Abstract: The statistical characteristics of materials parameter in the ductile fracture criterion proposed by the authors was first investigated by means of one step and two steps loading test of spheroidized mild steel (0.2%C) and the formula for estimating the parameter was derived also. It is found that the materials parameter assumes the characteristic of normal distribution and the derived formula is reasonable. The achievements of this study make it possible to reveal the damage evolution and to predict the workability of materials during metal forming processees by using the proposed ductile fracture criterion.

Key words: ductile fracture criterion, materials parameter, normal distribution