Type of forces definition for OptiStruct export


Two types of force definition are available:
  • If the drop-down menu Type of forces definition is set to Force at nodes, Flux writes nodal force values (vectors) in the exported file that will be imported in OptiStruct.
  • On the other hand, if the drop-down menu is set to Global forces [RBE3], Flux writes a global force for each group of related elements in the exported file. These global forces are located at the barycenter of each group. Then, when the exported file is imported in OptiStruct, the global force vectors will result equally distributed on each node of the group.

Forces at nodes

In a first hand, the user can usualy exports all the forces at nodes from Flux project to OptiStruct as shown in Figure 1

Figure 1. Tangential force at nodes at the stator teeth in a permanent magnet synchronous machine.

As a consequence of this type of export, the produced file contains more datas and can be more time consuming.

Global forces [RBE3]

In the other hand, an approach for exporting global forces computed in Flux projects to OptiStruct is also available. This feature is called Global forces [RBE3] and allows the user to export a global force. Global forces are located at the barycenter of each group of related elements.

A typical application of this method is exporting a single equivalent force per tooth in the stator of a rotating electric machine instead of one force per node. The situation is depicted in Figure 2:

Figure 2. Global normal forces at the stator teeth in a permanent magnet synchronous machine.

This approach has the advantage of creating more compact exported data files. Consequently, subsequent computations in OptiStruct are faster when compared to the nodal export approach.

This feature allowing the export of global forces is available in the I/O context, as shown in Figure 3.

Figure 3. Dialog box for creating an OptiStruct export file in Flux 2D, showing the export option Global forces [RBE3].
Note: In the Advanced tab, the user may choose several units to export the forces coordinates (meter, milimeter...)