Effect of intrinsic lattice resistance in strain gradient plasticity

The theory of mechanism-based strain gradient (MSG) plasticity is generaliz ed in this paper in order to account for the effect of intrinsic lattice re sistance in the Taylor dislocation model. A multiscale, hierarchical framew ork is adopted to link the strain gradient plasticity theory on the mesosca le to the Taylor dislocation model on the microscale. It is established tha t the interaction between the strain gradient effect and the friction stres s (intrinsic lattice resistance) is weak, The hardness increase due to intr insic lattice resistance is nearly independent of the strain gradient effec t. The linear relation between the square of microindentation hardness and reciprocal of indentation depth established by Nix and Gao has been extende d to explain experimental data for bee tungsten where the effect of intrins ic lattice resistance plays a significant role. (C) 2001 Acta Materialia In c. Published by Elsevier Science Ltd. All rights reserved.