Title: Critical behavior for impact fragmentation of spherical solid bodies sensitive to strain rate

Abstract: We consider the impact fragmentation of two spherical solid bodies sensitive to strain rate in a three-dimensional (3D) setting. We use both dimensional analysis and numerical simulations by smoothed-particle hydrodynamics (SPH) method to shed light on this problem. The key point of the work is the assumption of complete self-similarity of the problem under consideration with respect to the effective strain rate parameter Eeff, which is verified by numerical simulations. As a result we consider the two cases corresponding to the high-velocity Eeff >> 1, and low-velocity Eeff <<1 loading. The size of the system may be characterized by the total number of the SPH particles Ntot approximating each sphere. It is shown that for finite system the critical velocity of fragmentation at high-velocity loading exceeds that at low-velocity loading . With an unlimited increase in the system size these velocities become the same. It is shown that the critical velocity of fragmentation depend on the system size in a quadratic manner, i.e. Vc^2 -Vc(inf)^2 ~ Ntot ^(1/3nu) where nu is a correlation length exponent.