Patch recovery based on complementary energy

In this paper a new stress recovery procedure is presented. The formulation is very simple and based on improving stresses by enforcing compatibility over local patches of elements. This is obtained by minimizing the complementary energy, properly defined for the patch thought as a separate system, among an assumed set of equilibrated stress fields. The resultant implementation is simple, cost effective and numerically stable. Several numerical tests evidence an excellent performance which promises a wide applicability of the new procedure