Abstract

Particle dampers are a promising approach for passive reduction of vibrations over a wide frequency range. With additive manufacturing, it is possible to manufacture parts with embedded powder cavities. In previous investigations of additive manufactured particle dampers, the non-linear damping behavior was determined experimentally. The dynamic behavior of the metallic powder in the cavity is unknown. The goal of this thesis is to determine the dynamic behavior of the internal powder in an additive manufactured particle damper. The research questions are: • How can the energy dissipation of powder be characterized? • In addition, what are the main dependencies for the product development of additive manufactured particle dampers? In this thesis, the dynamic behavior of the stainless steel CL 20ES powder is modeled with the Discrete Element Method. The Discrete Element Method is a numerical method for simulation of particle motions and particle interactions. Due to the powder material used, which has particle sizes in the micrometer range and a high number of particles per volume, it is only possible to perform this investigation on scaled cavities in the millimeter range. The dynamic behavior of the powder is determined under harmonic base excitation of the cavity. The calculation of the energy dissipation is based on the reaction forces of the powder on the cavity. This work examines the influence of different cavity sizes, cavity shapes, excitation amplitudes and frequencies on the energy dissipation. The investigation shows that powder in cavities leads to high-energy dissipation under dynamic vibration. Due to this, it is an effective concept for passive reduction of vibrations. Additive manufactured particle dampers have a similar mechanism of energy dissipation as single particle impact dampers or vibration absorbers. The energy dissipation is caused by the inelastic collision between particles and cavity. The efficiency of the particle damper is only achieved when the excitation amplitude is large enough. The minimal required amplitude depends on the amount of particles in the cavity and on the cavity size. The simulation results provide a better understanding of the particle damping mechanisms, which may help in the design of the next generation of additive manufactured particle dampers. It can be said that (i) more powder leads to more energy dissipation, (ii) the powder should be positioned in the place with maximum amplitude to achieve greater energy dissipation and (iii) that the cavity length in the direction of movement has a more positive influence on the energy dissipation than the cross section in the direction of movement.