Non-symmetric results for symmetric model and load?

Agnes: Be my guest

And: Has anyone tried whether it was fixed in creo 2.0 M170?

Should be no problem because on december 28, 2015 Mark Fischer said in Enforced displacement, tangential direction, more than 1 revolution

That he would look into this.

He wrote:

Thank you for your post and I appreciate your feedback.  Comments like this are not taken lightly and I am looking into both issues referenced in the above thread (SPR 2848377 and SPR 2873817).

Surely by now Mark knows the status?

Erik

Hi all,

Let me provide an update to the issue.

In Creo Simulate, based on the component (solid or surface geometry) AutoGEM tries to create tetrahedral elements where applicable.  This is the default behavior.  Here is an image of the default mesh created in Simulate for the cone model provided.  There are 234 tetra elements created.

Now running the analysis, you will find the results do not match the expected max displacement of 2.367 mm as in the thread above (Abacus results).  Obviously, there is a discrepancy in the analysis.

An area we have been investigating was the defined size of the elements shown in the image above for this model.  Now Simulate does process the size of the elements based on a number of factors during AutoGEM - model size, size of thin walls, etc. The element size optimization helps provide accuracy in the results versus compute time needed to run the analysis.  In most cases, the element size optimization output is appropriate and helps provide accurate results.  However, in this example, due to the thin wall, we feel the size of the elements might need to be reduced beyond the optimized size produced from AutoGEM.  Development is investigating the algorithm and seeing if it can be tweaked to see how this will improve the results.....at the same time, not causing ill effects elsewhere.  By ill effects, I mean lengthening the process time for all analyses as a result of increased number of elements created by AutoGEM.  Note: this tweak would be a global setting, so we need to be cautious not to negatively impact Simulate. We will have more news on this upon completing our investigation.

Now for this model, we can show that reducing the element size can provide results closer to the expected max displacement.  To try this, you can add a Mesh Control Option - Max Element Size.  In my image below, I changed the max to 12 mm.  This will obviously increase the number of elements created.

Running the analysis, the results are very closer to the expected max displacement.....off by ~1%.  This assumes the results shown above from Abacus were correct.

Another approach would be to add other mesh control options, such as Thin Solids.  This will create both brick and wedge elements.

Again the results are very close within 1% of the Abacus results.

In both these cases, the user would need to add the control options - thin solid or max element size.  To help influence the analysis without the need to add the options is the reason why we are investigating a tweak to the optimization algorithm for element size.

In Creo 4.0, we have added a new option which will help automate the process of creating Thin Solids.  This option is available under the AutoGEM Settings dialog and is called 'Create automatic thin solids'.

This can also be controlled by the config option - 'sim_auto_create_thinsolids'.  Either checking the box in settings (session only) or adding the config option (all session), during AutoGEM, where applicable, brick and wedge elements will automatically be created.  Note: this will not create a thin solid node in the model tree under AutoGEM Controls.  This can be tested in the Creo 4.0 Sneak Peek. Running the analysis with the checkbox selected will provide the following results.....which is less than 1% off the expected max displacement.

I hope this helps explain the situation and the steps you can use to obtain the desired results.  In the meantime, PTC is also looking to improve Simulate to obtain these results out of the box.

Regards,

Mark