Dynamic Model And Characteristic Analysis Of Magnetostrictive Transducer Considering Eddy Current Loss

Magnetostrictive transducers are widely used in many fields such as precise driving,precise machining,ultrasonic transduction,vibration damping,etc.In the application of magnetic field excitation,the eddy current loss induced by magnetic field will reduce the efficiency of the device.While in the eddy current damping passive vibration under stress excitation,the eddy current loss induced by stress plays an important role in improving the vibration reduction of engineering structures.Therefore,the linear dynamic model and characteristics of eddy current loss of magnetostrictive materials(such as Terfenol-D and Galfenol)under magnetic field excitation and stress excitation are firstly studied in this paper.Then the nonlinear dynamic model of Galfenol eddy shunt damping system under stress excitation is established and its vibration damping performance is analyzed.Finally,the dynamic hysteresis model in the damper is established based on the finite element method and its performance is analyzed.The specific work is as follows:1.Based on Maxwell’s equations and the linear constitutive equations of magnetostrictive material,the linear eddy current field distribution model is established.By solving the eddy current field distribution model using Bessel function under magnetic field excitation and stress excitation respectively,the corresponding dimensionalized model of eddy current loss is derived.The corresponding dimensionless loss model is obtained using cut-off frequency.2.The material properties under magnetic field excitation and stress excitation are simulated by using the linear model of eddy current loss.The dynamic response curves of time-domain,frequency-domain and spatial distribution of dimensionless magnetic field intensity and magnetic induction are drawn,and the amplitude-frequency and phase-frequency performance curves of eddy current factors are also drawn.The reason of the change of response curves is explained from the perspectives of energy and eddy current loss.3.Based on the effective magnetic field expressions,the eddy current constitutive equations,the Armstrong hysteresis model and the electromechanical coupling model,the nonlinear coupling dynamic model of the Galfenol eddy shunt damping system under stress excitation is established.Through the comparison of simulation and experimental results,the validity of the model to describe the static major-loop,dynamic minor-loop and characteristic parameters of the Galfenol rod is verified,the damping performance of the system under different bias stress and shunt resistance is predicted by simulation.The simulation results show that eddy current induced by stress can significantly improve the vibration damping performance of the system,and the proper shunt resistance can also improve the vibration damping effect.These researches can provide theoretical guidance for device design,analysis and application.4.Based on the Armstrong hysteresis model,field-path coupled eddy current field distribution model and finite element method,the internal dynamic hysteresis model of the Galfenol eddy shunt damper is established.Through the comparison of simulation and experimental results,it is shown that the model can describe the magnetic induction-stress dynamic major-loop curves and strain-stress dynamic major-loop curves inside the damper well under the condition of high amplitude and high frequency of dynamic stress,and the model can also predict the influence of external shunt resistance on the curves.These researches lay a very important theoretical foundation for the application of devices under stress excitation with high amplitude and high frequency.