AN IMPROVED VARIATIONAL METHOD FOR FINITE-ELEMENT STRESS RECOVERY ANDA-POSTERIORI ERROR ESTIMATION

A new variational formulation is presented which serves as a foundatio n for an improved finite element stress recovery and a posteriori erro r estimation. In the case of stress predictions, interelement disconti nuous stress fields from finite element solutions are transformed into a C-1-continuous stress field with C-0-continuous stress gradients. T hese enhanced results are ideally suited for error estimation since th e stress gradients can be used to assess equilibrium satisfaction. The approach is employed as a post-processing step in finite element anal ysis. The variational statement used herein combines discrete-least sq uares, penalty-constraint, and curvature-control functionals, thus ena bling automated recovery of smooth stresses and stress gradients. The paper describes the mathematical foundation of the method and presents numerical examples including stress recovery in two-dimensional struc tures and built-up aircraft components, and error estimation for adapt ive mesh refinement procedures. (C) 1998 Elsevier Science S.A.