Plastic instabilities in porous cylinders under remote triaxial loading

Plastic instabilities under remote triaxial loading, including cylindrical cavity expansion, are studied in context of large strain plasticity and constrained plane-strain. Material hardening is taken into consideration and porosity is incorporated using the Gurson (1977) plasticity model. Spontaneous growth of central cavity due to constant applied triaxial remote load (cavitation instability) is examined in an infinite cylindrical medium. It is found that the remote field exhibits instability at a definite value of applied radial tension which may occur before onset of cavitation. That maximum is proposed as an approximation for field stability limit while, as shown, cavitation in the porous solid can occur only for relatively low values of initial porosity and within a limited range of remote loading triaxiality. Analysis is facilitated upon choice of effective stress as independent time-like parameter.