A numerical study of the effect of penalty parameters for membrane elements with independent rotation fields and penalized equilibrium

We offer a numerical investigation into the effect of penalty parameters in elements with drilling degrees of freedom and penalized equilibrium, for which the stress tensor σσ is not a priori assumed to be symmetric. The parameters under investigation are γγ, which relates the in-plane translations to the rotations, and αα, which results due to enforcement of stress equilibrium in assumed stress implementations of elements with drill rotations.Rather than simply reporting on the quantitative influence of the penalty parameter γγ on measures like displacement, rotation and stress, we directly assess the skewness of the nonsymmetric stress tensor σσ. Results are presented for both isotropic and orthotropic constitutive relationships.