Re: hydroforming : was water spark gaps

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "Bert Hickman" <bert.hickman-at-aquila-dot-net> 

Bob and all,

Underwater explosive metal forming requires a shaped die, and a vacuum
between the workpiece and the die. Doing this electrically requires a
BIG capacitor bank (10-100 kj or more) to generate a strong enough
shockwave. This process is NOT the same as hydroforming, which uses high
pressure (hydraulic), but low velocity. Either an underwater spark-gap
or an initiating exploding wire can be used to generate the shockwave.
The latter is necessary to "spread out" the shockwave for larger pieces.
When the resulting explosive shockwave hits the metal workpiece, it's
rapidly accelerated, slamming into the die at very high velocity. Using
a vacuum prevents the workpiece from being slowed down by air
compression prior to hitting the die. 

Fortunately, there's an excellent web site on high velocity
metalforming: Professor Glenn Daehn's "Resources on Electromagnetic and
High Velocity Forming" site at the University of Ohio. An entire book on
EMF can be downloaded if you desire! Some of the many useful references
at this site include:

http://www.metalforming-dot-com/MAGAZINE/1997/January/7mfjan5.htm

http://er6s1.eng.ohio-state.edu/~daehn/hyperplasticity/stateofartrept/index.
html

http://er6s1.eng.ohio-state.edu/~daehn/mahadevanthesis/index.html

http://er6s1.eng.ohio-state.edu/~daehn/metalforminghb/index.html

There are also a number of books that deal with explosive and
electromagnetic metal forming (EMF). Unfortunately, some of the best of
these are out of print, and hard to obtain. 

Bruno, E. J., ed., "High Velocity Forming of Metals", Revised edition,
ASTME, 1968, 227pp

Davies, R., Ausin, E. R., "Developments in High-Speed Metal Forming",
1st ed., NY Industrial Press, 1970, 284pp

Shewmon, P. G., Zackay, V. F., "Response of Metals to High Velocity
Deformation", Interscience, 1961, 491pp

US Dept of Commerce, "High Energy Rate Metal Forming", US Dept. of
Commerce, 1960

Wilson, Frank W., ed., "High-Velocity Forming of Metals", ASTME,
Prentice-Hall, 1964, 188pp

Frungel, Frank, "High Speed Pulse Technology", Vol 3, Academic Press,
1976, 498pp 

Bruno's and Wilson's books are probably the most "available". Both cover
both spark and explosive shockwave forming as well as electromagnetic
metalforming (high-speed, ultra-strong magnetic fields). Bruno's book is
presently available on the used book market via ABE or Bibliofind... :^)

Frungel's book is excellent, covering the effects of spark-gap
shockwaves as well as LOTS of other excellent technical information on
Capacitor Discharge engineering/applications.  Volume 3 contains an
excellent 28 page section dealing with underwater spark-generated
shockwaves and their use in high pressure physics and metal forming
(electrohydraulic forming). For research purposes, his bibliographies
are 2nd to none! Unfortunately, the book is very scarce and expensive...
:^( 

Finally, a book that will likely be the most readily available is the
American Society for Metals (ASM) "Metals Handbook". This is a
multi-volume work, containing about a dozen individual volumes on
properties, heat treating, welding, machining, etc. The volume you're
looking for will be the one dealing with "Forming". For example, in the
8th Edition, Volume 4 is entitled "Forming", and it has 15 pages dealing
with explosive and electromagnetic forming. These volumes are also
currently available on the Used Book market. 

Hope this helps!

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "bob golding" <yubba-at-clara-dot-net>
> 
> Hi all,
>         while looking around for info on hydroforming I noticed that
there is a
> related method that uses high pressure water/oil mixtures. This might be
> a safer method, at least for me ,I don't think the neighbours, or the
> police for that matter, would let me get away with explosives. I was
> thinking something like an hydraulic pump of an old JCB (back hoe) might
> do. It also has the advantage of being a bit more controllable
> /repeatable. Jim, any titles of books, I looked on Amazon, and came up
> with 169 titles.
> 
> cheers
>  bob golding
> 
<SNIP>