Issue with Tie Constraint on Shells

General Questions
1

Hi, I’m relatively new to FEA in general and very new to PrePoMax, Calculix and Salome. I’ve been working on a ground-mounted solar panel fixture, but am having repeatable issues using tie constraints between different shell components.

I’ve created tie constraints both manually and with “search contact pairs”, but the issue occurs with both where the tie constraint is seemingly ignored and the vertical column detaches from the fixture.

The issue I’m repeatedly facing is shown below:

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image1792×1145 411 KB

Being a new user I’m not able to upload my pmx file, but can send it other ways if needed. I’m using PrePoMax 2.0.3 Dev, but it also occurs on the stable release. Mesh was made in Salome.

Any ideas?

Thanks,

2

maybe change the tolerance or moving column part to half of flange thickness can solve the problem.

3

It’s sometimes better to use compound parts. But if you want to use tie constraints, make sure that adjustment is enabled and that tolerance is properly set.

2 Likes
4

How do you use compound parts correctly? Do these need to me merged in CAD, the Geometry step of PrePoMax or at the FE Model step of PrePoMax?

5

You don’t have to merge in CAD, you can import separate parts, select them, right-click and choose Create Compound Part in the Geometry tab.

6

You create compound parts only if you need them. You need them if you want to split a body into separate but connected bodies. Usually, this is used to apply different materials or to be able to perform structured mesh.

If you have separate parts from the design and would like to model them as connected, you can merge them in CAD or create a compound. In this case, there is no difference.

7

I have now used to create a compound out of three shells. However they dont stay together. Any ideas?

8

Depending on how the parts are connected, compound creation may fail to merge them: Deformation in 2 or more bodies - #10 by Matej

1 Like
9

For shells, the only real scenario in which the compound is needed is a non-manifold geometry. In other scenarios, a CAD merge is a better solution.