Material length scale of strain gradient plasticity: A physical interpretation

<p>These data are related to our paper &quot;Dabiao Liu*, and D. J. Dunstan. Material Length Scale of Strain Gradient Plasticity: A Physical Interpretation. International Journal of Plasticity, 98 (2017), 156-47.&quot; In this work,the length scales in&nbsp;strain&nbsp;gradient&nbsp;plasticity theories in which the plastic work density can be expressed as a function of the&nbsp;gradient-enhanced plastic&nbsp;strain&nbsp;are here derived from known physical quantities via critical thickness theory. A connection between the length scale and the fundamental physical quantities is elucidated. The combination of the&nbsp;strain&nbsp;and&nbsp;strain-gradient&nbsp;terms within the deformation theory of&nbsp;strain&nbsp;gradient&nbsp;plasticity is addressed. It is shown that, compared with the harmonic sum of the&nbsp;strain&nbsp;and&nbsp;strain-gradient&nbsp;terms in Fleck-Hutchinson theory, the linear combination gives a more reasonable value of length scale, several micrometers, which is close to that in the&nbsp;gradient&nbsp;theory of Aifantis. In contrast, the value of length scale in Nix-Gao theory is much larger, in the millimeter range. The length scales determined by critical thickness theory are in good agreement with those obtained by fitting to experimental data of wire torsion.</p>