Ansys Polydata will obtain boundary set information by converting structural nodal loads. The value of the nodal load itself is not important, with the exception that it cannot be zero (because all zero nodal loads will be discarded from the neutral or universal file). The load set index is used as a pointer to the Ansys Polyflow boundary set. You must change the load set index whenever you need to generate a different boundary set. In general, load set 1 will become boundary set 1, and so on. In Ansys Polyflow, nodes located at the intersection between two (or more) boundary sets belong to all of those boundary sets. The same rule must be respected in PATRAN or I-deas: you must include these nodes in each load set.
For example, in 2D, a node located at the intersection between BS1 and BS2 must be assigned a (nonzero) nodal load in load set 1, and another (nonzero) nodal load in load set 2. This extends to 3D meshes as well.
Nodal loads defined on internal nodes (that is, nodes that are not located on the domain boundary) are not taken into account by the conversion utility. Also, if there are segments (in 2D) or faces (in 3D) located on the domain boundary that are not assigned a boundary set index by the end of the conversion, Ansys Polydata will create a new boundary set (which is not linked to any load set) to collect these unassigned segments or faces. This new boundary set is called the "additional boundary set".
The creation of the additional boundary set is useful in two ways:
It is a convenient way for you to check if you have forgotten to define any nodal loads.
If selecting all the nodes that belong to a particular boundary set requires a significant amount of effort in PATRAN or I-deas, you can rely on the additional boundary set to collect these unassigned nodes. In this case, however, you are strongly encouraged to verify the number of segments or faces in all boundary sets.