A strain gradient plasticity theory with application to wire torsion

作者：Liu, J. X.^*; ElSayed, T.

来源：International Journal of Damage Mechanics, 2015, 24(4): 512-528.

DOI：10.1177/1056789514537920

• Strain gradient plasticity
• Taylor dislocation relation
• length scale effect
• geometrically necessary dislocation
• torsion
• strain dependence

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.

• 出版日期2015-5
• 单位KAUST; 江苏大学