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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 electron

      free electron New 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
      inner radius:4"
      outer radius:4.5"

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

      Thanks,
       
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    3. Lochnagar

      Lochnagar Well-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

      G*J/L =805KNm/rad
       
    4. free electron

      free electron New 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. Lochnagar

      Lochnagar Well-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 electron

      free electron New Member

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

      nileshjain New Member

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      Lochnagar is given perfect solution....Good Job..
       

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