Mechanism-based strain gradient plasticity - II. Analysis

Citation
Y. Huang et al., Mechanism-based strain gradient plasticity - II. Analysis, J MECH PHYS, 48(1), 2000, pp. 99-128
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Mechanical Engineering
Journal title
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
ISSN journal
0022-5096 → ACNP
Volume
48
Issue
1
Year of publication
2000
Pages
99 - 128
Database
ISI
SICI code
0022-5096(200001)48:1<99:MSGP-I>2.0.ZU;2-W
Abstract
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.