Moments of inertia calculations

[PeterTorresani]

I forgot my text books at work, and need an equation. Are there any engineers out there (or others so inclined) that know the equation for the torsional moment of inertia for a pipe.

I've got the bending moment, but need the torsional

Thanks in advance

[Ted Shrader]

Peter -

I can find it for a solid round bar but not a pipe. Sorry. Those rubber tables (CRC) usually come through.

Ted
BSEE

[Robert Ducharme]

The polar moment of intertia is:

(phi/32)(D*D*D*D - d*d*d*d)

where D is the outside diameter and d in the inside diameter. Sorry I don't know how to make equations on this system (D to the 4th power).

Do you want torsional deflection?

[PeterTorresani]

The polar moment of intertia is:

(phi/32)(D*D*D*D - d*d*d*d)

where D is the outside diameter and d in the inside diameter. Sorry I don't know how to make equations on this system (D to the 4th power).

Do you want torsional deflection?

Thanks Robert, That's what I was guessing, except I was thinking 16 instead of 32. I don't need the torsional deflection, I'm doing a stiffness comparison.

BTW, I believe the standard convention for exponent notation is D^4