Numerical implementation of pressure-dependent elasto-plastic cosserat continuum model in ABAQUS

The subroutine UEL embedded in commercial FEM software ABAQUS is utilized to develop a user element based on the material of pressure-dependent elasto-plastic cosserat continuum model. The user element adopt plane eight-node isoparametric unit which include three degree of freedom(two translation and one rotation) at each node, the Drucker-Prager material model with associate flow rule is used, the stress integration algorithm is four-order Runge-Kutta method. The user element is used to analysis the influence of mesh density and the material characteristic length on the material localization. The results show that the thickness of shear band and the equivalent plastic strain are independent of mesh density, with the increase of the material characteristic length, the thickness of shear band and the equivalent plastic strain decrease constantly.