Products: ABAQUS/Standard ABAQUS/CAE
Tied contact in ABAQUS/Standard:
ties two surfaces forming a contact pair together for the duration of a simulation;
can be used in mechanical, coupled temperature-displacement, coupled pore pressure-displacement, coupled thermal-electrical, or heat transfer simulations;
constrains each of the nodes on the slave surface to have the same value of displacement, temperature, pore pressure, or electrical potential as the point on the master surface that it contacts;
allows for rapid transitions in mesh density within the model;
requires the adjustment of the contact pair surfaces; and
cannot be used with self-contact or symmetric master-slave contact.
To “tie” the surfaces of a contact pair together for an analysis, you must also adjust the surfaces because, as described below, it is very important that the tied surfaces be precisely in contact at the start of the simulation. See “Adjusting initial surface positions and specifying initial clearances in ABAQUS/Standard contact pairs,” Section 29.2.5, for details on adjusting surfaces. As always, you must associate the contact pair with a contact interaction property definition.
| Input File Usage: | *CONTACT PAIR, TIED, ADJUST=a or node_set_label, INTERACTION=name |
| ABAQUS/CAE Usage: | Interaction module: Interaction |
When a contact pair uses the tied contact formulation, ABAQUS/Standard uses the undeformed configuration of the model to determine which slave nodes are precisely contacting the master surface at the start of the analysis. ABAQUS/Standard then forms constraints between these slave nodes and the surrounding nodes on the master surface. The algorithm used for choosing these master surface nodes is similar to that described for the small-sliding tracking approach in “Contact formulation for ABAQUS/Standard contact pairs,” Section 29.2.2.
The tied contact formulation constrains only translational degrees of freedom in mechanical simulations. ABAQUS/Standard places no constraints on the rotational degrees of freedom of structural elements involved in tied contact pairs.
Tied contact has not been implemented with self-contact. Self-contact is designed for finite-sliding situations in which it is not obvious from the original geometry which parts of the surface will come into contact during the deformation.
The tied contact capability can be used in models where the nodal degrees of freedom include electrical potential and/or temperature. Except for the nodal degree of freedom being constrained, ABAQUS/Standard uses exactly the same formulation for tied contact in nonmechanical simulations as it does for mechanical simulations.
ABAQUS/Standard does not constrain slave nodes to the master surface unless they are precisely in contact with the master surface at the start of the analysis. Any slave nodes not precisely in contact at the start of the analysis—e.g., either open or overclosed—will remain unconstrained for the duration of the simulation; they will never interact with the master surface. In mechanical simulations an unconstrained slave node can penetrate the master surface freely. In a thermal, electrical, or pore pressure simulation an unconstrained slave node will not exchange heat, electrical current, or pore fluid with the master surface.
To avoid such unconstrained nodes in tied contact pairs, use the capability for adjusting the surfaces of a contact pair described in “Adjusting initial surface positions and specifying initial clearances in ABAQUS/Standard contact pairs,” Section 29.2.5. This capability moves slave nodes onto the master surface before ABAQUS/Standard checks for the initial contact state. It is intended only for nodes that are close to the master surface and is not intended to correct large errors in the mesh geometry.
ABAQUS/Standard prints a table in the data (.dat) file listing each slave node and the master surface nodes with which it will interact. If ABAQUS/Standard cannot form a constraint for a given slave node, either because it is not in contact with the master surface or it cannot “see” the master surface, it will issue a warning message in the data file. For an explanation of when a slave node would not “see” a master surface and how to correct this problem, see “Contact formulation for ABAQUS/Standard contact pairs,” Section 29.2.2. When creating a model with tied contact, it is important to use this information provided by ABAQUS/Standard to identify any unconstrained nodes and to make any necessary modifications to the model to constrain them.
