# Coupling constraints

 The surface-based coupling constraint: couples the motion of a collection of nodes on a surface to the motion of a reference node; is of type kinematic when the group of nodes is coupled to the rigid body motion defined by the reference node; is of type distributing when the group of nodes can be constrained to the rigid body motion defined by a reference node in an average sense by allowing control over the transmission of forces through weight factors specified at the coupling nodes; automatically selects the coupling nodes located on a surface lying within a region of influence; can be used with two- or three-dimensional stress/displacement elements; and can be used in geometrically linear and nonlinear analysis. The following topics are discussed:
 Related Topics In Other Guides About surfaces *COUPLING *KINEMATIC *DISTRIBUTING Defining coupling constraints

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