SIF of thick wall bend

[Low Key Man]

Hi everyone!When I used CAESAR II to calculate a thick wall pipe,for instance,406.4x59mm,I found that the SIF of bend was 1.0,this is consistent with the formula in B31.3. But what puzzles me is why the bend SIF with a thick wall is 1.0 itself，or why this bend has no SIF ？Please help me,thanks a lot！

 

[LittleInch]

What's the radius of your "bend"? This sounds more like a pipeline terminology, not piping?

But that is an unreal thickness Why so thick??

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[Low Key Man]

It's hight pressure pipeline with 11.7Mpa,so the thick wall for the bend.I am just confused about the SIF，is it reasonable that equals 1.0？

 

[LittleInch]

But what is the radius of your bend?
What design code?

Which bit of B 31.3 - Help us out a bit here.

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Also: If you get a response it's polite to respond to it.

 

[Low Key Man]

The bend or elbow radius is 1.5 times the nominal diameter of the pipe,610mm. Elbow SIF in B31.3 APPENDIX D.

 

[LittleInch]

Ok, explain how you get to SIF of 1 as I can't be bothered to try and do the calculation and would rather you do and then others can check it.... Please.

I can only guess that it's because this elbow is very very thick that it reacts differently, but you do the maths and then we can maybe get somewhere.

Then do a few iterations and find out at what thickness the SIF gets to be >1

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Snickster]

I have a excel spreadsheet calculation for SIFs. I get 1.0 for both inplane and out of plane SIFs, and a flexibility factor of 1.34. It is what it is I guess.

 

[Low Key Man]

Thank you, friend! But your formula should be in B31.3. However, don't you think it's strange? Why is SIF of thick pipe elbow equal to 1.0? We know that the straight pipe is calculated based on the beam element, but the elbow is inconsistent with it. The elbow will produce non-circular deformation, which should lead to increased stress. Therefore, I don't think SIF here should be equal to 1.0

 

[Snickster]

My spreadsheet uses the B31.3 formulas. It is not that suprising that a 16 in. diameter x 2 3/8 in. pipe does not have a SIF. There is a lot of wall there so that the stress does not get concentrated but is well spread out.

 

[Low Key Man]

OK, thank you sincerely. Maybe you are right, but I still have to find a time to compare it with the finite element method. Only in this way can I convince myself. ha-ha..

 

[r6155]

Appendix D deleted.