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• # Typical Torsion coefficient of pipes?

Discussion in 'The main mechanical design forum' started by free electron, Dec 27, 2013.

1. ### free electronNew Member

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Hello, I am an electrical engineer so these are uncharted waters to me. I need to know the approximate typical torsion coefficient of pipe in n.m/rad (or ft.lb/rad). Assuming the followings:

steel pipe
length: 10 meter

I am just looking for typical, approximate, ballpark numbers. Nothing exact.

Thanks,

2.
3. ### LochnagarWell-Known Member

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The equation you need is (T/theta) = (G*J/L) (Nm/rad)

G = 80 *10^9 N/m^2 for steel

J=(PI/32)*(Do^4 -Di^4) polar moment of area of pipe

L= 10 m length of pipe

Substituting the values J= 106*10-6 m^4

4. ### free electronNew Member

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I am a little confused...

Do=4.5"=0.114m.
Di=4"=0.102m.
J=(3.14/32)*(0.114^4-0.102^4)=5.95E-6 m^4.

How did you get 106E-6 m^4?
thanks,

5. ### LochnagarWell-Known Member

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In your original posting you referred to an inner radius of 4" - which is 8" diameter. Also your outer radius was 4.5". Now you are saying the outer diameter is 4.5" - and the inner diameter is 4". Hope this explains the difference?

Last edited: Jan 2, 2014
6. ### free electronNew Member

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oops, you are right. I mixed radius and diameter.

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