ROTATIONAL DEPENDENCE OF THE SUPERCONVERGENT PATCH RECOVERY AND ITS REMEDY FOR 4-NODE ISOPARAMETRIC QUADRILATERAL ELEMENTS

The superconvergent patch recovery (SPR) with bilinear interpolation functions usually gives good values of recovered stresses in an element patch. However, when 4-node quadrilateral elements meeting at a node are rigidly rotated with the essential and natural boundary conditions unchanged, the recovered stresses obtained by the SPR change and depend upon the local rotation of the patch. This can be remedied either by including higher-order terms in the polynomials for the assumed stress distribution in an element patch, or by using linear interpolation functions, which gives inferior accuracy of the recovered stresses near the boundaries of the domain. Additional sampling points are suggested to compute the higher-order terms