I am trying to optimize a simulation model for speed so I can run through multiple design ideas fairly efficiently. My assembly is made a some thin walled solids so I converted those to shells. However, I am finding the calculation takes LONGER with the SHELL and SOLIDS, than than if I just left them all as SOLIDS. I was always under the impression that using shells would increase model speed. Instead, it seems like there is an additional step called "Forming surface-to-surface bonding" that adds to the overall solution time. Any thoughts?

Shell/Solid model

DOFs: 194,994

#of Elements: 27,712

#of Nodes: 56,655

Solution time: **00:02:30**

Solid model

DOFs: 292,566

#of Elements: 48,919

#of Nodes: 98,128

Solution time:** 00:00:32**

(I'm running a fairly coarse mesh just to baseline the speed of the new model)

One thing going on here is comparing tension of a continuous mesh to tension of a mesh with a seam holding the shell and solid together that has 3 rotational degrees of freedom. This can be fixtured so the rotational strain is zeroed out which would be a more similar case to the continuous mesh. A hunch I have is the solver time difference is smaller than that for the unrestrained rotation.