Enhancing the dissipative properties of particle dampers using rigid obstacle-grids

Abstract

Particle dampers (PDs) are becoming a popular alternative to conventional damping devices due to their simple design and their ability to dissipate energy over a wide frequency range. The energy dissipation in PDs takes place due to relative motion between solid particles within the PD enclosure. The degree of relative motion depends on various parameters, especially it is highly sensitive to vibration amplitude changes. Usually, the particle size is much smaller than that of the PD enclosure which, under low forcing conditions, leads to sub-optimal momentum transfer and thereby leads to lower energy dissipation. In this work a new approach is investigated, in which a complex 3D rigid obstacle-grid is deliberately introduced inside the PD enclosure in order to overcome the shortcomings of a conventional PD. In order to better understand the influence of various dissipation mechanisms, simulations were performed. The Discrete Element Method (DEM) is used to model the interactions between the solid particles and their surroundings. In the simulations, the rigid obstacle-grid is described using a triangular surface mesh and to speed-up the collision detection process, efficient bounding volume hierarchy data structures were used. Moreover, laboratory experiments were set up to test the validity of the simulation models. The experimental setup consists of an electromagnetic shaker used to excite, via elastic elements, a clamped beam on which a PD with a rigid obstacle-grid is mounted. The obstacle-grid used in the experiments is manufactured using a Stereolithography 3D printer. Simulations and experiments were observed to be in good agreement. Moreover, the damping performance of a PD with a rigid obstacle-grid is observed to be at least twice as good as a conventional PD. Visual observations indicate that particles which would have otherwise been hardly contributing to energy dissipation, move violently due to an obstacle-grid, and hence actively participate in the energy dissipation process. Furthermore, a numerical study indicates that the obstacle-grid cell-size has a profound effect on the dissipation, allowing it to be used as an additional parameter to tune the damping performance of PDs.