超磁致伸缩材料动态涡流损耗模型及试验分析

Eddy Current Losses of Giant Magnetostrictors:Modeling and Experimental Analysis

超磁致伸缩材料Terfenol-D以其大磁致伸缩系数、快速时间响应及高能量密度的特点较广泛应用于高频动态领域,如超声换能器及振动主动控制结构等。磁性材料在高频磁场驱动条件下会产生涡流损耗,工作频率越高,涡流损耗越大,导致超磁致伸缩器件的输出功率显著降低。通过分析影响涡流损耗大小的关键性因素涡流截止频率与集肤深度,得到有效抑制涡流损耗的方式包括降低材料的电导率以及采用叠堆结构材料。采用经典的基于麦克斯韦方程组的涡流损耗模型,分析高频条件下磁场在整体结构与叠堆结构内部的分布,并通过试验比较两种超磁致伸缩材料结构的涡流损耗对材料阻抗频谱曲线、振动幅度的影响。试验结果显示叠堆结构的超磁致伸缩材料能够大幅度地抑制涡流损耗,其模型与试验结果相吻合。

Giant magnetostrictive material Terfenol-D is widely used in dynamic applications such as ultrasonic transducers and active vibration control structures, with the advantages of large magnetostriction, quick time response and high energy density. Magnetic materials under alternating magnetic field generate eddy current losses. The higher of working frequency, the larger eddy current losses are generated, which causes the low output power efficiency with these devices. By analyzing the key factors of eddy current cut-off frequency and penetration depth that both affect eddy current losses, the methods to effectively restrain eddy current losses include decreasing conductivity of magnetostrictive materials and using laminated structure. The model of eddy current losses is established based on Maxwell＇s equations, and experiments are carried out to compare the effect of eddy current losses on both impedance curve and vibration velocity amplitude between laminated and monolithic magnetostrictive structures. Result shows the laminated type can reduce the eddy current losses drastically and it also matches eddy current loss model built above.