Simulation of cavitation processes in superplastic deformation

Abstract

Cavitation behavior during superplastic deformation is simulated by developing a three-dimensional model which incorporates the continuous nucleation, plastic growth, and coalescence of cavities. The cavity growth rate is determined by using an empirical relationship between the Poisson’s ratio and the cavity volume fraction, and cavities after coalescence are represented as overlapped spheres. The volumetric cavity growth-rate parameter (2.0 to 2.5) obtained from the simulation is consistent with the range of experimental observation. Comparison of the simulation with a modified Pilling’s model for cavity coalescence shows that the growth rates of the average cavity volume are consistent with each other at small strains, whereas they are higher in the former than in the latter at large strains. This is because multiple coalescence, rather than the pairwise coalescence assumed in the Pilling’s model, becomes predominant at large strains in the simulation. Between the simulation and experiments, close agreement is also found in the cavity-size distribution normalized with a maximum cavity size.