Influence of hydrostatic pressure and multiaxial straining on cavitating superplastic materials

Abstract

A plasticity theory describing isotropic cavitating material has been developed to relate the flow characteristics of the matrix material to the cavitated one. Expressions have been derived to describe the behavior of the cavitating superplastic material during uniaxial tension, equibiaxial stress, and plane strain deformation with superimposed pressure. It is shown that the presence of pressure reduces the strain softening due to cavitation, in addition to decreasing the cavity volume fraction. The reduction in the strain softening at a higher cavitation level is more pronounced for uniaxial tension than for the other modes of deformation. For equibiaxial stress and plane strain, the strain-rate-sensitivity parameter is shown to be drastically affected by applying gas pressure without cavity elimination. This reduction in the strain softening becomes higher when a matrix material has a lower strain-rate-sensitivity parameter, as well as when a material is tested at a lower strain rate.