A strain gradient plasticity theory with application to wire torsion

Liu, J. X.; El Sayed, Tamer S.

A strain gradient plasticity theory with application to wire torsion

Type

Article

Authors

Liu, J. X.
El Sayed, Tamer S.

KAUST Department

Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division
Physical Science and Engineering (PSE) Division

Online Publication Date

2014-06-05

Print Publication Date

2015-05

Date

2014-06-05

Abstract

Based on the framework of the existing strain gradient plasticity theories, we have examined three kinds of relations for the plastic strain dependence of the material intrinsic length scale, and thus developed updated strain gradient plasticity versions with deformation-dependent characteristic length scales. Wire torsion test is taken as an example to assess existing and newly built constitutive equations. For torsion tests, with increasing plastic strain, a constant intrinsic length predicts too high a torque, while a decreasing intrinsic length scale can produce better predictions instead of the increasing one, different from some published observations. If the Taylor dislocation rule is written in the Nix-Gao form, the derived constitutive equations become singular when the hardening exponent gets close to zero, which seems questionable and calls for further experimental clarifications on the exact coupling of hardening due to statistically stored dislocations and geometrically necessary dislocations. Particularly, when comparing the present model with the mechanism-based strain gradient plasticity, the present model satisfies the reciprocity relation naturally and gives different predictions even under the same parameter setting. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Citation

Liu J, ElSayed T (2014) A strain gradient plasticity theory with application to wire torsion. International Journal of Damage Mechanics 24: 512–528. Available: http://dx.doi.org/10.1177/1056789514537920.

Acknowledgements

The work of J.X. Liu was supported by the Jiangsu University and Jiangsu Specially-Appointed Professor grants, as well as by the KAUST baseline fund.