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Constraints
A rigid body has exactly six degrees of freedom (DOF) - 3 in the translational and 3 in the rotational direction.
Accordingly, a finite element model also needs to have all its DOF constrained.
Pro/Mechanica allows three commonly entities to be used: Point, Edge/Curve and Surface.
Insert > Displacement Constraint
For each of given entities (with the exception of Cyclic Symmetry), the constraints can be set as follows:
Once a constraint is specified, Pro/MECHANICA will attach a symbol to the entity indicating its status.
If a constraint set contains more than one constraint, not all entities need to have all 6 DOF constrained. However, all entities combined need to fully constrain the model.
It is important to remember, that only one constraint set at a time can be used to specify an analysis. So be sure to group individual constraints that need to be part of an analysis into a single constraint set..
Examples
Cantilevered Beam
The cantilevered beam shown below has its left end firmly attached to a wall, while its right end is free to move. The boundary condition for the left end prevents all translations and rotations, resulting in all 6 DOF constrained.
Table With Four Legs
Problem: How to model the interaction between the legs of the table and the floor.
