threading to distribute stresses at cylindrical aluminium / steel interface?
threading to distribute stresses at cylindrical aluminium / steel interface?
(OP)

A 20mm steel rod is held vertically by a dry plastic cylindrical bearing such that it can rotate freely in the horizontal plane.
An aluminium bar with a 20mm hole in it is slipped onto the rod and, supported by the bearing below, can rotate freely in the horizontal plane.
The bar must support a load and in order to distribute stresses at the interface between the aluminium bar and the rod it would be best if they were bonded.
What are the options for bonding the aluminium bar and the steel rod? Or other means for reducing stress concentrations under load?
Should I consider mild - rather than hardened - steel and thread the rod?





RE: threading to distribute stresses at cylindrical aluminium / steel interface?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
http://www.britishracer.com/images/RacerTrack%20si...
The fork tubes slide up through the outer holes and are clamped in place with the cross bolts.
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
What is the attachment assumed in your model?
In your analysis Are the highest stresses in the (hardened steel?) rod ?
What does the plastic bearing think of all this?
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
@Buggar: sensible as ever this remark. Need something smaller, however, and to find room for encoder and slipring (not mentioned here).
@Tmoose Stress scale just about visible in below image. Point of concern are those in the aluminium bar (red arrows) which seem reduced in the case connection with rod bonded rather than slipping.
Plastic ring used in this model has max tolerance of 35MPa, but that's the lowest rated of the Igus Dry-tech 20mm bearings. Also steel rod will pass through another similar bearing lower down....
Mostly concerned about the Aluminium to as to reduce the chances of deformation in case someone mischievously overloads the system. The combination of machining & installed electronics (not discussed here!) make it relatively costly whereas the plastic bearing could cheaply be swapped out.
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
Mike Halloran
Pembroke Pines, FL, USA
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
In "reality" the rod will reach downwards further and above will be flush with the top of the horizontal bar.
I did have a prototype quite similar and surprisingly the bar didn't seem to work upwards under load, though I couldn't be sure.
Nevertheless the plan is to have the rod fixed in the aluminium and looking for ideas.
Have seen people fixing aluminium to aluminium by heating the female half in a furnace to expand it, then inserting the male.
@GregLocock where do I look to better understand how tapers work mechanically? (You might have guessed I'm not a pro. mech. engineer.)
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
je suis charlie
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
RE: threading to distribute stresses at cylindrical aluminium / steel interface?
Making the Al bar thicker, even if just near the joint will help greatly.
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P.E. Metallurgy, Plymouth Tube