MEASUREMENTS OF IMPACT PROPERTIES OF SMALL, NEARLY SPHERICAL-PARTICLES

The authors report impact properties for collisions of small, nearly s pherical particles that present interesting experimental challenges. T hey consider difficulties arising with surface reflectivity, slight as phericity, surface damage and collisions with particles affixed to a r igid plate. To measure these impact properties, the authors refine the experimental technique of Foerster et al. To permit straightforward i ncorporation in rapid granular theories, the impacts are described wit h three coefficients. The first is the Newtonian coefficient of normal restitution. The second represents the frictional properties of the c ontact surfaces. The last characterizes the restitution of the tangent ial component of the contact point velocity for impacts that involve n egligible sliding.