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Keyword type: step
With this keyword a user-defined part of the input mesh consisting of C3D4 and C3D10 elements is refined according to certain criteria and the calculation is automatically restarted with the refined mesh. Temperatures, and volumetric distributed loading (e.g. centrifugal forces) are automatically modified. If the temperatures or volumetric distributed loading in the domain to be refined are applied using an amplitude (*AMPLITUDE), this amplitude should not vary within this domain. To determine the temperatures, initial displacements and initial velocities in the new mesh interpolation based on the unrefined mesh is done. Nodes belonging to single point or multiple point constraints, or in which a concentrated load is applied (using *CLOAD) are not moved during refinement and the nodes numbers are kept. Faces on which pressure (*DLOAD) is applied are allowed but are not refined. Their nodes or not moved ant their numbers are kept. This also applies to the element number to which the face belongs. Therefore, the *DLOAD card in the unrefined mesh remains valid.
The refinement is done in the step in which *REFINE MESH is used and is based on the results calculated in that step. In particular, the user should take care that any node subject to a SPC, MPC, concentrated load or distributed facial load is subject to this constraint or loading in the mesh refinement step. If not, a fake loading of zero can be applied. The keyword *REFINE MESH should occur at most once in the complete input deck. It is not allowed in a restart calculation (characterized by *RESTART,READ).
For the refinement the available criteria are the size of the displacements (label U), the velocity (label V), the stress (label S), the total strain (label E), the mechanical strain (label ME), the equivalent plastic strain (label PEEQ), the energy density (label ENER), the heat flux (label HFL), the gradient based error estimator (label ERR) or a user-defined function (user subroutine ucalculateh.f). The size is defined as the absolute value if it concerns a scalar quantity and the norm if it concerns a vector or tensor.
There is one required parameter LIMIT and three optional parameters ELSET, USER and SMOOTHING ONLY.
With the parameter LIMIT the user defines a positive value above which refinement is requested. For instance, if the limit is 50. and the value of the selected criterion is 200. a refinement by a factor of 4 is aimed at. The refinement is done iteratively (5 times), and each iteration induces a maximum refinement by a factor of 2.
The parameter ELSET allows the user to define an element set (which should consist of C3D4 and/or C3D10 elements only) to be refined. All other elements (no matter whether tetrahedral or not) are not changed. Notice that the interface between the part of the mesh to be refined and its complement is not changed, so multiple point constraints describing this interface still work after refinement. The element set name should not be longer than 60 characters.
With the parameter USER a new criterion for the refinement can be coded in user subroutine ucalculateh.f.
Finally, the parameter SMOOTHING ONLY the user can perform a smoothing of the existing mesh without refining the mesh, i.e. the existing nodes and elements and their numbering is kept. This option does not need any results, therefore, the parameter LIMIT does not make sense and no line specifying the criterion is needed either.
If the tetrahedral mesh in the input deck contains at least one quadratic element, the refined mesh contains C3D10 elements only, else it is a pure C3D4 mesh.
Finally, *REFINE MESH is only available in a *STATIC or *DYNAMIC step. If the job name is “test” the refined mesh is stored in input format in “test.rfn.inp” (can be visualized with CalculiX GraphiX using “cgx -c test.rfn.inp”) and the unrefined mesh in “test.urf.frd”.
First line:
Second line:
Example: *REFINE MESH,LIMIT=50. S
requests a refinement based on the size of the stress and a limit of 50.
Example files: circ10p.