Currently trying to model a large structure consisting of plate elements that range in thickness from .5 in to 2 in. The plates that act as a rib I have midplane meshed, but the rest of the parts are all set to All Tetrahedral at .5 in mesh size.
Under the element definition for the tetrahedrons, they're set to 2nd order, midside not included. Due to the size of the model, I really don't want to create a finer mesh, but I'm unsure whether the current mesh I have generated is accurately representing the stiffness of the model. I've read some posts here about using tets set to 2nd order to represent bending in plates, however that's the default setting for tet elements in Simulation 2012 so I wanted to confirm this is correct.
I've attached a picture that shows the vary thickness in plates as well as how they've been meshed. As you'll see, automatic geometry-based mesh size has been turned off per the advice I have recieved when I called Autodesk.
So basically I'm looking for confirmation that the current mesh that I've set up is accuratly representing all the plates in the model.
In comparing lateral defelection of this 3D solid model to a beam model the difference was about 18% (.011 in. in beam to .013 in on 3D solid) , though this was deemed acceptable due to the complicated structure that the beam model would have a fairly hard time capturing.
The mesh looks good to me. Of course, looks mean nothing.
It sounds like you are happy with this design and analysis, and just want to confirm that the mesh is accurate enough. An easy way to check this is to turn the midside nodes on and re-run the simulation. (You probably should copy the design scenario and make the change in the new one.)
If you have anything applied to the tet parts (constraints, other loads that appear at the nodes), take a quick inspection to make sure they are now at the midside nodes, too.
John Holtz, P.E.
Senior User Experience Designer, Simulation
Current version of Mechanical & Multiphysics: 2013 SP1 (2013.01.00.0012 28-Jun-2012)