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Chapter 8: Contact and Constraints Up Chapter 8: Contact and Constraints Section 8.2: Contact

## 8.1 Rigid Body Constraints

The degrees of freedom of rigid bodies can be constrained in the same way as any other degree of freedom in the model. Before you can apply a constraint to a rigid body, you need to define a rigid body. In FEBioStudio, rigid bodies are implicitly defined when you create a rigid body material. A rigid body constraint can now be applied using the Physics/Add Rigid Constraint menu. It is important to note that when a rigid body is created none of its degrees of freedom are initially constrained.
In the Add Rigid Constraint dialog box first select the step in which this constraint will be active (or the Initial step if the constraint is to be active in all steps). Next, select the rigid body to which this constraint will be applied. Then, select a constraint from the list of available constraints that can be applied to a rigid body degree of freedom. The Fixed Displacement/Rotation constraint fixes the degree of freedom to zero. This implies that the rigid body will not be able to move or rotate in that degree of freedom. The Prescribe Displacement/Rotation lets you prescribe the value of the degree of freedom over time. The Prescribe Force/Torque constraint lets you apply a force or a torque (with respect to the rigid body's center of mass) to a rigid degree of freedom. Note that the prescribed displacements and force constraints have a load curve associated with them that can be edited in the Curve Editor.
Chapter 8: Contact and Constraints Up Chapter 8: Contact and Constraints Section 8.2: Contact