Assembly Problems Non-Linear Analysis

[Angothoron]

Hello,

I am in the process of trying to learn this software, and am running into some issues with a sheet metal assembly which doesn't fit together perfectly, as is typical for CAD assemblies (Meaning that bonded connections don't work). I have had success getting the model to run reasonably well with a linear analysis and liberal use of the weld feature, which as far as I can tell uses a surface to tie the components together.

However when I try and run the non-linear analysis it claims there is an error, but works fine when the welds are removed, though now nothing is constraining the model, implying that the surfaces are not useful for non-linear analysis.

Short of remodeling this assembly as a single part, is there any way I can attach two surfaces either connected at an edge or a small gap together.

I have tried the following, and run into issues with each described below.

-Rigid links: Several components attach to a single one, and it won't allow enough connections, it gives me an interference error.
-Weighted links: Seems to only pass the edge forces to one point, and if I am honest I have no idea what I am doing with this.
-Weld feature: As above, does not work with nonlinear analysis.
-Bonded: Refuses to allow partial separation, of which I have a lot in my model.
-Contact Surfaces: Causes meshing problems.

I am not terribly worried about the accuracy of the forces at the welds, for the moment I just want to know what my options are to constrain this.

Any help is appreciated.

Thanks.

 

[shaun8567]

To start, Simulate/Mechanica has limited function for nonlinear analyses compared to linear analyses. For example, Simulate/Mechanica does not support shell, beam, and advanced spring elements in nonlinear analyses. A "Perimeter Weld" involves the creation of shell elements, so if you try to run a nonlinear analysis then the "Perimeter Weld" will be ignored.

It's hard to say what the best approach is for your model without looking at it. That being said, while it's true that most CAD assemblies don't have perfectly fitted parts, this is absolutely not the case for a finite element model. This is why it's common for analysts to modify/create new CAD for a FEM; the small gaps and imperfections can cause meshing and solving issues (even more so with assemblies). I almost always modify/create from scratch my own CAD data for a FEA to avoid issues like this down the road.