Mechanical APDL uses NLAD-ETCHG to apply nonlinear mesh adaptivity for element-type change as follows:
Converts the hex-dom mesh to a new (tetrahedral) mesh based on user-defined mesh-type-change criteria during the solution.
Transfers boundary conditions, loads, contact and target elements, and solution states from the hex-dom mesh to the tetrahedral mesh.
Recovers the model boundary from the deformed hex-dom elements by the tetrahedral elements.
Obtains the equilibrated solution on the new tetrahedral mesh by residual minimization (as occurs in conventional nonlinear mesh adaptivity).
After the conversion to a tetrahedral mesh, the solution progresses and subsequent mesh adaptivity on the tetrahedral mesh can occur based on standard nonlinear mesh adaptivity criteria that you define.
Mesh changes are global (that is, scoped to the body) in NLAD-ETCHG to avoid inconsistent mesh interfaces between the new tetrahedral elements and the other existing elements in the model.
NLAD-ETCHG applies to 3D problems only.
Supported elements are SOLID185 and SOLID186. NLAD-ETCHG remeshes those elements (in the deformed configuration) to tetrahedral SOLID187 elements during the solution process.
Mesh modifications occur via general remeshing. Loads, boundary conditions, contact conditions, solution variables, etc., transfer seamlessly to the new mesh as the solution progresses.