4 Replies Latest reply on Jun 15, 2016 6:13 AM by James Riddell

no penetration contact not taken into account

Adi Pro Jun 13, 2016 11:51 AM

Hello visitors,

There is an assembly composed of: a structure (1, see image) which is supported by four fixed parts (2). Contacts structure/support are

No Penetration Contact.

My goal is to observe the flextion of the structure (1).

The problem is that one of four contacts is not taken into account (there is a lack o support, a side of the structure is not supported => the stress is very low on this support) consequently there is an anormally high stress and torque on the opposite support (which is not normal).

Do you know:

1 why this contact fails?

2 and how to correct this failing contact?

thank you in advance for your ideas

P.S. I use Slidworks 2013

Re: no penetration contact not taken into account

James Riddell Jun 13, 2016 4:05 PM (in response to Adi Pro)

If you have set up the support points as non-penetration (doesn't look like an issue) and the structure deforms in such a way as to 'lift off' one of the points then there will be no stress in that area.

Depending on exact geometry, your 4th support may be holding the structure down (negative force) if they are rigidly attached in any way.
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- Re: no penetration contact not taken into account
  
  James Riddell Jun 14, 2016 6:02 AM (in response to James Riddell)
  
  In order to verify the above, try fixing the contact surfaces (leaving off the off mating parts) then check the reaction forces on those surfaces and verify that the resultants are heading in the direction(s) you expect to see.
  
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  - Re: no penetration contact not taken into account
    
    Adi Pro Jun 15, 2016 6:03 AM (in response to James Riddell)
    
    Hello James,
    
    Your idea to study the reaction force it'is a good way to identify where the problem comes from. However I succeed to run the model in a different way:by replacing two supports by an unique support (cf picture BEFORE/AFTER)
    
    By the way, the solver nocticed several times the message "Star stoped working" without explanation. I had to restart the PC and run the study: it worked.
    
    Thank you for your suggestions
    
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    - Re: no penetration contact not taken into account
      
      James Riddell Jun 15, 2016 6:13 AM (in response to Adi Pro)
      
      Sometimes "Star" gets confused. As long as your results look reasonable that's what matters. It is always a good idea to do a FBD and hand calculation to check.
      
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