A rigid body constraint defines an area within a model whose motion is defined by the motion of a single point. A rigid body can include nodes, elements, and analytical surfaces. The components of a rigid body maintain the same relative position to each other throughout a simulation. Pin Nodes vs. Tie NodesYou can specify nodes in the rigid body to be either pin or tie nodes:
For pin nodes only the translational degrees of freedom are part of the rigid body, and the motion of these degrees of freedom is constrained by the motion of the rigid body reference node. For tie nodes both the translational and rotational degrees of freedom are part of the rigid body and are constrained by the motion of the rigid body reference node. Pin nodes and tie nodes define only the degrees of freedom for the rigid body—they are not related in any way to tie connections or virtual pin connections. The tie nodes and pin nodes become part of the rigid body in addition to all nodes associated with the elements assigned to the rigid body. Nodes that are part of the set of pin nodes cannot also be contained in the set of tie nodes. The node type has important implications when the node is connected to rotary inertia elements, deformable structural elements, or connector elements or when the node has concentrated moments or follower loads applied to it. Rotary inertia elements and applied concentrated moments affect the rigid body only when associated with a tie node. Rigid body connections to deformable elements always involve the translational degrees of freedom; rigid body connections to deformable shell, beam, pipe, and connector elements also involve the rotational degrees of freedom if the connection is at a tie node. | ||||||