2. Principle of the test#

In DEFI_FISS_XFEM we can define the crack on a mesh by four different methods:

  • by groups of meshes that form the crack and its bottom. To create these two groups, the PROPA_FISS operator is used for simplicity (INITIALISATION method).

  • by analytical functions that allow the two level sets to be calculated directly:

\(\mathrm{lsn}=Z\)

\(\mathrm{lst}=Y-1\)

  • by a catalog of predefined shapes. In this case we use the form DEMI_PLAN.

  • by two fields at the nodes that represent the two level sets. For simplicity, these two fields are extracted from the crack defined by the catalog of predefined shapes above.

It is expected that the fields at the nodes that characterize the two level sets of the crack on the grid are the same as those that the level sets give on the mesh of the structure. If for the grid we use the same mesh as that used for the structure, we expect that the values of the two fields in each node of the grid are the same as those at the same node in the mesh of the structure. For each available method, the procedure is therefore as follows:

  • we calculate the level sets on the mesh of the structure and on the grid by DEFI_FISS_XFEM,

  • for each node in the mesh of the structure, we calculate the difference between the normal level set \(z\) defined and that at the same node in the grid mesh,

  • for each node in the mesh of the structure, we calculate the difference between the level set tangent \(y\) defined and that at the same node in the grid mesh,

  • we check that at each node the two differences calculated are equal to zero.

We do the same thing for interfaces with the difference that only one level set (the normal one) is used to define an interface.