## FG Kontinuumsmechanik und Materialtheorie

27 Items

**Inverse analysis of metamaterials and parameter determination by means of an automatized optimization problem**

*Shekarchizadeh, Navid ; Abali, Bilen Emek ; Barchiesi, Emilio ; Bersani, Alberto Maria* (2021-01-08)

In this paper, a novel parameter determination technique is developed for material models in continuum mechanics aimed at describing metamaterials. Owing to their peculiar mechanical properties and behaviors, such as extreme elasticity or high strength‐to‐weight ratio, metamaterials are of interest to be simulated by reduced‐order modeling by means of the generalized mechanics. Such models inco...

**Additive manufacturing introduced substructure and computational determination of metamaterials parameters by means of the asymptotic homogenization**

*Abali, Bilen Emek ; Barchiesi, Emilio* (2020-10-30)

Metamaterials exhibit materials response deviation from conventional elasticity. This phenomenon is captured by the generalized elasticity as a result of extending the theory at the expense of introducing additional parameters. These parameters are linked to internal length scales. Describing on a macroscopic level, a material possessing a substructure at a microscopic length scale calls for in...

**Size effects of mechanical metamaterials: a computational study based on a second-order asymptotic homogenization method**

*Yang, Hua ; Müller, Wolfgang H.* (2020-11-10)

In this paper, size effects exhibited by mechanical metamaterials have been studied. When the sizescale of the metamaterials is reduced, stiffening or softening responses are observed in experiments. In order to capture both the stiffening and softening size effects fully, a second-order asymptotic homogenization method based on strain gradient theory is used. By this method, the metamaterials ...

**Thermo-mechano-chemical modeling and computation of thermosetting polymers used in post-installed fastening systems in concrete structures**

*Abali, Bilen Emek ; Vorel, Jan ; Wan-Wendner, Roman* (2020-11-01)

As thermoset polymers find frequent implementation in engineering design, their application in structural engineering is rather limited. One key reason relies on the ongoing curing process in typical applications such as post-installed adhesive anchors, joints by structural elements or surface-mounted laminates glued by adhesive polymers. Mechanochemistry including curing and aging under therma...

**Distances of stiffnesses to symmetry classes**

*Stahn, Oliver ; Müller, Wolfgang H. ; Bertram, Albrecht* (2020-07-23)

For a given elastic stiffness tetrad an algorithm is provided to determine the distance of this particular tetrad to all tetrads of a prescribed symmetry class. If the particular tetrad already belongs to this class then the distance is zero and the presentation of this tetrad with respect to the symmetry axes can be obtained. If the distance turns out to be positive, the algorithm provides a m...

**Experimental validation of computational fluid dynamics for solving isothermal and incompressible viscous fluid flow**

*Abali, Bilen Emek ; Savaş, Ömer* (2020-08-11)

In order to validate a computational method for solving viscous fluid flows, experiments are carried out in an eccentric cylindrical cavity showing various flow formations over a range of R eynolds numbers. Especially, in numerical solution approaches for isothermal and incompressible flows, we search for simple experimental data for evaluating accuracy as well as performance of the computation...

**Effective strain gradient continuum model of metamaterials and size effects analysis**

*Yang, Hua ; Timofeev, Dmitry ; Giorgio, Ivan ; Müller, Wolfgang H.* (2020-08-28)

In this paper, a strain gradient continuum model for a metamaterial with a periodic lattice substructure is considered. A second gradient constitutive law is postulated at the macroscopic level. The effective classical and strain gradient stiffness tensors are obtained based on asymptotic homogenization techniques using the equivalence of energy at the macro- and microscales within a so-called ...

**Computation of brittle fracture propagation in strain gradient materials by the FEniCS library**

*Barchiesi, Emilio ; Yang, Hua ; Tran, C. A. ; Placidi, Luca ; Müller, Wolfgang H.* (2021-03-01)

Strain gradient continuum damage modelling has been applied to quasistatic brittle fracture within an approach based on a maximum energy-release rate principle. The model was implemented numerically, making use of the FEniCS open-source library. The considered model introduces non-locality by taking into account the strain gradient in the deformation energy. This allows for stable computations ...

**Experimental and theoretical studies of Cu-Sn intermetallic phase growth during high-temperature storage of eutectic SnAg interconnects**

*Morozov, Aleksandr ; Freidin, A. B. ; Klinkov, V. A. ; Semencha, A. V. ; Müller, Wolfgang H. ; Hauck, T.* (2020-09-18)

In this paper, the growth of intermetallic compound (IMC) layers is considered. After soldering, an IMC layer appears and establishes a mechanical contact between eutectic tin-silver solder bumps and Cu interconnects in microelectronic components. Intermetallics are relatively brittle in comparison with copper and tin. In addition, IMC formation is typically based on multi-component diffusion, ...

**Numerical and analytical studies of kinetics, equilibrium, and stability of the chemical reaction fronts in deformable solids**

*Morozov, Aleksandr* (2021)

In the present work, a chemical reaction between a solid and a diffusing constituent is considered. Many experimental observations show a coupling between mechanical stresses and the kinetics at a chemical reaction interface that propagates in a deformable solid. In general, two major processes control the chemical reaction: diffusion of a reactant through the reacted material and the consumpti...

**Commented translation of Erwin Schrödinger’s paper ‘On the dynamics of elastically coupled point systems’ (Zur Dynamik elastisch gekoppelter Punktsysteme)**

*Mühlich, Uwe ; Abali, Bilen Emek ; dell’Isola, Francesco* (2021-01-01)

The paper ‘Zur Dynamik elastisch gekoppelter Punktsysteme’ by Schrödinger (1914) does not seem to have attracted the attention that it deserves. We translate it into English here and we discuss its results in detail, with a view to its possible influence in the modern theories of generalised continua. The clever solution found, in terms of Bessel functions, by Schrödinger of the problem of the ...

**Variations in the length of day of the earth due to topographic core-mantle coupling in a stratified layer**

*Glane, Sebastian* (2021)

There is evidence that a stably stratified layer of fluid, which is not penetrated by the convective flow of fluid in the bulk of the outer core, is located below the Core-Mantle Boundary (CMB). The question considered in this thesis is whether such a layer also affects the core-mantle coupling. If so, minute variations in the Length of Day (LOD) can be explained by a core-mantle coupling mecha...

**ZnO/Nanocarbons‐Modified Fibrous Scaffolds for Stem Cell‐Based Osteogenic Differentiation**

*Xia, Yi ; Fan, Xin ; Yang, Hua ; Li, Ling ; He, Chao ; Cheng, Chong ; Haag, Rainer* (2020-08-19)

Currently, mesenchymal stem cells (MSCs)‐based therapies for bone regeneration and treatments have gained significant attention in clinical research. Though many chemical and physical cues which influence the osteogenic differentiation of MSCs have been explored, scaffolds combining the benefits of Zn2+ ions and unique nanostructures may become an ideal interface to enhance osteogenic and anti‐...

**Thence the moment of momentum**

*Müller, Wolfgang H. ; Rickert, Wilhelm ; Vilchevskaya, Elena N.* (2020-06-18)

Fifty years have passed since Truesdell's seminal paper on the origin and status of the balance for the moment of momentum was published in ZAMM. It is time to take stock: Important new developments in the theory of generalized continua with internal degrees of freedom and some fascinating fundamental applications need to be pointed out. Is there new evidence from classical papers regarding its...

**Kinetics and the Theoretical Aspects of Drug Release from PLA/HAp Thin Films**

*Macha, Innocent J. ; Ben-Nissan, Besim ; Müller, Wolfgang* (2017-11-15)

The theory of dissolution kinetics of gentamicin from polylactic acid-hydroxyapatite thin film composites is spotlighted with the combination of diffusion and polymer degradation modeling. The use of various mathematical models, characterizing diffusion, dissolution or/and erosion prevalence as well as a mix of dissolution-diffusion rate processes were employed in order to compare theory with e...

**Coupling and computation of electromagnetism and mechanics**

*Abali, Bilen Emek* (2019-09-04)

Accurate coupling of electromagnetism and mechanics is of interest in computations of transducers such as piezoelectric, pyroelectric, electromagnetic sensors and actuators. Balance equations in mechanics as well as the MAXWELL equations for electromagnetism have been established in science. However, if the coupling between these governing equations are necessary, several difficulties arise. He...

**Thin‐layer inertial effects in plasticity and dynamics in the Prandtl problem**

*Georgievskii, Dmitri V. ; Müller, Wolfgang H. ; Abali, Bilen Emek* (2019-10-23)

Especially in metal forming, large plastic deformation occurs in thin plates. The problem of compressing dies is analyzed to evaluate the spreading of a thin layer in between. The velocity of dies is a given function in time so that the kinematics of the process is known. This problem can be considered as a generalization of the classical Prandtl problem by taking inertial effects into account ...

**A note on couette flow of nematic crystals according to the Ericksen–Leslie theory**

*Rickert, Wilhelm ; Vilchevskaya, Elena N. ; Müller, Wolfgang H.* (2019-12-12)

In order to model the flow of nematic crystals, the theoretical framework according to Ericksen and Leslie is applied. The essentials of the theory are compiled and then specialized to Couette flow. The profiles for linear velocity and orientation angle will be computed and, in particular, we shall also study the rise in temperature due to viscous dissipation, which is frequently ignored by mec...

**Analysis and development of a monolithic computational approach for fluid–structure interaction by means of the finite element method**

*Piekny, Florian* (2019)

The phenomenon of fluid–structure interaction (FSI) appears in many engineering applications. Its computation allows to quantify the mechanical behaviour of both fluid and structure interacting with each other. For that purpose, appropriate field equations are specified for an incompressible, viscous fluid and a linear elastic solid. The domain movement is considered by utilizing the arbitrary ...

**A System for Retrieval and Incubation of Benthic Sediment Cores at In Situ Ambient Pressure and under Controlled or Manipulated Environmental Conditions**

*Jackson, Keith ; Witte, Ursula ; Chalmers, Stewart ; Anders, Erik ; Parkes, John* (2017)

The investigation of benthic biodiversity and biogeochemical processes in the deep sea is complicated by the need to conduct experiments at in situ pressures. Recovery of sediment samples to the surface without maintaining full-depth ambient pressure may damage the organisms that are of interest or cause physiological changes that could influence the processes being studied. It is possible to c...