Strange Lines in Contour Plot and Incorrect Stress Values in HyperMesh Post-Processing

fober

Hi Altair Community,

I'm encountering two issues while post-processing my FEA results in HyperMesh, and I hope someone can guide me:

Strange Lines in Contour Plot:
While viewing displacement or stress contour plots, I notice oddly colored lines along the boundaries between color bands (e.g., from green to yellow/light-green).

Is this a visualization artifact?
How can I remove these lines for smoother contour plots?

Incorrect Stress Values:
The maximum stress reported seems off compared to the solution given by my university. For example:
The stress values are slightly lower than anticipated, even in critical areas with sharp gradients.
I've checked material properties, and turned off nodal averaging (all as in the solution-steps described), but the issue persists.
Is this related to singularities, solver settings, or HyperMesh's post-processing?

Here’s what I’ve tried so far:
Ensured consistent units and material properties.
Since the input file was provided by my university already, I do not have to change any mesh sizes for example since I used the file, followed the solution (mainly applying the loads and SCP, defining load steps etc.) several times and still get wrong displacement results and the artifacts.

I’m using OptiStruct and HyperMesh version 2023.1, and the geometry includes the model of a wing connector, consisting of 3 parts. All this was provided and prepared by my university.

I have to mention, that I use Hypermesh and Optistruct which is running in a virtual machine using parallels desktop in a M2 Pro MacBook. Maybe this causes such graphical bugs?

Any advice on how to fix these issues or what else I could check would be greatly appreciated!

Thanks in advance,
Fabian

Michael Herve

hello @fober ,

we indeed do not recommend use of Parallel VM for HyperWorks applications as we have face several instabilities which we were not able to solve yet, despite some discussions with Parallel editor.

As we haven't get any similar feedback regarding contour unexpected lines, Parallel VM would then be my first guess.

Regarding your question about the result themselves, Parallel VM should not be a reason for OptiStruct to return different results. So the best would be to compare your model to the reference model from your university in order to understand where the difference(s) comes from.

Among the comparison to be done:

• visual comparison of model set up in HyperMesh
• run Model Checker (in Validate ribbon) for both models
• check connectivity of your parts in both models
• Plot displacement contours, animate the results to identify a possible difference of behavior

Hope that helps,

Michael