I want to use the pde toolbox for solving structural modal problems. For this I just started with the examples provided with matlab software.
Firstly I used the exmaple for calculating the natural frequencies of a square plate with dimensions 10x10x1:https://www.mathworks.com/help/pde/ug/vibration-of-a-square-plate.html. This script works fine and the natural frequencies are plausible. For training purpose, I just designed a simple beam and converted it to STL file and imported it with "importGeometry" functon. However, I clampled the beam one side and caluclated the natural frequencies, but I figured out that a.) takes very long and b.) I'am getting over thousand of natural frequencies which are similiar to each other. Also the modeshapes looks like I have some modes with spikes of the surface. I guessed that there is something wrong with the geometry, so I exported a square plate with 10x10x1 as mentioned in the example above and getting the same strange behaviour using the code of the example !
I think there can be an issue with the STL geometry.. So is there any special things I have to consider when I export STL files from the CAD software ?