Further development of the hybrid model for polycrystal deformation

The Kocks-Mecking hybrid model for polycrystal deformation has been develop ed further, in order to obtain an easy definition of polycrystalline behavi our, from knowledge of the single crystal stress-strain curves. The hybrid model is a one-parameter theory that considers the flow stress governed by total dislocation density. This is the addition of the statistically stored dislocations, independent of the grain size, and the geometrical dislocati ons, necessary to accommodate the deformation, and thus dependent on the gr ain size (as proposed by Ashby). The condition for the onset of necking is used to determine the parameters of the equation of the model. The analytic al description of the resulting flow law was used to analyse the tensile be haviour of copper sheets, with five different grain sizes, which were defor med at three different strain rates. (C) 2000 Acta Metallurgica Inc. Publis hed by Elsevier Science Ltd. AN rights reserved.