Ductile fracture of materials with high void volumefraction

In the present paper\ axisymmetric cell models containing one or two voids and a three!dimensional cell model containing two voids have been used to investigate void size and spacing e}ect on the ductile fracture in materials with high initial void volume fraction[ They are performed for round smooth and round notched specimens under uniaxial tension[ The example material used for comparison is a nodular cast iron material GGG!39 with initial void volume fraction of 6[6)[ The parameters considered in this paper are void size and shape for axisymmetric cell models containing a single void\ and void distribution pattern for axi! symmetric and 2D cell models containing two voids of di}erent sizes[ The results obtained from these cell models by usingFEMcalculations are compared with the Gurson model\ the Gurson Tvergaard Needleman model\ the Rice Tracey model and the modi_ed Rice Tracey model[ It can be stated that the in~uence of void size and void spacing on the growth in volume of voids is very large\ and it is dependent on the distribution of voids[ Using non!uniform void distribution\ the results of axisymmetric cell models can explain how a void can grow in an unstable state under very low stress triaxiality at very small strain as observed in experiments[ Calculations using cell models containing two voids give very di}erent results about the stable and unstable growth of voids which are strongly dependent on the con_guration of cell model