In Workbench Simulation - Reaction forces often do not match the applied loads. The documentation contains the following note about this, but what is the root cause?
Note (from Workbench Documentation)
A reported reaction may be inappropriate if that support shares a surface, edge, or vertex with another support, contact pair, or load. This is because the underlying finite element model will have both loads and supports applied to the same nodes.
If a model contains two or more supports that share an edge or vertex, use caution in evaluating the listed reaction forces at those supports. Calculation of reaction forces includes the force acting along bounding edges and vertices. When supports share edges or vertices the global summation of forces may not appear to balance. Reaction forces may be incorrect if they share an edge or surface with a contact region.
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This can happen for several reasons. Most obvious is when you have different boundary conditions sharing the same nodes. In ANSYS, each constrained node has a reaction force. Consider the case where 2 fixed supports share a vertex. For a given support in Workbench, the nodes are selected, the corresponding reaction forces are retrieved, then added. Thus, the shared vertex will be in the list twice and therefore the total reaction force will differ by that amount. For contact, there was an issue prior to V8.1 when a fixed support shared nodes with a bonded contact region. For Workbench/DesignSpace V8.0 and earlier, the reaction force was calculated via FSUM which did not handle the contact elements correctly. For Workbench/DesignSpace V8.1 and greater, the reaction force is obtained directly from the reaction solution which does handle contact elements correctly. |
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