Magnetic Shape Memory Motor

Magnetic shape memory motor
Project start: 2004-07-19

Magnetically controlled shape memory (MSM) materials are a new class of actuator and sensory materials. Dimensions of MSM materials change when a magnetic field is applied, due to reorientation of the fractions of different twin and martensite variants. Strains of up 6% are reached in Magnetis Shape Memory (MSM) materials in which changing magnetic fields causes motion of twin boundaries of the martensite microstructure. MSM materials show several types of magnetically induced deformations including axial strain, bending, shear and torsion, which allows differents kinds of actuating elements to be made. Actuating elements were produced from single crystalline Ni-Mn-Ga material. Several actuator embodiments were designed and tested. Inversely, magnetis field around the material alters when proportions of the variants are changed by mechanical loading. This effect can be utilized in sensors and in small scale power generation.

Magnetic shape-memory effects in La2-xSrxCuO4 (LSCD) crystals

Grahams Clarkes idea for a MSM motor, 2004-07-20:

With this idea the MSM material is mounted below the rotor and stator out of their magnetic field. Hanging below the rotor are two small magnets, one one each side te comes into contact with the MSM material. When this happens the MSM will stretch, spushing a piece of steel between the rotor and stator. This unbalances the attraction and repulsion, causing the rotor to rotate half a turn. The MSM material goes back down after it leaves the magnetic field, allowing the rotor to go back to the balanced position, where the process starts again. The MSM will be a piston, pushing a piece of steel up and down between the stator and rotor, on a non magnetic runner. Graham Clarke

I received a message from a scientist at Massachusetts Institute of Technology:
    > Eric, you can't get something for nothing.
    > If the springs are made of any magnetic shape memory alloy
    > they will have hysteresis. That is, when the field is strong enough
    > to extend the spring, the spring will NOT retract as it leaves the
    > field region unless there is a bias stress (centripetal force)
    > pushing it back. Unfortunately, when the spring expands, the
    > centrifugal force on the mass increases, counteracting much or all of
    > the centripetal bias force.
    > I doubt that it would work. Also, shape memory alloys are
    > not strong in tension.

And with that information Graham Clarke came up with another idea:

MSM Motor if MSM doesn't spring back The idea is that the rotor is repelled by the stator and the opposite site of the rotor is attracted to the stator. As it aligns with the stator, the magnet on the arm above or below the rotor, comes into contact with the MSM, making it exspand up or down, changing the field in the stator and repelling the rotor. The process will start again in the opposite direction, giving a full rotation. The MSM moves up or down, depending on what magnet arm comes into contact with it and because the material doesn't spring back, the opposite end of the rotor is attracted to the stator until the MSM reacts to the magnet on the arm. Graham Clarkes MSM Motor, 2004-07-20