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Thread: torsion calculator

  1. #1

    torsion calculator

    Hi, I'm new here and I would like help with a problem. I am trying to verify a torsion calculator for round tubing or pipe. However, I am having trouble trying to find a way to use a materials specified yeild strength and or tensile strrength(only info I have other than material type/grade) to find the shear modulus. Also, I'm just trying to find out the max torque that can be applied to a tube/shaft before it shears or deforms in any way. Any help with this problem would be greatly appreciated!

    OK, I think I have it, I just need some verification.

    If I use the formula:

    Torque(max) in LB = [ (max shear stress in psi)(polar second momentof area in inches^4)/R in inches]/12inches

    and I use the Von Mises contant/multiplier of 0.577 to convert minimum yield strength to maximum shear stress.

    Does this make sense to anyone else?
    Last edited by fzr400racer; 03-20-2012 at 10:42 AM. Reason: I have done more research/read other posts

  2. #2
    Associate Engineer
    Join Date
    May 2012
    Hi fzr400racer,

    Welcome to the forum.

    If you have the elastic modulus and poisson's ratio you should be able to calculate your shear modulus for your material with this:

    G = E/(2*(1+v)), where E is the elastic modulus, G is the shear modulus, and v is poissons ratio. For steel v is usually around 0.27 to 0.3, just do a google search for your material and go from there.

    0.577*min yield will give the approximate yield stress in torsion, but it could be more or less depending on the material.

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