Title: Dynamics of granular impact cratering

Author (Poster): Hiroaki Katsurgi, University of Pennsylvania

Abstract:

Dynamics of the granular impact cratering is studied by a new velocity measurement method. A steel ball was dropped from various heights h(=0-83 cm) to a glass beads layer. We measured each dropping velocity with 50 kHz frame rate and 0.0038 mm/ pixel magnification. From the velocity data, penetration depth and acceleration were calculated. The data reproduce several empirical laws reported by different research groups. We found the data is well described by a unified stopping force law. The stopping force consists of depth dependent friction and inertial drag. We also measured impacts with various density and size projectiles and some granular media. The data show a universal scaling for granular inertial drag.