An extended finite element method (XFEM) for linear elastic fracture with smooth nodal stress

We present a method to achieve smooth nodal stresses in the XFEM. The salient feature of the method is to introduce an 'average' gradient into the construction of the approximation. Due to the higher-order polynomial basis provided by the interpolants, the new approximation enhances the smoothness of the solution without requiring an increased number of degrees of freedom. We conclude from numerical tests that the proposed method tends to be an efficient alternative to the classical XFEM, bypassing any postprocessing step to obtain smooth nodal stress fields and providing a direct means to compute local stress error measures.