Deformation of rubber...

[blckwtr]

I am looking on an application which needs to compress a rubber tube, diameter 2" x 1.35", the rubber tube is then filled with liquid. Compressing the rubber tube will deform it such that it expand to a diameter of 8.9" when it is restrained by the surrounding pipe.

Let's say for now that the rubber is viton 80 (FPM or something similar). I need to know;
-- how long the tube needs to be? (initially)
-- what is the elongation at it's maximum?
-- which shape can one assume? (does it need to be steel reinforced)

some drawing or input on the subject would be appriciated... I can provide with more info if needed or if something is unclear...

Regards

Tommy

 

[Dtuck]

You can't compress the rubber to make it expand. I think you'll have to be more specific as to what you're after.

 

[blckwtr]

It is not easy to explain, but see attached. I know rubber is difficult to calculate... But I want to displace a liquid inside the "pipe" to expand the rubber, and also shorten the distance between the attach-points... I just want to know if it is possible to do this with a rubber type...

 

[GrahamBennett]

From the information provided and the .pdf image, I suspect you will be asking the part to expand very close to or even beyond its elongation at break or elastic yield point and, therefore, failing on its first inflation.

 

[blckwtr]

The elastomer would be exposed to a circumferental elongation of 345%, so I know Viton 80 isn't going to work. I would also think that a reinforcement axially is needed here (fibres, steel etc.)

 

[btrueblood]

I think you may want to do a Google search for "inflatable seal", see for instance Pneuma-Seal as one brand of the type.

 

[blckwtr]

I would have wished for some kind of standard material, but surely for the rubber element we will contact producers or rubber specialists. No standard application this, so the design job is ours to complete, including the rest of the mechanism...

Thank's anyway

 

[Dtuck]

Go to the design manual on Marshbellofram.com for fabric reinforced diaprhagms. It would take some hardware but what you need can be easily done as shown in the manual. The rubber can't just be allowed to expand that much because it will fail.