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A surface-based tie constraint joins two surfaces by eliminating the nodes on the secondary surface with multi-point constraints. Multiple surface-based tie constraint definitions may intersect. At these intersections the secondary nodes are involved in an overconstraint. Only one surface-based tie constraint is needed to eliminate a secondary node. Additional surface-based tie constraint definitions are not needed.

In these tests intersecting surface-based tie constraint definitions are used such that one or more secondary nodes are included in more than one surface-based tie constraint pair. Only one surface-based tie constraint should be enforced at any secondary node.

A rigid body constraint eliminates all the degrees of freedom at the nodes of the rigid body in favor of the degrees of freedom at the reference node. Therefore, any surface-based tie constraints used to tie surfaces inside a single rigid body or between rigid bodies is a consistent overconstraint. In this case the surface-based tie constraint is ignored. Similarly, if the surface-based tie constraint is used to tie a rigid surface to a deformable surface and the surface on the rigid body is the secondary surface, a consistent overconstraint exists for the tie nodes on the rigid body. If possible, Abaqus reverses the main/secondary pair.

In these tests the surface-based tie constraints tie surfaces within a rigid body, between rigid bodies, or between a secondary rigid body and a main deformable body.

If the rigid body constraint refers to nodes or elements that are already part of a rigid body, the common nodes will be involved in a consistent overconstraint.

In these tests rigid body constraints are used to create a single rigid body from other individual rigid bodies or to define a rigid body that includes a part of another rigid body.

A surface-based tie constraint eliminates the degrees of freedom at the secondary nodes using multi-point constraints. If a boundary condition is imposed on the secondary node, an overconstraint results.

In these tests two surfaces are tied and boundary conditions are assigned to the secondary nodes such that a consistent overconstraint is created.

Rigid body constraints create a rigid body that eliminates the degrees of freedom at all the nodes on the rigid body in favor of the degrees of freedom at the reference node. If a boundary condition is defined at one of the eliminated nodes, an overconstraint results.

In these tests a rigid body is defined and boundary conditions are assigned to the eliminated nodes on the rigid body such that a consistent overconstraint is created.

If connector elements are used to connect nodes within a rigid body, a consistent overconstraint is introduced since the nodes at both ends of the connector element already have a rigid constraint. In this case the connector element should be removed. If multiple connector elements are used between rigid bodies, all kinematic constraints beyond three translational constraints and three rotational constraints (in three dimensions) or two translational constraints and one rotational constraint (in two dimensions) are overconstraints. In the case when the connector elements produce a consistent overconstraint between the two rigid bodies, all the connector elements are removed and a connector element of type BEAM is attached between the two rigid body reference nodes.

In these tests connector elements are connected either between nodes within a rigid body or between nodes on different rigid bodies.

Rigid body constraints eliminate all the degrees of freedom at the nodes belonging to the rigid body. If coupling constraints are also used, an overconstraint may occur. Abaqus/Standard will automatically eliminate the unnecessary coupling constraints.

A surface-based tie constraint eliminates the degrees of freedom at the secondary node through multi-point constraints. If the tied surfaces intersect a surface where a contact interaction is defined (normal contact with or without Lagrange friction), the contact interactions at the secondary node are overconstraints.

In these tests surface-based tie constraints intersect surfaces with contact interactions.

Contact interactions and prescribed boundary conditions may lead to overconstraints if either normal contact with the default “hard contact” formulation or Lagrange frictional contact is used.

In these tests hard contact or Lagrange friction is defined and boundary conditions are applied to contact secondary nodes.