I am analyzing a bronze bellows as both a 2d cross section (axi-symmetric) and a 3d shelled revlove. both models have at same material properties and thickness (bronze, .008" thick) and both have the same deflection and internal pressure (.01" delta and 340 psi). for some unknown reason, the 3d shelled revolve has stress levels about 2x the 2d model. Not sure which is more accurate or why there is such a large difference. Any help would be greatly appreciated.

Also, is there a way to use the results of the 2d analysis for a fatigue study? Thanks in advance.

Hi Steve, I took a look at the model that you had attached. The mesh is insufficient in crucial areas and the element type is first-order "Draft" quality, which are not suited for bending applications. PDF attached with comments.

I made some modifications to both the shell model and the 2D axi-symmetric one, attached. For the shell model, I created a mid-surface by offsetting one of the sides, and cut the model down to only 30° to take advantage of symmetry so that one can add more elements without adding too much more solver time. The result that works well here is the 3rd principal stress on the bottom, since the inside is under compression.

The 2D problem, I decreased mesh size globally and added mesh controls around the bends like I did for shell model. For the results, I used von Mises and focused on the inside, because that's what the other posts showed. Bonus, the 2D results are shown with a 3D visualization... see below.