ON THE THERMAL ELASTOPLASTIC TRANSITION IN VISCOPLASTICITY OF METALS 1 M. V. Mi´ cunovi´ c Professor, Faculty of Mechanical Engineering, Svetozar Markovi´ c University, Kragujevac, Yugoslavia Abstract The objective of this paper is to describe viscoplastic behaviour of a metal body in the vicinity of yield limit in the initial as well as subsequent elastic ranges with special account to the transition from elastic into viscoplastic behaviour. Mechanical as well as thermal isotropy in the initial elastic range is assumed. Using an engineering picture of deformation process, with finite plastic strain and small thermoelastic strain as well as small plastic strain rate, the extended irreversible thermodynamics of M¨ uller’s type has been applied to a general set of nonassociate viscoplastic constitutive equations. The obtained restrictions on constitutive equations show explicitly me- chanical as well as thermal anisotropy induced by plastic deformation. The experimentally observed fact that the yield limit is accompanied by a singular point on temperature curve is analytically predicted. Keywords: nonassociate viscoplasticity, extended thermodynamics, ther- momechanical Bauschinger effect, elastoplastic temperature transition 1 The paper published in: Facta Universitatis, Nis, Vol.l, No.2, p.155-168, 1992.