Dynamic nonlinear model with eddy current effect for stress-driven Galfenol energy

The energy harvester using magnetostrictive materials (e.g., Metglas, Terfenol-D and Galfenol) is receiving increased attention. However, prediction of performance for the magnetostrictive harvester is complicated because the device exhibits nonlinear magnetomechanical coupling characteristics and the stress-induced eddy current loss, which is the leading limiting factor of the device. Different models are presented, including the basic linear ones and the more accurate nonlinear ones. The linear models based on the linear magnetomechanical coupling equations of magnetostrictive materials can not describe the nonlinear effects of the pre-stress and bias magnetic field on the output voltage and power of the device. A FEM eddy current model combined a nonlinear magnetomechanical coupling model of Terfenol-D can better describe some nonlinear dynamic characteristics of the stress-driven Terfenol-D harvester. But this model can not provide the direct relationship among the input stress, the output voltage and power for the device. Moreover, the model also can not describe the nonlinear characteristics of the Galfenol harvester because the nonlinear behaviors of Galfenol and Terfenol-D are different. Galfenol has outstanding features, such as small saturated magnetic field, low brittleness and high tensile strength, thus is more suitable for harvesting the vibration energy than Terfenol-D and piezoceramics. In this paper, a dynamic nonlinear model with eddy current effect of a stress-driven Galfenol energy harvester is founded, and the effects of the varied operating conditions on the performance of the device are calculated and analyzed.