Study on the Magnetostrictive Actuator’s Efficiency Considering Eddy Currents and Hysteresis Losses

Terfenol-D as a giant magnetostrictive material is widely used in fabrication of transducers and actuators. In most of these actuators and transducers, the axial time-variable magnetic field created by a coil is applied on a Terfenol-D rod to create vibrations. During the conversion of magnetic energy to mechanical energy in these devices, power losses occur which leads to reduction of efficiency. In this paper, effects of eddy currents and hysteresis losses on the efficiency of Terfenol-D actuator are investigated. First, mathematical models for eddy currents and hysteresis losses based on Maxwell’s equations of electromagnetism are derived and effective parameters on the actuator’s efficiency are recognized. Then, an experimental set-up is fabricated and different tests in different frequencies are performed to obtain input data for mathematical models. Results show that eddy currents and hysteresis losses have remarkable effects on the efficiency of Terfenol-D actuator especially in high frequencies; however their effects are different.