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Item type:Publication, Access status: without files , On the combination of pyrolysis and plasma to create Parylene C thin films(VDE Verlag, 2025); ; ; ; Pyrolysis for Parylene C deposition is a safe way to produce biocompatible hermetic thin films above 1 µm. For thin films below that thickness, the use of plasma is a well-researched process, but these films lack biocompatibility. With the combination of pyrolysis and Argon-plasma (30 W, 50 W), a new process was used to create Parylene C thin films and investigate thickness, Young’s Modulus, FTIR spectra, and the surface via SEM. The use of 50 W Argon-plasma shows an increase of thickness (1.6 µm) and Young’s Modulus (26.34 GPa) compared to pyrolysis (t=0.9 µm, E=7 GPa).Publicationtype: Conference Paper98 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Simulation-based design of hybrid particle dampers with application to flexible multibody systemsParticle damping technology is a passive damping technique used to reduce structural vibrations. Either containers attached to the vibrating structure or holes within the vibrating structure are filled with a granular material. By structural vibrations, momentum is transferred to the granular material causing granular interactions. By these interactions, energy dissipation occurs due to inelastic normal collisions and frictional losses. This reduces the structural vibration. Although particle dampers have already been applied to some technical applications, their wide industrial usage is still limited. The main reason for this is the nonlinear damping behavior of this technique and the multitude of influence parameters. Hence, the goal of this project is the development of a new design methodology in form of a toolchain for passive vibration damping of lightweight structures and machines using particle dampers. Thereby, using simulations that are verified by experiments, also a deeper understanding of the micro-mechanical processes in the dampers are obtained. This is crucial in the systematic design of particle dampers using numerical methods. Using the developed toolchain single particle damper units with predefined characteristics are developed which do not rely on a specific application. Hereby, hybrid approaches are used to increase the efficiency of the individual particle dampers. Hence, it is possible to extend particle dampers to a variety of very different applications.Publicationtype: Book part90 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Systematic design of particle dampers for transient vertical vibrationsA multilevel design toolchain is used for the development of particle dampers for vertical transient vibrating structures. Thereby various experimental tests and numerical models are combined. The design toolchain consists of three levels. The frst level deals with the micro-mechanical behavior of single particle–particle and particle–wall impacts. The resulting coeffcient of restitution is then used on the second level. Within, the second level the properties of vertical vibrated granular matters inside a container under harmonic motion are analyzed. The resulting motion modes and energy dissipation of the granular matter strongly depend on the excitation conditions, i. e. the excitation amplitude and excitation frequency. Multiple analytical formulations for the diferent motion modes, i. e. solid-like state and collect-and-collide motion mode, are derived to describe the energy dissipation within the particle damper. These analytical descriptions are in good agreement with numerical discrete element simulations. Finally, the third level of the design toolchain deals with designing a damper for a desired structure. The analytical formulations describing the energy dissipation within the particle damper are used to optimize a particle damper confguration for a simple beam-like structure undergoing a vertical transient vibration. The efciency of the optimized particle damper dissipation is proven experimentally.Publicationtype: Journal ArticleScopus© Citations 2 92 336 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Design of robust particle dampers using inner structures and coated container wallsClassical particle dampers suffer from their non-robust damping behavior, \ie they can only be efficiently applied to a specific frequency range and amplitude range. The reason for that is that particle motion, also called motion mode, and damper efficiency show a strong correlation. By changing particle or container properties the motion modes are shifted to other excitation conditions but their efficient range is not much affected. To increase the damping performance and robustness of particle dampers, two approaches are presented here by introducing new motion modes. Therefore, the particle dampers are analyzed experimentally using a shaker setup and numerically using the discrete element method. The first design approach uses inner structures inside the particle damper, manufactured by a 3D printer. The inner structures consist of different numbers of beams, placed perpendicular to the container moving direction. They lead to a much more robust damper as the transition between the motion modes gets smoother. For the second approach, the container walls are equipped with different soft polymers. In this way a new motion mode at low excitation intensities is observed, leading to a high efficiency possibly on a large excitation intensity range. For an easy calculation of the necessary wall's Young's modulus an analytical formula based on Hertz impact theory is derived.Publicationtype: Journal Article105 410 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Systematic design of particle dampers for passive vibration attenuationThe nonlinear damping behavior of particle dampers and the multitude of influence parameters hinder their wide industrial usage. Hence, the goal of this work is the development of a new design methodology in form of a toolchain enabling a systematic damper design. On that account, various numerical models and experimental tests are combined. The toolchain commences with investigations of the micro-mechanical behavior of single particle impacts, continues with analyzing the properties of vibrating granular matter inside different containers and ends with designing a particle damper for a desired vibrating structure. The good agreement of the experimental and numerical models and their efficiency for the damper design and dimensioning are demonstrated on multiple examples.Publicationtype: Doctoral Thesis235 3805 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Material and particle size sensitivity analysis on coefficient of restitution in low-velocity normal impactsIn many granular processes, impacts play a crucial role. These impacts are often described by the coefficient of restitution (COR). This COR does not only depend on impact velocity but also on the material pairing, the shape of impacting bodies, number of impacts, etc. This paper analyzes and compares the sensitivity of the COR for often seen material pairings metal–metal and metal–polymer. For experimental investigations, a steel sphere impacts different planar material probes in a defined manner, e.g., a sphere–wall contact is reproduced. While the metal–metal impacts show a significant dependency on impact velocity, the metal–polymer impacts show only little influence of the impact velocity. Also, repeated impacts onto the same spot have a significant influence on metal–metal impacts, while metal–polymer impacts are not affected. To gain insights not only about the macroscopic behavior of impacts but also about the microscopic behavior, finite element simulations are performed using an efficient 2D axisymmetric model and viscoelastic and elastic–viscoplastic material models. A good agreement between experiments and FEM simulations are achieved for the utilized material pairings. Then, the influence of the sphere’s size is studied. Afterward, a deeper look into the energy dissipation process during contact is investigated. Finally, the contact duration and normal force in the contact zone are studied experimentally.Publicationtype: Journal ArticleScopus© Citations 6 128 671 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Energy dissipation in horizontally driven particle dampers of low acceleration intensitiesThe energy dissipation in sinusoidally driven particle dampers is highly dependent on the motion mode of the particle bed. Especially, for applications of low acceleration intensity, i.e., acceleration amplitude below gravitational acceleration, only small energy dissipation rates are obtained so far, due to sticking of particles. Here, a new and more efficient design of particle dampers is introduced for such applications, whereby the focus is on horizontal vibrations. The proposed design makes use of the rolling property of spheres inside particle containers with flat bases. First, a cuboid container shape is studied. Two different motion modes are observed experimentally within this container shape. For low driving amplitudes, the particle bed is showing a scattered behavior resulting in a low damping efficiency. For high driving amplitudes instead, the rolling collect-and-collide state is observed resulting in much higher efficiency. Analytical descriptions for the energy dissipation are derived for both motion modes, being in good agreement with experimental measurements. It is obtained that the optimal working point of such dampers, i.e., the optimal stroke, is only depending on the filling ratio of the damper. Additionally, the optimal working point separates both motion modes. For lower strokes as the optimal one, the scattered state is observed, while for higher strokes the rolling collect-and-collide mode is seen. Sensitivity analyses are performed using the experimental setup and discrete element simulations. It is obtained that especially a low friction coefficient and a high particle radius are beneficial. On the other hand, a small tilt around the container’s longitudinal or pitch axis might significantly decrease the efficiency of the damper. Besides the cuboid container, the effect of a cylindrical container heading against gravity is analyzed. While the particle bed motion modes are only little influenced, the efficiency of the damper becomes independent of the excitation direction in the horizontal plane. Thus, such dampers could be applied to a large field of applications in mechanical and civil engineering.Publicationtype: Journal ArticleScopus© Citations 7 140 550 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Systematic design of particle dampers for horizontal vibrations with application to a lightweight manipulator(2021-10-13); ; ; Particle damping has become a favorable passive damping technique for lightweight structures, however, its complex dimensioning process hinder its wide use in technical applications. In this paper, a multilevel design tool chain is presented to enable a systematic design and dimensioning process of particle dampers. Thereby various numerical models and experimental tests are combined. This starts with investigations of the micro-mechanical behavior of single particle impacts. Continuing, with analyzing the properties of vibrated granular matters inside a container and ending with designing a damper for a desired structure. The good agreement of the models and their efficiency for the damper design and dimensioning are finally demonstrated on an elastic lightweight manipulator undergoing a horizontal, transient vibration. Using this design toolchain, a new and much more efficient damper design for low amplitude vibrations is introduced using the rolling attribute of spheres. By separating the particle damper into several layers, high damping of the elastic lightweight manipulator is achieved.Publicationtype: Journal Article75 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimal design of particle dampers for structures with low first eigenfrequency under forced vibrationRecently, the rolling attribute of spheres has been used to develop efficient particle dampers for horizontal low amplitude vibrations. As long as the particle container’s acceleration stays below the gravitational acceleration, this rolling effect of spheres can be used. Hereby, the estimation of the damper’s energy dissipation is accurately possible using analytical formulas. In this paper, the workflow for a systematic damper design for an underlying structure of low first eigenfrequency under forced vibration is presented. The analytical formulas describing the dampers energy dissipation are coupled to a modal reduced model of the utilized vibrating structure. Then an analytical expression for an optimal damper design is derived. Also, the calculation scheme to obtain the frequency response function of the system is presented. As application example, a simple beam-like structure is used, whereby its base point is subjected to a harmonic motion of variable frequency using a linear drive. The particle damper is mounted at the tip of the beam and its velocity is measured using a laser scanning vibrometer. Thus, the frequency response function is obtained experimentally. A good agreement between analytical and experimental obtained frequency response function is achieved for the optimized particle damper, validating the presented approach.Publicationtype: Conference PaperScopus© Citations 2 147 338 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Damping prediction of particle dampers for structures under forced vibration using effective fieldsParticle damping is a promising damping technique for a variety of technical applications. However, their non-linear behavior and multitude of influence parameters, hinder currently its wide practical use. So far, most researchers focus either on determining the energy dissipation inside the damper or on the overall damping behavior when coupled to a structure. Indeed, currently almost no knowledge exchange between both approaches occurs. Here, a bridge is build to combine both techniques for systems under forced vibrations by coupling the energy dissipation field and effective particle mass field of a particle damper with a reduced model of a vibrating structure. Thus, the overall damping of the structure is estimated very quickly. This combination of both techniques is essential for an overall efficient dimensioning process and also provides a deeper understanding of the dynamical processes. The accuracy of the proposed coupling method is demonstrated via a simple application example. Hereby, the energy dissipation and effective mass of the particle damper are analyzed for a large excitation range first using a shaker setup. The particle damper exhibits multiple areas of different efficiency. The underlying structure is modeled using FEM and modal reduction techniques. By coupling both parts it is shown that multiple eigenmodes of the structure are highly damped using the particle damper. The damping prediction using the developed coupling procedure is validated via experiments of the overall structure with particle damper.Publicationtype: Journal ArticleScopus© Citations 15 162 528