5.5.8. Multi-Point Constraint (MPC) Contact for Fracture

The internally generated crack mesh is created after an initial base mesh is generated. Since the crack mesh is defined based on the crack object, while the base mesh is created based on the geometry and mesh parameters, the two meshes may not perfectly match at the boundaries of the fracture affected zone. For more information on the fracture affected zone, see the Fracture Meshing section.

Note:

  • The application does not create a contact pair when you set the Mesh Method to Tetrahedrons when meshing any analytical crack.

  • The application does not create a contact pair for Arbitrary crack meshing.

When a solution is performed on an analysis which contains an internally generated crack mesh, a contact region using Multi-Point Constraint (MPC) formulation is automatically created between the crack mesh and the base mesh at the boundaries of the fracture-affected zone. This contact is applicable to static structural analysis, transient structural analysis, modal analysis, steady-state thermal analysis, and transient thermal analysis. For more information about the MPC contact formulation, see Contact Formulation Theory. This contact is only created for an analytical crack object which support the Hex Dominant Mesh Method and is not applicable to the Pre-Meshed Crack object.

The characteristics/settings of the MPC contact are shown below. For more information about the different contact settings, see Advanced Settings.

  • Bonded surface-to-surface contact is defined between the crack mesh and the base mesh at the boundary of the fracture-affected zone. The contact element CONTA174 is created on the faces of the base mesh, and the target element TARGE170 is created on the faces of the crack mesh.

  • The contact is asymmetric in nature. The contact can be made auto asymmetric by setting the use auto symmetric variable to 1 in the Variable Manager.

  • Nodal contact detection, normal from the contact surface, will be defined.

  • The initial gap and penetration are ignored.

  • For steady-state thermal and transient thermal analysis, the temperature degree of freedom is selected.

For more information about contact settings, refer to the CONTA174 documentation in the Element Reference. For more information about the MPC constraint, see Multipoint Constraints and Assemblies in the Contact Technology Guide.