Flexible Body Model Builder - What causes unexpected error?

Hello everyone,

I'm working with a relatively complex goemetry in the FlexibleBodyModelBuilder tool. It's a thin-walled structure with the thinnest walls being 1mm thick. I set the min element size to 0,5mm. I've tried both ROM generators and run into unexpected errors

Any idea what could be wrong? Is my geometry just too complex? Any insights are much apprecieated!

Best regards,

Atli

Answer 1

[Simar]

Hi Atli,

I understand that you are working with Flexible Body Model Builder tool in MATLAB and encountering issues with Reduced Order Model (ROM) generation, especially with complex geometries like thin-walled structures. Here is a breakdown of potential issues and workarounds to troubleshoot and resolve them:

1. Complexity of the Geometry:

• Generating meshes and ROMs for thin-walled structures is challenging due to need for high aspect ratio elements to accurately depict the geometry. Using a minimum element size, like 0.5mm, significantly raises model complexity and computational demands, while also introducing numerical issues.
• Workaround- Try simplifying geometry to reduce complexity while maintaining essential characteristics of model that influence its behaviour. Instead of uniformly refining the mesh across entire geometry, focus on areas where higher accuracy is critical. This approach can help manage the model's complexity.

2. Numerical Instabilities:

• Elements with high aspect ratios, which are common in meshes of thin-walled structures, can lead to numerical instabilities in both the simulation and the ROM generation process. Additionally, incorrectly specified material properties or boundary conditions can also lead to errors in simulations, affecting the ROM generation.
• Workaround- Check Material Properties and ensure that they accurately represent the physical materials. Verify that the boundary conditions applied to the model are also appropriate for the simulation scenario.

3. ROM Generation Method:

• The settings and parameters used in the ROM generation process (e.g., order of the ROM, tolerance levels) might need adjustments to better suit the model's specifics.
• Workaround- Explore different ROM Techniques to see if they are more successful with current model. Try adjusting parameters of ROM generation process, by reducing ROM's order or changing tolerance levels, to find a configuration that works for the model.

Hope it helps!

Best Regards,

Simar

[Atli Tobiasson]

Hi

That is all possible, but doesn't seem to be the real cause of my issue.

This error occurs always after roughly 1-2 minutes generation time. For every setting and for every model. Even if I use very simple models and models that have worked in the past. My guess is something is wrong with the Integro-Differential Modeling Framework, and I'm going to try to reinstall it.

Best regards,

Atli