Knife Edge-Allowable Loading?

[IngenieroSuarez]

I have an arm assembly that is made out of two square tubes. One is smaller than the other and extends in and out of the larger one. Their are small tabs welded to the walls of the tubes that prevent them from sliding completely out. The arm is loaded with a point load at the end of the smaller tube, similiar to a cantaliver beam.

I am trying to figure out how to determine the allowable loading on the two knife edge contacts at the pivot and reaction(see FBD-1).

Also, how would I anlyze the stress inside the larger square tube(see FBD-2). I have looked through a few books and could not find anything.

 

[MikeHalloran]

A theoretical line contact in compression either brinells or fractures or wears away until the contact area becomes finite and the stress becomes reasonable. Once it's reached that state of equilibrium, you can measure the contact area and compute the stress. That's one way to figure the allowable loading.

Figuring out what the load actually is, is just kinematics. You know, sum the forces and moments, all that stuff?



Mike Halloran
Pembroke Pines, FL, USA