UNDERSTANDING THE ROLE OF ATTRACTIVE FORCES IN ADDITIVELY MANUFACTURED PARTS WITH INTERNAL PARTICLE DAMPERS

Captured powder damping, creating a particle damper inside an additively manufactured part by leaving behind a pocket of unfused powder, is a technology that allows significant vibration reduction with no additional cost or weight. This is attractive for aerospace applications where weight is at a premium and high cycle fatigue issues are common. Previous work in this area has mostly been experimental, with some modeling, but the modeling has been primarily limited to a fixed excitation amplitude. Recent experimental work suggests the damping is strongly dependent on the excitation amplitude, with an order of magnitude change in quality factor possible as excitation is varied. Previous models of additively manufactured components with embedded internal particle dampers were unable to accurately capture this variation. This work advances beyond those models by incorporating attractive (van der Waals) forces. Upon introducing attractive forces into the model, the match with experiment is significantly improved. This is demonstrated on a real-world part (a wind tunnel rake) over three orders of magnitude of base excitation. This proves for the first time that particle dampers using fine powder can exhibit different behaviors than dampers using macro-sized particles (for which van der Waals forces are negligible). The improved model can be used to help optimize particle damper design for specific applications.