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BV_107924436-Contributor
6-Contributor
June 20, 2024
Question

Creo Simulate, Cracks are stoping my analysis from running

  • June 20, 2024
  • 1 reply
  • 3271 views

I am trying to run a structure mode analysis for a support plate assembly i have put together. Ive put together an assembly (fully constrained, and all part materials are defined) but I keep getting errors saying that i have cracks in my model.  This prevents me from running any sort of simulation. 

Ive looked online as to what creo means by cracks and from what i see.  
"A crack exists in the model, probably caused by adjacent placement of free or contact
interfaces and bonded interfaces in a configuration that results in multiple coincident
curves connecting the same pair of nodes. Please modify the interfaces to avoid this."

Im unsure of what to do since everything is fully constrained.  nothing is overlapping or has any duplicate parts, and i cant really put the braze in that will hold everything together when this is manufactured. because of this, alot of the assembly has .002 or the like spacing.  

1 reply

K
KenFarley21-Topaz II
21-Topaz II
June 20, 2024

But it seems you have exactly told us why your model isn't working. You can't have gaps between parts or the software will not behave. Almost every assembly I use for analysis has to be simplified or "derived" specifically for the sake of doing the analysis. For example, using analysis defined fasteners rather than using actual bolts. There are usually a lot of features and other characteristics of the actual models that will not be used to make the parts and the models I use for analysis. Very small rounds, for example, will wreak havoc when I try to mesh models for an analysis.

For your situation, if I understand things, you probably will have to make a special analysis model that doesn't have the gaps you've incorporated for brazing.

B
BV_107924436-ContributorAuthor
6-Contributor
June 20, 2024

Mind you, by the way, these are cylindrical items that are being put together.  

 

The braze components do have a full surface to surface contact in the z direction where the cylinder meets the larger stepped cylinder and the tolerance zones are not seeing load and are gapped, or have tolerance zones, in the x direction.  

Would this still create issues even though the load is seeing all of the correct surface to surface areas for simulation. 

PS: I did do a simplified test where i had a larger gap between said objects in the x direction, with a coincidence connection in the z direction that has full face to face contact. and that worked. 

PPS: I ran another test on the cylinder stack up alone, and this also works. it seems to be the assembly between this piece and the plate assembly (cylinder assembly stacked on to a plate for support) where im seeing these cracks appear


S
SweetPeasHub17-Peridot
17-Peridot
June 20, 2024

I would look closely at Review Geometry, and Diagnostics. If the design gap is not to be welded together then you may need to put a free interface condition, as it may be sometimes within "bonded" tolerance and sometimes outside of that tolerance. (The tolerance of how close surfaces need to be to bond). These types of problems may also be a result of poor geometry tolerance settings in CAD and or SIMULATE side. The simulate side is in the dropdown from the AutoGEM button. I use absolute tolerances and have a mapkey to set those how I like them. I use 0.01mm for the three length tolerances there and also set to 0.01mm absolute on the CAD side. Our assemblies are ~500mm or less. Other sizes may need adjustments in proportion, keeping in mind the smallest features you need to represent.

SweetPeasHub_0-1718915149652.png

Also, when you talk about gaps and coincident connections, hopefully you realize the simulate side does not use the assembly constraints setup in the CAD side. Connections must be redefined in the simulate side using the default interface or explicitly define interfaces as bonded, free, or contact. This is what the review geometry is checking.

 

All that said, cylinders and spheres have unique issues in Creo Simulate and can take special considerations to make them mate and bond, most especially if the geometry was not mastered in Creo. Please let the community know if you happen to be using imported geometry so the help can be more focused. We really could use some screenshots of the error and anything Creo highlighted when the crack error came up (Diagnostics?) , as well as the same area shown using the Review Geometry button.

 

 

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