Overconstraint Checks

An overconstraint means applying multiple consistent or inconsistent kinematic constraints. Many models have nodal degrees of freedom that are overconstrained. Such overconstraints may lead to inaccurate solutions or nonconvergence. Common examples of situations that may lead to overconstraints include (but are not limited to):

  • contact slave nodes that are involved in boundary conditions or multi-point constraints;

  • edges of surfaces involved in a surface-based tie constraint that are included in contact slave surfaces or have symmetry boundary conditions; and

  • boundary conditions applied to nodes already involved in coupling or rigid body constraints.

The overconstraint checks performed in Abaqus/Standard:

  • check for overconstraints caused by combinations of the following: base motions, boundary conditions, contact pairs, coupling constraints, linear constraint equations, mesh-independent spot welds, multi-point constraints, rigid body constraints, and surface-based tie constraints;

  • check for overconstraints resulting from kinematic constraints introduced through connector elements, coupling elements, special-purpose contact elements, and elements with incompressible material behavior;

  • identify through detailed messages the constraints that cause overconstraints;

  • automatically resolve a limited set of consistent overconstraints detected during model preprocessing and during an Abaqus/Standard analysis;

  • use the equation solver to detect overconstraints that cannot be resolved automatically; and

  • can have the default behavior modified.

The following topics are discussed:

Related Topics
General multi-point constraints
Mesh tie constraints
Coupling constraints
Mesh-independent fasteners
In Other Guides
Rigid body definition
About connectors
Boundary conditions in Abaqus/Standard and Abaqus/Explicit
About contact pairs in Abaqus/Standard