If the task specified by the user is iso or all_iterations, the result of the calculation is the isosurface generated by isocut and possibly modified by the smoothing and data reduction. After these operations are successively finished, the user gets the message that looks as follows:
For solid models, the volume displayed in this message is the ratio of the volume of solid(s) defined by the isosurface to the original volume, which is the sum of the volumes of all solid elements used in the topology optimization, except those excluded using the group commands. The original volume is also equal to the volume of the solid(s) defined by the surface produced from the same model file using the surface task, provided that the data reduction is turned off. For shell element models, the definition is the same except that "volume" should be replaced with "area". If the model contains both solid and shell elements, only the solid elements are considered. In order to achieve a required relative volume, the user might change the isovalue and recalculate the isosurface, keeping in mind that larger isovalues usually lead to smaller volumes. The same result can be achieved using the automatic approach implemented in Tosca Structure.smooth. In order to turn it on, the parameter
The maximal number of iterations is fixed (currently 20).
If the model contains several design areas, different target relative volumes might be needed for one or more regions. For this reason, the possibility to define isovalues and target volumes differently for each group is implemented in Tosca Structure.smooth; however, it is not supported in Tosca Structure.gui. The command
with For other groups, the isovalue can be specified directly using the following command:
For the rest of the material, the default isovalue given
by
After the isovalues for all groups with the specified target relative volumes are calculated, they are interpolated to get the nodal isovalues, which are then used for the isocut. Therefore, in an area between two regions with different isovalues the average values are used. This leads to smooth transition between the regions, but also might change the relative volumes of the regions; additional error might be introduced by the surface smoothing. Generally, the number of elements in the transition region is relatively small, therefore the error can be neglected. |