If you want a thermal 'fuse' that produces a mechanical effect as you put it, have you thought about a disc spring that is bi-stable, like a bigger version of those sometimes used inside a thermostat. Depending on the size you could get a few Newtons out of it and you would get a very sharp step response with temperature, very similar to a fuse action if that is what you want.
Dr. Finlay Evans
Senior Design Engineer
Group Engineering
Renishaw Plc
New Mills, Wotton-under-Edge,
Gloucestershire GL12 8JR. UK
-----Original Message-----
From: David Meeker [mailto:dcm3c@xxxxxxxxxxxxx]
Sent: 03 October 2002 21:01
To: femm@xxxxxxxxxxxxxxx
Subject: [femm] Re: Temperature dependence of PM materials
--- In femm@xxxx, "fj_emtc" <fije29@xxxx>wrote:
> --- In femm@xxxx, David Meeker <dmeeker@xxxx>wrote:
> > I'm looking at sort of an odd application in which it would be
> desirable
> > to have a PM material with a very strong temperature dependence.
>
> Thermoflux (VaC) is a soft magnetic material with very high
> temperature dependency in the requiered range. Perhaps this could be
> used as a sort of back-iron together with 'standard' permanent
> material?? Hard to say without knowing more of the application, but
> another way of looking at the problem.
>
>
> Finn Jensen\
Thanks a lot for the pointer--I wasn't aware of this material. This
could be just the ticket--it's sort of a fuse-like application where
we want a change in temperature to produce a mechanical change (e.g. a
change in force on a linchpin or something) w/out havingto provide
outside power, sensing, etc.
The best that I could come up with otherwise was just what Marc was
talking about--high-strength magnets. I was thinking that I could run
them in repulsion so that they were operating very low on the
demagnetization curve. With relatively small changes in temperature,
the magnets would demagnetize each other.
Anyhow, thanks again to all. I'll have to see if I can scrounge up
something on "ferrites with curie point near room temperature," as
suggested by Kirk. (btw, is Thermoflux an example of such a material?)
Dave.
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