Need Help With High Impact Loading - LS-Dyna

Good afternoon all,

I'm trying to simulate high impact loading and fragmentation of concrete for my dissertation.

I have defined my two solids (sphere and plate) and their material
properties(sphere from steel with initial velocity to induce the impact -
and concrete square plate of 8cm thickness using MAT_72R3). For contact I am using eroding_surface_to_surface.
The problem is that the plate behaves a little bit elastic (see
attached pic) at the impacted top surface without showing cratering
effects and the rear surface seems to bulge ,but I get no fracture. The
mesh is bulging a little and then comes in its original position. What
is the problem? Is it the contact wrong? Do I have to use also
MAT_Add_erosion  besides eroding surface? Any advice?

Thank you in advance

Kind Regards,

Theo