Effect of intrinsic lattice resistance in strain gradient plasticity

The theory of mechanism-based strain gradient (MSG) plasticity is generalized in this paper in order to account for the effect of intrinsic lattice resistance in the Taylor dislocation model. A multiscale, hierarchical framework is adopted to link the strain gradient plasticity theory on the mesoscale to the Taylor dislocation model on the microscale. It is established that the interaction between the strain gradient effect and the friction stress (intrinsic lattice resistance) is weak, The hardness increase due to intrinsic lattice resistance is nearly independent of the strain gradient effect. The linear relation between the square of microindentation hardness and reciprocal of indentation depth established by Nix and Gao has been extended to explain experimental data for bee tungsten where the effect of intrinsic lattice resistance plays a significant role. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.