# torsion calculator

• 03-20-2012, 08:15 AM
fzr400racer
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?
• 01-25-2013, 09:56 AM
Patman52
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.