Boundary conditions and loading

After refining the mesh the boundary conditions and the loading have to be moved from the old (= unrefined) mesh to the new (= refined) mesh. This includes SPC's, MPC's, point loads, distributed facial load, distributed volumentric load and temperature loading.

In the past SPC's, MPC's and point loads were taken care of by creating MPC's connecting the old node in which the SPC, MPC or point load was applied with the nodes of the element in the new mesh within which the old node was located. This, however, let to high concentrated stresses in the new mesh. Therefore, it was decided these old nodes are not to be moved during mesh refinement. Furthermore, their node number is kept. Therefore, the *BOUNDARY, *EQUATION and *CLOAD cards in the unrefined mesh remain valid.

The same applies to the faces loading by facial distributed loading: the nodes of such faces are not moved during mesh refinement, their numbers are kept as well as the element number of the adjacent element. Therefore, the *DLOAD card in the unrefined mesh remains valid.

The volumetric distributed loading (centrifugal loading, gravity) in an element of the refined mesh is inherited from its parent element. The same applies to the material properties. Therefore, mesh refinement should not be performed across a material border.

Temperatures in the refined mesh are interpolated within each step from the temperature for that step in the unrefined mesh.

If an input deck contains several steps, in one of which refinement is performed, the decision in which nodes are not to be moved is based on the boundary conditions and loading in that step. If in another step other nodes are loaded, the latter will not be loading leading to wrong results. Therefore, the user should take care to include any node loaded or constrained in any step of the input deck in the mesh refinement step, e.g. by applying a zero point load.