A mechanism-based theory of strain gradient (MSG) plasticity has been propo
sed in Part I of this paper. The theory is based on a multiscale framework
linking the microscale notion of statistically stored acid geometrically ne
cessary dislocations to the mesoscale notion of plastic strain and strain g
radient. This theory is motivated by our recent analysis of indentation exp
eriments which strongly suggest a linear dependence of the square of plasti
c flow stress on strain gradient. Such a linear dependence is consistent wi
th the Taylor plastic work hardening model relating the flow stress to disl
ocation density. This part of this paper provides a detailed analysis of th
e new theory, including equilibrium equations and boundary conditions, cons
titutive equations for the mechanism-based strain gradient plasticity, and
kinematic relations among strains, strain gradients and displacements. The
theory is used to investigate several phenomena that are influenced by plas
tic strain gradients. In bending of thin beams and torsion of thin wires, m
echanism-based strain gradient plasticity gives a significant increase in s
caled bending moment and scaled torque due to strain gradient effects. For
the growth of microvoids and cavitation instabilities, however, it is found
that strain gradients have little effect on micron-sized voids, but submic
ron-sized voids can have a larger resistance against void growth. finally,
it is shown from the study of bimaterials in shear that the mesoscale cell
size has little effect on global physical quantities (e,g, applied stresses
), but may affect the local deformation field significantly. (C) 1999 Elsev
ier Science Ltd. All rights reserved.