bluuebunny/crossref_metadata_2025_split huggingface dataset:
MHD flow of submerged jets behind the inlet disturbance
Authors: Krasnov Dmitry , Listratov Yaroslav , Belyaev Ivan , Kolesnikov Yuri , Sviridov Evgeny , Zikanov Oleg 
Published: March 2023

AbstractIn a broad variety of configurations in technology and industrial applications, the properties of liquid metal flows subjected to strong magnetic fields, are largely governed by the dynamics of coherent structures, known to settle several basic types, such as thin shear layers, forming near the walls or within the fluid domain, vortices extended along the field, or planar and round jets. In some cases, these structures are created by the design, like a submerged jet formed by a sudden expansion from the nozzle into a blanket channel, or jets formed behind some flow obstruction. In the other cases this may be due to instability and evolution of secondary structures, for example, descending and ascending jets appearing as a result of convective instability in blanket channels. In this study, we undertake an attempt to affect liquid metal flow via inlet disturbance formed by a simple rod placed along the magnetic induction lines. The disturbance can generate flat jets behind the rod and, furthermore, a sustainable flow of anisotropic vortical perturbations further downstream the flow. We seek to analyze the most important mechanisms of the flow dynamics and effects of magnetic field on the integral system properties of enhancing mixing, mass and heat transport for such flow. The most optimal regimes of vortex generation are found to be governed by the magnetic interaction parameter (Stuart number). The exact ratio of the optimal Stuart number is found to be in a range between 20 and 40, based on the channel double width as a characteristic size. The observed vortices attain quasi‐2D shape and exist at a length of dozens of duct calibers, being the strongest at higher flow rates. The obtained flow regimes and their turbulent properties are also found to resemble significant similarity to the results on quasi‐2D turbulence found in prior studies of channel and duct flows under spanwise magnetic field.
Thermo‐chemo‐mechanical modelling of a curing process combined with mean‐field homogenization methods at large strains
Authors: Lenz Peter , Mahnken Rolf 
Published: March 2023

AbstractNowadays, polymeric materials have several applications, where carbon and glass fibre‐reinforced composite materials, epoxy laminates and (nano‐)particle‐reinforced polymer structures are typical examples. Starting with an initial uncured state of the matrix, a mixture of resin and curing agent undergoes a polymerization process which cures the matrix to a solid material. The curing process is highly temperature dependent and influences the mechanical, thermal and chemical properties of a composite strongly. There are different options to treat such an inhomogeneous material. One option are the semi‐analytical mean‐field homogenization methods. Mean‐field homogenization methods are originally developed for linear elastic materials. To account for non‐linear materials a special treatment is needed. A mean‐field homogenization framework is derived for constitutive multiscale (micro‐meso‐macro) modelling of a coupled thermo‐chemo‐mechanical problem. The macroscale represents a homogeneous material, whereas the mesoscale is decomposed into a polymer based material and inclusions. The microscale represents a step‐growth polymerization mechanism, modelled as a system of multiple growing spheres decomposed into a solid, resin and curing agent material phase. A numerical example shows the capability of the presented framework.
Dynamic fracture with a continuum‐kinematics‐based peridynamic and a phase‐field approach
Authors: Friebertshäuser Kai , Thomas Marita , Tornquist Sven , Weinberg Kerstin , Wieners Christian 
Published: March 2023

AbstractThe notion of dynamic fracture with continuum‐kinematics‐based peridynamics is presented in this work. A geometrically precise version of peridynamics called continuum‐kinematics‐based peridynamics adds surface‐ or volume‐based interactions to the traditional peridynamic bonds, accurately capturing the finite deformation kinematics. The point families produced from the horizon of the material points are used to construct the surfaces and volumes taken into account for these non‐local interactions.In continuum kinematics‐based peridynamics, the traditional bond‐stretch damage technique is insufficient for fracture. Due to the loss of strength in the internal force densities of the material points, it is now extended to the surface‐ and volume‐based interactions by new failure factors. Numerical examples demonstrate that the proposed approach effectively manages crack propagation, impact damage, and spontaneous crack initiation under dynamic loading circumstances with large deformations. When the results are compared to phase‐field calculations, there is a remarkable agreement concerning the damage patterns.
A particle‐continuum coupling method for amorphous polymers with multiple particle‐based domains
Authors: Torres Huamani David , Zhao Wuyang , Pfaller Sebastian 
Published: March 2023

AbstractThis contribution presents a partitioned‐domain particle‐continuum coupling method for amorphous polymers with multiple particle‐based domains. The coupling method treats the particle‐based domains with molecular dynamics (MD) simulations and the continuum domain discretized by the Finite Element (FE) method. In the continuum domain, a viscoelastic‐viscoplastic (VE‐VP) constitutive model derived from MD simulation results of the polymer at molecular resolution is employed. The effects of the minimum distances between the domains, the distribution and the number of the MD domains as well as the strain rates are studied under uniaxial tension. This method is a precursor for multiscale simulations of polymer‐based nanocomposites (PNC).
Parametric Stability Score for Local Solutions of Constrained Parametric Nonlinear Programs
Authors: Mykhailiuk Ivan , Büskens Christof 
Published: March 2023

AbstractNonlinear optimization problems arise in the context of many engineering processes and other real‐world applications. Depending on the complexity of modeled phenomena and constraints, such problems can feature multiple local solutions of different nature. Primarily, the quality of a solution is measured by the value of an objective function, and hence, one aims to find a global optimum. In many cases, however, additional criteria arise. For instance, nonlinear programs, in addition to decision variables, might depend on parameters undergoing perturbations. Such disturbances might be caused by noisy measurement data, changes in the environment in a real‐time setting or other factors. In this case, apart from good optimality, a practitioner might be interested in the behaviour of a solution under changes in parameters. Recently, the parametric stability score was introduced as a quality measure for solutions of unconstrained problems with respect to the influence of parameter perturbations. In this paper, we extend the concept to constrained optimization problems. The score is defined as the largest magnitude of a perturbation for which the perturbed solution does not deviate from the nominal one beyond an allowed tolerance. Our work is based on the results of parametric sensitivity analysis. This framework enables us to give a formal definition of the parametric stability score and provides tools for its efficient numerical approximation. We illustrate the approach with an example and discuss possible application scenarios for the concept.
A phase field model for fractures in ice shelves
Authors: Sondershaus Rabea , Humbert Angelika , Müller Ralf 
Published: March 2023

AbstractIce shelves are large floating ice masses, that are formed when glaciers are becoming afloat at the margin of ice sheets. One dominating mass loss mechanism of ice shelves is calving, describing the detachment of icebergs at the front. Ice shelves stabilize inland ice glaciers due to buttressing. If the stabilizing effect of an ice shelf vanishes because of disintegration or thinning, the corresponding glacier accelerates resulting in sea level rise.To describe calving and disintegration of ice shelves, it is important to investigate fracture propagation in ice. A powerful method in fracture mechanics is the phase field method which is based on Griffith's theory. It approximates cracks in a diffuse manner by using a continuous scalar field. We propose a phase field fracture model for ice considering its characteristic material properties. The material behavior of ice depends on the considered time scales. On short time scales it behaves like a solid and while it acts like a fluid on long time scales, which classifies it as a viscoelastic material of Maxwell type. This has been verified by observations. The phase field method allows us to simulate typical fracture situations of ice shelves in Antarctica and Greenland.
Extension of the stimulus expansion model for photo‐thermo‐sensitive hydrogels
Authors: Mählich Daniel , Ehrenhofer Adrian , Wallmersperger Thomas 
Published: March 2023

AbstractThe stimulus expansion model uses the analogy of thermal expansion in order to model the mechanical swelling behavior of a polymer gel. In the current work, we present an approach to extend the stimulus expansion model for photo‐thermo‐sensitive hydrogels. We describe the swelling behavior by using the stimulus properties, in our case light, as input values and the volume change of the hydrogel as the result by physical coherences. Further, we consider the energy conversion from light into heat within the polymer gel, due to absorption by particles. This phenomenon is considered by an energy balance which depicts the energy input by applying Lambert‐Beer's law. for the absorption of light. By evaluating the energy balance, we can calculate the light dependent temperature increase of the thermo‐sensitive hydrogel. Afterwards, the hydrogel's swelling is modeled by using the thermal expansion analogy. This detailed description of the stimulus behavior allows to study a hydrogel composite without having specific experimental data for this certain combination, but for all the involved components. Furthermore, the time‐dependent stimulus behavior of the considered sample is shown. Based on this approach, the effect of light power variation, particle volume fraction variation and different ambient temperature is studied.
Influence of pore‐structure characteristics on the mechanical properties of open‐porous cellular materials
Authors: Aney Shivangi , Ratke Lorenz , Milow Barbara , Rege Ameya 
Published: March 2023

AbstractThe influence of the pore structure characteristics on the macroscopic mechanical properties of open‐porous cellular materials has been computationally investigated in this contribution. While the effects of the pore‐size distribution on the macroscopic mechanical response of open‐porous cellular materials have been studied previously, the investigations regarding the effects of the pore structure characteristics are relatively scarce. The pore walls of open porous cellular materials are often modelled as beams and the pore wall structure is assumed to have a constant cross section. Although this assumption is valid for a large class of materials, insights into the influence of this assumption on the calculations of the properties of those materials that exhibit a rather pearl‐necklace‐like pore wall morphology are described in this paper. On comparing the simulation results for a corrugated pore‐wall with that having a constant cross‐section, it is observed that the maximal stresses in the pore wall may differ significantly.
Preconditioning for the integration of a spatiotemporal pharmacodynamic system
Authors: Duintjer Tebbens Jurjen , Lanzendörfer Martin , Matonoha Ctirad , Papáček Štěpán 
Published: March 2023

AbstractWe address efficient modeling of the intracellular action of a drug binding to the nuclear pregnane X receptor. The binded complex enters the cell nucleus and acts on DNA, resulting in enhanced production of an enzyme which metabolizes, among others, co‐administered drugs. Pharmacodynamic modeling is traditionally based on a compartmental approach, which simplifies the complex processes in the human body through the definition of a small number of compartments representing organs, tissues, cells, cytoplasm or abstract units. Inside a compartment, the concentrations of all substances are assumed to be distributed homogeneously, i.e. there is no spatial dependence. They lead to a system of ODEs for the time‐dependence of the concentrations of the active substances. We will present an extension of a model from the literature for the action of the tuberculose‐drug Rifampicin. The extension consists of a first attempt to add spatial resolution for substances that are active in the cytoplasm. Spatial resolution can be benecifial to analyze important issues like, among others, local exceeding of toxic drug levels, delay of transport and drug‐drug interactions. We address efficient solution of the linear systems arising when numerically integrating the resulting PDE's and consider some preconditioning techniques based on properties of the underlying biochemical network.
Forerunners of the power iteration method in the 16th and 18th centuries
Authors: Ullrich Peter 
Published: March 2023

AbstractThe power iteration method for determining eigenvectors is usually credited to Richard von Mises (1883–1953) and Hilda Pollaczek‐Geiringer (1893–1973). But their 1929 article was declared a “Zusammenfassender Bericht” (= “Summary report”), not a research paper. It is therefore not surprising that this method or a least its basic ideas can already be found in several publications from mechanics, applied and even pure mathematics since the last decades of the 19th century.Special cases of the power iteration method are documented in even older texts. The first example is the algorithm that the constructor of astronomical clocks and globes Jost Bürgi (1552–1632) invented in the 1580ies for the approximation of values of the sine function. In the second text, of 1747, the organist, composer and music theorist Christoph Gottlieb Schröter (1699–1782) gave simultaneous approximations for the first 12 natural powers of the 12th root of 2 in order to divide a monochord according to the equal temperament scale.
A two‐surface damage‐plasticity model based on a Drucker—Prager yield criterion
Authors: Zhang Jian , Brepols Tim , Reese Stefanie 
Published: March 2023

AbstractA gradient‐extended two‐surface damage‐plasticity model based on a von Mises yield criterion has been proposed by [1, 2], which can be flexibly adapted to (quasi‐)brittle‐like, ductile‐like, or various material behaviors in between. However, the von Mises yield criterion does not take into account the effect of hydrostatic pressure, therefore it can hardly model the failure behavior of pressure‐sensitive materials such as geomaterials and some metals. For this reason, a pressure‐dependent two‐surface damage‐plasticity model based on the Drucker‐Prager yield criterion is proposed in the current work, and the nonlinear hardening is also included. Plasticity and damage are treated as distinct but coupled dissipative phenomena by a two‐surface approach. Furthermore, the numerical implementation of the Drucker‐Prager yield criterion is discussed in this study, and the return mapping procedures of the smooth portion and the vertex of the cone are discussed in detail.
Averaging techniques for microstructures with localization bands due to damage progression
Authors: Simon Jaan-Willem , Poggenpohl Lukas , Holthusen Hagen 
Published: March 2023

AbstractIn multiscale analysis, homogenization methods are needed to up‐scale the micromechanical response obtained from investigating the underlying microstructure to the next higher scale. The standard homogenization schemes are based on volume averaging over the entire microstructure following Hill's approach, which requires that the virtual energies generated on the two involved scales equalize. However, these standard homogenization schemes are not applicable to softening phenomena due to localization, and representativeness of the considered microscale volume is lost. One way to overcome these drawbacks is to perform the volume averaging only within the localizing failure zone. Thereby, representative results can be achieved even in the softening region. In this paper, we apply the failure zone homogenization approach to both, mode I and mode II loading scenarios, as well as mixed‐mode loading of long fiber reinforced plastics. For an accurate description of material failure within the epoxy matrix, a scalar damage model at large strains with gradient enhancement is used, such that the obtained results are mesh‐independent. As a result, we show that for all considered cases representative volume element (RVE) sizes can be determined by using the failure zone homogenization scheme. Nevertheless, the energy distributions of all involved mechanisms have to be considered carefully in order to allow generalizations.
Consideration of nonlinear multipoint constraints in finite element analyses based on a master‐slave elimination scheme operating at the global level
Authors: Boungard Jonas , Wackerfuß Jens 
Published: March 2023

AbstractA method to consider nonlinear multipoint constraints in finite element analysis based on a master‐slave elimination scheme operating at the global level is presented. We focus on systems with nonlinear constraints in which the number of constraints is of the same order of magnitude as the number of degrees of freedom. Therefore, we rely on the master‐slave elimination which gives us the huge benefit of drastically reducing the problem size. In the literature the presented master‐slave elimination schemes for linear constraints are based on the manipulation of the system equations (global level), but the master‐slave elimination schemes for nonlinear constraints are based on manipulation of the element formulation (local level). In contrast to that we use a global approach for which the nonlinear constraints are applied directly on the system equations in analogy to linear constraints. Thus, the method is independent of the underlying element formulation and the type of constraints which makes it more flexible.
Numerical modelling of stress‐strain response and deformation‐induced martensite in metastable austenitic stainless steels under monotonic tensile loading
Authors: Thammineni Hari Kisan , Zhu Tong , Smaga Marek , Beck Tilmann , Müller Ralf 
Published: March 2023

AbstractA constitutive model describing the deformation‐induced martensite transformation in metastable austenitic CrNi steels is presented. In line with the previous work of Stringfellow et al. [1], the material is considered to have a composite response of the underlying austenite and the evolving martensite phases. The stresses and strains in the individual phases are described using viscoplastic models. The effective properties of the material are then computed by a homogenization method. Strain hardening in the individual phases is represented using separate flow rules. Furthermore, based on the plastic strain in the austenitic phase, a transformation kinetics model describes the evolution of the martensite volume, in the two‐phase composite.A numerical implementation of the model is done in the finite element program FEAP [2]. The parameters in model are identified by experimental data using the least‐squares optimization. Finally, some results are presented using an illustrative boundary value problem of a structured surface.
A phenomenological model to describe cracking and fibre pull‐out in ultra high‐performance fibre reinforced concrete
Authors: Gietz Lena , Kowalsky Ursula , Dinkler Dieter 
Published: March 2023

AbstractIn ultra‐high performance concrete (UHPC) embedded micro steel fibres increase the ductility and improve the post cracking load‐bearing behaviour under tensile loading. For an efficent and economical dimensioning of components, especially for fatigue susceptible structures, it is necessary to characterise the crack‐bridging load‐bearing effect of the micro steel fibres and the associated processes taking place in the intersection between both material components. Thus, the development of model equations to predict the deformation and damage behaviour of UHPFRC with numerical simulations on the macro‐level is very useful. In the contribution, a material model, which describes the phenomenological damage processes of the composite material, is presented. The numerical realisation with the finite element method applies a hybrid‐mixed element formulation, where a direct coupling with the material model is performed. Numerical studies of the material behaviour of UHPFRC are presented by means of an illustrative example.
Methods of Model Order Reduction for Coupled Systems Applied to a Brake Disc‐Wheel Composite
Authors: Matter Fabian , Iroz Igor , Eberhard Peter 
Published: March 2023

AbstractIn this contribution, investigations on model order reduction for coupled systems composed from components of a passenger car are shown. In today's development processes, the simulation of mechanical components is indispensable and large Finite Element models are often used for this purpose. For the calculation of time‐domain or frequency‐domain analyses, for example, a lot of computing power is required. However, with the application of model order reduction methods, this effort can be reduced, but this results in a trade‐off between the reduction error and the computational time. Since the computation of reduction bases for complete systems can be computationally expensive, it is of interest to be able to reduce components individually and then assemble them into a reduced overall model. This can result in both, a saving of computational effort when creating the bases, as well as a saving of the required memory space. Furthermore, there are many possible combinations of components in the modular systems of today's automotive industry, which emphasizes the model order reduction by parts and not by assemblies. In this work, methods of model order reduction for coupled systems are presented and will be tested on components in the chassis of a sports car. Therefore, an assembly consisting of a brake disc and wheel rim together with the wheel hub are investigated. For this purpose, the eigenmodes and transfer functions of the overall model, the reduced overall model and the assembly built from individual reduced bodies are compared.