Ring Expansion Test

[a.matos]

How can a ring of a material be outwardly expanded in the radial direction using a loading mechanism?
I want to set up an experiment to study the dynamic tensile failure of materials. Materials of interest would be ceramics and metals.
There already exist methods of expansion by press fitting a ring around a cylinder and putting explosives inside said cylinder and that detonation will expand the ring.
I am wondering if a more simple set up to uniformly expand a ring exists already. 
Thank you!

 

[ehbadger]

Depending on the size of the sample, some sort of inflatable bladder could work

 

[EdStainless]

What strain rate are you looking for? If normal range then I have seen these done with expanding mandrels.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[metengr]

Very easily and uniformally accomplished using a set of roller expanders to radially expand the ID surface, used for installing tubes into tubesheets.

 

[Tmoose]

http://www.lislecorp.com/divisions/products/?product=565&division=1&category=5

Some folks use a hydraulic cylinder to pull on the screw in place of a wrench or impact.

For more even expansion maybe sliding up a gradual taper.

Diameters?
Wall thickness?

 

[WKTaylor]

We cold expand holes in metal for fatigue life improvement using the sleeve and mandrel system supplied by companies like Fatigue Technologies Inc [FTI].

Drill/ream a hole to a precision starting diameter, then insert a lubricated high strength thin-wall sleeve on a expansion mandrel into the hole, then 'pull' the mandrel thru the sleeve to cold expand the hole.

Perhaps a variation on this method might work in low ductility materials? NOTE. Since the mandrel typically pulls toward the 'hydraulic puller' [duhhhh], the opposite side of the hole is typically loaded in expansion first... and then the rest of the hole is loaded in compression as the mandrel progresses thru.

http://www.fatiguetech.com/products-split-sleeve-cold-expansion.asp

Also there is a fastener that has very high shank expansion: Monogram Aerospace Fasteners [MAF] Radial Lok. The expansion forces can be controlled from ~very light [larger hole] to very high [slightly smaller-tighter hole]. This is the ONLY blind bolt I respect for fatigue critical applications.

http://www.monogramaerospace.com/products/blind_bolts/radial-lok

Or, perhaps...

The MAF Adjustable Bushing system provides 'pure' radial expansion... the illustration clearly shows how the system works. Testing/instrumentation would be able to define stresses during the torqueing of the nut.

http://www.monogramaerospace.com/products/adjustable_bushing

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]