Welding Torsion Resistace

[huxf]

I have a design, which uses 7/16 fillet welds to weld a tube to a pipe (Centerline of the tube is perpendicaular to the centerline of the pipe). The welding length is about Lw= 57*2= 114in and Fexx =70ksi
90k-ft torsion needes to be transfered.
I calculated like this:
Tn = 0.6* Fexx * (7/16* 0.707) *Lw *(7/16") /12
and Tn/2 only gives me 27 kips-ft

Something is wrong with the calculation. Can anybody help? Thank you very much.

 

[csd72]

A bit more info.

what size tube? what size pipe? is the weld all around? if so is it square or circular?

 

[Lion06]

Tn = 0.6* Fexx * (7/16* 0.707) *Lw *(7/16") /12
and Tn/2 only gives me 27 kips-ft
It seems to me you are calcing the k/in strength of the weld and applying a 7/16" moment arm to the weld. I don't where that is coming from, but it doesn't sound right. You should be using the Ip for the weld group.
Please explain in more detail the weld group.

 

[JohnNevets]

I don't know if this is quite what you are asking, but the polar moment of inertia of a circular weld is J=(Pi*d^3)/4. To end up with an actual strength/in I would use your Moment (or applied torque)*d/J With your allowable strength/in being .6*Fexx(7/16*0.707).


If your asking about a square rectangle tube I'd just use the standard J values for those [J=((short length*long length)^3)/6 and making sure to use the actual (increased for the curve) length of the weld that is perpendicular to the pipe.

Hope that helps,

John

 

[desertfox]

Hi huxf

Have alook at this site:-

http://www.gowelding.com/calcs/

regards

desertfox