Serrated flow and rupture by evolution of internal inhomogeneities

The plastic stability and ductile rupture under evolution of cavity-damage and local strength inhomogeneities are examined theoretically for uniaxial tension. Analytical solutions are derived for that arbitrary strain-induced formations modified to stress-triaxiality evolution during necking. With increasing rate of damage formation necking is enhanced and ductility as well as load drop reduces more pronounced at large strain rate sensivities m and weak initial inhomogeneities. Effects of particle concentration and external pressure deduced for nucleation controlled damage generation by particle-deponding agree with ductility observations. An inhomogeneity degradation reduces neck growth and localized flow development. Above a critical hardening rate ''plastic metastability'' appears with stochastic flow through structural pulsed micro-neck formation and resolution which promotes ductility. Amplitude and frequency of resulted load serrations, which quantify local structural changes correlate and depend mainly upon m. Simultaneous multiple necking becomes stable only at superplastic or irradiation creep conditions. (orig.)