Why is it that displacement for a cone is not rotational symmetric for an internal pressure?
A sample model is attached (Creo 3.0) I've brought it back to the bare minimum. 1/4 cone, symmetry, default mesh etc.
It doesn't help if you refine to enormous amounts of elements, Large deformationm analysis makes it slightly better, but it is never right?
Why is that? it should not happen.
How do we solve this?
Extra: I've added a full 360 degree version in Creo2.0 format
It is a conical shape with an internal uniform pressure load. Fixed at the flange end.
Here is the exact same model with the exact same loads run in SolidWorks Simulation.
Hi,
geometry transfer from parametric to simulate is inaccurate:
30°, 60°, 90°, 120° etc.error expand
As assembly 180x2°:
Paul
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
Dear Mark
Thank you very much for your detailed answer, but I'm afraid it is a typical case of: too little too late.
It's taken your company 17 months to provide me with the answer that I need a finer mesh. With your product placement (every good designer should be able to use this simulation tool) it is hard to convince your typical user that something easily recognizable (a round-ish thing that becomes un-round-ish with a uniform load) needs extra attention, and still trust results obtained for more realistic products like the one shown below, which is, by the way, not likely to mesh very well in thin solids.
- If this is support, I consider it not present.
- I've seen Jose Coronado's "PTC Creo Simulate Roadmap" of March 2016, containing not much more than cosmetic changes for Creo Simulate 4.0.
As far as I can tell PTC continues to be commercially interested in this product, but seems to have lost the will to back this with technical effort.
--> So why am I paying maintenance for a product that is not supported and not developed?
I regret to have to say that after being a very loyal customer for more than 20 years through various employers, I've informed my reseller two months ago that I will discontinue PTC maintenance as of September 6.
It's a shame.
Kind regards
Erik Haenen
Hi,
cone 49500 bricks as part: non-symmetric result
cone 100 bricks as assembly: better
Paul
Test in stand-alone Pro/MECHANICA STRUCTURE without creo parametric , revolve 1 brick:
revolve feature in structure ist wrong
cylinder is OK:
Paul
Hi Paul,
You are right, geometry description is wrong, not AutoGEM.
Other comparison that show the issue.
Model with mesh.
Model Version1: Feature Revolve
Model Version2: Boundary Blend with option developable (surface from boundary curve)
Regards,
Jerzy
Jerzy,
great work,
geometry description is wrong, all revolve simulate-features, torus too.
Regards,
Paul
