采用弹性基底的磁电复合结构有限元分析

介绍了一种将磁致伸缩材料和压电材料粘贴于弹性基底上构成的磁电复合结构,并针对Terfenol-D尺寸确定情况下,PZT-5H长度及弹性基底长度对结构一阶纵向谐振时的磁电特性的影响,采用有限元方法进行了优化分析和设计。结果表明:PZT-5H的最优长度与Terfenol-D等长时,弹性基底存在最优长度,可使结构磁电转换系数最高,且改变弹性基底长度可以调整结构的谐振频率,并进行了实验验证。     

Terfenol-D/PZT和弹性基板阵列换能器的磁电效应研究

利用共振原理,将磁致伸缩材料(Terfenol-D)、压电材料(PZT-8)复合于弹性基板上构造了一种新型的换能器.当激励磁场的频率等于或者接近于弹性基板的固有频率时,Terfenol-D将驱动弹性基板振动并发生共振,粘结于弹性基板上的压电材料的输出电压将达到最大.实验研究表明,在800 Oe偏置磁场和1Oe交变磁场激励下,在谐振点392 kHz处,阵列结构换能器的最大磁电耦合电压系数和最大输出功率分别达到了235.5 mWOe和2.403μW,相比MP层合结构换能器,分别提高了13.77%和33.7%.     

磁致伸缩材料与石英音叉复合低阻尼谐振磁电效应

采用磁致伸缩材料与石英音叉谐振器复合设计了一种低阻尼的谐振式磁电敏感单元。石英音叉工作在弯曲振动模式,音叉叉指结合区域(底部)产生的应力/应变方向相反、弯矩相互抵消,实际为解耦区域。将底部与磁致伸缩材料粘接复合设计谐振式磁电敏感单元的Q值主要取决于音叉谐振器自身的高Q值,磁致伸缩材料的高磁机阻尼被隔离。动态磁场作用下,磁-机-电转换过程可看作一个受迫振动过程,当激励磁场频率接近于音叉谐振频率时,输出电信号最大。实验结果表明:磁电敏感单元Q值高达5 034;谐振磁电电流系数达到799.2 nA/Oe;在接近谐振频率32.774 kHz信号激励下,磁电电流系数相对偏置磁场变化的灵敏度达到5 (nA/Oe)/Oe。     

磁致/压电/磁致层合材料磁电响应分析

对沿长度方向振动(LT模式)的磁致/压电/磁致(MPM)层合材料的磁电响应进行了理论分析,其中磁致层沿长度方向磁化,压电层沿厚度方向极化.从压电效应和压磁效应本构方程出发,结合材料的机械运动学方程和电路状态方程,重新推导了LT模式下MPM结构的等效电路,完善了文献中的方法,得到了复合材料的磁电电压系数、开路电流、材料内阻、可供电功率与压电、磁致材料各物理参数以及体积参数之间的关系式.以Terfenol-D/PZT/Terfenol-D层合材料为例,对材料磁电响应进行了数值计算,将计算结果与相关实验结果进行了比较.利用磁电响应仿真结果,对磁电层合材料用于磁敏传感器以及自供电换能器进行了讨论.     

采用同轴反相激励非晶合金/压电复合磁电双单元非线性磁电效应的磁传感器

具有高磁导率的非晶合金在低于10Oe磁场激励下就发生饱和磁化,从而非晶合金/压电复合材料在较高幅度、频率为f₀f₀的交变磁场激励下产生非线性磁电效应,通过解调奇次谐波(f₀,3f₀,…)输出,可实现静态/准静态弱磁场测量,且无需另外施加偏置磁场。利用两个同轴配置的FeNiMoSiB/PZT/FeNiMoSiB复合结构单元,设计180°反相磁场激励,并且采用压电双晶片的电连接方式配置两磁电单元压电层输出,从而实现传感器灵敏度倍增和共模噪声抑制。磁电电压信号经差分放大和锁相解调后,得到传感输出信号。测试结果表明：在±100μT线性区范围内,传感器的灵敏度达到2.77×10⁴μV/μT;对频率为1 Hz磁场的最低探测极限为10 nT。     

GMM 、PZT和超声变幅杆复合结构磁电换能器研究

将超磁致伸缩材料(GMM)、压电材料(PZT-5H)与超声变幅杆复合,构造了一种新型的磁电换能器.超声变幅杆具有聚能和放大应变的功能,可以数十到数百倍增强换能过程中对压电材料的激励,提高机电换能输出和增强磁电耦合效应.实验表明,在800 Oe偏置磁场和峰峰值为1 Oe交变磁场激励下,谐振点处的磁电耦合电压峰峰值达到498 mV,在负载电阻为2.55 kΩ时,输出功率达到4.08 μW.     

MEMS压电-磁电复合式振动驱动微能源的设计

在单一效应的MEMS振动驱动微能源的基础上,提出了一种MEMS压电-磁电复合振动驱动微能源器件。该微能源由八悬臂梁-中心质量块结构和永磁铁两部分组成,环境振动使中心质量块振动,PZT压电敏感单元由于压电效应产生电势差;同时中心质量块上集成的高密度线圈切割磁感线产生感应电动势,将压电转换与磁电转换相结合把振动能转换为电能。建立了该结构的数学模型并用有限分析软件Ansys12.0对该器件进行力学特性分析,最后对加工出的微能源进行性能测试。测试结果表明,该微能源谐振频率为8 Hz,易与环境发生共振;在共振条件下,施加1 gn 的加速度,器件压电发电开路输出电压峰峰值达154 mV,磁电发电开路输出电压峰-峰值达8 mV,有望为无线传感网络节点提供稳定的能源。     

埋入式压电陶瓷厚度对激励声能影响的有限元分析

将压电陶瓷埋入混凝土构成压电埋入式混凝土机敏模块,利用压电陶瓷的逆压电效应实现对混凝土结构的实时健康检测。为保证接收信号质量,采用具有压电陶瓷谐振频率的周期脉冲作为激励。而不同厚度的压电陶瓷具有不同的谐振频率,对于不同厚度的压电陶瓷,激励频率的选择对接收端的超声波信号有较大影响。通过Ansys软件仿真研究压电陶瓷谐振频率随厚度的变化规律,模拟混凝土中压电陶瓷振动辐射的超声波,分析压电陶瓷厚度对辐射超声波的影响。研究表明:压电陶瓷的振幅随厚度的增加逐渐减小;压电陶瓷的厚度小于1 mm时,最大振幅对应的谐振频率变化趋势出现多个拐点;厚度大于1 mm时,谐振频率随着厚度的增加而减小,辐射超声波中心点声压随厚度的增加而增大。     

一种高频宽带水声换能器的研制

研制了一种宽带、高频压电复合材料圆环阵水声换能器.该换能器的宽带结果是通过采用降低压电材料机械品质因数Qm值和多模耦合振动两种方法实现的.通过径向切割压电陶瓷圆环、灌注环氧树脂得到压电复合材料圆环,再将不同壁厚的压电复合材料圆环轴向叠堆而成敏感元件,对敏感元件进行模具封装,引出电极引线,得到换能器.利用ANSYS软件对结构进行仿真,得到敏感元件谐振频率和带宽随压电陶瓷圆环厚度、高度和平均半径的变化规律,并根据仿真结果确定了换能器敏感元件的最优设计方案.将由最优参数得到的两个压电复合材料圆环轴向叠堆,制作了双圆环叠堆复合材料换能器.经测试,该换能器形成了明显的双模耦合振动,该换能器谐振频率为375 kHz,其-3 dBd工作带宽为90 kHz,最大发送电压响应达148 dB.实现了换能器的高频、宽带、水平全向发射声波的设计目标.     

直角复合梁压电俘能器多方向能量收集

提出了一种可进行多方向能量收集的直角复合梁压电俘能器。使用有限元分析法得到了直角复合梁压电俘能器的功率频响曲线,并与常规复合梁压电俘能器进行了发电能力比较研究,随后参数化分析了金属主梁长度和附加质量对直角复合梁输出功率的影响关系。结果表明,相比于常规的复合梁,直角复合梁压电俘能器可以进一步减小两个谐振频率之间的距离,并且在两个激励方向（x向和z向）有较高的峰值功率密度。x方向激励时,通过合理调节金属主梁长度和末端质量,直角复合梁压电俘能器可以得到两个更接近的峰值功率密度;z方向激励时,随着金属主梁长度和末端质量的增加,直角复合梁压电俘能器的峰值功率密度增加。     

Magnetoelectric transducer with high quality factor for wireless power receiving

To achieve strong power coupling, a resonance-type magnetoelectric (ME) transducer with high quality factor is developed to achieve strong ME coupling. The ME transducer employs a type of iron–nickel-based ferromagnetic alloy with constant elasticity and piezoelectric Pb(Zr,Ti)O₃ (PZT8) material. The dynamic magnetomechanical behavior of the ferromagnetic alloy is investigated. The result indicates that the strain coefficient of the ferromagnetic alloy at resonance achieves 557.07 nm/A due to the high effective mechanical quality factor of the alloy. The transducer is designed to operate as a half-wavelength, longitudinal resonator. The dynamic performance of the transducer is evaluated by measuring its electrical and vibrational characteristics. The results reveal that (1) the resonance of the transducer occurs at the frequency of 26.9336 kHz with a strain coefficient of 314.74 nm/A, an effective mechanical quality factor of 1600; (2) the ME voltage coefficient achieves 30.07 V/Oe (i.e., 375.875 V/cm Oe) at resonance; (3) the ME output power density at optimal load resistance of 25 kΩ achieves 0.956 mW/cm³ under 0.3 Oe root-mean-square AC magnetic field. The performances indicate that the transducer is promising for ME energy conversion application.     

Robust miniaturized amplification unit for piezoelectric actuators: comparison of single crystal silicon and superelastic nickel titanium as membrane materials

In this work, amplification units made of robust metallic nickel titanium (NiTi) and single crystal silicon are compared and evaluated for the application in miniaturized piezoelectric actuators for flow control purposes. The amplification mechanism with a sliced membrane structure is based on a mechanical lever in order to amplify the low piezoelectrically induced deformation. Therefore, an enhanced output stroke can be provided up to high frequencies. The different membrane fabrication processes using laser ablation for the NiTi alloy and deep reactive ion etching for the silicon substrate, as well as the results of finite element simulations and experimental measurements are reported. An amplification factor of 9 has been achieved for an optimized load transmission point position. The dynamic response shows a quality factor of 25 and 494 at the first fundamental mode for NiTi and silicon membranes, respectively. Compared to silicon, NiTi shows enhanced properties against failure and facilitates the integration process.     

A piezoelectric/elastic spring-coupled surface profiler

A piezoelectric element/elastic spring-coupled system is analyzed to simulate the mechanical and electrical characteristics of the surface profile probe. The coupled system includes a piezoelectric element with an elastic spring attached at the free end, and the spring is fixed at another end. The electro-elasticity theory is derived to formulate and solve the governing equations of the system. Two types of the piezoelectric element/elastic spring-coupled system are analyzed for the displacement, stress, resonant and anti-resonant frequencies, and with emphasis on the electromechanical coupling coefficient. Application of a d₃₁-mode piezoelectric ceramic used as a surface profile probe is simulated for analysis of the frequency response, the resolution of displacement, and the contact force. Finally, a multilayered d₃₃-mode piezoelectric ceramic/elastic spring-coupled specimen is constructed for experimental measurements. The agreement between theoretical and experimental results confirms the validity of the study.     

Nonlinear dynamic characteristics of piezoelectric bending actuators under strong applied electric field

Dynamic characteristics of piezoelectric bending actuators under low and high electric fields are studied using the asymptotic theory of nonstationary vibrations. The proposed nonlinear model predicts the changes in fundamental resonant frequencies of the piezoelectric cantilever. The predicted resonance amplitude of the tip deflections of the piezoelectric actuators, which increases with the increase in the magnitude of the electric field, well agrees with the experimental results. Additionally, the decrease in the mechanical quality factor with the increase in the electric field, the tip deflection of piezoelectric actuators near resonance frequency,and the amplitude of the tip deflection at the fundamental vibration tone under an applied electric field varying with time have also been obtained using the present model.     

悬臂梁压电式振动发电机材料性能优化研究

具有高能量密度的微型压电振动发电机可以无限、持续地为无线传感器网络提供能量。为了提高有限体积悬臂梁压电式振动发电机的发电能力,通过力学模型及有限元仿真分析了单晶片型式、双晶片并联型式和双晶片串联型式压电振动发电机的材料参数与输出电压及固有频率之间的关系。结果表明,在低频工作环境下,应优先选择PZT-4、PZT-5A、PZT-5H的压电材料和不锈钢、镍合金的基板材料。     

基于差动电容传感器的微动定位系统设计

设计并加工了一种结构简单、小巧的微动定位系统,该系统精度较高、扫描范围大且成本低廉.采用簧片结构设计系统的机械结构,使用压电陶瓷作为执行器件,使用差动电容传感器作为位移反馈,实现闭环控制,从而有效克服了压电陶瓷执行器件的迟滞和蠕变效应.介绍了微动定位系统的机械组成和差动电容传感器信号检测电路的工作原理,并对系统进行了测试和标定实验.实验结果显示:该平台能够实现15 μm的扫描,精度约为15 nm,且动态性能良好.     

Analysis of intrinsic damping in vibrating piezoelectric microcantilevers

The intrinsic damping of a piezoelectric microcantilever is studied under high vacuum conditions, where the influence of fluid damping on the quality factor is negligible. This paper investigates three major intrinsic damping effects, which are anchor loss, thermoelastic damping (TED) and coating loss. Since the different damping mechanisms generally appear mixed with each other, it is difficult to separate them experimentally. Anchor loss and TED are investigated by using a combination of both analytical and numerical methods, while the coating loss mechanism is explored by measuring a series of cantilevers being coated by a piezo-electrode stack with 20–100 % coverage of the beam length. Finally, experimental validations are conducted on different structures of piezoelectric microcantilevers, showing a good qualitative match with the analytical findings.     

双晶悬臂梁式压电换能器建模与结构参数分析

针对如何提高悬臂梁压电发电效率的问题,通过对压电换能器进行力学分析并建立了一个电路等效模型,从而得到了悬臂梁谐振角振频率和输出功率的计算公式。通过代入数值进行计算仿真得出结构参数对输出功率的影响的曲线。通过分析得出:在设计悬臂梁的结构参数时尽量在结构强度允许的条件下选择更重的附加质量块,电极长度和梁的长度比值为0.8,压电陶瓷和金属层厚度比为0.25,能提高换能效率等结论。     

微型之字形压电式能量收集器输出电压的建模和仿真

为了有效解决无线传感器网络节点的供电难题,提出之字形结构的微型压电式能量收集器。相比于传统的直悬臂梁,此结构等效加大了压电梁的长度,降低了系统的固有振动频率。建立了之字形压电梁的本构方程和受迫振动方程,推导得到其输出电压的频域表达式。基于之字形压电梁的结构,利用ANSYS软件对其进行了谐响应分析。仿真结果表明,压电梁的输出电压在各阶固有振动频率处存在极值,符合理论分析的结果;输出电压大小随压电梁长度增加而降低,随压电梁宽度增加而升高,但均为非线性关系;压电梁末端质量块的长度和厚度、基体层厚度减小时,会导致输出电压的增大。在论文中所提出的结构尺寸下,10根直梁构成的之字形结构压电梁,在其一阶固有振动频率处,输出电压可达10 V以上,符合无线传感器网络节点的实际供电需求,证明了之字形压电梁结构的有效性。