Acoustic energy harvesting via magnetic shape memory alloys

Abstract

This study investigates acoustic energy harvesting via magnetic shape memory alloys (MSMA). The acoustic pressure impacts the neck of a Helmholtz resonator (HR) with a flexible face made of an elastic membrane. The design of the proposed energy harvester let radial force in the membrane be tunable. An MSMA is clamped to the membrane, and a proof mass is attached to the other end. The enhanced sound pressure vibrates the membrane and, therefore, excites the base of the MSMA specimen made of Ni-Mn-Ga to apply strain to it. Inserting strain onto the MSMA leads to variant reorientation and change of magnetization vectors, resulting in a change in flux passing through the pickup coil. Therefore, based on Faraday's law of induction, the voltage will be generated in the coil surrounding the MSMA element. On the other hand, an electrical circuit with a resistor and a capacitor is added to the energy harvester to obtain electrical resonance. After obtaining the governing equations of motion, the modeling approach is verified based on the experimental results reported in the literature. The equations are solved numerically to study the effect of different factors on the power generated by the proposed energy harvester. According to the obtained numerical results, changing the geometric parameters and the proof mass, one can obtain power from the MSMAbased acoustic energy harvester as comparable as that from the piezoelectric one.

Investigation of low field response of metamagnetic Heusler alloys as multiphysic memory alloys

“…Recently, the use of particular Heusler alloys [11][12][13] allowed introducing a third physical domain, namely the magnetic aspect, in the SMA coupling, enabling the concept of 'multiphysic memory alloys' (MPMAs) as a particular multifunctional material. With the inclusion of this third physical field, new applications can be truly envisioned, such as efficient magnetocaloric devices [14][15][16][17][18] or thermal energy harvesters [19,20]. In particular, tailoring the material to obtain several types of phase transitions such as structural and magnetic ones around the same temperature, and preferably close to room temperature, has been successfully achieved by introducing indium in nickel-cobalt-manganese compounds for instance [14,[21][22][23][24].…”