If you specify an expression field for an interaction or prescribed condition, ABAQUS/CAE must evaluate the expression field as the first step in determining the values to submit for the analysis. Expressions are evaluated as Python input; entries containing errors will generate standard Python errors. For cylindrical and spherical coordinate systems, the values for Th and P are evaluated in radians in the range from 
to 
. ABAQUS/CAE evaluates the expression field when the input file is written.
ABAQUS/CAE evaluates the expression field at different locations on the model depending on the type of region that you selected when you created the interaction or prescribed conditon. Table 39–2 indicates the locations on the model that ABAQUS/CAE uses for evaluation of the expression field.
Table 39–2 Expression field evaluation locations.
| Region type | Location of expression field evaluation |
|---|---|
| Node or vertex | At the node or vertex |
| Edge | At the midpoint of the edge of each element |
| Surface or face | Centroid of each element face contained in the region |
| Cell | Centroid of the element |
Next, ABAQUS/CAE multiplies the magnitude that you specify for the spatially varying parameter, such as a pressure magnitude, by the evaluated expression at each element or node to determine the final values that are submitted to the analysis. The expression field is applied to magnitudes in the interaction or prescribed condition, including the real and imaginary parts of complex magnitudes. Beam and shell gradient values, such as gradients in temperature, are not affected by the expression field. Sink temperatures in film conditions are also not affected by the expression field. During the analysis, ABAQUS applies any amplitude that you have specified for the interaction or prescribed condition.