Shrink Fits for compound tubes 3

[bennygod]

Hi, does anyone have any idea where I might find useful information (i.e. formulas, theory, etc) that will enable me to calculate a compound shrink fit for 3 or more cylinders? That is a cylinder fitted in a cylinder fitted in a cylinder?

Many thanks

 

[Wrenchbender]

One area where successive shrink fits of thick-wall cylinders has been exhaustively studied was for large caliber guns. For example, Naval 16-Inch guns used a built-up barrel consisting of between 2 and 4 cylinders. Since weapons of this type are no longer used (modern artillery tubes are autofrettaged), the details of their design has become archival information. You might try searching out old government reports and publications in DTIC,

http://www.dtic.mil/dtic/.

Agencies that would have prepared them would be Watertown Arsenal, Benet Labs, or Army Materiel Command. If you can find a copy of AMC Pamphlet 706-108, that may be useful.

If you can’t find exactly want you want, at least getting smart on the math techniques would allow you to set up something, possibly on a spreadsheet, for your own applications.

 

[TVP]

Tooling for cold forming/forging/extrusion use interference fits to create prestressed dies by implementing one or more stress rings (also known as shrink rings). Probably the most comprehensive reference on this subject, including detailed equations and nomograms, is ICFG Document No. 5/82 Calculation methods for cold forging tools. It is based on research, experiments, and successful industrial practice that Karl Sieber and others conducted in Europe (mostly Germany and Great Britain) starting in the 1950's. This particular document was published in 1982. You can obtain it for 30 Euros from Meisenbach Verlag by using the following link:

http://www.lft.uni-erlangen.de/SEITEN/ICFG/document.htm

 

[MartinSr00]

I use Roark thick cylinder formulas with boundary conditions. So, a given pair is one cylinder under external pressure, the other under internal pressure. The final diameter under load is equal for both parts.

The frictional load is the unit load times the contact area times an assumed coefficient of friction.

You could do it closed form, or use a numerical solver to find a solution.

I know that's kind of general, but in the end, you have a quantity of cylinders that are under external or internal pressure that have a single diameter at each interface.

 

[bobgrec]

Depending upon your application, there is a Danish company manufacturing stripwound containers which may fit your needs. The calculations are based upon Lame' equations, well documented. They were originally used to calculate shrink fits for cannon barrels. Website for stripwound containers is:

http://www.strecon.com

 

[desertfox]

Hi bennygod

I haven't come across three cylinders shrink fitted together
before, I found this site for dealing with two:-

http://www.utm.edu/departments/engin/lemaster/Machine Design/Lecture 14.pdf

desertfox

 

[Pressed]

When three rings are used it is usually because two wouldn't perform, so it is extreme. There is an associated risk to the health of the assemblers and operators of those rings. Inexperienced design just adds more risk.

Going with Strecon utilizes the best mechanical property of metal containers. Once you give Strecon your force parameters their experience will be the best bet for success and safety.

Of course if your application isn't large rings with large pressure than this won't apply so much.

===================================
Forging

http://mech.e.tripod.com

-------------------------------------------------
Ddraig Breuddwydia....

http://www.tailofthedragon.com

 

[unclesyd]

You might try to get this book as it has some design considerations for layer vessels

http://books.google.com/books?id=SZ...v=onepage&q=concrete pressure vessels&f=false

 

[DAVIDSTECKER]

The July 26th, 1990 issue of Machine Design magazine has just such an article.

 

[MikeHalloran]

Watertown doesn't have an Arsenal.
Watervliet does.



Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

Here is another book that has some discussions on the design of combined pressure vessels. In scanning it there is quite a discussion on two element vessels but when it come to multi-layer it refers to autofrettage.

I also have a copy from a code, not a specific code, package at the old work place on three multi-layer vessels, I thought we had only one, where it appears that the stress information was developed by calculating the contact stress for each layer and in some way combining them to arrive at the actual stress at operating conditions, 1250 paig @ 250C. The calculations were originally copied by mimeograph and are not in very good shape, extremely hard to read with parts completely missing. They are attempting to find the original hand calculation, graphite on paper. They closed our or technical library and in so doing destroyed a lot of this type information.

I.L. Spain also has another book on high pressure.

http://books.google.com/booksid=gLFh4KbRRfEC&dq=compound+pre

ssure+vessels&source=gbs_navlinks_s

You might be able to find this and other books in a library near you.

http://www.worldcat.org/

Another approach might be to find information on the large "casks' that hold the apparatus for making synthetic diamonds. The casks were made by the combined method.

 

[unclesyd]

In my previous post the word combined should be compound.