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Registered Member #1681
Joined: Fri Sept 05 2008, 07:39PM
Location: Tokyo, Japan
Posts: 16
There are two kinds of permalloy. One is 78.5%-Ni permalloy, and the other is 45%-Ni permalloy. Are there some differences if I use these materials as a projectile? And Are there some differences between a projectile made of Fe and of permalloy?
Registered Member #968
Joined: Fri Aug 24 2007, 04:54PM
Location: Norman, Oklahoma
Posts: 104
I believe 78.5% Ni permalloy has a higher max permeability but saturates faster.
I attempted to get some of this stuff this week and was unable.. Not only is it very expensive, but the forger I talked to could not produce it in small diameter because it is brittle(I requested 5/16").
He recommended another steel alloy for this use(ASTM A848) and I will have some at the end of the week. I will let you know how it goes.
Registered Member #1681
Joined: Fri Sept 05 2008, 07:39PM
Location: Tokyo, Japan
Posts: 16
>quitardude012 If a projectile saturates completely, is there some problem? Is it about hysteresis curve? I think A848 behaves like permalloy. I look forward to getting your reply. Good luck! >rp181 Could you tell me the characteristics(especially permeability) of Hymu-80?
Registered Member #90
Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301
nicora wrote ... I think that the more the permeability of a projectile increases, the more the efficiency of a coil-gun increases. Is this right?
Yes, because a coilgun (like other dc motors) operates on the saliency ratio. That is, the ratio of maximum and minimum inductance. A higher permeability leads to a higher ratio of inductance.
On the other hand, the velocity decreases as the density of the projectile goes up. For maximum velocity a useful comparison between materials is the ratio of permeability to unit mass.
Note that efficiency is not affected by density, just velocity, because efficiency simply depends on the magnetic properties. So two otherwise-identical materials of different density will gain the same kinetic energy; but the heavier one will move slower in the relation KE=1/2 m v^2.
Registered Member #1681
Joined: Fri Sept 05 2008, 07:39PM
Location: Tokyo, Japan
Posts: 16
>Barry Thank you for your kind comments. But I have a question still. According to your ideas, if a permeability of a projectile increases unlimitedly, the velocity of the projectile increases unlimitedly. So I think that there is a supremum(in other words, saturation value) if we use the law of energy conservation. Is this way of thinking right?
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The characteristics of a projectile made of permalloy
