Particle Damping Applications

Abstract

Particle damping is a generalization of impact damping technology (also known as acceleration dampers), but also provide additional damping mechanisms when compared with other kinetic energy based vibration dissipation devices. Due to their inherent design simplicity, in recent years there has been considerable interest in this technology. Most of the reported results have been obtained empirically, however, recently there has been some activity in the construction of analytical/numerical models to simulate the energy dissipating performance of particle dampers. The work described in this paper documents experimental work and representative test results of various particle dampers used to suppress excessive vibration of cantilever type space structural subsystems of various sizes subjected to transient and steady-state vibratory disturbances. It is experimentally demonstrates that the performance of these devices are highly amplitude dependant. It is also experimentally shown that there are three distinct damping performance regions for transient type excitations. In addition to partially filled cavity particle dampers, other particle dampers are also investigated such as particles-in-ball and preloaded particle dampers. In its simplest form, a particle damper consists of a cavity box of various shapes and sizes that are partially filled with particles. Particles can be metallic, ceramic, polymeric, composite or a mixture of various materials. The particle size may vary from application to application and may vary from a few micro-inches to a tenth of an inch or more. The shape of the particles may be near spherical, cylindrical or irregular in shape. The shape, size and material of the particles will influence flow characteristics of the particles in the cavity. Other particle damper configurations are also experimentally studies. In one configuration a polymeric ball is partially filled with particles. The ball is then placed in a cavity that is secured to a vibrating structure. The vibration sets the ball in motion in the cavity. Since the ball is only partially filled with particles, any rolling action of the ball will set the particles in motion against one another and maintain a new surface level, similar to a fluid leveling itself to maintain equilibrium due to gravity. The ball will eventually collide with cavity walls thus functioning as an impact damper with additional frictional losses due to particle friction and other losses due to elastic/plastic deformation of particles and the polymeric material of the ball. In another application, the particles are placed in a confined elastic cavity such as a metallic bellows or a rubber tube and sealed at the ends. The elastic walls of the rubber tube will induce compressive forces on the particles as more and more particles are stuffed into the tube. The amount of particles in the elastic cavity will determine the amount of preload on the particles. Any bending action of the particle filled elastic tube will be accompanied with relative rubbing motion among the particles, thus dissipating energy by dry friction.