DIRECT AND REFINED CHARACTERIZATION OF REBOUND FOR IRREGULARLY SHAPED, HIGH-SPEED PARTICLES INCIDENT ON AEROSPACE GRADE TITANIUM

Abstract

The observed stochasticity in rebounding trajectories for particle-surface interactions is often attributed to irregular particle shape. However, at higher speeds, surface plastic deformation can significantly influence the rebounding particle trajectory. The interaction between particle shape and surface plastic deformation at high speeds and the effect that it has on the observed spread in rebounding trajectories is explored. Two parameters often used to characterize particle-surface interactions are the coefficient of restitution (COR) and rebounding angle. A fully time-resolved two-dimensional Particle Tracking Velocimetry system is employed on a high-speed free jet rig to study particle-surface interactions for 150 μm – 250 μm crushed quartz incident on Grade 4 Titanium. Particle speeds range between 50 m/s and 130 m/s and nominal incidence angles of 30° and 90° are studied. In this work, a novel approach that couples the study of both the particle and particle- surface interactions is discussed. Additionally, a source of random uncertainty in velocity and rebounding angle measurements is presented. A model from the literature is modified to include the effects that particle shape has on the normal coefficient of restitution. A sensitivity study of particle shape to coefficient of restitution and rebounding angle is performed. It is shown that increases in plastic deformation decrease the sensitivity of the COR (both total and normal) to particle shape, reducing the spread of COR values. In contrast, the spread in rebounding angles is dominated by particle shape irregularities and incidence angle with little dependence on plastic deformation.