I would wait until you hear from some of the guys who are much more familiar with this type of structure and SolidWorks Simulation, but I would put more faith in the shell model. With the same size mesh for solids, you only have one element through the thickness of your parts. That isn't enough to get a realistic result. You need at least two, preferably three or more.
Couple questions, Patrick:
- Did both shell and solid element models active converged stress results?
- Can you post the displacement plots for both shell and solid?
- Can you post the strain energy plots for both?
- Can you post a plot of the jacobian for each mesh type?
this comes up once every 6 months or so, you may want to check the forum for previous discussions
you've posted stress and FOS results, have you looked at displacements?
before you go trying to troubleshoot a software bug or your model, i'd suggest building some really simple beam models with solids and shells to give yourself the warm and fuzzy about shells vs solids being equivalent when setup the same. from there you can start addressing some of the questions that shaun suggested.
i would guess the setups aren't the same or your evaluation method is not valid, ie use displacement to compare, not stress
Thanks for all the responses.
Jerry - I had originally created the shell study because I had heard the rule that you need minimum of 2 elements across the thickness to get accurate results. I feel like shells is the right way to handle this study but looking at the results it seems like the shells study isn't producing meaningful data that I would expect. Hopefully I can get it fixed up because I really need to learn more about dealing with shells.
Shaun - I'm sorry but I don't understand your first questions. I can do some basics in simulation but unfortunately I don't work with FEA often enough to progress out of the rookie status. Please see the attached pictures you requested. I did not even know you could do mesh quality plots. Do you know of a good resource that would give me more information on using and interpreting them?
Jared - I will go back and do a more careful search to see if I can find any of the older relevant discussions. I have confidence that shells and solids will produce the same results if I can set them up with in the parameters of their capability. It's more a lack of confidence in my portion of setting them up correctly. We don't have anyone I would consider an expert in simulation in my office so I'm hoping to get more insight from the folks here.
Appreciate all the help guys. See my notes on the screen shots below.
I had a follow up question. I did my contact sets for the shells in groups. There are three tubes with a bonded contact to the shell surface above it. Is this an acceptable method?
Shells - Displacement
Shells - Jacobian
Shells - Strain
Solid - Displacement
Solid - Jacobian
Solid - Strain
Can you zip and email me your model (using Pack and Go)? The peak displacement on your solid element model is more than twice that of your shell element model, so there's a major setup difference between the two somewhere.
Certainly. What email would you like it sent to?
" It's more a lack of confidence in my portion of setting them up correctly. "
once you nail down the shells vs solids in a simple part
start with your assembly and 1 part, shells vs solids, make that work.
then move on to add more parts until you run into an issue. and then investigate.
"I had a follow up question. I did my contact sets for the shells in groups. There are three tubes with a bonded contact to the shell surface above it. Is this an acceptable method?"
shouldn't be an issue, if you have concerns, i would recommend creating separate contacts, see if there is a difference
then do a solid solid and compare to shell solid contact
as shaun mentions, if your displacements are way different, your material or shell thickness is probably different or you have a load that is different. that is the first place i would check. or use the method i described at the beginning of this post to narrow down where the issue is coming from.