Particle damping is the general name for a family of loss mechanisms that can occur when particles are placed in a container that is in or on a vibrating structure. Friction and impact interactions between the particles themselves and with the cavity walls can lead to appreciable increases in damping of the structure. CSA Engineering has several ongoing projects to develop numerical modeling capability and to examine the feasibility of using particle damping to address damping needs over extremely wide temperatures (up to 1000°F) and applied quasi-static accelerations (up to 60,000 G's).

The plot below compares the slopes (equivalent to damping) versus the amplitude or response of the first mode ring down of a test object with

• no added damping treatment (blue)
• with a single particle impact damper treatment (green)
• multiple particle damper treatment (red)

It is clear that both types of treatments (single and multiple particle) are nonlinear (i.e. damping varies with amplitude) but also that they can add significant damping. Single particle impact damping has the best results, but only over a very narrow operating amplitude range. Multiple particle damping has better performance over a wider range, and more importantly, at higher amplitudes where it is more likely that damping is desired. It is also interesting to note, that once below their regions of optimal performance, both types of treatments return to the nominal baseline undamped performance at low amplitudes.