Actually, the stress error estimation is based on the
principle of the continuity of stress. The resulting stress
distribution of a finite element analysis is generally
discontinuous. The nodal stresses of each element are averaged to
smooth the discontinuity in the element stresses. The stress error
in each element is defined as the difference between the element
stress and the average of the nodal stresses corrected using the
form functions. This error is used to calculate the energy norm
error for each element. COSMOS Products allow the user to plot a
contour of the percentage of the elemental energy norm error
relative to the average elemental energy.