Apr 20th, 1:00 PM - 3:00 PM
The Use of Magnetic Shape Memory Alloys in Power Generation Devices
Dr. Peter Müllner and Dr. Paul Lindquist
Magnetic shape memory alloys (MSMA), once deformed, can recover to their “memory” shape through an applied magnetic field. Deformation can occur through an applied stress, which is inverse magnetoplasticity (IMP), or by applying the magnetic field in a different direction. For the IMP, the applied stress results in plastic deformation, as well as a change of magnetization, both carried via the motion of twin boundaries. The MSMA can be cyclically stressed within a static bias field inside a helical electromagnetic coil where a voltage is induced due to the variation of the magnetization. With the application of a static bias magnetic field, as well as the removal of the applied stress, the twin boundaries re-orient themselves and restore the MSMA’s initial geometry. This process can be repeated via a periodic force applied with a variable speed motor. The induced voltage depends strongly on the actuation rate. A Ni-Mn-Ga MSMA single crystal with approximate dimensions 5.4 x 3.9 x 3.1 mm3 served as a magneto-mechanical transducer. Actuator frequencies up to 2.25 Hz are what we investigated, what we saw was an output voltage of up to 3.8 mV. We interpreted the results to be a power output of up to 80 nW. From the investigation we found an improvement of the MSMA material properties, a new transducer-driven motor and an improved pickup coil could help produce much higher frequencies, induced voltages and higher power production.