A SUPERCONVERGENT STRESS RECOVERY TECHNIQUE WITH EQUILIBRIUM CONSTRAINT

A stress recovery technique is developed to extract more accurate noda l stress values from the raw stress values obtained directly from the finite element analysis. In the present method a stress field is assum ed 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 eff ectiveness of the present method. The introduction of an equilibrium c onstraint allows a patch stress field of higher order than is possible without the equilibrium constraint and this leads to a recovered stre ss field of higher accuracy. Because the residual of equilibrium is ex pressed in the virtual work form, the proposed method can easily be ap plied to arbitrarily curved shell structures.