant for plates with small transverse shear stiffness or small length to thickness ratio. The supporting effect of the surrounding structure is represented by laterally attached rotational restraints. The present analysis approach uses a simple energy‐based formulation in the form of a Rayleigh‐quotient for which specific shape functions for the out‐of‐plane buckling deformations as well as for the rotational degrees of freedom are employed. A comparison of the results with the Lévy‐type solution shows that the analysis approach works with satisfying accuracy, thus making it suitable for engineering analysis of plates with arbitrary thickness especially when computational time and effort are essential factors.
Revisiting Mindlin's theory with regard to a gradient extended phase‐field model for fracture
Authors: Makvandi Resam , Abali Bilen Emek , Eisenträger Sascha , Juhre Daniel 
Published: January 2021

AbstractThe application of generalized continuum mechanics is rapidly increasing in different fields of science and engineering. In the literature, there are several theories extending the classical first‐order continuum mechanics formulation to include size‐effects [1]. One approach is the strain gradient theory with the intrinsic features of regularizing singular stress fields occurring, e.g., near crack tips. It is crucial to realize that using this theory, the strain energy density is still localized around the crack tip, but does not exhibit any signs of a singularity. Therefore, these models seem to be appropriate choices for studying cracks in mechanical problems. Over the past several years, the phase‐field method has gathered considerable popularity in the computational mechanics community, in particular in the field of fracture mechanics [2]. Recently, the authors have shown that integrating the strain gradient theory into the phase‐field fracture framework is likely to improve the quality of the final results due to the inherent non‐singular nature of this theory [3]. In the present work, we will focus on a general formulation of the first strain gradient theory. To this end, the homogenization approach introduced in Ref. [4] is employed. It is based on a series of systematic finite element simulations using different loading cases to determine the equivalent material coefficients on the macro‐scale (i.e., for a strain gradient elastic material) by taking the underlying micro‐structure into account.
Towards a physiologically accurate ECG from numerical simulations: comparative analyses in a simplified tissue model
Authors: Ogiermann Dennis , Perotti Luigi E. , Balzani Daniel 
Published: January 2021

AbstractNumerical simulations of the human heart can guide medical doctors and researchers only if properly validated. This work presents a computational framework to validate mathematical models of cardiac electrophysiology at the tissue level. Specifically, we focus on the transmural wedge experiment as proposed by Antzelevitch in 1996. This experimental setup is easily reproduced and allows to probe key modeling assumptions and components before organ level simulations are performed. Our results highlight the need to further investigate the conductivity tensor, which, by modifying wave propagation, will affect the ECG morphology at the organ level.
Damage and failure mechanisms of ductile metals in biaxial experiments with non‐proportional loading paths
Authors: Zistl Moritz , Gerke Steffen , Brünig Michael 
Published: January 2021

AbstractThe paper deals with an experimental series and corresponding numerical simulations of the biaxial X0‐specimen to study the loading path dependence of ductile damage and fracture under non‐proportional loading. Experimentally the specimen surfaces have been monitored by digital image correlation (DIC). The experimental–numerical technique applied to the non‐proportional biaxial experiments provides new insights of the stress and load‐history dependent damage and fracture processes.
Adaptive Orientation of Exponential Finite Elements for a Phase Field Fracture Model
Authors: Olesch Darius , Kuhn Charlotte , Schlüter Alexander , Müller Ralf 
Published: January 2021

AbstractOne technique to describe the failure of mechanical structures is a phase field model for fracture. Phase field models for fracture consider an independent scalar field variable in addition to the mechanical displacement [1]. The phase field ansatz approximates crack surfaces as a continuous transition zone in which the phase field variable varies from a value that indicates intact material to another value that represents cracks. For a good approximation of cracks, these transition zones are required to be narrow, which leads to steep gradients in the fracture field. As a consequence, the required mesh density in a finite element simulation and thus the computational effort increases. In order to circumvent this efficiency problem, exponential shape functions were introduced in the discretization of the phase field variable, see [2]. Compared to the bilinear shape functions these special shape functions allow for a better approximation of the steep transition with less elements. Unfortunately, the exponential shape functions are not symmetric, which requires a certain orientation of elements relative to the crack surfaces. This adaptation is not uniquely determined and needs to be set up in the correct way in order to improve the approximation of smooth cracks. The issue is solved in this work by reorientating the exponential shape functions according to the nodal value of phase field gradient in a particular element. To be precise, this work discusses an adaptive algorithm that implements such a reorientation for 2d and 3d situations.
The Influence of ground inclination on the energy efficiency of a bipedal walking robot
Authors: Luo Yinnan , Römer Ulrich J. , Fidlin Alexander 
Published: January 2021

AbstractOne of the major tasks in developing bipedal walking robots is to improve energy efficiency of their locomotion. In this paper a method for extending this research by considering ground inclinations is introduced. The investigated robot is driven by electric motors in its revolute joints. Robot's gaits for different walking speeds are generated via numerical optimization, minimizing energy consumption during locomotion. Energy efficiency can be increased for differently inclined grounds where the robot utilizes its natural dynamics and gravity.
Probabilistic damage simulation for strengthening design of concrete structures
Authors: Molod Mohammad Amin , Barthold Franz-Joseph , Spyridis Panagiotis 
Published: January 2021

AbstractShape memory alloy (SMA) is a smart material that can be applied as an internal and external reinforcement of reinforced concrete flexural elements in order to increase ductility and strength of the members. Column‐beam joint is a critical section of a concrete structure which under seismic and unexpected heavy loads may lead to failure of entire of the structure. Therefore, this numerical investigation aims to increase strength and mitigate risk of failure of the joint by employment of SMA plate. To do so, an experimentally investigated joint under 1000 load combinations has been simulated in Ansys APDL. Each load combo contained two axial loads and one bending moment; load values have been randomly selected through a procedure in MATLAB. Some nodes in plastic hinge region of the joint were chosen as control points. Generated load values were applied in the simulation, and stress of the control nodes was recorded. This process continued for all 1000 combos. Then, obtained results were imported into MATLAB for a probabilistic analysis. Probability of 0.95 quantile of stress of each node was calculated in order to design the required plate thickness at each node. Some numerical examples were applied on the designed plate. Results demonstrated that the designed SMA plate gets the risk of failure from the joint away and increase strength of the joint.
Local Refinement in Isogeometric Analysis of Complex Tire Models
Authors: Israfilova Alina , Garcia Mario A. , Kaliske Michael 
Published: January 2021

AbstractThe capability of Non‐Uniform Rational B‐Splines (NURBS) to exactly represent conic sections exactly makes Isogeometric Analysis (IGA) an attractive alternative to classical Finite Element Method (FEM) for tire simulation. Application of NURBS as basis functions for geometry representation simplifies the generation of the computational mesh that can be directly obtained from the software for graphical design. NURBS‐based approximations of the field variables lead to higher convergence rates and allow higher continuity across the element boundaries. Moreover, the tensor structure of these functions permits the usage of additional advanced refinement techniques.The contribution at hand focuses on the application of hierarchically nested basis functions in tire analysis. The developed framework is based on the introduction of the global multilevel Bézier extraction operator [1]. This approach allows local refinement in the existing isoparametric FEM code without violating its architecture. Within the introduced framework, material models developed for standard FEM can be retained.Special attention is paid to the modelling of rebar elements within the framework of IGA and local refinement in particular. The from standard FEM adopted unconventional method avoids the drawbacks of smeared formulations common in tire numerical analysis and does not require an explicit definition of the reinforcing bars [2]. An additional check of the volumetric content of rebar in the material allows the compatibility of the employed concept with locally improved meshes.Numerical simulations for rolling tires using IGA are presented. The complex multilevel composite structure of tire‐models is obtained by means of CAD‐software. All simulations are performed under the consideration of steady‐state rolling within the Arbitrary Lagrangian‐Eulerian (ALE) description including finite deformations. A benchmark study of IGA and FEM for tire analysis closes this presentation.
Topology evolution of composite structures based on a phase field model
Authors: Wulf Jan Bernd , Muench Ingo 
Published: January 2021

AbstractThe composition of fibers and matrix is of great importance in several fields of engineering, such as steel reinforcement in concrete for civil engineering or lightweight applications in the automotive and aviation industry, as it allows combining the advantages of both materials. If the bond between fibers and matrix is ideally strong enough, the mechanical deformation can be assumed to be equal in both materials. With this assumption we set up a phase field model evolving the topology of reinforcement. The phase field parameter represents regions of reinforcement in the sense of averaged increased stiffness since we do not intend to simulate single fibers. A similar model but for topology optimization based on equivalent stresses was introduced by Muench et al. [1]. In many matrix materials, viscoelastic behavior is observed. Therefore, we also consider viscoelasticity in our model for the matrix.
A multifield computational model explains the underlying mechanisms of cortical malformations in the developing brain
Authors: Zarzor M. S. , Kaessmair S. , Steinmann P. , Budday S. 
Published: January 2021

AbstractThe convoluted macroscopic shape of the mammalian brain plays an important role for brain function. To date, the link between the cellular processes during brain development and normal or abnormal cortical folding remains insufficiently understood. In the early stages of development, progenitor cells divide symmetrically and asymmetrically in the inner layers of our brain. The newly generated neurons then migrate from the inner layers towards the outer surface to form the cortex. After about 20 weeks of gestation, the neuronal cells in the cortex start to interconnect, which causes a significant expansion of the outer brain layers. As this expansion is constrained by slower growing inner layers, compressive stresses emerge, which eventually induce mechanical instabilities and cortical folding. Disruption of cellular division, migration, or connectivity may lead to malformations of cortical development associated with neurological disorders like schizophrenia, autism, or epilepsy. Here we present a computational model describing cellular division and migration on the cellular scale, as well as growth and cortical folding on the tissue or organ scale, in a continuous way by a coupled finite growth and advection‐diffusion model. We introduce the cell density as independent field controlling the volumetric growth. This allow us to study the influence of the migration velocity, the cell diffusivity, the local stiffness, and the local connectivity of cells on the cortical folding process during normal and abnormal brain development numerically. We show how disrupted cell migration leads to a thickened cortex and the absence of normal folds in patients with the malformation lissencephaly. When calibrated using clinical data, the presented model can help to understand and diagnose neurological disorders arising from abnormal cellular development and cortical malformations.
A deep learning driven uncertain full‐field homogenization method
Authors: Henkes Alexander , Caylak Ismail , Mahnken Rolf 
Published: January 2021

AbstractThis work is directed to uncertainty quantification of homogenized effective properties of composite materials with a complex, three dimensional microstructure. The uncertainties arise in the material parameters of the single constituents as well as in the fiber volume fraction. They are taken into account by multivariate random variables. Uncertainty quantification is carried out by an efficient surrogate model based on pseudospectral polynomial chaos expansion and artificial neural networks, which is trained on a fast Fourier transformation based homogenization method. The numerical example deals with the comparison of the presented method to Monte Carlo‐type simulation for uncertain homogenization of spherical inclusions in a matrix material.
Forced harmonic vibrations of multi‐span Euler‐Bernoulli beams carrying spring‐damper‐mass systems
Authors: Klanner Michael , Ellermann Katrin 
Published: January 2021

AbstractA spring‐damper‐mass system can be used as a passive vibration absorber, which can reduce the vibration amplitudes of a system at certain frequencies or in a broad band. In this paper, a highly efficient computational method called Numerical Assembly Technique (NAT) is extended to vibration problems of beams under arbitrarily distributed loads carrying spring‐damper‐mass systems, to identify the optimal set of parameters of the passive vibration absorbers. The method is quasi‐analytical in the sense that the governing equations are fulfilled exactly and only minor numerical errors due to double‐precision arithmetic are introduced in the boundary and interface conditions.
Experimental investigations on rising bubbles in vertical capillaries
Authors: Grünendahl Sabrina , Brandner Dean Martin , Ehrhard Peter 
Published: January 2021

AbstractWe investigate how the walls of cylindrical capillaries affect the velocity of rising gas bubbles of various diameters. Of course, as the capillary diameter increases, the velocity of the rising bubble will approach the case of free rising. Such systematic experiments on bubble rise in capillaries, in which the ratio of bubble diameter and capillary diameter is varied from one towards smaller values, can hardly be found in literature. First orienting experiments within the system water/air have been conducted and will be discussed in this paper.
Projection Methods in Adaptive Isogeometric Analysis and its Application to Topology Optimization
Authors: Hennig Paul , Heindel Leonhard , Carraturo Massimo , Reali Alessandro , Auricchio Ferdinando , Kästner Markus 
Published: January 2021

AbstractIn this contribution, we apply adaptive isogeometric analysis to a phase‐field model for topology optimization. To increase the efficiency of the computation, we perform local mesh refinement and coarsening between the time increments of the simulation. To provide a trial solution for the iterative solver of the next increment, state variables have to be transferred from the old to the new mesh. We therefore compare the application of a discrete least squares fit with an L2‐projection in well known two‐ and three‐dimensional benchmarks and analyze the influence of these methods on the quality of the results.
Ritz‐type surface homogenization: from atomistic to continuum surface models of copper despite imperfect bulk models
Authors: Kurzeja Patrick , Sievers Christian , Brendel Lothar , Mosler Jörn 
Published: January 2021

AbstractSurfaces possess mechanical features on smaller scales that stand out against bulk phases, e.g., scaling of stiffness, curvature‐dependence, surfactant control and anchoring‐induced anisotropy. Continuum properties for the respective scales are often derived from ab initio simulations. This scale‐bridging however bears conceptual challenges and we highlight three aspects for the example of pure copper. First, free surface atoms relax and alter the boundary region in terms of interatomistic distances and resulting initital stresses. Second, eliminating the influence of finite thickness on the two‐dimensional continuum surface can be achieved by different averages or limit definitions, not all being physically consistent. Third, the continuum model of the surface is usually coupled to a continuum model of the bulk, which causes an approximation error itself. However, the bulk phase can not be eliminated direclty from the examination and simple averaging may even mask the aforementioned influences on the surface mechanics. A thermodynamically sound parameter identification across the scales is hence required. We present a Ritz‐type modeling approach for surfaces that ensures energy equivalence between atmostic and continuum simulations. The influences of relaxation, finite thickness and bulk approximation are identified by a mismatch in the energy contributions and accounted for by using appropriate homogenization limits.
Experimental investigations of viscoelastic and ferroelectric heating in PZT–5H
Authors: Warkentin Andreas , Ricoeur Andreas 
Published: January 2021

AbstractThis contribution focuses on the separation of two effects causing a temperature change in experiments with electrically loaded ferroelectrics. These materials are often subjected to cyclic loading, where viscoelasticity prevails at lower electric fields, whereas dissipative heating by domain switching governs the heating above the coercive field. Different frequencies and load amplitudes are investigated experimentally.