Using of the finite element method for analysis of the impact problems became an usual solving way. Thereare some very powerful programs, specialized in this type of problems, which are able to say not only if aprojectile perforates or not an armor plate, but to calculate some parameters used in protection appreciation,in characterizing of the materials etc. Next to these aspects, using of the finite element method allow us tosimulate just the fracture of the material in a manner very closed of reality. The modeling of the materialfracture can be made using appropriate material models.This paper presents some consideration upon the most used material models which can simulate thematerial fracture. A special attention is paid to the Cowper-Symonds coefficients and to the Johnson-Cookmaterial model.
