Experimental study of cavity growth in ductile rupture

Composite materials made of a steel matrix and spherical alumina particles were prepared to study the growth of cavities nucleated from Al₂O₃ inclusions during deformation at room temperature. Two materials containing different volume fractions of Al₂O₃ particles, i.e. ? = 0.5% and 2%, were investigated. Axisymmetric notched specimens were employed to determine the effect of stress triaxiality on cavity growth rate. These specimens were calculated by finite element method. They were predeformed at room temperature and subsequently broken at ? 196°C. The experimental results are in broad agreement with the theoretical results derived from Rice and Tracey model. In particular it is observed that the cavity growth is proportional to the local strain obtained from the finite element calculations. Moreover the effect of stress triaxiality intervenes exponentially as predicted by the Rice and Tracey model. However, the theoretical proportionality factor in front of the exponential term is lower than the experimental one. The reasons for this discrepancy, especially the effect of interactions between neighbouring inclusions which are not taken into account in this model, are briefly discussed.