high speed and violent nature of the break-up process, observations are usually restricted to the final state of impact experiments, where information has to be extracted from the remaining pieces of the body. Hence, computer simulation of models of agglomerate break-up is an indispensable tool in this field. Simulations of realistic models provide a deeper inside into the break-up process and can even complement the experimental findings directly supporting the design of industrial processing of these materials. Analytic approaches have limited capabilities in this field since they cannot capture the disordered microstructure of the material.

The finite element approach and the discrete element modeling have been successfully applied to describe the stress field, crack propagation, and fragment formation in impacting spherical particles [@agglomerate; @bk; @imp_agglo; @poto; @simu; @tsoungui; @imp_ang; @poschel1; @poschel2]. Recent simulations of ball impact revealed two types of crack patterns: oblique cracks radiating from impact point, and secondary cracks perpendicular to the oblique ones. In the framework of the discrete element method it was clarified that depending on the impact velocity the result of the break-up process can be localized damage around the contact zone, fragmentation, or shattering. The evolution of several characteristic quantities of the break-up process 