The computation of derived data (data derived from nodal unknowns) is discussed in Structures with Geometric Nonlinearities through Acoustics. Derived nodal data is available for solid and shell elements (except SHELL61). Available data include stresses, strains, thermal gradients, thermal fluxes, pressure gradients, electric fields, electric flux densities, magnetic field intensities, magnetic flux densities, and magnetic forces. Structural nonlinear data is processed in a similar fashion and includes equivalent stress, stress state ratio, hydrostatic pressure, accumulated equivalent plastic strain, plastic state variable, and plastic work.
POST1 averages the component tensor or vector data at corner nodes used by more than one element.
 | (17–1) |
where:
| σik = average derived data component i at node k |
| σijk = derived data component i of element j at node k |
| Nk = number of elements connecting to node k |
For higher-order elements, component tensor or vector data at midside nodes are calculated by directly averaging the averaged corner node values, so Equation 17–1 is not used for midside nodes. Midside node values are printed or plotted only via PowerGraphics (/GRAPHICS,POWER) and /EFACET,2.
Combining principal tensor data (principal stress, principal strain) or vector magnitudes at the nodes may either be computed using the averaged component data (KEY = 0, AVPRIN command):
 | (17–2) |
where:
| f(σik) = function to compute principal data from component data as given in Structures with Geometric Nonlinearities through Acoustics. |
or be directly averaged (KEY = 1, AVPRIN command):
 | (17–3) |
where:
| σck = averaged combined principal data at node k |
| σcjk = combined principal data of element j at node k |