Modeling size effects in microwire torsion: A comparison between a Lagrange multiplier-based and a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e1676" altimg="si408.svg"><mml:mrow><mml:mi>C</mml:mi><mml:mi>u</mml:mi><mml:mi>r</mml:mi><mml:mi>l</mml:mi><mml:msup><mml:mrow><mml:mi>F</mml:mi></mml:mrow><mml:mrow><mml:mi>p</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math> gradient crystal plasticity model

The size-dependent response of metallic microwires under monotonic and cyclic torsion is modeled taking a reduced-order strain gradient crystal plasticity approach involving single scalar-valued micromorphic variable. It compared with the predicted by CurlFp model proposed in Kaiser Menzel (2019a), which based on complete dislocation density tensor. shown that, non-uniform plastic deformation processes, internal variable predicts isotropic hardening contrast to kinematic-type produced due dislocation-induced back-stress component. arising size effect tests described normalized torque T/R3 as function ratio microwire radius R characteristic length scale ℓ. In domain, characterized an inflection point corresponding curve, scaling law T/R3∼(R/ℓ)n can be identified, explicit relations are found for power n. relative evolution Statistically Stored Dislocation (SSD) Geometrically Necessary (GND) densities during detail.