Sharp corner fea

[Creech]

I'm running a flange through solidworks Cosmos Express FEA and I'm finding if I put a small fillet in the inside corner, say .06in, the part is substantially weaker than if there was no fillet. As I increment up to .25 Rad, it equals the strength of the original sharp corner. Can someone tell me if this makes sense and or elaborate. Thanks ahead of time. The flange is 2.25in Dia x .75 thick and body is .75in dia 1in long. and I restrain at the .75 area and add 5000 lb to flange. Thanks

 

[mloew]

Creech,

The strength should not change. You mean the stress changes, right? The sharp corner represents a singularity and is not accurate or realistic.


Best regards,

Matthew Ian Loew
"Organizations cannot make a genius out of an incompetent. On the other hand, disorganization can scarcely fail to result in efficiency." -- Dwight D. Eisenhower

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Creech]

FEA is not at all my specialty. This software calculates the Safty Factor after inputting a set of restrictions and a set of forces. And this particular example, the safety factor of the flange is say 6 for a sharp corner and the safety factor is 3 for a .06 rad. yet if I draw a .25 rad in the corner, the safety factor goes back up to 6 with all other things the same.
I was assuming that the saftey factor would not change very drastically.
Thanks

 

[corus]

As Matthew says, ignore the results for the sharp corner where theoretically the safety factor would be zero. If you want to confirm the results then check Peterson or Roark for stress concentration factors and how they change with a variable fillet radius.

corus

 

[Creech]

Thank you both