memory metals
hunt...@ardec.arpa
While many are familiar with temperature-dependent deforming metals (...I
forget the name...used frequently in thermostats), another class exists
which will change length within the presence of a magnetic field. If my
spelling is correct, they were referred to as "magnitostrictive" devices.
Theory is that the magnetic field forces an allignment within the
material. Note that the change in dimensions of the material is very
small...it's closer to the order of magnitude normally found in stress/strain
caused dimensional changes than what you'd measure with a yardstick.
Vadali Mahadev
>forget the name...used frequently in thermostats), another class exists
>which will change length within the presence of a magnetic field. If my
>spelling is correct, they were referred to as "magnitostrictive" devices.
Magnetostrictive materials are not memmory devices in the sense that they actually donot change their physical shape or size (etc) when there is no external field is acting on them, unlike the shape memmory materials which once deformed retain the deformed shape and on suitable treatment like heating they return to the original shape or size.
By the way, Piezoelectric materials are the electric field analog of Magnetostrictive materials (also known as electrostrictive materials), and are now-a-days being used in High tech. applications. One of the uses is base of an microscope. Since the changes in dimensions are typically of the order of a few microns (at the most), they are used to move the samples by application of fields. There are several other applications, of which one very intersting device was shown in a Japaneese
exhibition. This is a sort of a game. Here a ball falls on a small piezoelectric disk, the contraction involved leads to a reverse electric field which makes the disk expand, giving enough thrust to push the ball right up again. This looks like violating Physics (as coeff. of restitution seems to be greater than 1) for any common man.
Mah...@cb.ecn.purdue.edu