Homogenised elastic-viscoplastic constitutive behaviour of periodic open structures subjected to internal pressure and macrostrain

This paper describes constitutive modelling of the homogenised elastic-viscoplastic behaviour of periodic open structures subjected to internal pressure and macrostrain. We consider periodic structures, made of metallic materials, having open spaces in which internal pressure acts independently of macrostrain. First, a homogenised elastic constitutive model of this class of periodic structures is rationally developed by evaluating analytically the anisotropic macrostress induced by internal pressure. This elastic model is then extended to a homogenised elastic-viscoplastic model on the assumption that macrostrain rate is additively decomposed into elastic and viscoplastic parts. It is shown that the viscoplastic macrostrain rate depends on the difference between macrostress and internal pressure. The homogenised constitutive model developed is verified by applying it to an ultrafine plate-fin structure operating at a high temperature.