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    Item type:Project, Access status: without files ,
    SPP 1897: Calm, Smooth and Smart - Novel Approaches for Influencing Vibrations by Means of Deliberately Introduced Dissipation: Subproject "Simulation-based Design of Calm Hybrid Particle Dampers with Application to Flexible Multibody Systems"
    Particle dampers are simply designed passive damping elements. Granular particles are embedded in a container attached to a vibrating structure or within holes embedded in the vibrating structure. Due to the structural vibrations momentum is transferred to the granular material and energy is dissipated due to inter-particle impacts and frictional effects. In the last decades there has been an increased interest in particle dampers. Particle damping is easy to apply even in already existing hardware and it has been shown that it can be at least as effective as other damping techniques. This effectiveness in dissipating energy is not restricted to a single frequency but exists over a broader frequency range which is not usual in conventional damping solutions. Moreover, particle dampers are highly adaptive with various forms and sizes and a variety of particle types and materials.Numerical and experimental analysis performed in the first project phase has shown that the vast portion of kinetic energy dissipation is due to impacts. Thus, the coefficient of restitution (COR) should be as small as possible to dissipate maximal energy. In order to allow the transfer of significant kinetic energy from the vibrating structure onto the particles, heavy metallic particles such as steel, brass or even tungsten are advantageous. For these materials FE simulation show that the COR is relatively high for inter-particle impacts, providing a limitation on the kinetic energy dissipation. Another major drawback of particle dampers using metallic particles is the generation of considerable noise due to impacts. There have been first attempts using particle dampers made of polymer particles, however due to their much lower particle weight their damping effect is smaller than using heavier metallic particles.The research objective is the further development of a new simulation-based design methodology for passive vibration damping of lightweight structures and machines using distributed particle dampers. Hereby this project aims to develop a completely new type of hybrid particle dampers. Thereby, additional design degrees of freedom are introduced by using two different types of materials to decouple in some extend the mass and the coefficient of restitution of the individual contacts. Hereby, a heavy metallic material should be paired with a viscoelastic material with high damping capability during dynamic loading. With this approach, a completely new design philosophy should be developed to obtain small particle dampers, which dissipate significant more energy than optimized homogenous particle dampers of comparable mass. As a side-effect it is also expected, that these hybrid particle dampers are significantly calmer than the classical particle dampers. 
      207
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    Item type:Project, Access status: without files ,
    Simulation-based design of passive vibration damping using distributed particle dampers with application to active flexible multibody systems
    Particle dampers are simply designed passive damping elements. Granular particles are embedded in a container attached to a vibrating structure or within holes embedded in the vibrating structure. Due to the structural vibrations momentum is transferred to the granular material and energy is dissipated due to inter-particle impacts and frictional effects. In the last decades there has been an increased interest in particle dampers. Particle damping is easy to apply even in already existing hardware and it has been shown that it can be at least as effective as other damping techniques. This effectiveness in dissipating energy is not restricted to a single frequency but exists over a broader frequency range which is not usual in conventional damping solutions. Moreover, particle dampers are highly adaptive with various forms and sizes and a variety of particle types and materials.Despite the efficiency of particle dampers which was demonstrated experimentally, so far they have been used only in few different engineering applications, mostly designed for a very specific system. This might be due to the fact, that the processes in the particle dampers are very complex and not fully understood yet. Also the design process is currently mostly based on experimental trial-and-error strategies.The research objective is the development of a new simulation-based design methodology for passive vibration damping of lightweight structures and machines using distributed particle dampers. By such a new simulation-based design methodology, which is in parts independent of the specific application, it will be possible to extend particle dampers to a variety of very different applications. This is especially of interest for lightweight systems where currently often efficient passive vibration damping methods are lacking. Firstly, independent of the application, it is aimed to develop small particle damper units with predefined characteristics. These individual particle dampers should form an assembly set, which is ultimately used in the overall damping concept for specific applications. Thereby, several of these particle dampers, possibly with different characteristics, should be distributed optimally over a flexible body in order to achieve a maximal damping efficiency over a wide range of frequencies and amplitudes. For numerical studies Discrete-Element-Method models and macro-models, which can be more easily integrated in flexible multibody systems, are developed. These models are the basis for the damper development. The numerical work is closely accompanied by experimental investigations. As motivation example the application of the developed methods on an active flexible multibody system is chosen.
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