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Constraints and spotwelds

Constraint nodes

1. Common translational degrees of freedom in common

  • x, y, or z translational DOF
  • x-y, y-z, or x-z translational DOF
  • x-y-z translational DOF

2. Rigid massless truss (rivet)


Force vector always in direction of the rigid truss.

3. Rigid massless beam (spotweld)


Transmission of moments, shear and normal forces

Brittle failure of the spotweld occur when


Spotweld failure due to plastic straining occurs when the e ective nodal plastic strain exceeds the input value

This option can model the tearing out of a spotweld from the sheet metal due to plasticity in the material surrounding the spotweld.

Constraints between nodes and surfaces

4. Contact type 8: nodes spotwelded to surface

Slave nodes are tied to the masters until a failure criterion is reached. Thereafter they can slide on or separate from the masters as in a type 5 contact surface. This type of surface can be used to represent spot-welded or bolted connections.

Failure criterion:


Constraints between surfaces

5. Contact type 1: sliding

Sliding only, no separation. Only sliding along the contact surfaces, no separation.

6. Contact type 2: tied

Tying surfaces with translational degrees of freedom. Nodes of one surface are tied to the opposite surface and vice versa.

7. Contact type 9: tiebreak interface

This is similar to type 8 except that failure is based on stress rather than force at individual nodes.