In this study, a constitutive model of the homogenized elastic-viscoplastic behavior of periodic open structures subjected to internal pressure and macro-strain is developed. We consider periodic structures, made of metallic materials, having open spaces in which internal pressure acts independently of macro-strain. First, a homogenized elastic constitutive model of this class of periodic structures is rationally developed by evaluating analytically the anisotropic macro-stress induced by internal pressure. This elastic model is, then, extended to a homogenized elastic-viscoplastic model on the assumption that macro-strain rate is additively decomposed into elastic and viscoplastic parts. It is shown that the viscoplastic macro-strain rate depends on the difference between macro-stress and internal pressure. The homogenized constitutive model developed is verified by applying it to a plate-fin structure.
