An equilibrium approach to plane problems

A finite element approach to the stress analysis of plane problems in the presence of body forces is presented, based upon the assumption of fully equilibrated stress fields. The formulation is intended to analyse plane stress and plane strain structures in the range of non-linearities which depend on the presence of plasticity and/or cracks. The goal is to obtain an accurate description of the stress field, so as to enforce the yield conditions on the basis of reliable estimates of the stresses, and to model plastic flows and cracks with full respect of the boundary stress conditions. The peculiarities of the method are recalled and specific developments for the evaluation of the displacements and for the introduction of internal openings and cracks are illustrated.