ACCURATE STRESS EXTRACTION FOR NEARLY INCOMPRESSIBLE MATERIALS BY THEDISPLACEMENT FORMULATION OF THE P-VERSION FEM

Direct methods for computing the pointwise stresses for nearly incompr essible elastic materials fail to provide meaningful results when appl ied to the displacement formulation of the finite element method (FEM) . A new extraction method for accurate computation of pointwise stress es for nearly incompressible elastic materials is presented. It is bas ed on the complementary energy principle applied over a local domain i n the postprocessing phase in conjunction with the p-version finite el ement solution. It is shown that accurate pointwise stresses are obtai ned, that the relative error in the pointwise stresses converges at a rate which is as fast as the relative error measured in the energy nor m or faster, and importantly, the extracted stresses are virtually ind ependent of Poisson's ratio. Numerical results for two problems, one h aving a smooth solution and the other containing a singular point, are provided.