Impact of thin plates with losses of contact

This paper outlines the phenomena met during the impact of a clamped rectangular plate of steel used in shipbuilding. The problem is studied both numerically and experimentally with an apparatus propelling the projectile with a crossbow. The speed of the hemispherically-ended projectile is about 20m/s. During impact, losses of contact between the plate and the striker have been detected. They seem to be due to strain waves propagating into the plate and the projectile. Strain gages bonded to the plate are used to study this waves. Numerical analysis was carried out using the LS-DYNA finite element code for various test conditions and the results are compared with experimental results. In order to understand losses of contact, strain-gages signal is compared to the one obtained with the finite element simulation of the problem.