Generation of Tangential Force

A tangential force can be generated when a penetrated node is sliding without friction. This behavior is due to the gaps overlapping around the edges. Figure 1 illustrates that by the cylindrical gap around the edges, the force is no longer normal to the shell mid-surface.

Figure 1. Generation of Tangential Force
Note: No problems were observed in crash simulations, but in metal forming where friction is very important this can seriously decrease the accuracy.


  1. It is always advised to post-process the contact forces. If they are too large, taking into account the physical understanding, the model must be checked.
  2. To post-process the forces for symmetric contact, the interface can be split into four interfaces. For example, for two parts A and B, you can create:
    • Interface 1 with A Secondary and B Main
    • +Interface 2 with A Main and B Secondary
    • +Interface 3 with A Main and Secondary
    • +Interface 4 with B Main and Secondary