Bearing stress on hole

[daspferd88]

For a hollow tube inside a hollow tube, with a pin passing through both and a force pushing down on the innermost tube, what would the bearing stress be on the holes (assuming tube wall thickness is equal)? Would the equivalent reaction force be F/4 since the pin is passing through 4 holes? So for example, say this is a jack stand with a 36,000 pound load on it. Would the bearing stress for each hole then be, 36,000/4 = 9000. Then bearing stress = F/td ? 9000/td Where t is wall thickness of tube and d is hole diameter?

 

[MikeHalloran]

Reaction force, at each point where the pin is loaded, = F/2.

Mike Halloran
Pembroke Pines, FL, USA

 

[desertfox]

http://www.ewp.rpi.edu/hartford/~kw...es/Edward Kwon - Preliminary Final Report.pdf

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[rb1957]

F/2 ... yes, 4 holes but the load is being applied on two of them (the ones in the inner tube) and getting reacted on the 2 holes on the outer tube. then, yes, bearing stress = P/dt ... compare to the material bearing allowable (not Ftu).

another day in paradise, or is paradise one day closer ?

 

[chicopee]

Do a free body diagram. First take the inner rod and you'll notice that the pin will exert F/2 load on each hole of the inner rod; then take the rod which is resisting the sum of the two F/2 which is F and in turn subject the outer rod two hole a load of F/2.
A free body diagram always helps determining forces and reactions.

 

[ColinPearson]

A sketch would proabbly help, but what do you mean by "bearing stress on the holes"? I picture this arrangement to be horizontal, but then you mentioned a jack stand; In that case there is a friction, or a piece that mechanically engages like a pawl, if I'm thinking about this correctly. However, saying that bearing stress would be F/td makes it seem that you're projecting the force from teh inner tube across the inner tube's dull diameter and teh thickness of the outer tube. Couple things: a) Isn't that really a shear stress, in which case you'd want to be looking at double plane shear. If you were using the full inner tube diamter, I think you'd be looking at F/dL where L is the length of the tube; and b) I would look at the size of the inner tube outside diam compared to the outer tube inside diam. Unless is a very tight fir, you won't have full contact and thus would project the force F across the full inner tube OD, d. You might look at Duerr 2008, "ASME BTH-1 Pinned Connection Design Provisions", and ASME BTH-1-2014; they both include a provision for estimating the actual contact width of a pinned connection.

Just $0.02, apologies if I've misunderstood your setup here and this doesn't apply.