Particle damping

Particle damping is the use of particles moving freely in a cavity to produce a damping effect. Particle damping is the use of particles moving freely in a cavity to produce a damping effect. Active and passive damping techniques are common methods of attenuating the resonant vibrations excited in a structure. Active damping techniques are not applicable under all circumstances due, for example, to power requirements, cost, environment, etc. Under such circumstances, passive damping techniques are a viable alternative. Various forms of passive damping exist, including viscous damping, viscoelastic damping, friction damping, and impact damping. Viscous and viscoelastic damping usually have a relatively strong dependence on temperature. Friction dampers, while applicable over wide temperature ranges, may degrade with wear. Due to these limitations, attention has been focused on impact dampers, particularly for application in cryogenic environments or at elevated temperatures. Particle damping technology is a derivative of impact damping with several advantages. Impact damping refers to only a single (somewhat larger) auxiliary mass in a cavity, whereas particle damping is used to imply multiple auxiliary masses of small size in a cavity. The principle behind particle damping is the removal of vibratory energy through losses that occur during impact of granular particles which move freely within the boundaries of a cavity attached to a primary system. In practice, particle dampers are highly nonlinear dampers whose energy dissipation, or damping, is derived from a combination of loss mechanisms, including friction and momentum exchange. Because of the ability of particle dampers to perform through a wide range of temperatures and frequencies and survive for a longer life, they have been used in applications such as the weightless environments of outer space, in aircraft structures, to attenuate vibrations of civil structures, and even in tennis rackets.