Inst. Mechanik

214 Items

Recent Submissions
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...

Evaluation of rapeseed varieties using novel integrated fuzzy PIPRECIA – Fuzzy MABAC model

Nedeljković, Miroslav ; Puška, Adis ; Doljanica, Suzana ; Jovanović, Saša Virijević ; Brzaković, Pavle ; Stević, Željko ; Marinkovic, Dragan (2021-02-25)

Decision making is constantly present in agriculture. Choosing the wrong variety carries the risk that the investment in terms of sowing does not pay off at all. Therefore, it is necessary to choose the variety that gives the best results. In order to achieve this, it is necessary to apply multi-criteria decision-making of available varieties, which is, in this paper, done on the example of hyb...

Influence of Chemical Heterogeneity and Third Body on Adhesive Strength: Experiment and Simulation

Lyashenko, Iakov A. ; Li, Qiang ; Popov, Valentin L. (2021-03-24)

We investigate experimentally and numerically the influence of chemical heterogeneity and of third-body particles on adhesive contact. Chemical heterogeneity is generated by chemical treatment of the contacting bodies changing locally the surface energy. For studying the influence of the third body, two types of particles are used: sand particles with various geometrical shapes and sizes, and s...

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...

Editorial: Contact Mechanics Perspective of Tribology

Goryacheva, Irina G. ; Paggi, Marco ; Popov, Valentin L. (2021-03-19)

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Artificial neural network modeling of sliding wear

Argatov, Ivan I. ; Chai, Young S. (2021-04-01)

A widely used type of artificial neural networks, called multilayer perceptron, is applied for data-driven modeling of the wear coefficient in sliding wear under constant testing conditions. The integral and differential forms of wear equation are utilized for designing an artificial neural network-based model for the wear rate. The developed artificial neural network modeling framework can be ...

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 ...

Synovial Joints. Tribology, Regeneration, Regenerative Rehabilitation and Arthroplasty

Popov, Valentin L. ; Poliakov, Aleksandr M. ; Pakhaliuk, Vladimir I. (2021-02-02)

Synovial joints are unique biological tribosystems that allow a person to perform a wide range of movements with minimal energy consumption. In recent years, they have been increasingly called “smart friction units” due to their ability to self-repair and adapt to changing operating conditions. However, in reality, the elements of the internal structure of the joints under the influence of many...

Calculation for High Pressure Behaviour of Potential Solar Cell Materials Cu2FeSnS4 and Cu2MnSnS4

Küllmey, Tim ; González, Miguel ; Heppke, Eva M. ; Paulus, Beate (2021-02-02)

Exploring alternatives to the Cu2ZnSnS4 kesterite solar cell absorber, we have calculated first principle enthalpies of different plausible structural models (kesterite, stannite, P4¯ and GeSb type) for Cu2FeSnS4 and Cu2MnSnS4 to identify low and high pressure phases. Due to the magnetic nature of Fe and Mn atoms we included a ferromagnetic (FM) and anti-ferromagnetic (AM) phase for each struct...

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...

Adhesion and friction in hard and soft contacts: theory and experiment

Popov, Valentin L. ; Li, Qiang ; Lyashenko, Iakov A. ; Pohrt, Roman (2021-01-29)

This paper is devoted to an analytical, numerical, and experimental analysis of adhesive contacts subjected to tangential motion. In particular, it addresses the phenomenon of instable, jerky movement of the boundary of the adhesive contact zone and its dependence on the surface roughness. We argue that the “adhesion instabilities” with instable movements of the contact boundary cause energy di...

Dynamic stiction without static friction: The role of friction vector rotation

Nakano, Ken ; Popov, Valentin L. (2020-12-10)

In the textbook formulation of dry friction laws, static and dynamic friction (stick and slip) are qualitatively different and sharply separated phenomena. However, accurate measurements of stick-slip motion generally show that static friction is not truly static but characterized by a slow creep that, upon increasing tangential load, smoothly accelerates into bulk sliding. Microscopic, contact...

Principios y aplicaciones de la mecánica de contacto en tribología, fricción y adherencia

Popov, Valentin L. (2020)

Este libro actualizado hasta 2019 sobre la mecánica del contacto es multidisciplinar y constituye una herramienta muy útil para los ingenieros, los físicos, geólogos y los investigadores en el campo de los materiales y los adhesivos. La existencia de una obra en castellano sobre esta temática constituye una novedad que abre el campo de trabajo de los hispano-hablantes a una disciplina raramente...

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 ...