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JacksonLevi1-Visitor
1-Visitor
May 17, 2018
Question

Help with Contact analysis and convergence

  • May 17, 2018
  • 1 reply
  • 1838 views

Hello everyone,

 

I am JacksonLevi, i am new to this forum, I am working in one of the Animated video production studio. I am having some issue and i need your help.I have been trying to run a cantilevered link and pin analysis with contact in Mechanica. The results look reasonable to the eye but I cannot make any firm conclusions as the analysis never manages to converge.I suspect that it it the contacting elements that are not converging, and the rest of the model is OK, but I can't find a way to prove it. Using P-level plots can show where element edges have not converged, but not the elements themselves.Is there a way that I can show the problem area is purely the contacting regions? Please help.

 

Any help would be greatly appreciated!!!!

 

Thank you.

1 reply

S
SweetPeasHub17-Peridot
17-Peridot
May 17, 2018

Hello JacksonLevi,

I think it would help if you included an image or sketch of your model with the constraints, loads, and contacts.

I might attempt the nearest modelling method that does not have contacts before doing contacts. (like maybe weighted links with general springs for joint compliance)

Sometime I find adding a soft spring between contacting parts or to ground will help convergence.

Some things I would ask about my model.

Is it a static case and constrained properly?

If contact with friction, are my coefficients too high?

If no friction then is it unconstrained in some aspect?  would real friction add damping to possible oscillations?

are my element sizes compatible with the contact?

do I have very local high stress due to contact pressure that elements are too large to converge stress.

do I have sharp corners near contacts?  Should I fillet nearby surfaces and include the fillets in the contact definition?

Do I have enough load steps to gradually apply the load? (max is 99)

should I increase/decrease the contact tolerance?

Can I accept increased contact penetration depth form default of 5%?

Something wrong with material?  Can never reach the load required - large or infinite strain needed?

 

Not everything but what comes to mind.  Contacts are tricky and analysis can take a very long time.

We have much better luck with contacts in other FEA softwares than Creo but prefer the CAD integration features of Creo.

Sweetpeahub.

 

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