2 Replies Latest reply on Sep 24, 2009 9:59 PM by 1-HISDYY

Discrepancy between solid mesh and beam Mesh for a simple cantilever

1-HISDYY Sep 23, 2009 4:20 AM

Hi All

I have a strange result for a simple cantilever made of aluminium round tube. This is part of an assembly.

With the beam mesh the result matches manual calculation, with solid mesh the result is far above theoretical value (normal bending stress). I guess this has a simple explanation and solution, however I couldn't find out myself. Similar problem with rectangular cross section gives acceptable values.

I really appreciate if someone takes a look and give me advice.

Regards,

cantilever.SLDPRT.zip 39.8 KB

Re: Discrepancy between solid mesh and beam Mesh for a simple cantilever

Robert Stupplebeen Sep 23, 2009 8:09 AM (in response to 1-HISDYY)

Without opening your part here are my suggestions. Crank up the mesh density. As a rule of thumb you need at least 3 elements through the thickness to account for bending in first order elements even more with tets like cosmos uses. Ignore the values near the constraints for comparison even though they may be real. Beam theory does not account for stress concentrations near boundary conditions. I hope this helps.

Rob Stupplebeen
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- Re: Discrepancy between solid mesh and beam Mesh for a simple cantilever
  
  1-HISDYY Sep 24, 2009 9:59 PM (in response to Robert Stupplebeen)
  
  Robert
  
  Thanks for your reply and comments. When I refine the mesh around supports the deviation becomes worse. I'm wondering why this deviation can only be observed for round bars or tubes. With a solid square section there is no difference between using Solid or Beam mesh. How can I find the average maximum bending stress apart form those stress concentration areas? The results shouldn't be that different from beam flexural formula.
  
  Regards,
  
  Reza
  
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