Submodeling from pie-slice with symmetric BC

[omega_heiki]

Hello! I am working on the analysis of a pressure vessel in Abaqus. The vessel has pressure loads, bolted joint loads, thermal displacement, etc. which are all axisymmetric so I have done it as a 1/4 section. The nozzles on this vessel are built in connections with tapped holes, so I don't expect significant stresses to be imparted to the vessel, and I was planning on checking the nozzle loads via a submodel. However I realized now that one of the nozzles is on the vessel axis.

Does anyone know a way to take the state of stress from around that nozzle (which is close enough to 1/4 symmetric for my needs) and apply that to a submodel? Or some other technique that would be helpful here?

 

[FEA way]

You can still use submodeling for regions touching the symmetry planes. From the documentation:

Be careful with submodel boundary nodes that are also on planes of symmetry, where both forms of boundary conditions can be applied. It may be helpful in such cases to apply boundary conditions in a local coordinate system. The local coordinate system should be applied only to the boundary conditions that are intended to override the submodel boundary conditions, since the submodel boundary conditions are always output in the global coordinate directions by the global model.

 

[omega_heiki]

That makes sense to me, but it's not exactly what I'm looking for. What I would like to do is make the quarter section into the full part in the submodel so I can apply some relatively small but asymmetrical loads, like shear in the x direction on the nozzle

 

[FEA way]

Ok, I see now. Abaqus has features called Symmetric Model Generation and Symmetric Results Transfer. They can be used to create a full 3D model from a symmetric one and transfer the results so that the full model has the same material state as the symmetric one and can be used for subsequent analyses. You could try combining this approach with submodeling.

Btw. apart from the classic submodeling, there's an alternative approach via *FIELD IMPORT, SUBMODEL and *EXTERNAL FIELD keywords since Abaqus 2020. It can give you a bit more flexibility in some ways.

 

[omega_heiki]

Great! Thanks