Multiphysics modeling and design of Galfenol-based unimorph harvesters

Iron-gallium alloys, known as Galfenol, are a class of magnetostrictive materials that convert mechanical energy to magnetic energy and vice versa. Galfenol devices especially unimorph consisting of a Galfenol beam bonded to a passive substrate, have great potential in energy harvesting applications, but advanced multiphysics models are lacking for these smart devices. This study presents a comprehensive finite element model for Galfenol unimorph harvesters which incorporates magnetic, mechanical, and electrical dynamics. Experiments considering impulsive tip excitations under purely resistive or resistive-capacitive electrical loads are conducted to validate the proposed model. The energy conversion efficiency and peak power density of a unimorph beam with a natural frequency of 139.5 Hz are analyzed experimentally. The maximum energy conversion efficiency is 5.93% when a 74 S2 resistor and a 2 mu F capacitor are connected in parallel to the pickup coil in parallel. The maximum power density observed in experiments is 10.72 mW/cm(3) when load resistance is 74 Omega. This performance may be optimized in the future utilizing the proposed finite element model.