@article{LangMonkman, author = {Lang, Alexander and Monkman, Gareth J.}, title = {An analysis of the electrical capacitance between two conducting spheres}, series = {Journal of Electrostatics}, volume = {108}, journal = {Journal of Electrostatics}, publisher = {Elsevier}, doi = {10.1016/j.elstat.2020.103518}, abstract = {Many modern composites consist of dielectric polymer matrices containing embedded spherical particles. These particles can be electrically conducting and often have magnetic properties. In order to accurately model and simulate such materials, precise calculation of the electrical capacitance between identically sized spheres is required. This is of particular relevance at microscopic dimensions where many smart material-based micro devices are concerned. This may appear trivial for a small number of particles. However, many methods or their analysis appear to be questionable or not applicable at reduced dimensions. In this work, the various methods of analysis are scrutinized before being compared with both simulation and direct measurements. It is surprising to note that of the many works investigated only 3 are in close agreement with both simulation and measurement. Graphical abstract This paper deals with the precise calculation of the electrical capacitance between two conducting spheres of equal, or near equal size.The calculations have been verified by both experimental measurements and simulation. Algorithms in MatLab (Octave) format have been included in the supporting information.}, language = {en} } @article{MetschSchmidtSindersbergeretal., author = {Metsch, P. and Schmidt, Henrik and Sindersberger, Dirk and Kalina, K. A. and Brummund, J. and Auernhammer, G{\"u}nter and Monkman, Gareth J. and K{\"a}stner, Markus}, title = {Field-Induced Interactions in Magneto-Active Elastomers}, series = {Smart Materials and Structures}, volume = {29}, journal = {Smart Materials and Structures}, number = {8}, publisher = {IOPscience}, doi = {10.1088/1361-665X/ab92dc}, pages = {1 -- 10}, abstract = {In this contribution, field-induced interactions of magnetizable particles embedded into a soft elastomer matrix are analyzed with regard to the resulting mechanical deformations. By comparing experiments for two-, three- and four-particle systems with the results of finite element simulations, a fully coupled continuum model for magneto-active elastomers is validated with the help of real data for the first time. The model under consideration permits the investigation of magneto-active elastomers with arbitrary particle distances, shapes and volume fractions as well as magnetic and mechanical properties of the individual constituents. It thus represents a basis for future studies on more complex, realistic systems. Our results show a very good agreement between experiments and numerical simulations—the deformation behavior of all systems is captured by the model qualitatively as well as quantitatively. Within a sensitivity analysis, the influence of the initial particle positions on the systems' response is examined. Furthermore, a comparison of the full three-dimensional model with the often used, simplified two-dimensional approach shows the typical overestimation of resulting interactions in magneto-active elastomers.}, language = {en} } @techreport{RankHeberlSterner, author = {Rank, Daniel and Heberl, Michael and Sterner, Michael}, title = {Die CO2-Bilanz der OTH [Ostbayerischen Technische Hochschule Regenburg]}, language = {de} } @article{RomeisKostrovKramarenkoetal., author = {Romeis, Dirk and Kostrov, Sergei A. and Kramarenko, Elena Yu and Stepanov, Gennady V. and Shamonin (Chamonine), Mikhail and Saphiannikova, Marina}, title = {Magnetic-field-induced stress in confined magnetoactive elastomers}, series = {Soft Matter}, volume = {16}, journal = {Soft Matter}, number = {39}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, doi = {10.1039/D0SM01337D}, pages = {9047 -- 9058}, abstract = {We present a theoretical approach for calculating the state of stress induced by a uniform magnetic field in confined magnetoactive elastomers of arbitrary shape. The theory explicitly includes the magnetic field generated by magnetizable spherical inclusions in the sample interior assuming a non-linear magnetization behavior. The initial spatial distribution of particles and its change in an external magnetic field are considered. This is achieved by the introduction of an effective demagnetizing factor where both the sample shape and the material microstructure are taken into account. Theoretical predictions are fitted to the stress data measured using a specifically designed experimental setup. It is shown that the theory enables the quantification of the effect of material microstructure upon introducing a specific microstructural factor and its derivative with respect to the extensional strain in the undeformed state. The experimentally observed differences between isotropic and anisotropic samples, compliant and stiff elastomer matrices are explained.}, language = {en} } @article{SnarskiiShamoninChamonineYuskevichetal., author = {Snarskii, Andrei A. and Shamonin (Chamonine), Mikhail and Yuskevich, Pavel and Savelev, Dmitrii V. and Belyaeva, Inna A.}, title = {Induced anisotropy in composite materials with reconfigurable microstructure: Effective medium model with movable percolation threshold}, series = {Physica A: Statistical Mechanics and its Applications}, volume = {560}, journal = {Physica A: Statistical Mechanics and its Applications}, number = {December}, publisher = {Elsevier}, doi = {10.1016/j.physa.2020.125170}, abstract = {In composite materials, with field-dependent restructuring of the filler material (changes in the mutual arrangement of inclusions), the presence of an external magnetic field induces anisotropy of the dielectric properties, even if the composite is isotropic in the absence of an external field. A modified effective medium approximation is proposed for the calculation of the components of effective permittivity within a class of composites with reconfigurable microstructure, where both phases (the filler and the matrix) are isotropic and the inclusions have spherical shape. The effective physical properties are calculated in the parallel and perpendicular directions to an applied field. The appearance of the anisotropy of the permittivity is simulated by the introduction of two not-equal, possibly variable (field-dependent) percolation thresholds. The implications, of the proposed theoretical approach, are demonstrated for the case of the dielectric properties of magnetoactive elastomers (MAEs). In MAEs with soft polymer matrices, the mutual arrangement of micrometer-sized magnetic inclusions can significantly change in an applied magnetic field. A reasonable agreement between theory and experiment at a measurement frequency of 1 kHz is found, and is improved in comparison to the previous models. The components of the effective permittivity tensor, characterizing the dielectric properties along the direction of the applied magnetic field and in the orthogonal direction, grow with an increasing field. This growth is more pronounced for the permittivity component in the field direction. The possible extensions of the theoretical model and future directions of research are discussed. The presented theoretical approach can be useful for the application-driven development of a number of smart materials, in particular electro- and magnetorheological gels, elastomers and fluids.}, language = {en} } @article{SavelevBelyaevaChashinetal., author = {Savelev, Dmitrii V. and Belyaeva, Inna A. and Chashin, Dmitri V. and Fetisov, Leonid Y. and Romeis, Dirk and Kettl, Wolfgang and Kramarenko, Elena Yu and Saphiannikova, Marina and Stepanov, Gennady V. and Shamonin (Chamonine), Mikhail}, title = {Giant extensional strain of magnetoactive elastomeric cylinders in uniform magnetic fields}, series = {Materials}, volume = {13}, journal = {Materials}, number = {15}, publisher = {MDPI}, address = {Basel}, issn = {1996-1944}, doi = {10.3390/ma13153297}, pages = {1 -- 17}, abstract = {Elongations of magnetoactive elastomers (MAEs) under ascending-descending uniform magnetic fields were studied experimentally using a laboratory apparatus specifically designed to measure large extensional strains (up to 20\%) in compliant MAEs. In the literature, such a phenomenon is usually denoted as giant magnetostriction. The synthesized cylindrical MAE samples were based on polydimethylsiloxane matrices filled with micrometer-sized particles of carbonyl iron. The impact of both the macroscopic shape factor of the samples and their magneto-mechanical characteristics were evaluated. For this purpose, the aspect ratio of the MAE cylindrical samples, the concentration of magnetic particles in MAEs and the effective shear modulus were systematically varied. It was shown that the magnetically induced elongation of MAE cylinders in the maximum magnetic field of about 400 kA/m, applied along the cylinder axis, grew with the increasing aspect ratio. The effect of the sample composition is discussed in terms of magnetic filler rearrangements in magnetic fields and the observed experimental tendencies are rationalized by simple theoretical estimates. The obtained results can be used for the design of new smart materials with magnetic-field-controlled deformation properties, e.g., for soft robotics.}, language = {en} } @article{SavelevBelyaevaChashinetal., author = {Savelev, Dmitrii V. and Belyaeva, Inna A. and Chashin, Dmitri V. and Fetisov, Leonid Y. and Shamonin (Chamonine), Mikhail}, title = {Large Wiedemann effect in a magnetoactive elastomer}, series = {Journal of Magnetism and Magnetic Materials}, volume = {511}, journal = {Journal of Magnetism and Magnetic Materials}, number = {October}, publisher = {Elsevier}, doi = {10.1016/j.jmmm.2020.166969}, abstract = {Large twists of a soft tube (hollow cylinder) in helical magnetic fields are presented for the first time. Such a phenomenon is usually denoted as the Wiedemann effect. The tube is fabricated from a soft magnetoactive elastomer material with the shear modulus of about 56 kPa. The composite material comprises 80 mass\% of micrometer-sized iron particles embedded into a polydimethylsiloxane matrix. The circular magnetic field is generated by an electric current in a straight wire passing through the inner hole of the tube. The maximum value of approximately 350″/cm is observed in a longitudinal magnetic field of a few kA/m overlapped with a circumferential magnetic field of about 1.4 kA/m on the surface of the inner hole. A pronounced hysteresis in the dependence of the Wiedemann effect on the circular magnetic field is found. The ways to enhance the Wiedemann twist in magnetoactive elastomers are discussed. The observed large effect is promising for application in magnetic-field controlled torsional actuators, in particular for soft robotics.}, language = {en} } @inproceedings{MuehlbauerRablRottengruber, author = {M{\"u}hlbauer, Christian and Rabl, Hans-Peter and Rottengruber, Hermann}, title = {Development of a Methodology for Acoustic Analysis and Optimization of Mechatronic Fuel Injection Systems}, series = {Automotive Acoustics Conference 2019: Proceedings, 5. Internationale ATZ-Fachtagung Fahrzeugakustik}, booktitle = {Automotive Acoustics Conference 2019: Proceedings, 5. Internationale ATZ-Fachtagung Fahrzeugakustik}, editor = {Siebenpfeiffer, Wolfgang}, publisher = {Springer Vieweg}, address = {Wiesbaden}, isbn = {978-3-658-27668-3}, doi = {10.1007/978-3-658-27669-0_15}, pages = {211 -- 225}, abstract = {To identify the sound quality of fuel injection systems as a frontloading measure, a system test bench has been developed that simulates the structure and airborne noise emission. The setup of the system test bench includes an assembly of the acoustical relevant engine parts and an encapsulated drive for the high-pressure pump. A specific control unit enables a high variability for the operation strategy of the injection system. The focus of this study is on the development of a methodology to analyze and optimize the sound quality of gasoline direct injectors in critical operation points by suitable active means. For this, the injection parameters in engine idle have been identified and subsequently transferred to the system test bench. Additionally, the injection parameters have been optimized acoustically and the impacts on the key functions regarding injection rating and shot-to-shot scattering of the injected fuel mass are discussed.}, language = {en} } @misc{SchwanzerDietrichGadereretal., author = {Schwanzer, Peter and Dietrich, Markus and Gaderer, Matthias and Rabl, Hans-Peter}, title = {Monitoring von Partikelfiltern f{\"u}r den Einsatz in Fahrzeugen mit direkt- einspritzenden Ottomotoren mit einer Radio-Frequenz (RF-) Antenne}, series = {Kolloquium des Bayerischen Wissenschaftsforum}, journal = {Kolloquium des Bayerischen Wissenschaftsforum}, language = {de} } @misc{AltmannRablGaderer, author = {Altmann, Robert and Rabl, Hans-Peter and Gaderer, Matthias}, title = {Ph{\"a}nomenologische Untersuchung des Einspritzverhaltens von Pflanzen{\"o}lkraftstoff}, series = {3. Tagung der Fuels Joint Research Group (FJRG) "Kraftstoffe f{\"u}r die Mobilit{\"a}t von Morgen"}, journal = {3. Tagung der Fuels Joint Research Group (FJRG) "Kraftstoffe f{\"u}r die Mobilit{\"a}t von Morgen"}, language = {de} }