Larger stress for solid mesh than plate mesh
Larger stress for solid mesh than plate mesh
(OP)
I'm making a model for a pressure vessel. First i made one quickly with 3D solid mesh tetra10 noded. But because i wanted to make some adjustments it was easier to make a plate mesh. Locally the stress is larger for my plate mesh than my solid mesh and i don't understand why. Thicknesses are similar and displacement also.



Does anyone know how this could be? Is there something wrong with one of my models or is there a fundamental difference between the elements that causes this?



Does anyone know how this could be? Is there something wrong with one of my models or is there a fundamental difference between the elements that causes this?





RE: Larger stress for solid mesh than plate mesh
The two peak stresses on the left of the plate mesh look like a point connection to me. Are you sure the different plates are properly connected all the way along their edges? Check the deformed view to see if any gaps open up.
The highest stress from FEA is usually at an infinite stress concentration so it's meaningless and often different between shells and solids. Perhaps you've already eliminated this by capping the maximum value for the plot? In either case, compare values a small distance away from any internal corners/etc. and don't move closer as you refine the mesh.
Have you checked for convergence with mesh refinement? If not, then you can't really expect two different kinds of elements to match. One could need more refinement than the other.
RE: Larger stress for solid mesh than plate mesh
What concerns me is that the for the plate mesh i have a larger red spot than for the solid mesh. The solid mesh only has one node that is larger than 227. For the plate mesh there are multiple elements that exceed 227Mpa, even on the plate at the left which has a huge red spot for the plate mesh but not for the solid mesh.
I was under the assumption that globally the stress should be the same for both models. But for me this seems like a significant difference. I could perhaps accept the stress for the solid model because i know i will have some thick welds at the location of the peak stress. But for the plate model I cannot accept the large stresses.
I did check my model for free edges and i do not have any.
RE: Larger stress for solid mesh than plate mesh
Have you checked with mesh refinement? That's quite important since you can't make much of a claim about accuracy without it. It will at least tell you which high stresses don't matter (don't converge) and which do converge to different values.
An idea to check if it's caused by a limitation of shell elements is try redoing both with thinner walls which should reduce the error of shells. See if that brings them closer together.
Other general things to check if you haven't already:
RE: Larger stress for solid mesh than plate mesh
RE: Larger stress for solid mesh than plate mesh
RE: Larger stress for solid mesh than plate mesh
RE: Larger stress for solid mesh than plate mesh