Surface-based constraints

Tie constraints are used to tie together two surfaces for the duration of a simulation. Each node on the slave surface is constrained to have the same motion as the point on the master surface to which it is closest. For a structural analysis this means the translational (and, optionally, the rotational) degrees of freedom are constrained.

Abaqus uses the undeformed configuration of the model to determine which slave nodes are tied to the master surface. By default, all slave nodes that lie within a given distance of the master surface are tied. The default distance is based on the typical element size of the master surface. This default can be overridden in one of two ways: by specifying the distance within which slave nodes must lie from the master surface to be constrained or by specifying the name of a set containing the nodes that will be constrained.

Slave nodes can also be adjusted so that they lie exactly on the master surface. If slave nodes have to be adjusted by distances that are a large fraction of the length of the side of the element (to which the slave node is attached), the element can become severely distorted; avoid large adjustments if possible.

Tie constraints are particularly useful for rapid mesh refinement between dissimilar meshes.