will placing magnets in repel mode will demagnetize them.

[grogmark]

thanks all

I went to http://www.dextermag.com/Magnetization-Demagnetization.aspx and found this info.  I'm not sure if understand these points

1. Generally, as an Nd-Fe-B material's maximum energy product goes up, Hci goes down. When and why should I care?
You should care if the magnet is going to be exposed to elevated temperature(above 150 ?F/ 65 ?C), if the magnets will be in repulsion, or if the magnets will go into quadrature or Halbach assemblies.
 
You should care because low Hci magnets will irreversibly lose a lot of magnetic strength. Usually this can be recovered by remagnetizing, but if they are in a complicated assembly, you might have to take it apart




2. Do magnets knock down the instant they are repelled?
Magnetic flux lines can not cross each other, so magnets in repulsion develop radial vectors whose intensity increases as the magnets approach each other. To the extent that the amplitude of the radial component of flux density exceeds coercivity of magnetic domains, there will be changes to the properties of the magnet. These changes ate due to reorientation of these domains.
 
Materials such as Nd-Fe-B, Sm-Co, Ceramic, and bonded Nd-Fe-B will typically see very small permanent changes, if any. This will be noticeable as a change in the external flux density, and the total flux available to the magnetic circuit. Magnets with a 'knee' in their second quadrant normal curve, such as Alnico 5 or true Ceramic 5 can see experience significant demagnetization.



3. What amount of energy is required to magnetize each of the magnet materials?
To fully saturate a magnet, it must be exposed to a magnetizing field of sufficient amplitude for a time long enough to orient all of the mass of magnet.
 
Alnico requires 3000+ Oersteds - longer pulse times may be needed to overcome eddy currents in large sections. Ceramic requires 10,000+ Oersteds. Sm-Co typically requires 20,000+ Oersteds but may require over 40,000+ Oersteds on some grades. Nd-Fe-B typically requires 30,000+ Oersteds but may require over 40,000+ Oersteds on some grades. Bonded Nd-Fe-B or NeoForm requires 35,000+ Oersteds.


so if the magnets need to be remagnetized, how would much energy would it actually take? I have no idea what 35,000+ Oersteds is. If someone successfully builds magnet fueled generator this would be a very importent detail. Seems to me someone who has worked with Halbach assemblies might have this info.

anybody?

thanks
Mark

[Dingus Mungus]

Oersteds = (1.257*(coil turns)*amperage)/length of the coil in centimeters. Just another way to calculate flux and guass. This preticular method equates to grams of force per second @ 1 centimeter from a pole (or) one gilbert/centimeter of flux (or) about 0.7958 A/m (or) 1 guass (or) .000001 Tesla. I doubt that really helped all that much, but its not a simple answer. A whole lot of power is required to magnetize anything, but the goal here is to not demagnetize them in a single human life time.

To really answer your question we would need: Material type, Heat it was forged at, Geometric shape/volume, Temp... Basically more data then I would know how to plug in to an equation.

Good luck on your research,
~Dingus Mungus

[grogmark]

thank you Dingus, but you're right, that's more math than I can handle right now. One of my sons is a Math major so I might ask him to look at this stuff.

Maybe it was a foolish question and I'm getting ahead of myself but I think its important. I think it's only a matter of time before someone invents a machine that works, maybe its already happened, but if enough people cann't afford to buy/build one I don't know how much good it would do.

anyway, thanks you've been very helpful

[Dingus Mungus]

thank you Dingus, but you're right, that's more math than I can handle right now. One of my sons is a Math major so I might ask him to look at this stuff.

Maybe it was a foolish question and I'm getting ahead of myself but I think its important. I think it's only a matter of time before someone invents a machine that works, maybe its already happened, but if enough people cann't afford to buy/build one I don't know how much good it would do.

anyway, thanks you've been very helpful

I don't know what your overall goal is with this question, but the bottom line is don't ruin your materials! Ballance them...

Example:
Small stout round fields should have a higher HCi and coefficient of coercivity when acting against a stationary (higher MGOe/more cylidrical field) or its poles will distort or even flip with time. You can avoid this by using two different magnetic materials or any other number of changed variables like: length, width, materials, Mgo, seconary fields, all sorts of things. Also magnets with 2 or more holes/slots in them are well known for developing a fliped pole between dominant poles. Equal size and rating magnets are not all really the same... Thats a huge misconception. BUT, if they are truely tested and indeed of equal strength and geometry they should be in equalibrium due to the fact that niether could overpower the other in any aspect that could permanently influence the poles.

You can't demagnetize with it, but I have a program for simulating magnetics and electromagnetics. Its called FEMM. You can use it to view 2d flux simulations and see how the flux flows in an idea involving magnetic fields. It'll change the way you look at magnets forever, by enabling you to see how geometry and materials directly effect field strength and geometry. Magnetic fields usually resemble a compressed torus more than they resemble their host materials. Google FEMM "Finite Element Method Magnetics". There is no time variable to check lifespans, but it may help answer your field interaction questions better than my garbled math. Just simulate, save a still, repeat, and then you can compair flux density and how the fields appear to conform and contort to one another.

Good luck on your quest for knowledge my best advice is to read everything you can and develope opinions only after experimentation.

~Dingus Mungus

[Dingus Mungus]

 

Its really late and I was just thinking... (dangerous)

You could use a single large diam neo with a lifetime greater than yours and use it to magnetize iron bars manually, realigned iron bars are terrible magnets, but you wouldn't have to sweat lifetime as it would be super easy to fix. DIY iron bar magnets can last 1-100 years depending on MGOe and the presence of stronger fields.

I get goofy ideas around this time of night,
~Dingus Mungus