EFFECT OF POROSITY ON THE ELASTIC RESPONSE OF BRITTLE MATERIALS - AN EMBEDDED-ATOM METHOD APPROACH

The values for Young's modulus of porous single-crystal Ni in the [100 ] and [111] directions are computed using the embedded-atom method (EA M). Both pore volume fraction and pore size (defined by ratio S/R of t he flaw size to pore radius) are varied. A reduction in Young's modulu s with increasing pore volume fraction and with increasing S/R ratio i s observed in the EAM simulations, in good agreement with a recent the oretical model proposed by Krstic and Erickson. A porous Sigma = 5, [1 00] grain boundary also demonstrates a marked reduction in Young's mod ulus compared with the pore-free Sigma = 5, [100] grain boundary. Thes e results suggest that recent literature values demonstrating greatly reduced Young's modulus for some nanocrystalline materials (compared w ith conventional polycrystalline materials) may be a consequence of re sidual porosity in the material. Poisson's ratio is calculated for ali gned pores with stress applied in the [100] direction. The crack-openi ng displacement is qualitatively and quantitatively confirmed for pore s containing annular flaws.