SUMMARY

Particle impact dampers (PIDs) or shot mass dampers are known to provide high loss factors on vibrating structures by dissipating kinetic energy through particle-enclosure and particle-particle collisions. The rate of energy dissipation is amplitude dependent, which makes the particle damping highly nonlinear. Previous studies have focused on horizontal excitation (perpendicular to gravity) for particle damping. Vertically excited systems (parallel to gravity) have also been studied in the literature, in which the excitation has generally been considered to be harmonic. However, harmonic disturbances do not accurately represent some cases where repetitive impacts occur, such as manufacturing and maintaining aircraft structures with the operations of riveting and chiseling. The proposed research is concerned with developing analysis methods for PIDs under periodic impulse excitation in the vertical direction. Particle damping is going to be analyzed for i) a single PID, ii) a cantilever beam with multiple PIDs attached to various locations on the beam, and iii) a simply supported plate with multiple PIDs attached to various locations on the plate. These analyses will be used for an optimization of a distributed array of PIDs on a cantilever beam and on a simply supported plate.

The method of assumed modes and Lagrange’s equations will be used to model a cantilever beam and a simply supported plate. In order to simulate the PID response, the use of Linear Time Invariant methods are found to be most efficient, because the PID is never truly in a steady-state condition. Finally, a heuristic algorithm, such as a genetic algorithm, will be used to optimize the distributed array of PIDs because of the complexity and nonlinearity of the problem.