Tetrahedral finite element with rotational degrees of freedom for Cosserat and Cauchy continuum problems

This study formulates a simple tetrahedral finite element equipped with rotational degrees of freedom that can be used effectively to solve problems for both Cosserat and Cauchy continua. The formulation makes no assumption regarding the symmetry of the stress tensor, and such symmetry is achieved at convergence for the Cauchy problems. The numerical implementation of the new element is straightforward, and numerical tests demonstrate second-order accuracy in the case of both Cosserat and Cauchy elasticity.