Magnetostrictive materials exhibit coupling between magnetic and mechanical energies. Magnetostrictive materials exhibit mechanical deformation when driven by a magnetic field or vice versa. Therefore, they can be employed for actuation, sensing, and energy harvesting. All ferromagnetic materials exhibit the magnetostrictive effect, but only certain iron–rare earth alloys, iron–gallium alloys, amorphous metals, and iron‐ aluminum alloys exhibit sufficiently high magnetostriction for commercial use. Magnetostrictive materials are suitable for harsh environments (i.e., high temperature, radiation) and biomedical applications.
Ultrasonic waveguide thermometer (Active)
Sponsor: DOE Advanced Sensors & Instrumentation (ASI) Program
Ultrasonic thermometry has the potential to improve upon temperature sensors currently used for in-core temperature measurements. Ultrasonic thermometers (UTs) work on the principle that the speed at which sound travels through a material (acoustic velocity) is dependent on the temperature of the material. Temperature may be derived by introducing a short acoustic pulse to the sensor and measuring the time delay of acoustic reflections generated at acoustic discontinuities along the length of the sensor. UT temperature measurements may be made near the melting point of the sensor material, allowing monitoring of temperatures potentially in excess of 3000°C.
The figure above shows a typical UT design based on iron-gallium alloys or Galfenol. We have developed an accurate and efficient multiphysics model that is able to capture the acoustic wave propagation in the waveguide.
Additive manufacturing of magnetostrictive materials
Sponsor: NASA Idaho Space Grant Consortium (ISGC) grant
Our group has successfully printed magnetically-active composites by dispersing magnetostrictive particles in polymeric matrices. By printing magnetostrictive composites on top of passive substrates, we further developed cantilever actuators, also known as unimorph actuators, as shown in the figure on the left. When a magnetic field is applied along the longitudinal direction of the beam, the magnetostrictive layer deforms while the passive substrate tends to maintain flat. Therefore, the unimorph actuator outputs micro-scale and butterfly-shape tip deflection. This actuator can be potentially used for precision drug delivery or optical instrument control.