ABAQUS user-element subroutine (UEL) for Gudmundson (2004) higher order strain gradient plasticity formulation, including both energetic and dissipative length scales.
Paper: E. Martínez-Pañeda, V.S. Deshpande, C.F. Niordson, N.A. Fleck. The role of plastic strain gradients in the crack growth resistance of metals. Journal of the Mechanics and Physics of Solids, 126: 136-150 (2019)