On stress computation in displacement finite element models (Q1059436)

The problem of stress description in displacement finite element models is dealt with. Because of kinematic restraints, such models are able to provide only a global average information on stresses, given in terms of generalized (natural) variables. Expressions for local stress fields as functions of these variables are proposed, which meet a condition of consistency with the assumed displacement model. Such a condition appears as the only requirement which stresses have to comply with and it is shown that it does not define a unique legitimate stress distribution in the element. The implications of possible alternatives are examined with reference to some frequently used plane elements.