Yielding in Bearing

[jike]

I have an unusual situation where there is a large diameter pin (4.5" diameter) that is bearing on a 1.5" plate but is not perfectly perpendicular to that plate. It is, perhaps, off by one degree (approx. 1 in 50). The bearing stress was very high with the pin being perfectly square but now with it skewed to the hole it is into an area where I am sure it would yield.

Any comments or suggestions?

 

[dik]

Can you shim it into a better bearing condition... over time, by yielding, it may bind even more.

Dik

 

[civilperson]

Bearing at the limit always assumes yield since the radius of the hole and the pin are different. The theoretical point bearing from differing angles or radii must deform to supply sufficient area to be less than yield.

 

[dik]

I was thinking that if you could shim the bearing you might be able to influence the forces on the pin and reduce any 'galling' or binding...

Dik

 

[SteelMover]

It probably already has yielded, is that a large consideration for your case? If you force a rotation of the pin across the suface you see that out at the edge you quickly get to yield in the material. Is there a lot of movement at this connection?

With moving pinned connections we typically provide a sleeve bearing by Rexnord (PTFE coated fiber matix) or a spherical bearing by RBC or Aurora. Again we always use the PTFE lined ones, they have a high capacity and are pretty economical.

 

[shepherd]

Not sure about your detailing, but you could perhaps weld hemisphereical plates (with the pin diameter) on each exterior face of the plate with a beveled edge to match the pin angle.

 

[shepherd]

that should read semicircular not hemispherical.

 

[rb1957]

presumably the hole is also off perpendicular and a neat fit around the pin. but what of the fitting loading the pin ? drilled to suit the mis-alignment ?

if everything is slightly off-axis, i'd think it isn't too much of a problem, i think the load would peak slightly on the near side.

 

[jike]

I am concerned about the edge of the plate cutting into the pin, creating a notch. This could create a stress concentration that may lead to a secondary failure. I am trying to find out the strength of the plate and the strength of the pin to find out which might yield first.

 

[rb1957]

why would that be significantly different if the pin is properly perpendicular ?

 

[jike]

rb1957: Perhaps I don't undestand your comment but with the pin skewed, the plate edge can cut (notch) into the pin. With the pin perpendicular, it cannot.

 

[IFRs]

Does the pin rotate? Is there fatigue loading? High or low temperatures? Corrosive environment? Local yielding may not be a real issue.

 

[jike]

Pin does not rotate. No fatigue. Normal temperatures. No corrosive environment.

Yielding is not a concern, notching of the pin leading to failure is.

Thanks for reviewing those issues!

 

[dimjim]

Can you fillet radius the hole to have the contact hit lower into the plate?