Hi,
Your post is similar to some old posts I replied to on the Mecway forum. I went back and analyzed those files in more detail. I made a lot of changes to get agreement to classical calculations and to show a true buckling failure.
With the thin shell model that you are trying to solve, it doesn’t agree well to classical calcs. It also doesn’t seem to fail via buckling. I keep seeing stresses way beyond the yield point. This is why I changed things a lot.
In doing the updates I found that having a fixed base and free top gave the best agreement to classical methods. The fea software doesn’t have the right bc to simulate the other constraints. In any event, just as a simple pure buckling example, the attached should suffice for most people. You can shorten the beam and compare to Johnson’s formula. I ended up lengthening the beam and comparing to Euler’s formula for this particular example. I can get good agreement with either type of beam.
I created the entire model in Mecway and solved within the software using the ccx solver and intel pardiso. To get the buckling mode to appear I deleted some elements from the column. This would simulate something like corrosion or damage of some kind.
You can see that the displacement is nonlinear even though the stress is well below yield. So this is what buckling is about.
Hope this helps
I don’t see a way to upload *.inp files or *.pdf files. So here is a link to those:
I’ll keep the link active for a few months.
This is a good website for classical buckling info: