This section describes the limitations for the generation of a crack mesh on the supported analytical crack types (Arbitrary Crack, Semi-Elliptical Crack, Elliptical Crack, Ring Crack, Corner Crack, Edge Crack, Through Crack, and Cylindrical Crack). In addition, it describes the limitations in the computation of fracture parameters for these crack types, including the Pre-Meshed Crack object.
A Fracture analysis does not support adaptive mesh refinement.
For Arbitrary Crack, Semi-Elliptical Crack, Elliptical Crack, Ring Crack Corner Crack, Edge Crack, Through Crack, and Cylindrical Crack objects, crack meshing requires that the base mesh is a quadratic tetrahedron mesh. Linear elements may exist farther away from the buffer zone on the same body to which these cracks are scoped.
Important: If you have a hex-dominant base mesh, you can convert it to quadratic tetrahedrons using the Re-mesh Hex-dominant to Tetrahedral property on the Fracture folder.
Only 3D analyses support analytical crack types (Arbitrary, Semi-Elliptical, Elliptical, Ring, Corner, Edge, Through, and Cylindrical).
You should define Semi-Elliptical cracks on the surfaces of a solid body only, and the crack cannot span more than one face.
When you scope any analytical crack type to multiple bodies:
All bodies must be from a single multi-body part with shared topology - edges or faces.
All scoped bodies must be included in a Material Assignment object so that each has the same material identifier.
The Mesh Method property must be set to .
The Semi-Elliptical Crack does not support multiple body scoping.
When the crack dimensions of an Elliptical Crack or a Ring Crack intersect with the free surfaces of the solid body, the application only supports the option of the Mesh Method property.
The Stiffness Behavior property of the geometry scoped to any crack or Crack Initiation object must be set to .
For an Arbitrary Crack, you can only scope the Crack Surface property of the crack to a single surface body.
The Pre-Meshed Crack:
Only supports the planar crack definition. The nodes of the node-based Named Selection specified for the Crack Front must be in a single plane.
Requires that the geometry used to create the node-based Named Selection specified for the crack front have the Stiffness Behavior property set to .
Is the only crack type that supports VCCT based fracture parameter computations because this technique is only supported for lower order crack mesh.
It is not recommended that you specify a Part Transformation on a body that includes an Arbitrary Crack. This could lead to the application detecting an incorrect extension direction for the crack front nodes.
Arbitrary, Corner, Edge, Through, and Cylindrical cracks can only be meshed using tetrahedrons (Mesh Method set to ).
In order to retain restart points when the Fracture property (Analysis Settings > Fracture Controls), is set to , you must set the Retain Files After Full Solve property to .
Analytical crack or arbitrary crack top and bottom face nodes are not connected through any constraint equation. Therefore, the nodes of the top face can penetrate the bottom face or vice versa based on the applied loads and constraints. In these scenarios, you may need to create a constraint equation between crack faces for the solution using the Commands (APDL) object.
The graphical view of a Semi-Elliptical Crack, Elliptical Crack, Ring Crack, Corner Crack, Edge Crack, Through Crack, or Cylindrical Crack may differ from the generated mesh. For more information, see the section on Cracks.
The Arbitrary Crack, Semi-Elliptical Crack, Elliptical Crack, Ring Crack, Corner Crack, Edge Crack, Through Crack, or Cylindrical Crack objects are not supported in combination with the following features:
Cyclic Region
Structural Linear Periodic Symmetry Region
Interpolated displacements for the facets in a surface construction object may fail to demonstrate the proper deformation of a Semi-Elliptical crack. For more information, see Surface Displays and Fracture.
In order to use the Fracture Tool to extract the fracture results and probe results from the results file of another analysis using the option, it is necessary that the meshes from both systems, including the crack mesh, match.
Fracture parameter calculations based on domain integrations such as SIFs, J-integral, or Material Force are not supported when contact elements exist inside the domain. The calculations may become path-dependent unless the contact pressure is negligible.
If you have a Hyperelastic material assigned in the analysis, only Material Force fracture results are supported.
When the C*-Integral property (Analysis Settings > Fracture Controls) is turned , which requires a creep material and the Creep Effects property set to , the application does not compute any other fracture parameters.
Only the J-Integral and Material Force fracture parameter computations are supported when the Large Deformation property is set to .
Graphical Display Limitations
Fracture results for a crack scoped to multiple bodies could display solid bodies less transparent compared to when scoped to a single body and may require additional time to graphically display compared to those results for the crack scoped to single bodies.