3 Replies Latest reply on Jun 3, 2009 3:06 PM by Robert Stupplebeen

Incorrect Von Mises stress

1-HISDYY Jun 2, 2009 5:30 AM

Hi all

I have a model which is a bracket made of 8mm-thick plates and is bolted to a fixed plate by four bolts and a 1KN load on the other end .
I created four bolt connections and run the simulation. The maximum principal stresses are 96.2, 63.4 and 22.1 MPa, but the maximum resultant Von Mises stress calculated by the program is 290 MPa. I assume this should be around 90MPa. I cannot justify the jump in magnitude of stress based on Von Mises stress formula.
Could you please give me some advice in this regard?

Regards,

Reza Kharrazi

Incorrect Von Mises stress

Stephen Endersby Jun 2, 2009 2:54 PM (in response to 1-HISDYY)

Is the high stress at one node or over an area? Also is the node in a sharp corner?
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- Incorrect Von Mises stress
  
  1-HISDYY Jun 2, 2009 11:06 PM (in response to Stephen Endersby)
  
  Stephen
  
  Thanks for your reply. Yes, it is around the edge of one of the holes where the bolt connections have been defined. The edge is located between two plates on nut side.
  My questions are:
  
  First, why I can't see this high stress concentration in principal stress' values as well.
  Second, how should I interpret the results? Since this Von Mises stress is far above yield stress.
  Third, what measures do I have to take to reduce the effect of this high stress? The part a simple support bracket made of steel plate.
  
  Many thanks in advance,
  
  Reza
  
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Incorrect Von Mises stress

Robert Stupplebeen Jun 3, 2009 3:06 PM (in response to 1-HISDYY)

What are the minimum principle values? Near the bolts the bracket might be in compression hence a negative value. I hope this helps.

Rob Stupplebeen
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