Why are my Nondesign spaces tearing off?

If your Nondesign spaces are tearing off, your result looks something like the picture below.

If a boundary condition is applied on one of these Nondesign spaces an error will occur and the optimisation will stop. The model is no longer complete and it doesn’t make sense to continue with the optimisation.

If no boundary condition is applied on one of these Nondesign spaces, a warning will occur but the optimisation will continue.

Reasons why the Nondesign spaces are tearing off:

either no force or displacement is applied → no stresses are available for the stress optimisation to prevent the material from being reduced
or the force applied is too small
or the additional fixation is not needed for the defined boundary conditions and optimisation constraints
If you are using the symmetry function with the whole model, the optimiser won't use the symmetrical Nondesign spaces and will notify you thereof - don’t worry everything is just as it is supposed to be

Steps to prevent this behaviour:

Prevent the tearing off by:
- increasing the Complexity → more elements are available and a finer model is possible (calculation effort increases!)
- reducing the optimisation stress goal
- increasing the applied force so that the stresses and therefore the relevance of the Nondesign space is increased
- creating an extra load case in which fixations and loads are switched
Either it is a design proposal you can accept/want to achieve in order to reduce the number of fixation points
- To reduce the number of fixations, the fixation has to be applied on all Nondesign spaces at once as one boundary condition (multi-selection)
  - Thus individual Fixations can tear off without an occurring error

Boundary condition multiselection of Nondesign spaces to enable tearing off of Fixations.