Scale-dependent deformation of porous single crystals

An elasto-viscoplastic strain gradient crystal plasticity formulation is ap plied to study the deformation of a porous single crystal and its macroscop ic stress carrying capacity under plane strain condition. Both uniaxial and biaxial loadings are considered. Computational model is a unit cell contai ning one single void. Attention is focused on investigating the effects of varying void size with respect to a representative constitutive length scal e l, at arbitrarily fixed void volume fractions, on its growth rate, the lo cal strain distribution around the void and the macroscopic stress sustaine d by the material. It is found that both void growth rate and the local str ain gradient is decreased by several times when its radius is reduced to l. This indicates that "small" voids are less susceptible to growth than 'lar ge' voids. Computations also show that strain gradient effects significantl y elevates the macroscopic stress, especially under large biaxiality of loa ding. Overall, as the void size increases, the gradient theory predictions gradually approach the classical theory predictions which are size-independ ent. (C) 1998 Elsevier Science Ltd. All rights reserved.