一种磁耦合激励的涡轮式压电气流俘能器EI北大核心CSCD

为满足气流管道监测系统的自供电需求,提出一种磁耦合激励的涡轮式压电气流俘能器。建立了俘能器的理论模型并进行了仿真分析,设计制作了样机并进行了试验测试,获得了磁铁排布、附加质量、压电振子串并联及负载电阻对其输出特性的影响规律。结果表明:在其他条件确定时,存在多个较佳气压使输出电压出现峰值,主频峰值的大小和分频的位置均与激励磁铁排布有关;通过附加质量可以调节最佳气压和输出电压峰值,采用多个不同附加质量的压电振子串联或并联可以拓宽俘能器的气压适应范围;存在不同的最佳负载使多个压电振子串联和并联时俘能器的输出功率达到最大,最佳负载及其所对应的最大输出功率分别为(40 kΩ,41 mW),(15 kΩ,50 mW)。     

宽频压电振动俘能器的研究现状综述EI北大核心CSCD

随着便携式电子设备、微机电系统(MEMS)和无线传感器网络的广泛应用,化学电池供能的弊端日益显现。压电振动俘能器可以将环境中的振动能转换成电能,实现低功耗微电子产品的无线供能或能量自给。在实际应用中,为了增强俘能器的环境适应能力,提高其俘能效率,宽频压电俘能技术成为当前的研究热点。介绍了压电振动俘能器的工作原理、常用压电材料和工作模式,综述了宽频压电俘能技术的国内外研究现状,分析了当前研究中存在的问题和不足,提出了未来可能的研究方向。压电振动俘能技术为低功耗微电子产品提供了一种稳定、安全、长久的新供能方式,具有良好的应用前景。     

双向激励下非线性压电俘能系统的稳态响应分析EI北大核心CSCD

基于基础激励的多向性和实际环境中的低频率环境,研究了在固定基础端受到水平和垂直双向激励的附加端部质量块悬臂梁压电俘能系统的非线性稳态响应问题。通过Hamilton原理对一个附加端部质量块悬臂梁双晶片压电俘能系统模型的非线性偏微分方程进行理论推导和计算分析。假设此悬臂梁为轴向不可伸长的Euler-Bernoulli梁,此模型主要包含几何非线性和阻尼非线性。利用Galerkin法将非线性偏微分方程降阶得到双向激励作用下附加端部质量块悬臂式压电俘能系统的机电耦合运动微分方程。采用多尺度法研究压电俘能系统在其主要的一阶共振情况下的响应,获得了俘能系统的垂直位移、输出电压和输出功率的解析表达式。得到其主要一阶垂直位移幅值,输出电压幅值和输出功率幅值。分析了不同激励情况下,激励相位等对压电俘能系统俘能性能的影响。     

线形-拱形组合梁式压电俘能器振动特性研究

为揭示线形-拱形组合梁式双稳态压电俘能器系统参数对其动力学响应特性影响规律,利用磁化电流法及广义Hamilton变分原理,分别建立压电俘能器非线性磁力模型及系统分布式参数模型;采用谐波平衡法对俘能系统响应特性进行分析,讨论不同磁铁间距、激励幅值、负载阻抗等参数对系统幅频响应及输出功率的影响规律,并进行实验验证.研究结果...     

压电俘能技术研究现状综述

摘要：随着微电子、无线网络和MEMS等低耗能产品的应用日益广泛,以化学电池为其主要供能方式存在着诸多弊端,而压电俘能器具有结构简单、不发热、无电磁干扰、无污染和易于实现机构的微小化、集成化等诸多优点,且能满足此类低耗能产品的供能需求而备受关注。综述了压电俘能技术的国内外研究现状。围绕提高压电俘能效率,从压电振子构成形式、能量存储电路和能量存储元件等方面进行了系统的介绍,并对压电俘能技术的发展方向进行了预测。压电俘能技术可应用于导弹引信,海啸预警、桥梁安全监测、石油输油管道监测等重要领域的安全检测装置的自供能系统中,同时也可为无线网络、嵌入式系统和MEMS等低耗能产品的实现无线供能,展现出了压电俘能技术的良好应用前景。     

预应力式压电能量采集器的模型和试验分析EI北大核心CSCD

为提高振动能量的采集效率,设计了一种基于预应力梁的压电能量采集器。基于欧拉-伯努利梁理论,建立了基础激励条件下含预应力压电陶瓷悬臂梁的动力学模型,并利用数值仿真的方法对其输出功率、电压等性能进行分析。最后搭建了试验平台对上述预应力能量采集器的样品进试验测试,对其输出电压、输出功率和自由端位移与预应力大小关系进行分析和研究。试验结果显示在相同条件下,5.9 N轴向预拉力作用下的压电能量采集器的开路电压比无预应力条件下提高了11.6 V。对相同容量的电容的充电试验结果表明,含5.9 N轴向预拉力的压电能量采集的平均充电电压比无预应力情况下提高了1.55 V。数值仿真和试验结果均显示含预应力的PEH的能量采集效率得到明显提高。     

双自由度磁悬浮式轨道车辆振动俘能器的研究EI北大核心CSCD

提出了一种双自由度磁悬浮轨道车辆振动俘能器,该俘能器安装于轨道车辆转向架处,与单自由度磁悬浮轨道车辆振动俘能器相比振动能量收集效率得到显著提高。建立了双自由度振动俘能系统的物理以及数学模型,并对其动力学特性进行了分析,运用龙格库塔法计算得到双自由度俘能系统在简谐振动激励和轨道车辆垂向振动激励下的振动特性和输出功率并与单自由度俘能系统进行对比,研究结果表明:双自由度俘能系统共有两个共振峰,拓宽了俘能器的工作频带范围,通过改变尺寸参数可以提升系统针对目标频率的俘能效率;在简谐激励和轨道车辆振动激励下双自由度俘能系统的输出功率是单自由度俘能系统的1.5倍,能够高效俘获轨道车辆的振动能量。     

基于MFC的地铁轨道振动能量收集研究EI北大核心CSCD

压电陶瓷极限受拉承载力弱,导致传统悬臂型俘能器在工程应用中极易开裂损坏,与其持续供能的初衷相违背。压电纤维复合材料(MFC)具有优异的柔韧性、耐久性,恰恰弥补了这一缺陷。然而以MFC材料为基础的俘能器在地铁轨道振动能量俘获中的应用鲜有研究。首先建立地铁车辆-轨道耦合系统模型,得到钢轨在车辆荷载作用下的动力响应。紧接着基于混合规则和代表体积元建立型悬臂式MFC俘能器的力电耦合模型,并将钢轨的动力响应作为俘能器的输入荷载预测其电能输出,讨论了材料参数、几何参数及车辆荷载特性对输出电能的影响。并进一步通过试验研究,验证了所建立理论分析模型的正确性。最后基于LTC3588-1能量管理芯片进行了能量收集-存储模拟,验证了MFC俘能器用于无线传感器供能的可行性。     

基于相场函数的压电复合材料俘能器拓扑优化设计

提出了一种基于相场函数的压电俘能器拓扑优化设计方法,通过设计俘能器的材料分布提高其工作效率。其中,利用相场函数描述俘能器上压电材料与基体材料(环氧基树脂)的分布,并建立以相场函数节点值为设计变量,以特定频率激励下俘能器的能量转换因子最大化为目标的拓扑优化模型。该文给出了目标函数和约束函数的灵敏度分析,并采用移动渐近线方法对优化问题进行求解。数值算例验证了所提出的数学模型与设计方法的可行性和有效性。     

拱形-线形非线性磁力耦合压电俘能器建模与特性分析

为分析拱形-线形非线性磁力耦合压电俘能器振动特性,利用磁化电流法建立了磁力模型,实验测量并通过数据拟合方法获取了拱形-线形结构非线性恢复力模型,利用广义Hamilton变分原理建立系统的动力学方程.采用谐波平衡法对动力学方程进行了求解,揭示了不同激励条件、不同磁距对俘能器振动特性的影响关系并开展实验研究.结果 表明:拱...     

Experimental and numerical results of dynamics behavior of a nonlinear piezoelectric beam

This article presents a numerical formulation and experimental implementation for the dynamics behavior verification of the nonlinear piezoelectric beam through harmonic excitation. The nonlinear piezoelectric beam dynamic analysis program is developed with MATLAB software. To verify the nonlinear piezoelectric beam dynamic analysis results, the experimental results are used for the vibration analysis of a piezoelectric beam to the harmonic excitation of the base of the beam. Then, the piezoelectric effect on the output voltage, velocity, acceleration values, and the time response are obtained. Afterwards, the effects of the excitation velocity and the position of concentrated mass on the output voltage are verified.     

Flexible highly-effective energy harvester via crystallographic and computational control of nanointerfacial morphotropic piezoelectric thin film

Controlling the properties of piezoelectric thin films is a key aspect for designing highly effident flexible electromechanical devices.In this stud~ the crystallographic phenomena of PbZr1-xTixO3 (PZT) thin films caused by distinguished interfacial effects are deeply investigated by overlooking views,including not only an experimental demonstration but also ab initio modeling.The polymorphic phase balance and crystallinity,as well as the crystal orientation of PZT thin films at the morphotropic phase boundary (MPB),can be stably modulated using interfacial crystal structures.Here,interactions with MgO stabilize the PZT crystallographic system well and induce the texturing influences,while the PZT film remains quasi-stable on a conventional Al2O3 wafer.On the basis of this fundamental understanding,a high-output flexible energy harvester is developed using the controlled-PZT system,which shows significantly higher performance than the unmodified PZT generator.The voltage,current,and power densities are improved by 556％,503％,and 822％,respectively,in comparison with the previous flexional single-crystalline piezoelectric device.Finally,the improved flexible generator is applied to harvest tiny vibrational energy from a real traffic system,and it is used to operate a commercial electronic unit.These results clearly indicate that atomic-scale designs can produce significant impacts on macroscopic applications.     

被动湍流控制圆柱驰振能量收集的等效电路研究

为更好的预测驰振压电能量收获机的性能,首先建立了等效电路仿真模型(ECM)并通过实验验证,最大误差不超过10%。采用该方法分析了被动湍流控制(PTC)下圆柱驰振压电能量收集的仿真模型,且该方法可将驰振能量转化系统的质量-弹簧-阻尼(M-C-K)控制方程中各参数用等效电路的电子元件来表示,从而可以分析过往仿真手段所不能解决的直流电路耦合问题。其次,从能量收集效率角度分析了交流-直流等效电路中临界风速(Ucr)随外接载荷的变化规律,及输出电压与功率随不同风速和外界载荷的变化规律。结果表明,交流电路中Ucr随载荷的增大先增大后减小,直流电路中Ucr随载荷的增大逐渐减小。当风速达到Ucr的最大值时,驰振在任一电阻下均会发生。U≥Ucr时,驰振出现锁定现象,输出电压和功率均随着风速的增大而增大。当风速过大时,增长率有减小趋势。输出电压均随着电阻的增大而增大,功率随电阻的增大先增大后减小。相比于交流电路,直流电路的最佳负载由1.1 MΩ提高到2.0 MΩ,同时功率峰值从0.08 mW降低到0.04 mW。     

Evaluation of power extraction circuits on piezo‐transducers operating under low‐frequency vibration‐induced strains in bridges

The concept of piezoelectric energy harvesting (PEH) provides a promising solution for perpetually running low‐power electronic devices such as wireless sensor networks by harvesting ambient vibrations generated from civil structures such as long span bridges, city flyovers, elevated metro corridors, which are constantly under dynamic loads. However, its successful industrial‐scale deployment on civil structures is still not realised because of the low‐frequency of vibrations (typically <5 Hz) encountered there, coupled with the low levels of voltage generation. The vast majority of PEH‐related studies have only focused on PEH configurations and geometries, Often entailing secondary structures. d₃₁ mode, which is the most natural mode of excitation, has not been investigated in depth for piezo‐patches directly bonded on the main structure. Studies, which have focused on electronic conditioning circuitry, have been restricted to typically high‐voltage and high‐frequency scenarios only. This paper focuses on systematically studying the issues inflicting energy harvesting from the ambient vibrations induced flexural strains civil structures, such as city flyovers, using piezo elements in d₃₁ mode. Vibration measurements are first undertaken from a typical city flyover consisting of steel girders supporting a reinforced concrete (RC) deck. The basic site measurements are employed to perform a laboratory‐based parametric study to investigate the influence of parameters such as vibration frequency, voltage, and circuit components like diodes on PEH. On the basis of the experimental results, it can be concluded that power in microwatts range can be typically harvested from these civil structures through directly bonded piezo patches in d₃₁ mode. However, there are still issues associated with electronic circuitry accompanying harvesters, such as diodes and storage elements. The same are summarised and future directions envisioned.     

Compatibilization of PLA/starch composite with electron beam irradiation in the presence of a reactive compatibilizer

The aim of this study is to improve the compatibility of poly (lactic acid) (PLA)/starch composite by electron beam irradiation in the presence of glycidyl methacrylate (GMA) as a reactive compatibilizer. Compatibilization process has been done by melt mixing the PLA/starch and GMA with a twin screw extruder and exposing the PLA/starch/GMA mixture to electron beam at room temperature. The exposure process was carried out to induce definite interfacial adhesion at the interface between PLA and starch through electron beam-initiated graft copolymerization by the medium of the GMA. To testify the effect of this compatibilization strategy, rheological, mechanical, and morphological properties of the composite were analyzed. The scanning electron micrographs of the cryofracture and tensile fracture surfaces of the composites revealed that the interfacial adhesion between PLA and starch was greatly improved by this strategy. Fourier transform infrared study confirmed the grafting reaction between PLA and starch. The reaction schemes were proposed to understand the reaction mechanisms at the interface.     

密肋复合墙结构体系抗震性能的试验研究

密肋复合墙结构独特的构造使结构在地震作用下表现出填块→框格→外框的破坏模式,实现对地震能量的分级释放,形成结构抗震的三道防线。为了探讨密肋复合墙体中各道抗震防线对抗震性能的影响,进行了2组复合墙体的试验研究。观察了墙体的主要破坏形态和破坏过程,分析了墙体的承载力、滞回特征、延性、刚度、耗能能力等抗震性能。研究表明：肋格约束下的填充砌块极限承载力明显提高,屈服位移减小,延性降低。加外框的墙体比不加外框的墙板承载力明显提高。屈服荷载之前主要为砌块开裂耗能,屈服荷载后主要为裂缝的开裂闭合及相互摩擦耗能,标准墙板中的砌块及墙板内裂缝分别受到肋格和外框的约束,摩擦耗能较为充分。在密肋结构中,可以通过调整每道防线的设计参数来改变三道抗震防线的发生顺序及耗能性能,实现三道抗震防线的量化设计。     

压电复合材料的共线周期性裂纹平面问题的电弹性场分析

利用复变函数知识、半逆解法及待定系数法, 研究了压电复合材料的共线周期性裂纹问题, 给出了在电不可渗透边界条件下的应力、电位移、应力强度因子、电位移强度因子和机械应变能释放率的解析解。当裂纹间距趋于无穷时, 共线周期性裂纹退化为一条单裂纹, 得到了压电复合材料一条单裂纹的结果。通过数值算例讨论了共线周期性裂纹的裂纹长度、裂纹间距和机电载荷对机械应变能释放率的影响规律。结果表明, 机械应变能释放率随着共线周期性裂纹的裂纹长度、共线周期性裂纹的裂纹间距、机械载荷和正电场的增大而增大, 随着负电场的增大而减小。     

Thermo-mechanical vibration analysis of sandwich beams with functionally graded carbon nanotube-reinforced composite face sheets based on a higher-order shear deformation beam theory

This article proposes a higher-order shear deformation beam theory for free vibration analysis of functionally graded carbon nanotube-reinforced composite sandwich beams in a thermal environment. The temperature-dependent material properties of functionally graded carbon nanotube-reinforced composite beams are supposed to vary continuously in the thickness direction and are estimated through the rule of mixture. The governing equations and boundary conditions are derived by using Hamilton's principle, and the Navier solution procedure is used to achieve the natural frequencies of the sandwich beam in a thermal environment. A parametric study is led to carry out the effects of carbon nanotube volume fractions, slenderness ratio, and core-to-face sheet thickness ratio on free vibration behavior of sandwich beams with functionally graded carbon nanotube-reinforced composite face sheets. Numerical results are also presented in order to compare the behavior of sandwich beams including uniformly distributed carbon nanotube-reinforced composite face sheets to those including functionally graded carbon nanotube-reinforced composite face sheets.     

钢筋混凝土复合防护梁的抗撞性能研究

传统结构构件设计较少考虑碰撞效应,因此有可能因碰撞荷载而引起严重的冲击破坏。鉴于此,在前期提出的刚柔复合防护结构体系的基础上,针对钢筋混凝土复合防护梁的抗撞性能进行了分析研究。在数值模拟的过程中,分别考虑了无防护、刚性防护、柔性防护和刚柔复合防护四种不同的措施以及两端固支、两端铰支和一端固支一端铰支三种不同的梁端约束形式。通过观测钢筋混凝土梁的应变、位移、加速度和冲击力等参数,可评价相应的抗撞效果。数值结果表明,提议的复合防护体系效果最好,可以有效抑制受撞构件的冲击响应;同时,构件约束形式对抗撞性能的影响也是不容忽视的。     

Control of thermomechanical anisotropy in high-speed microrotor with permanent magnet for energy conversion

Abstract

A microturbine for energy harvesting is analyzed, and a design approach is assessed. A magnetic dipole, applied to a microrotor to convert energy of either a fluid or a gas into mechanical power, exhibits anisotropy of thermomechanical properties. The rotor dynamics, stability, and unbalance response are predicted. The coupled effect of rotation and temperature is then investigated, to detect the actual influence of the thermomechanical anisotropy of magnet, to be controlled by the contact pressure applied through an outer layer of carbon fibers. This methodology allowed a refinement of system requirements, and defining a design procedure to prevent damage.