Steel Tubing Beam Torsion Calculation 3

[greenengr1]

How do you calculate the torsion stress in an open ended steel tube that has a torsional load applied? The tubing is 10mm wall x 125mm tall x 100mm wide and the 2500 lb load is applied perpendicular to the tube via a 1495mm long arm.

 

[rb1957]

funnily 'nough there is just about nothing out there for the torsional stress on a thin walled open section, other than the maximum stress = 3*T/(b*t^2), where b is the length (perimeter) of the section.

ok, you can fudge 'round with the "3" factor if your section isn't really "thin" ...

 

[greenengr1]

Thank you for the reply.

Just for clarification for the maximum stress formula:

T = torque applied
b = perimeter of section
t = ?

Do you "fudge" the "3" factor up or down as the wall thickens?

I appreciate your help.

 

[Bribyk]

I don't think greenengr1's referring to an open cross section.

Greenengr1, could you fill the tube with water if it had caps on the ends?

 

[greenengr1]

The tube is a rectangular structural tubing open through the middle. In this configuration, water would run right through it. There are no caps. I'm attaching a pdf of a model my CAD guy drafted.

 

[greenengr1]

The arm is attached to the tube with a pin through a welded clevis.

 

[Bribyk]

Okay, the picture clears things up a bit. You don't have an open section, just a hollow structural section. See page 12 in the link below, it's easier than explaining it here.

http://www.scribd.com/doc/8604517/Design-Guide-09-Torsional-Analysis-of-Structural-Steel-Membe

 

[GregLocock]

Roarke also has the equations. You should get a reasonable answer, your section size is not too thin.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[BAretired]

Ref. Theory of Elasticity by Timoshenko and Goodier

For a closed shape such as a tube, the torsional shear stress is given by:

Tau = Mt/(2*A*t)

where tau is the shear stress

Mt is the torsional moment

A is the area enclosed by the centerline of the ring section of the tube

t is the thickness of the tube

The angle of twist per unit of length is:

theta = Mt*s/(4A^2*G*t)

where s = length of centerline of ring section of tube

G is shear modulus





Best regards,

BA

 

[greenengr1]

Thanks all for helping this industrial engineer solve a mechanical problem. The reference info is exactly what I needed.

Steve