Hi to everybody
Could anybody explain difference in results (between creo simulate and PPM/Calculix.
Significant difference exists on 3 ribs which is visible on screen shot. It is simple linear static basic calculation
It’s hard to say based on just those screenshots. What is the difference in values ? Are you sure that everything is the same in setup ? What about the mesh ?
I can send model (pmx and frd and step
That would be helpful but there’s still a matter of making sure that the same setup is used in the orher software and carefully comparing the results.
Strange results are at the bottom ends of ribs rest is more less ok
arek2.pmx (3.4 MB)
Ribs are not under load and there should be no stresses
But why ?
Should be the same results
Best regards and thank you for help
Tie constraints may sometimes influence the stress distribution and cause artificial stress concentrations so it’s better to avoid them near the regions of interest. It’s often safer to merge meshes/parts.
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Ok but when I m merging bigger models then mesher fails
Best regards
You may have to merge the parts in CAD software (before importing them to PrePoMax) and/or modify the geometry to make it mergeable (models should be adapted for FEA anyway).
In the past I was doing stp as one parts but prepomax -mesher had problems with meshing one big part.
Hi Michal,
Don’t forget that Creo Simulate uses a completely different mesh technology, p-adaptive (or HP-adaptive in certain situations, e.g. contact), so in order to get a reasonable comparison with h-adaptive elements, you should carry out some mesh convergence studies using ProPoMax. The UK RAE requires at least six mesh refinement iterations if using h-adaptive elements, plus convergence on displacement and strain energy.
The mesh density at the corner looks too low on the PrePoMax result. Have you checked that the reactions and deflections are comparable?
Regards,
Rod
(30+ years experience with Creo Simulate, but a novice with PrePoMax)
I’m using creo simulate for decades , I know difference between SPA and MPA and H method and P method , but results should be more less the same . Results from Creo are ok but from calculix not especially
Will it be corrected in next versions ? I would like to work on software which I have full confidence for results
What do you mean by fixing Michal?
Last time we made a more detailed comparison in one of your models I pointed you some loads were set up in different directions and you later found some others were missing.
I would consider some possible human error factor too.
ÂżHave you performed the modal vibration to check contacts before applying any load.?
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That would be a question to Guido since it depends on CalculiX, not PrePoMax which is just a pre- and postprocessor for that solver.
However, I’ve noticed that even swapping the master/slave surfaces for that tie constraint connecting the middle rib to the front plate might be sufficient to eliminate that spurious stress concentration:
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In a free-body modal analysis, six rigid-body modes should result.
Why do the last three modes deform the model?
Is it possible that some boundary condition is still active even though it has been deactivated?
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I would not be surprised if there are issues with the solver, spooles or pastix. Generally, pardiso works out very well with modal extractions, in my experience.
Then you are using the wrong software: ccx, and many other open-source codes are “research”-level codes that assume their users know there are bugs and can be easily spotted with a trained eye. Expecting “full confidence” in research-level code sets you up for disappointment… but then is only free software 
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