Investigation of impact craters on flat surface of cylindrical targets based on experiments and numerical simulations

We carried out impact experiments using cylindrical gypsum targets with various radii and investigated the crater on the top (flat) surface. At a ratio of projectile and target radii ∼1/20, the crater size abruptly increases; the spallation extends to the side surface of the targets. The results are closely similar to the previous ones on the curved surfaces. A shock wave propagation model, introduced by Suzuki et al. (2018, Icarus 301, 1-8), can represent such results as the steep increase of the size of the spallation zone in both cases of spherical and cylindrical targets. Using this model, the maximum fragment size is evaluated and agrees well with the experimental results. We found that the enlargement of the spallation zone is crucial to the transition from cratering to catastrophic disruption. We also carried out numerical calculations with iSALE code capable of simulating impact processes in solid materials. The maximum pressure distribution shows that the most parts of the spallation zone are not metamorphosed by shock waves. Also, the crater depth is represented by iSALE without damage models, while the "spallation" seems not to be well reproduced by iSALE even with the damage models.