Mesh Control

It is rarely necessary to use a uniformly fine mesh throughout the structure being analyzed. You can use a finer mesh mainly in the areas of high stress gradients and use a coarser mesh in areas of low stress gradients or where the magnitude of the stresses is not of interest.

Mesh control refers to specifying different element sizes at different regions in the model. A smaller element size in a region improves the accuracy of results in the region of interest.

For example, the figure below shows a mesh that is designed to give an accurate prediction of the stress concentration at the bottom of the hole.

Mesh refined around the hole

The results from the simulation with this locally refined mesh show that they are comparable to those from the very fine mesh. The simulation with the locally refined mesh required considerably less CPU time than the analysis with the very fine mesh.

Table 1. Mesh refinement (control) around the hole
MeshMax displacement at bottom inner surface of hole (in)Max von Mises stress at bottom inner surface of hole (psi)Relative CPU time
Very fine3.15E-4345.E622.5
Locally refined3.15E-4346.E63.44

You can often predict the locations of the highly stressed regions of a model (and, hence, the regions where a fine mesh is required) using your knowledge of similar components or with hand calculations. This information can also be gained by setting a coarse mesh initially to identify the regions of high stress and then refining the mesh in these regions. It is simple to mesh the geometry coarsely for the initial simulation and then to refine the mesh in the appropriate regions, as indicated by the stress results from the coarse simulation.