Holes

Holes in the model are treated differently depending on their size. If they are small enough they will be removed already in the idealisation step. A hole in the idealized model with an area bigger than the intended element size or intersecting a seam will be integrated into the plating as a free edge.

For the remaining holes they will lead to a thickness reduction of the shell element containing them. There are two parameters that can be given to control thickness reduction: the absolute minimum thickness and the minimum percentage of the remaining material. When the resulting thickness is less than any of the given values the shell element will be removed from the model.

The remaining material is measured along two directions taken from the orientation of the hole. Imagine we have the situation below:

Example:

Figure 6:18. Holes

First the hole's main direction is checked, this is the dashed line. Here the shell element width is 1000 and the hole is 600 leaving 400. The remaining area factor is then 400/1000 = 0.4 which is above the default factor (0.25). However in the direction perpendicular to the main direction (dashed-dotted line) the shell element width is 500 and the hole is 400 leaving 100. The factor is then 100/500 = 0.2 that is below the limit and the shell element will be removed! So if the hole weakens the shell element too much in any of these two directions the shell element is removed.

Regarding the hole radii it is always removed in the FE model as it only contains straight lines. However in the idealized panels the radii always remain. The simplification of the hole radii in the FE model is controlled by the intended element size. If the size is small enough the radii will appear to be there even in the FE model, but if you zoom enough you will see the lines.