A SUPERCONVERGENT STRESS RECOVERY TECHNIQUE WITH EQUILIBRIUM CONSTRAINT

A stress recovery technique is developed to extract more accurate nodal stress values from the raw stress values obtained directly from the nite element analysis. In the present method a stress eld is assumed over a patch of elements, and a least-squares functional is formed using the discrete stress errors at the superconvergent stress points and the residual of the equilibrium equation expressed in the virtual work form. The results of numerical tests conducted on one-dimensional and two-dimensional example problems demonstrate the validity and e ectiveness of the present method. The introduction of an equilibrium constraint allows a patch stress eld of higher order than is possible without the equilibrium constraint and this leads to a recovered stress eld of higher accuracy. Because the residual of equilibrium is expressed in the virtual work form, the proposed method can easily be applied to arbitrarily curved shell structures.