Post-Processing Time

[ahad29]

I am using Pro/Mechanica 2001 structure module. I have 6 loads in my load-set. During post-processing I look at Von Mises stress for different load combinations. The results window takes about 7-10 minutes to show up. My model has 15,000 elements and I have analyzed it for 6th degree polynomial but still I wish it did it faster since it is post-processing. My computer has 2GHz processor. Has anyone run into similar situation? Thanks

ahad

 

[Nettuno]

Hi ahad,

I am using Pro/Mechanica 2001 structure module too, and my experience about Static Analysis brings me to analyse models with no more than 7000 elements using the maximum degree polynomial, because calculation and post processing time become unacceptable (and sometime the program suddenly fail). In order to decrease number of elements I usually suppress all those features in the model that are useless like: very little holes, rounds, chamfers, little cuts ...
How long did ProMechanica calculate your model to get results?
Did it converge?

Regards!

 

[ahad29]

My model has about 15,250 elements and believe me I took out all the fancy stuff. I set it up for a polynomial order of 6 and it took about 7hrs and 15min. As for convergence I have six load sets and all of them converged to less than 4% on Von Mises stress. But the interesting thing is when I ran the same analysis again with same poly-order it created about 14,800 elements it took 3 and half hours to run it with not very impressive convergence. This brings me to another question that is there anyway to control the number of elements it creats and the convergence it reaches (other than setting the poly-order).

ahad

 

[Nettuno]

ahad,

I hope this information about control number of elements (in INTEGRATED MODE) could be usefull, I took this information from PTC Knowledge Base Site.

Suggested Technique for Preparing Model

In Pro/MECHANICA Structure and Thermal, elements need to be generated in the part or assembly as the first step in the analysis. In Integrated mode elements are automatically created using AutoGEM as part of the analysis. In most cases AutoGEM will complete a properly built model without any user intervention. In certain situations, including models with geometric inconsistencies or small features, AutoGEM needs to be assisted in order to successfully complete the mesh.

Procedure
1. Surpress all unnecessary features - this will reduce the total number of elements generated and may also simplify the geometry to a point where AutoGEM is able to mesh it successfully. It is especially important to surpress features which can create small or difficult to mesh surfaces. Features likely to create these surfaces include; rounds, unaligned features and variable section blends and sweeps.

2. Check the following items inside of Pro/ENGINEER to ensure that the geometry is fully specified within Pro/ENGINEER.
Info, GeomCheck - Highlights any geometry with unclear Pro/ENGINEER design intent. All GeomChecks must be cleaned up for successful AutoGEM.
Analysis, Surface Analysis, Slope - colors the part according to surface slope. This allows easy determinition of whether or not edges are sharp and also ensures that geometry changes are smooth in blends and sweeps.
Analysis, Model Analysis,  ShortEdge - highlights small edges
Analysis, Model Analysis, Global Inteference - highlights any areas of interference for assemblies. Interference should be avoided in assemblies that will be meshed with solids. Interpenetration can be a useful technique for lining up mid-planes in shell compressed models and will work in the majority of cases. In a small number of cases, interference in shell compressed assemblies will create incorrect geometry. Because of this, interference should be removed when trying to debug AutoGEM issues on shell compressed assemblies.

3. Modify the model to clean up any geometry which appears questionable. In cases where small surfaces or edges with rounds create problems, the commands Tweak, Replace; Tweak, Patch; and Protrusion, UseQuilt may be useful. Adding sections to blends and sweeps and adding points in variable radius rounds may be helpful.

Regards!

 

[ahad29]

Thanks Nettuno,
I do all this but the models that I deal with are very complicated and even after removing all these stuff I end up with large number of elements. When I say control the number of elements I dont mean to say decrease. I mean in terms of giving the software the exact number of elements you wish to have in the model. I dont think there is a way to do that. Thanks