5.5.7.1. Interface Delamination Application

The Interface Delamination feature employs either the Virtual Crack Closure Technique (VCCT) method or the Cohesive-Zone Model (CZM) method for defining failure criteria. The VCCT method is a fracture mechanics based method and therefore requires an initial crack (in the form of a Pre-Meshed Crack) in the geometry. The CZM method uses relationships between the separations and tractions along the interface. Note that the CZM method is sensitive to mesh size and material parameters. The convergence of CZM models can generate issues, such as loading step size and stabilization.

Important:  The Interface Delamination feature is not supported with Semi-Elliptical or Arbitrary cracks.

To correctly insert the structural interface elements (INTER202 through INTER205) into the mesh, the Interface Delamination feature requires that the sides of the interface have identical element patterns.

Both the VCCT and CZM methods provide the option to use either the Matched Meshing or the Node Matching generation method. Matched Meshing requires that you create a Mesh Match Control at the delamination interface.

A Match Control requires that both faces referenced by the Match Control belong to the same part, so it is necessary that you create a multi-body part without shared topology. This can be accomplished in a CAD application, such as DesignModeler. Matched Meshing is the recommended Generation Method because it quickly obtains the matching node pairs from the mesh.

Caution:  The application will not respect mesh matching controls when one or more mesh Refinement controls exist. This may result in mismatched node pairs and element faces.

If using a Match Control is not an option and it is necessary to use the Node Matching method, you must ensure that node pairs and element faces match. Because it is necessary for Mechanical to search the scoped geometry for matching node pairs within the specified Distance Tolerance, this method can be slower and less robust than the Matched Meshing method.

Note:  The Interface Delamination feature does not support adaptive mesh refinement.

Also see the Interface Delamination Object Reference page for information about the properties of this feature.

Apply Interface Delamination

To specify Interface Delamination:

  1. Insert a Fracture folder in the Tree Outline. The Fracture object becomes active by default.

  2. On the Fracture Context Tab: click Interface Delamination. Or, right-click:

    • the Fracture tree object and select Insert>Interface Delamination.

      Or...

    • in the Geometry window and select Insert>Interface Delamination.

  3. Select the desired Method: either VCCT (default) or CZM. The properties vary based on your selection.

VCCT Method

  1. Specify the Failure Criteria Option property: either Energy-Release Rate (default) or Material Data Table.

  2. Based on the selected Failure Criteria Option:

    • If specified as Energy-Release Rate: enter a Critical Rate value. This value determines the energy release rate in one direction.

    • If specified as Material Data Table: specify a Material. This property defines the energy release rate in all three fracture modes. This property is defined in Engineering Data. See the Static Structural & Transient Structural section of the Engineering Data Help for additional information about the Cohesive Zone properties used by this feature.

  3. Based on the Generation Method selected, either Matched Meshing (default) or Node Matching, perform one of the following:

    Matched Meshing

    If Matched Meshing, specify a Match Control by selecting a pre-defined Match Control. The Match Control that is referenced by the property requires that the delamination occurs between two independent parts that have the same element/node pattern.

    Node Matching

    If Node Matching, specify:

    1. Scoping Method

    2. Source

    3. Target

    Note:  This option assumes that the existing mesh is already matched.

  4. Define the Initial Crack by selecting a user-defined Pre-Meshed Crack.

  5. Specify the Auto Time Stepping property as either Program Controlled (default) or Manual. The following properties can be modified if Manual is selected, otherwise they are read-only.

    1. Initial Time Step

    2. Minimum Time Step

    3. Maximum Time Step

    Note:

    • The Auto Time Stepping property must be set to On in the Step Controls category of the Analysis Setting object.

    • Time stepping values take effect when crack growth is detected.

  6. If Node Matching is selected as the Generation Type, the Node Matching Tolerance category displays.

    Specify the Tolerance Type property as either Program Controlled (default) or Manual. The Distance Tolerance property can be modified if Manual is selected, otherwise it is read-only.

CZM Method

  1. Specify a Material. This property is defined in Engineering Data. See the Static Structural & Transient Structural section of the Engineering Data Help for additional information about the Cohesive Zone properties used by this feature.

  2. Define the Generation Method property as either Matched Meshing (default) or Node Matching.

  3. Based on the Generation Method selected, either Matched Meshing or Node Matching, perform one of the following:

    Matched Meshing

    For the Matched MeshingGeneration Method, select a pre-defined Match Control. The Match Control that is referenced by the property requires that the delamination occurs between two independent parts that have the same element/node pattern.

    Node Matching

    If Node Matching is the Generation Method, then specify:

    1. Scoping Method

    2. Source

    3. Target

    Note:  This option assumes that the existing mesh is already matched.

  4. If Node Matching is selected as the Generation Type, the Node Matching Tolerance category displays.

    Specify the Tolerance Type property as either Program Controlled (default) or Manual. The Distance Tolerance property can be modified if Manual is selected, otherwise it is read-only.