Eddy Current Damping Application Optimization

[mmbanaz]

Hello,
I want to use eddy current damping for my application.
My design is attached.
Grey part is the main vibrating system.
NdFeB Arc magnets(in yellow) are attracted to steel in both sides.
Pink part is copper like material.
When an acceleration occur on copper material in radial direction,I want to create an eddy current damping and suppress acceleration of copper part.(copper moving radially related to arc magnets)
To manage this, I used arc magnets.Inner faces of magnets are in opposide poles to create a stronger magnetic field on that area.
But,I suspect on some issues on this design since I’m not familiar with magnetics.
First one is,the shape of magnets.Do you think it is logical to use arc magnets?Or should I use radially magnetized ring to create stronger magnetic field ?When I make radially magnetized ring,I suspect that no magnetic field(flux) will occur.I sthat true?
Second,I suspect that big gap between magnets will not create any magnetic field.The gap between inner faces of magnets is appx. 20 mm.Hollow copper diameter is 17,40 mm.
I want to model this design with different alternatives on finite element software to find optimum results.Can you suggest me some FEM Softwares can do this?
Thank you in advance.

 

[prex]

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[mmbanaz]

I added again.

 

[EdStainless]

radial? as in side to side?
It won't dampen.
You need for your conductor to be cutting across the lines of flux to generate currents.
It would serve to dampen axial motion.

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P.E. Metallurgy, Plymouth Tube

 

[prex]

If the small tube inside the copper was in carbon steel, if it had a reasonably larger thickness, if the tile magnets were shorter and mounted with alternating polarities, if the outer tube was also in carbon steel, then ... you get damping only for an axial motion, as pointed out by EdStainless. Also the magnetic forces on the inner tube need be accounted for, depending on how the inner and outer tube are connected.
You could try with a somewhat harder steel in the place of copper, the hysteresis effect would produce some damping, but I'm not sure whether this would be significant. In this case the use of full ring magnets would be beneficial.
Anyway what you are trying to do is a quite complex application, many parameters are critical, so FEM won't be of much help: you need to deepen your knowledge in magnetics.

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[mmbanaz]

Thank you Guys,
I was suspicious about the design and now I'm sure that it will not work in a way that I want.
If I place magnets in axial direction,then I guess eddy current damping can occur.
In that case,since copper length is appx.150 mm,the gap between magnets (located in the ends of copper) might not create magnetic field.
Can single magnet in axial direction can create eddy current damping on copper?

 

[EdStainless]

Not enough to cause significant dampening.
In these configurations often active magnetic systems are used, like in magnetic bearings.
These are fairly involved, and the controls are very specialized.

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P.E. Metallurgy, Plymouth Tube

 

[MagBen]

you have to know the principle of damping: creating eddy current to counteract the source magnetic field. so you got nothing when your magnets are magnetized axially since the Copper sees no magnetic field. Your current design is very poor even with a radical magnetic direction, the main problem is the majority of your copper does not see the CHANGE of flux, but only the both ends at the most.
Adding back steel, concentrating the flux etc, can increase the flux, but the key, the principle is to increase the change of flux, so higher eddy current, so better damping effect.

 

[Compositepro]

All the magnetic dampers I have seen use a sheet of aluminum the passes through a narrow gap between magnetic poles, so the motion of the sheet is perpendicular to the magnetic field.