Hello Everyone, Thanks for reading

[Zinov]

Hello Everyone, Thanks for reading my post.
I continue to check the resistance of my <tubes> to torque load on solidworks.
I have a high discrepancy between FEA and hand calculation
Please see attached file for results :167 MPa (by hand) and 402.3 (Cosmos)
My questions are :
1-Is my hand calculation acceptable?
2-Which result should I rely on : FEA or hand calculation?
3-Where can I find the stress concentration factors for such a notch shape?
4-For me stress concentration factor of 4.8 is little high (402.3/83.5=4.8), what do you think about it?

Thanks in advance,
Zinov

 

[mmar2087]

Hi.
Perhaps I shouldn't answer because I'm not familiar with the stress-concentration factor in your hand calculation.
But until you get a better answer...

First, the spotty look on the stress concentration (red area) indicates that your mesh is to coarse in this area. (no convergence).
Second, your calculation isn't handling the radii where the stress concentration occurs, or am I missing something?

Depending on the depth of the U-shaped grove, your stress in the radii will change. A deeper grove = higher stress in the radii.
You have no dimension on this value, and the 3d looks different from your sketch.
(Once again, I'm not familiar with the stress-concentration factor in your calc)

If you look at the max P1 stress at a section where the groove is visible (similar to the sketch in upper right corner in your picture), the max stress is about 83 MPa in my study.
Not so far from the first result in your calculation before adding the factor.