How to create a constraint to make the "prescribed displacement" surface planar [COMSOL]

[tugni925]

I am doing a linear buckling analysis and having trouble with it as the solver used in the buckling study cannot find any eigenmodes, so I dont get buckling mode or critical load factor. I keep getting the error

"The following feature has encountered a problem:
- Feature: Eigenvalue Solver 1 (sol1/e1)
No eigenvalues found.
- Error on node 1: No eigenvalues found.
- Error on node 2: No eigenvalues found.
.......on node 15: No eigenvalues found."

I want to create a constraint to make the "prescribed displacement" surface planar (so the structure can't deform in ways I don't want) and then apply a load to it, and see if maybe this will help.

I have applied prescribed displacement to the blue area, and similarly a fixed end on the opposite side:

But how could I make a suface planar (red) and then apply load or displacement to it in COMSOL?

 

[FEA way]

You could create rigid surface and push it towards the structure (of course with contact defined). But in this software it might be difficult so you can use Rigid Connector feature in Solid Mechanics module. As the name suggests, it makes the selected surface rigid and boundary conditions/loads can be applied to it.

 

[tugni925]

Do you think this is the right way to do it? - I disabled the original fixed constraint and prescribed displacement:

Applied displacement via rigid connector:

Fixed end via rigid connector:

 

[FEA way]

This feature works like a rigid body constraint in Abaqus so yes, you can use it this way to apply BCs while keeping the faces rigid. It’s also very useful when calculating torsion with solid models.