Tear out of parent material at base of padeye 4

[tnteng]

I've got a padeye welded to square tubing that has a 1/4" wall. Load on padeye is parallel to the axis of the tubing. I am trying to find out if there is a standard way to check the stresses in the tubing if the load on the padeye puts a moment into the weld at the base of the padeye. The bottom of the padeye at the base would tend to punch into the tubing and the top of the padeye at the base would tend to pull out from the tubing.

Thanks in advance for help with this problem.

Tony Billeaud
Mechanical Engineer

 

[MikeHalloran]

I think it's accepted practice to put a doubler between the padeye and the tubing, to carry the moment to the tube corners where the tube is strong.



Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

How hard will this pad eye exercize the tubing? Is it the source of all loading? Is the loading really guaranteed parallel to the tube, or is it possible for the padeye to receive some tranverse force, which would try to fold the padeye around the tube and subject the tube wall to localized bending?

Before unleashing FEA I'd calculate the stresses in the actual square tube by arbitrarily assuming the gusset was attached just at the ends (maybe 1/10 actual gusset lenght), and apply the full force to a simply supported beam (even though the ends really receive some bending resitance from the perpendicular tube walls) with length = equal tube width, and beam width = 25% gusset length. If the stresses wer only a few thousand psi I'd stop there.

If the padeye will be required to work for a living, I'd start with the Lincoln Electric welded design manuals' sections on load path and allowable stresses in welded materials. This is especially true with loading applied by motorized source ( at just 1000 rpm the number of load cycles can be in the millions after 24 hours).

http://www.axess.no/news/images/730-900_01Bildeavkranmodell_000.jpg

Home-made, but showing an effort to provide a load path into the "sides" of the tubing, especially if the portion crossing the tube wer clearanced and not welded.

http://www.homemetalshopclub.org/projects/crane/rollweld.jpg

Here are examples of how generally NOT to gusset a joint subjected to cyclic loads, although if the original butt joints were ALMOST OK then any improvement can be enough.

http://www.synthx.com/articles/trailer-str4.gif

http://atv.off-road.com/atv/data/articlestandard/atv/442005/191491/gusset_frame.gif

http://dirtbike.off-road.com/dirtbike/data/articlestandard/dirtbike/232006/331313/corner gussets.jpg

 

[tnteng]

Thanks Tmoose,

I have a pic of what the loading and padeye orientation looks like. How can the pic be attached to my reply to this post?






Tony Billeaud
Mechanical Engineer

 

[desertfox]

Hi tnteng

Another way would be to weld a pair of pad eyes on the corners of the square tube in line with the wall thickness so the load is transferred through the whole depth of the tube.


regards

desertfox

 

[JStephen]

Note that if you insert a doubler, then you have the problem of analyzing the doubler itself.

For a picture, post on photobucket or some similar site with a link here.

I believe some of the pressure vessel handbooks have information for cylindrical tubing/ vessel walls.

 

[arto]

AWS D1.1 Structural Welding Code has info on local failure, punching shear, tearout etc for square &round tubular construction.
Also in Troistsky's "Tubular Steel Structures" (older - sim to D1.1-1981)