bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐temperature torsion of aluminum bars
Authors: Piao Yinguang , Le Khanh Chau 
Published: November 2019

AbstractThis paper studies high‐temperature torsion of aluminum bars within the simplified thermodynamic dislocation theory that ignores the excess dislocations. Employing a small set of physics‐based parameters, we are able to fit experimental torque‐twist curves for five different twist rates. The thermal softening effect is shown to be essential at high twist rates.
High‐order shape functions for interior acoustics
Authors: Duvigneau Fabian , Duczek Sascha 
Published: November 2019

AbstractThe acoustic behavior of structures has lately been in the focus of industrial applications, due to the fact that the acoustic emission of a product is one major parameter which significantly influences the customer perception with respect to comfort and functionality. In this context, the numerical simulation of vibroacoustic problems needs to provide reliable information in order to be able to evaluate the acoustic behavior of new products already in an early stage of the product development cycle. With the help of a suitable simulation model expensive experimental studies can be reduced and acoustically improved designs can be developed. However, there are already commercial software tools available which offer the opportunity to solve coupled vibroacoustic problems. These tools are typically based on conventional low‐order finite element methods (h‐FEM) for solving the governing partial differential equations (PDEs) of the problem. In this contribution, the advantages of high‐order finite element methods, such as a possibly exponential rates of convergence, will be exploited. Based on this approach a similar accuracy compared to classical h‐FEM simulations using significantly less degrees of freedom (dof) can be achieved. Consequently, the computational time required for the analysis can be notably reduced for a given error threshold. Reducing the computational effort is of special importance when investigating complex structures of practical relevance. Even today, the overall efficiency of the simulation process is still an issue, despite the ever growing computational power. To exploit the described advantages, high‐order FEMs have to be extended to acoustical problems. In this contribution the developed high‐order simulation approach is discussed and the obtained results are compared to commercial finite element solutions focussing on the accuracy and the computational effort of the different approaches.
Size effect caused by excess dislocations in twisted micro‐wires
Authors: Le Khanh Chau , Piao Yinguang 
Published: November 2019

AbstractThis paper applies thermodynamic dislocation theory to simulate the torque‐twist curves of copper micro‐wires subjected to torsion. The size effect due to the pile‐up of excess dislocations is essential for wire's radii in micron range.
Efficient Simulations for Contamination of Groundwater Aquifers under Uncertainties
Authors: Litvinenko Alexander , Logashenko Dmitry , Tempone Raul , Wittum Gabriel , Keyes David 
Published: November 2019

AbstractAccurate modeling of contamination in subsurface flow and water aquifers is crucial for agriculture and environmental protection. Here, we demonstrate a parallel method to quantify the propagation of the uncertainty in the dispersal of pollution in density‐driven flow. We solve an Elder‐like problem, where we use random fields to model the limited knowledge on the porosity and permeability. The uncertain solution, mass fraction, is approximated via low‐cost generalized polynomial chaos expansion (gPCE). Parallelization is done in both the physical and parametric spaces.
Numerical Analysis of Vibration Patterns in Hydropower Units
Authors: Sperber Christian , Weber Wilhelm , Eberhard Peter 
Published: November 2019

AbstractEvery manufactured hydropower rotor shows some degree of unbalance and other imperfections that cause vibrations. In this contribution, a non‐linear dynamic model is used to calculate the lateral vibrations of vertical rotors in hydropower units due to generator unbalance and coupling misalignment. The vibrations are analyzed and distinguishing features are identified. Using the identified features, it is possible to diagnose the vibration cause from vibrational data for the described model. This can be done even when some model parameters like bearing properties are not known with high accuracy.
Logistic regression for potential modeling
Authors: Kost Samuel , Rheinbach Oliver , Schaeben Helmut 
Published: November 2019

AbstractRegression or regression‐like models are often employed in potential modeling, i.e., for the targeting of resources, either based on 2D map images or 3D geomodels both in raster mode or based on spatial point processes. Recently, machine learning techniques such as artificial neural networks have gained popularity also in potential modeling. Using artificial neural networks, decent results in the prediction of the target event are obtained. However, insight into the problem, e.g., about importance of specific covariables, is difficult to obtain. On the other hand, logistic regression has a well understood statistical foundation and works with an explicit model from which knowledge can be gained about the underlying problem. However, establishing such an explicit model is rather difficult for real world problems. We propose a model selection strategy for logistic regression, which includes nonlinearities for improved classification results. At the same time, interpretability of the results is preserved.
Perimetric blowing at the rear of a bluff body: consequences on the wake dynamics and drag reduction
Authors: Lorite-Díez Manuel , Jiménez-González José-Ignacio , Martínez-Bazán Carlos , Cadot Olivier , Pastur Luc 
Published: November 2019

AbstractIn a perspective of active flow control of the bistable wake of a square‐back Ahmed body, we show that the steady blowing through a perimetric slit at the rear of the body is not equivalent to a material rear perimetric cavity, the latter being able to suppress the bistable dynamics and symmetrize the wake flow, while the former cannot achieve any of the two targets, indicating that the steady perimetric blowing has no control authority on the symmetric unstable steady solution of the system.
Palmgren, Gaßner and the challenges of fatigue behavior of components at variable amplitudes
Authors: Wächter Michael , Hinkelmann Karsten , Esderts Alfons , Zenner Harald 
Published: November 2019

AbstractThe focus of this contribution is on the work of the German engineer Ernst Gaßner. He invented the first fatigue tests at variable amplitude loading and introduced the field of “Betriebsfestigkeit” to the engineering community.
A variational material model for shape memory alloys under thermal cycling
Authors: Waimann Johanna , Hackl Klaus , Junker Philipp 
Published: November 2019

AbstractDue to their special material behavior– namely the superelasticity as well as the one‐way and two‐way effect– shape memory alloys are very attractive materials for industrial applications. The solid/solid phase transformation between austenite and martensite is however accompanied by a formation of dislocations which influence the cyclic behavior of this special class of smart materials. For mechanical cycling, the formed dislocations favor the transformation from austenite to martensite and delay the reverse transformation. But for thermal cycling, they have the opposite effect and thus result in a decrease of the transformation temperature and in a delayed transformation from austenite to martensite.We present a material model which is able to show both effects and hence displays microstructural evolution for a mechanically and thermally cycled material. Based on the variational method of the principle of the minimum of the dissipation potential, we model the so called effect of functional fatigue by storage of the transformation history of the observed material. In addition to that and for numerical efficiency, we use an evolving orientation distribution function to account for the polycrystalline structure of shape memory alloys, see [2]. Finally, we present first numerical results which verify the micromechanical model's functionality.
A thermomechanical modelling framework for selective laser melting based on phase transformations
Authors: Guschke Isabelle , Bartel Thorsten , Menzel Andreas 
Published: November 2019

AbstractSLM (selective laser melting) is one of many processes belonging to the additive manufacturing sector, where a laser beam completely melts the particles of the manufactured part layer by layer. In contrast to common models, this framework is based on the minimisation of the free energy density where the phase transformation from powder to molten pool to re‐solidified material is modelled explicitly. The goal is to develop a more sophisticated model which is based on the material behaviour itself rather than on the use of temperature dependent material parameters. The following model is adapted from phase transformations in shape memory alloys, cf. [1]. With this at hand, more insight into the process is gained and the deformation as well as the residual stresses are predictable.
Multi‐dimensional Sum‐Up Rounding using Hilbert curve iterates
Authors: Manns Paul , Kirches Christian 
Published: November 2019

AbstractMixed‐integer optimal control problems can be reformulated by means of partial outer convexification, which introduces binary‐valued switching functions for the different realizations of a discrete‐valued control variable. They can be relaxed naturally by allowing them to take values in [0, 1]. Sum‐Up Rounding (SUR) algorithms approximate feasible switching functions of the relaxation with binary ones. If the controls are distributed in one dimension, the approximants are known to converge in the weak∗ topology of L∞. We show that this still holds true for controls that are distributed in more than one dimension if an appropriate grid refinement strategy that is coupled with a deliberate ordering of the grid cells is chosen. This condition is satisfied by the iterates of space‐filling curves, e.g. the Hilbert curve.
Continuum Limit and Homogenization of Stochastic and Periodic Discrete Systems – Fracture in Composite Materials
Authors: Lauerbach Laura , Neukamm Stefan , Schäffner Mathias , Schlömerkemper Anja 
Published: November 2019

AbstractThe limiting behaviour of a one‐dimensional discrete system is studied by means of Γ‐convergence. We consider a toy model of a chain of atoms. The interaction potentials are of Lennard‐Jones type and periodically or stochastically distributed. The energy of the system is considered in the discrete to continuum limit, i.e. as the number of atoms tends to infinity. During that limit, a homogenization process takes place. The limiting functional is discussed, especially with regard to fracture. Secondly, we consider a rescaled version of the problem, which yields a limiting energy of Griffith's type consisting of a quadratic integral term and a jump contribution. The periodic case can be found in [8], the stochastic case in [6,7].
Analytical investigation of the motion of lapping particles
Authors: Bilz Raphael , de Payrebrune Kristin M. 
Published: November 2019

AbstractLapping is a machining process that improves technical surfaces that require a high level of precision and accuracy. Smooth surfaces can be very important to avoid cracks in components exposed to high loads. During lapping, the workpiece is placed on the lapping plate with a complex relative movement between both parts. In the gap between both parts, the lapping fluid with abrasive particles is placed. The moving particles can deform or cut the material of the workpiece, and iteratively smooth its surface. With appropriate operating parameters, as fluid and particle material, size and proportion, very high quality surfaces can be achieved.To describe lapping processes, it is essential to understand the kinematics of the particles that influence the outcome of the manufacturing process, which can be accomplished by experiments, numerical studies and analytical approaches. Here we will investigate the kinematics of lapping particles analytically. Using a straightforward model, geometry‐dependent threshold values for the coefficient of friction can be found that significantly influence the system behavior. We expect that the findings will contribute to extending the knowledge of the underlying physics in the lapping process so that we can adapt it to specific requirements.
A Novel Two‐Step Model to Investigate Turbulent Gas Flows Shearing Thin Liquid Films
Authors: Bender Achim , Stroh Alexander , Frohnapfel Bettina , Stephan Peter , Gambaryan-Roisman Tatiana 
Published: November 2019

AbstractIn this work a two‐step model to investigate a thin liquid film sheared by a turbulent gas flow is presented. In a first step, a direct numerical simulation of the gas phase is conducted. The turbulent shear stress at the lower wall is stored and used as a boundary condition for the long‐wave evolution of the liquid film, which is calculated in a second step. Results show that the turbulent shear stress fluctuations have to be considered when evaluating turbulent‐two‐phase channel flows.
High‐performance modeling of concrete ageing
Authors: Habera Michal , Zilian Andreas 
Published: November 2019

AbstractLong‐term behaviour of concrete structural elements is very important for evaluation of its health and serviceability range. The phenomena that must be considered are complex and lead to coupled multiphysics formulations. Such formulations are difficult not only from physical perspective, but also from computational perspective.In this contribution attention to computational efficiency and effective implementation is payed. Presented model for concrete ageing is based on microprestress‐solidification (MPS) theory of Bazant [1], Kunzel's model for heat and moisture transport [2] and Mazars model for damage [3]. Ageing linear viscoelastic response, which is immanent to MPS theory and concrete creep, leads to ordinary differetial equation for internal variables solved for every quadrature/nodal point. Numerical structure of the finite element discretisation is examined. Few simplifications on physical model lead to a very efficient linear algebra problem for which standard preconditioned Krylov solvers are reviewed. In parallel, weak and strong scaling tests are performed. All results are produced within open‐source finite element framework FEniCS [4].These models are usually a basis for more involved thermo‐hygro‐chemo‐mechanical (THCM) models with migrating chemical species. It is anticipated, that presented results will help practitioners or other structural engineerers with the choice of suitable and efficient methods for long‐term concrete modeling.
Application of different plasticity models to PC/ABS blends within micromechanical approaches
Authors: Hund Jonas , Seelig Thomas 
Published: November 2019

AbstractRubber‐toughened thermoplastic polymers such as PC/ABS blends exhibit a non‐monotonic dependence of fracture toughness on composition, e.g. [6]. The key parameters determining the mechanical response of PC/ABS are the PC vs. ABS ratio and the rubber content in ABS. In this contribution, two micromechanical modeling approaches (single particle unit cell models, random representative volume elements) are considered to investigate this behavior. Thereby, different visco‐plasticity models are utilized to capture the specific deformation behavior of each phase. Computational studies of both micromechanical modeling approaches are compared to each other as well as to experimental data.
On phase field modeling in the context of cyclic mechanical fatigue
Authors: Schreiber Christoph , Kuhn Charlotte , Müller Ralf 
Published: November 2019

AbstractIn this work the phenomenon of cyclic fatigue is integrated within a phase field model for brittle fracture by means of an additional contribution in the internal energy formulation in order to achieve a dependency of the crack evolution on the number of load cycles. Results of numerical fatigue crack growth simulations are presented.
Coupled atomistic‐continuum simulation of the mechanical properties of single‐layered graphene sheets
Authors: Zheng Qige , Wackerfuß Jens 
Published: November 2019

AbstractThe purpose of this work is the multiscale modeling of a single‐layered graphene sheet. The model is divided into three parts. One is an atomistic domain which is simulated with the atomic‐scale finite element method (AFEM). Another is a continuum domain. In this domain, the mechanical properties are investigated by using a finite element based on a nonlocal continuum shell model with a high order strain gradient. To be exact, it is a 4‐node 60‐generalized degree of freedom (DOF) Mindlin–Reissner finite shell element with a second order strain gradient. In the third part, a new transitional finite element is developed for smoothing the transition between the atomistic domain and continuum domain.
Motivating the development of a virtual process chain for sheet molding compound composites
Authors: Görthofer Johannes , Meyer Nils , Pallicity Tarkes Dora , Schöttl Ludwig , Trauth Anna , Schemmann Malte , Hohberg Martin , Pinter Pascal , Elsner Peter , Henning Frank , Hrymak Andrew , Seelig Thomas , Weidenmann Kay , Kärger Luise , Böhlke Thomas 
Published: November 2019

AbstractThis contribution presents a physical process chain and the corresponding virtual process chain for sheet molding compound (SMC) composites. Here, focus lies on the physical process chain as a motivation for the virtual process chain as discussed in the authors' publication [1]. The key steps of the virtual process chain are the identification of initial and boundary conditions, the compression molding simulation, the mapping of data and the structural simulation. The so established virtual process chain is validated via experimental investigations on a demonstrator structure. Both, the predicted results of the compression molding simulation, as well as the results of the structural simulation are in good accordance with the experiments.
On the electro‐chemo‐mechanical modelling of stomach smooth muscle contraction
Authors: Klemm Lisa , Seydewitz Robert , Morales-Orcajo Enrique , Böl Markus 
Published: November 2019

AbstractDuring the ingestion of a meal the activation of smooth muscle cells (SMC) in the stomach wall lead to different types of contraction and relaxation processes, enabling the stomach to perform its main functions, which are the storage, mixing and transport of food. A three‐dimensional multi‐field and multi‐scale model of the gastric smooth muscle contraction is presented and its ability is tested in simulations performed on a tissue strip as well as on the whole organ.
An FFT‐based solver for brittle fracture on heterogeneous microstructures
Authors: Ernesti Felix , Schneider Matti , Böhlke Thomas 
Published: November 2019

AbstractThe description of material failure as an energy minimization problem, i.e., the Francfort–Marigo model, has been studied widely in recent years. The approximation of the crack surface as a phase field, i.e., smeared interface, enjoys great popularity, as it allows describing fracture as a set of partial differential equations. In numerical homogenization, FFT‐based solution methods have been established over the past two decades. Their purpose is to compute the overall response of a heterogeneous microstruture w.r.t. a macroscopic loading and can be applied to a variety of nonlinear materials. The benefits lie in a fast implementation and the possibility to use image data like CT‐scans as input without further need for meshing. Based on the results of the master thesis of the first author, we investigate phase field crack propagation on heterogeneous microstructures using FFT‐based solvers.
Lattice Boltzmann Simulation of the Dynamic Behavior of Solids
Authors: Reinirkens Thomas , Schlüter Alexander , Müller Ralf , Kuhn Charlotte 
Published: November 2019

AbstractThe Lattice Boltzmann Method (LBM) is a numerical method that is mainly used to simulate fluid flows but it can be applied to structural problems as well. In this work, different LBMs for solids subject to antiplane shear deformation are investigated with regard to their convergence and energy conservation behavior. In particular, the two‐dimensional models of Guangwu [1] and Chopard et al. [2] are analyzed. To compare the two models, the evolution of the total energy and theL2norm of a global error measure are analyzed.
A posteriori error analysis for the mixed Laplace eigenvalue problem: investigations for the BDM‐element
Authors: Bertrand Fleurianne , Boffi Daniele , Stenberg Rolf 
Published: November 2019

AbstractA posteriori error estimates for the mixed numerical approximation of the Laplace eigenvalue problem can be derived using a reconstruction in the standard

‐conforming space for the primal variable of the mixed problem. In the case of Raviart–Thomas finite elements of arbitrary polynomial degree the resulting error estimator constitutes a guaranteed upper bound for the error and is shown to be local efficient. This paper shows that the extension for the BDM‐element is not straightforward.
An experimental model for the analysis of energy dissipation in particle dampers
Authors: Meyer Niklas , Seifried Robert 
Published: November 2019

AbstractParticle damping is a very promising passive damping technique, however, it is still rarely used in technical applications due to its complex dimensioning. An experimental model is developed in order to investigate the energy dissipation of the dampers regardless of the underlying structure. The testbed consists of a particle box with a free‐free boundary condition which is excited by an acceleration controlled shaker. The loss factor and the energy dissipation are obtained via the complex power. The particle damper can be analyzed over a wide frequency and acceleration range. Different particle numbers are used showing the high potential of particle dampers for different excitation ranges.
Optimal Control and Asymptotic Analysis of the Cattaneo Equation
Authors: Blauth Sebastian , Andres Matthias , Pinnau René , Totzeck Claudia 
Published: November 2019

AbstractWe compare the classical Fourier model for heat transfer to the Cattaneo model for delayed heat transfer. In particular, we consider the asymptotic behavior of the Cattaneo model for a vanishing delay time in the context of an optimal control problem with tracking type cost functional. It is possible to rigorously prove that both optimal controls and states for this problem constrained by the Cattaneo equation converge to the respective optimal control and state of the problem constrained by the heat equation (cf. [1]). Here, we present a short overview of the topic as well as some numerical results for the limit process.
A Hashin‐Shtrikman type semi‐analytical homogenization procedure
Authors: Jaworek David , Gierden Christian , Waimann Johanna , Wulfinghoff Stephan , Reese Stefanie 
Published: November 2019

AbstractHeterogeneous materials are important for a vast amount of applications e.g. in automotive industry or in aerospace. For instance when producing components, it can be desired to use materials with a heterogeneous microstructure in order to achieve specific material properties. Thus, it is beneficial to take the materials' microscopic structure into account and couple its behavior to the macroscopic response. As multiscale methods (e.g. FE2, FE‐FFT) are computationally expensive, semi‐analytical homogenization procedures are investigated to account for the transition between different length scales. In this work, the focus lies on applying a Hashin‐Shtrikman type method to elasto‐plasticity.