基于磁场传感器的磁电层状复合材料逆磁电效应研究

运用等效电路法对LT型磁致伸缩/压电多层磁电复合材料的逆磁电系数进行了理论推导,得到了其逆磁电系数方程.该方程显示逆磁电系数取决于磁致伸缩层与压电层的性能参数和其体积比.以三层磁电复合材料为例进行计算,理论结果与实验结果吻合较好,且计算结果发现当压电层体积份数n为0.64时,逆磁电系数最大值为199mG/V.研究结果为磁电层状复合材料在电-机-磁耦合方面的应用提供了理论依据,有助于优化以层状磁电复合材料为核心的磁场传感器的结构.     

L-L模式磁电双层复合材料的正、逆磁电效应研究

基于纵向磁化磁致伸缩材料的压磁本构方程、纵向极化压电材料的压电本构方程及磁电材料的运动方程,分别建立了正、逆磁电效应的磁机电等效电路,并推导了纵向磁化与极化(L-L)模式磁电双层复合材料的正、逆磁电系数的计算公式。获得了正、逆磁电效应随频率的变化关系;同时,该计算公式还能研究压电材料参数或磁致伸缩材料参数对正、逆磁电效应的影响。研究表明,对于L-L模式磁电双层复合材料产生的纵向振动模式,理论结果与实验有很好的一致性,因此,期望该理论能在磁电换能器件及能量捕获器件的设计中获得应用。     

GMM在机械电子工程中的应用研究现状

介绍了超磁致伸缩材料（GMM）及其基本特性,并在查阅大量文献的基础上,较全面的论述了GMM在机械电子工程中的应用研究现状及进一步展望。     

Terfenol-D/PZT/Terfenol-D层状磁电复合传感器研究

采用树脂黏结法制备了Terfenol-D/PZT/Terfenol-D层状磁电复合传感器,测量了传感器中Terfenol-D层的静态磁致伸缩性能和传感器的磁电电压性能,研究了直流偏置电流和交流驱动电流对复合传感器磁电性能的影响.结果表明:直流偏置电流对磁电复合传感器磁电电压峰-峰值V(p-p)的影响较大,磁电电压峰-峰值V(p-p)随直流偏置电流的变化规律与Terfenol-D层的磁致伸缩λ对偏置电流的变化率随偏置电流的变化规律相似;交流驱动电流对磁电复合传感器磁电电压峰-峰值V(p-p)的影响也较为明显.     

GMM高频微小泵的性能分析

该文提出了一种新型的液压动力元件—超磁致伸缩高频微小液压泵,它是由GMM驱动器和一个单柱塞泵两部分组成;并设计研制了超磁致伸缩高频微小液压泵的具体结构,介绍了其工作原理和性能特点。分析和计算了GMM高频微小泵的压力、流量、排量、功率和效率等重要基本性能参数。结果表明:超磁致伸缩材料高频微小液压泵具有响应速度快,精度高和易于微型化等优越的动态性能。为进一步的应用研究提供了设计和理论依据。     

磁场加载方式对磁电器件磁电效应影响的研究

将磁致伸缩材料(Terfenol-D)和压电材料(PZT-8)复合,利用谐振原理构造了一种磁电器件.当激励磁场的频率等于或者接近于Terfenol-D的固有频率时,Terfenol-D将驱动PZT-8振动并发生共振,压电材料的输出电压将达到极大.在不同的偏置磁场和交变磁场的加载方式下,研究了谐振状态下的磁电层合器件在强、弱偏置磁场强度下的磁电特性,研究表明,当偏置磁场和交变磁场分别沿长度和宽度方向施加时,相比在弱磁场下,强磁场下磁电层合器件的磁电电压系数分别提高了43.3%和近2倍.     

GMM的热处理工艺及分析

通过实验对比以及金相和衍射分析,定向凝固工艺所生产的稀土超磁致伸缩材料(GMM)在900～950℃范围内,保温1～2h退火后,可以明显提高材料的应变值λ和(dλ/dH)值,从而改善材料的磁致伸缩特性。     

超磁致伸缩薄膜微机械变形镜驱动器的研究

分析了微机械变形镜MEMS驱动器的种类及其特点,并在磁致伸缩薄膜具有低磁场下的大形变、低功耗、高响应速度等特性基础上,提出了超磁致伸缩薄膜MEMS驱动器的原理.由于TbFe磁致伸缩薄膜在外加磁场作用下,微桥将在水平方向上产生伸长变形,从而引起微桥在垂直方向上发生位移.根据这一原理,设计了一种用于微机械变形镜MEMS驱动器的超磁致伸缩薄膜驱动结构,同时提出制作磁致伸缩薄膜连续式微机械变形镜的工艺流程.     

多铁性层状复合材料中平行界面上的多裂纹问题

与压电/压磁颗粒复合材料相比,压电/压磁层状复合材料结构简单,而且常温下的磁电耦合系数较大,因而具有更大的应用前景。然而,在力电磁载荷的作用下,压磁层和压电层的界面难免会发生开裂。这是因为:第一,夹杂、空穴等制造缺陷一般集中在界面区域;第二,长时间工作之后,压电/压磁复合材料界面处的导电银胶可能发生老化,在载荷作用下,老化的界面易于产生损伤甚至开裂;第三,界面两侧压磁层与压电层的材料性能失配往往会导致界面附近区域产生应力集中,从而引起界面开裂。因此,各层间界面上的裂纹问题也十分值得研究。该类复合材料一般是由多层压电相与压磁相交替粘接而成,为了简化起见,本文仅研究由中间的压磁层和两侧的压电层所组成的三层复合材料中两个平行界面上的多裂纹问题。现有文献在对压电/压磁层状复合材料开展断裂力学分析时,一般都不计压电层的导磁性与压磁层的介电性。然而,实际上它们却往往未必可以忽略。因此,在本文的分析中,我们假定压电层的磁导率与压磁层的介电系数同时都不为零。在此基础上,本文对压电/压磁层状复合材料的界面非等长多裂纹问题进行理论推导和数值计算,探讨几何参数和物理参数对界面断裂规律的影响,为工程中的界面防断裂设计提供理论参考。     

超磁致伸缩致动器的新型磁路设计与分析

本文提出了超磁伸缩致动器(GMA)的新型磁路结构,从而对GMA中存在的温升问题提出了解决方案。对现有GMA及其磁路进行了分析,在此基础上提出新型磁路结构。此磁路由环形超磁致伸缩材料(GMM)及导磁材料构成。新型GMA结构中线圈所产生的功耗要远低于现有GMA,并且环状GMM可以有效地将线圈和GMM隔离,从而降低了由于温升过大导致GMM棒热变形的影响。     

一种基于超磁致伸缩材料的发音头盔

在分析了超磁致伸缩材料工作特性的基础上，提出了一种基于超磁致伸缩材料的发音头盔。介绍了发音头盔的工作原理和结构，超磁致伸缩驱动器以及在头盔中固定机构的设计。该发音头盔极大地提高了头盔的使用性能，具有广阔的推广应用前景。     

超磁致伸缩材料在电液伺服阀中的应用现状

超磁致伸缩材料是一种具有响应速度快、磁致伸缩应变大、能量密度高等优良特性的新型功能材料,针对其研究和应用已经成为当前热点。基于现代工业对高性能电液伺服阀的需求,描述了该材料的磁致伸缩效应,并对其基本性能及物理效应作了阐述,同时通过对比压电陶瓷、形状记忆合金的性能参数,分析了超磁致伸缩材料的性能优势。最后着重介绍了该材料在喷嘴挡板阀、射流管阀及直接驱动式电液伺服阀当中的应用现状,并基于此现状对研制高性能的超磁致伸缩电液伺服阀关键技术进行了展望。     

Vibration control efficiency of piezoelectric shunt damping system

The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight, and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively control structural vibration, the piezoelectric materials must be bonded on or embedded in host structure where large strain is induced during vibration, thus to ensure vibrational mechanical energy to be transformed into electrical energy as much as possible. In this paper, the concept of vibration control efficiency of a piezoelectric shunt damping system is proposed and studied theoretically and experimentally. In the study, PZT patches are used as energy converter, and the vibration control efficiency is expressed by the vibration reduction rate per area of the PZT patches. Emphasis is laid on the effect of the generalized electromechanical coupling coefficient K₃₁ on the vibration control efficiency. Four PZT patches with different sizes are bonded on the geometrical central area of four similar clamped aluminum plates, respectively, and vibration control experiments are conducted for these plates using the R-L shunt circuit. The results indicate that the bigger the coupling coefficient K₃₁, the larger the rate of vibration reduction, and hence, the higher the vibration control efficiency. It also shows that the vibration responses of the first mode of the plates bonded with different PZT patches can be reduced by about 30.5%，48.58%，85.47%, and 89.91%, respectively. It comes to a conclusion that the vibration control efficiency of the piezoelectric shunt damping system decreases with the increase of the area of the PZT patch, whereas the vibration reduction of the plate increases with the area of the PZT patch. Therefore, it is necessary to make topology optimization for the PZT patch in the vibration control utilizing the piezoelectric shunt damping technique.     

Adaptive vibration control of micro-cantilever beam with piezoelectric actuator in MEMS

This paper proposes a dynamical model and the governing equations of motion of the micro-cantilever beams based MEMS with piezoelectric actuator (PZT). The Rayleigh–Ritz method is used to reduce the order of the system and the state equations are presented in modal space. The first ten mode frequencies and mode shapes of the micro-cantilever beam with and without PZT are studied. The effects of PZT on the modal frequencies and shapes of the beam system can be ignored for the reason that the beam holds larger nature frequencies and Q values in micro-scale. A rational linearizing feedback controller with a high gain observer is designed to eliminate the unwanted deflection of the micro-cantilever beam system. The open-loop step response and the effects of situated places of PZT on the frequency responses of the system are discussed. Various frequency responses of the beam system, subject to different applied control voltages and feedback gains, are illustrated. The four resonances are well controlled, while the anti-resonance has little change. Computer simulations are provided to demonstrate the performance of the designed control scheme.     

Dynamic responses of a precision positioning table impacted by a soft-mounted piezoelectric actuator

The piezoelectric actuator, lead zirconate titanate (PZT) actuator, has been used for precision positioning from micrometer down to nanometer scale. In this paper, a soft-mounted PZT actuator is designed with a low-stiffness spring element to achieve a high-accuracy and large-displacement characteristic in precision positioning motion. The motion of the sliding table, the contact force between the hammer and the sliding table, and the stick-slip frictional force caused by the grinded groove are investigated. The governing equations of the distributed and lumped parameter systems are formulated to obtain the dynamic responses, which agree well with the experimental results.     

超磁致伸缩材料动态涡流损耗模型及试验分析

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。     

Vibration control efficiency of piezoelectric shunt damping system

The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight, and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively control structural vibration, the piezoelectric materials must be bonded on or embedded in host structure where large strain is induced during vibration, thus to ensure vibrational mechanical energy to be transformed into electrical energy as much as possible. In this paper, the concept of vibration control efficiency of a piezoelectric shunt damping system is proposed and studied theoretically and experimentally. In the study, PZT patches are used as energy converter, and the vibration control efficiency is expressed by the vibration reduction rate per area of the PZT patches. Emphasis is laid on the effect of the generalized electromechanical coupling coefficient K ₃₁ on the vibration control efficiency. Four PZT patches with different sizes are bonded on the geometrical central area of four similar clamped aluminum plates, respectively, and vibration control experiments are conducted for these plates using the R-L shunt circuit. The results indicate that the bigger the coupling coefficient K ₃₁, the larger the rate of vibration reduction, and hence, the higher the vibration control efficiency. It also shows that the vibration responses of the first mode of the plates bonded with different PZT patches can be reduced by about 30.5%, 48.58%, 85.47%, and 89.91%, respectively. It comes to a conclusion that the vibration control efficiency of the piezoelectric shunt damping system decreases with the increase of the area of the PZT patch, whereas the vibration reduction of the plate increases with the area of the PZT patch. Therefore, it is necessary to make topology optimization for the PZT patch in the vibration control utilizing the piezoelectric shunt damping technique.     

Study on dynamic of giant magnetostrictive material transducer with spring of nonlinear stiffness

To study the dynamics of giant magnetostrictive material (GMM) transducer, its model was developed, according to the dynamic experiment results of GMM and the influence of unsymmetrical piece-wise linear stiffness of the prepressing spring. Based on the one degree of freedom its vibration model of a GMM transducer, unsymmetrical piecewise linear nonlinear characteristic of pre-pressing spring was investigated. The first order harmonic motion component of the GMM transducer was obtained by the analysis of KBM method. By the numerical simulation the complicated bifurcation and chaos behavior of the nonlinear vibration system were founded, which should to be taken account of in the design of GMM transducer.     

The efficiency of a broadband piezoelectric transducer with allowance for losses in the piezoceramic and matching-layer materials

The problem of determining the total (acousto-electric) efficiency of a plate-type broadband piezoelectric transducer, which is loaded into an aqueous medium, was considered. The problem was solved taking the mechanical and dielectric losses in the piezoelectric material and the mechanical loss in a matching-layer material into account. Analytical expressions that determine the efficiency of a transducer and radiated acoustic power with account for losses were obtained. Numerical studies determined the main trends in changes in the total efficiency of this type of transducer in a wide range of values of both the mechanical quality factors of the ceramic and layer materials and the dielectric loss tangent for the ceramic material. These data can be of interest when designing piezoelectric devices for different purposes.