TbDyFe磁致伸缩薄膜悬臂梁弯曲性能的研究

以TbDyFe磁致伸缩薄膜悬臂梁为研究对象,采用有限元分析方法(FEM)对薄膜厚度及薄膜与衬底材料的弹性模量比对悬臂梁最大挠度值的影响规律进行了研究.通过FEM计算发现:当薄膜厚度小于衬底厚度的十分之一时,最大挠度值随薄膜厚度线性增加,计算结果与文献的理论计算结果吻合很好;当薄膜厚度为衬底厚度的一半时,悬臂梁的自由端挠度值达到最大.磁性薄膜与衬底材料有效弹性膜量比值的增加可以显著地提高悬臂梁的挠度值,同时挠度最大值向薄膜/衬底厚度比减少的方向移动.     

超磁致伸缩微位移致动器的研究

 基于超磁致伸缩材料的磁致伸缩特性设计了一种用于微位移驱动的致动器．分析了致动器工作磁场的组成，计算了线圈的工作电流，并以此为依据设计了稳流电源．分析结果表明，设计的稳流电源满足工作要求；线圈提供的工作磁场能够保证超磁致伸缩棒工作在线性区域。     

我国稀土超磁致伸缩材料的研究与应用现状

概述了稀土超磁致伸缩材料的性能特点和应用领域，介绍了材料的制备方法和工艺特点，着重讨论了我国稀土超磁致伸缩材料成分、工艺的研究进展及应用现状。     

低场高性能稀土超磁致伸缩材料

所属领域 新材料领域项目简介 国家“863”支持项目采用一种新的制造技术,制造〈110〉轴向取向多晶棒材,在5MPa预应力和5000e磁场下的磁致伸缩系数达／／=950～1150ppm,重复性好,一致性高,工艺易于控制,成品率高。已获国家发明专利,拥有自主知识产权。     

超磁致伸缩驱动器设计准则的建立

在分析超磁致伸缩材料的工作特性、超磁致伸缩驱动器的基本结构与工作原理的基础上,给出了超磁致伸缩驱动器的设计准则．在所提出的设计准则指导下,开发了用于振动主动控制的超磁致伸缩驱动器,并对其主要特性参数进行了测量．实验结果表明,该驱动器的输出性能达到了设计要求。验证了该设计准则的有效性和实用性．     

电容位移测量仪的校准与薄膜的磁致伸缩测量

自制了一套电容位移测量仪的校准装置,并对DWS型电容位移测量仪进行了校准和标定,使位移测量仪在较宽的量程范围内获得的悬臂梁位移测量值的误差≤5％。通过采用经改进校准和标定的位移测量仪,利用悬臂梁-电容法测定了稀土超磁致伸缩薄膜样品的磁致伸缩系数λ,提高了测量精度。     

基于超磁致伸缩和压电陶瓷的XY超精密定位工作台

基于蠕动运动原理,利用超磁致伸缩材料作为驱动元件研制了直线式蠕动进给机构,同时还研制了压电陶瓷-柔性框架式蠕动进给机构．后者放置于前者之上,构成了具有毫米级行程、纳米级定位精度的XY二维精密定位工作台．在计算机控制下,对XY向位移分别进行了闭环反馈控制并测试了它们的步进性能．试验结果表明,工作台在X和Y方向上可以稳定地蠕动步进或后退,X向蠕动机构定位精度为±15 nm,Y向蠕动机构定位精度为±50 nm．     

巨磁致伸缩薄膜-衬底悬臂梁系统的力学特性

利用四参量能量极小化方法求解了任意薄膜／衬底厚度比悬臂梁系统的弯曲问题．在此基础上重点分析了磁膜应力和应变与构成悬臂梁的两种材料的几何参数和物理参数的关系,给出了这些参数对磁膜-衬底悬臂梁系统中平面弯曲特性的影响．计算结果表明,中平面在一般情况下是各向异性的,且随着磁膜厚度的增加中平面迅速下降;磁膜应力随着膜厚增加而减小,应变随膜厚增加而增加;材料泊松比对垂直于磁化方向的应力和应变以及中平面的影响很大,但是,泊松比对磁化方向的应力、应变和中平面的影响很小,可以忽略不计．     

凝固速率对稀土超磁致伸缩材料定向凝固取向的影响

通过对稀土超磁致伸缩材料定向凝固过程的分析，在现代凝固理论的基础上，结合凝固设备的热传导特点，导出了制备具有〈１１２〉择优取向的Ｔｂ－Ｄｙ－Ｆｅ合金样品的必要控制条件，并运用该条件检验和分析了定向凝固Ｔｂ－Ｄｙ－Ｆｅ合金样品取向，结果表明，在约１００Ｋ／ｍｍ的温度梯度条件下，直径小于１１．５ｍｍ的Ｔｂ－Ｄｙ－Ｆｅ合金样品，在２００μｍ／ｓ以下的凝固速率都能获得轴向〈１１２〉取向。随样品直径增大，凝固速率应该减小。在低于１００μｍ／ｓ凝固速率时，直径２０ｍｍ样品也获得了整体轴向〈１１２〉取向。更大直径的样品要求凝固设备的加热速度和冷却强度与之相匹配。     

磁致伸缩液位变送器的原理与应用

磁致伸缩液位变送器是基于磁致伸缩原理和现代数字技术,能达到本质安全标准的新一代高精液位变送器,广泛应用于石油、化工、食品、制药、冶金等行业。本文主要分析了磁致伸缩液位变送器的工作原理,阐述了其主要技术参数和特点,分析了其常见的故障,并对磁致伸缩液位变送器的应用进行了探讨。     

Low-cycle fatigue in rotating cantilever under bending II: experimental investigations on smooth specimens

Low-cycle fatigue of rotating cantilever beams under both load- and deflection-controlled conditions are conducted on four grades of high-strength medium-alloy steel of hardness 280, 310, 350 and 380 HB. The cyclic stress-strain response and strain-life fatigue curves are determined. A numerical methodology derived from a recent theoretical analysis is utilized, which permits the determination of cyclic stress-strain response (n′ and K′) and strain-life curve of any material from its measured rotating bending data, namely: the nominal bending stress and both the vertical and horizontal deflections of a tapered rotating cantilever specimen. The cyclic strain-hardening exponent, fatigue strength exponent and fatigue ductility exponent were found to be almost constant, being 0.104, 0.074 and 0.68, respectively. On the other hand, the cyclic strength coefficient was found to increase with hardness, while the fatigue-ductility coefficient was found to increase with the corresponding true ductility. From the knowledge of the monotonic properties of the tested materials, the strain-life curves for these materials predicted by using the modified universal slopes equation were in excellent agreement with the corresponding experimental curves, in contrast with the original universal slopes equation which overestimates fatigue lives in the low-cycle regime.     

薄膜厚度对多层膜巨磁阻抗效应的影响研究

采用磁控溅射方法在玻璃基片上制备了FeSiB／Cu／FeSiB多层膜,在100kHz～40MHz范围内研究了FeSiB薄膜厚度对FeSiB／Cu／FeSiB多层膜巨磁阻抗效应的影响。当磁场施加在薄膜的纵向时,巨磁阻抗效应随磁场的增加而增加,在某一磁场下达到最大值,然后随磁场的增加而下降到负的巨磁阻抗效应。当FeSiB薄膜的厚度为1．8μm时,在频率3．2MHz、磁场2．4kA／m时,多层膜巨磁阻抗效应达最大值13．5％;在磁场为9．6kA／m时,巨磁阻抗效应为-9．2％。然而,当FeSiB薄膜的厚度为1μm时,多层膜的巨磁阻抗效应在频率40MHz、磁场1．6kA／m时达最大值5．8％。另外,当磁场施加在薄膜的横向时,薄膜表现出负的巨磁阻抗效应。对于膜厚为1．8μm的FeSiB薄膜,在频率5．2MHz、磁场9．6kA／m时,巨磁阻抗效应为-12％。可见巨磁阻抗效应的最大值及负的巨磁阻抗效应与多层膜中磁各向异性轴的取向及FeSiB薄膜的厚度有关。     

Simultaneous combination resonances in a parametrically excited cantilever beam

The effects of parametric excitation of a simple structure are such that very large responses may be generated in a plane perpendicular to that of the excitation as a result of relatively small accelerations, provided that the frequency of the excitation is related to that of the excited mode or modes in a certain manner. It is shown that it is possible for two or more resonances to be excited simultaneously, and that an effect generated by a weaker type of coupling can in fact modify that of a stronger coupling to a significant extent. A vertically oriented, thin and flexible cantilever beam of rectangular uniform cross-section with a lumped end inertia, is modelled both to first and second order of approximation, and theoretical and experimental results for the stability zoning of the resonances are presented. An additional model is proposed which examines the combined effect of two resonances for two tuning cases, and this is compared with measurements of vibratory responses and strain on an experimental system. It is thus shown that the theoretical model postulated for the simultaneous excitation of two resonances accurately predicts the observed behaviour of the laboratory system within a specific range of excitation accelerations.     

悬臂梁压电发电装置的实验研究

为了进行压电陶瓷材料发电性能测试与研究,研制了一套悬臂梁压电振子发电系统.设计了悬臂梁压电振子,并对压电振子进行了有限元分析和电导测试.在此基础上,设计了能量存储电路,并在低频下对悬臂梁压电振子发电性能进行了实验研究.研究结果表明,当悬臂梁压电振子处于谐振频率状态下振动时,输出电压和功率达到最大.输出电压随着负载的增大而增大,输出功率并不随着负载的增大而增大;压电振子存在-个最佳阻抗,当负载与最佳阻抗匹配时,此时压电振子的能量转化效率最高且输出功率最大.利用本实验系统进行压电发电实验测试,当负载为50 kΩ时,压电振子输出电压为7 V;当负载电阻为15 kΩ时,此时的输出功率最大可达到1.4 mW,产生的功率可以满足无线传感器等低耗能产品的供能需求.     

含裂纹悬臂梁的振动与疲劳耦合分析

基于Paris方程和同步分析方法考虑振动与疲劳裂纹扩展耦合之影响,提出一种含裂纹梁的振动疲劳寿命分析思路.振动分析过程中,利用线性弹簧等效裂纹段,复弹性模量引入阻尼损耗因子,得到考虑裂纹扩展、激励频率和阻尼等因素影响的动应力响应.结果表明:裂纹扩展、激励频率和阻尼等因素对疲劳寿命具有重要的影响.通过振动分析与疲劳裂纹扩展寿命估算同步进行,可进一步提高疲劳寿命估算精度.     

复合材料悬臂板系统的多脉冲同宿轨道

针对复合材料悬臂板系统的非线性动力学行为进行了分析。模型考虑高阶横向剪切效应、几何大变形和横向阻尼的影响,基于Reddy的高阶剪切变形理von Karman的大变形理论,利用Hamilton原理,Galerkin离散和多尺度法得到系统横向位移的平均方程。应用广义Melnikov方法研究了复合材料悬臂板的非线性混沌动力学行为。分析了在共振带附近,复合材料悬臂板系统存在的Shilnikov类型多脉冲跳跃同宿轨道。最后结合数值模拟,进一步揭示系统存在多脉冲跳跃现象。     

Nonsteady thermal bending of multilayered plates with internal cooling

We have derived approximate analytical expressions to estimate the nonsteady values of temperature and thermal bending for multilayered plates with internal cooling.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 6, pp. 1005–1010, December, 1989.     

Thermo-mechanical vibration of orthotropic cantilever and propped cantilever nanoplate using generalized differential quadrature method

In this article, the vibration frequency of an orthotropic nanoplate under the effect of temperature change is investigated. Using nonlocal elasticity theory, governing equations are derived. Based on the generalized differential quadrature method for cantilever and propped cantilever boundary conditions, the frequencies of orthotropic nanoplates are considered and the obtained results are compared with valid reported results in the literature. The effects of temperature variation, small scale, different boundary conditions, aspect ratio, and length on natural nondimensional frequencies are studied. The present analysis is applicable for the design of rotating and nonrotating nano-devices that make use of thermo-mechanical vibration characteristics of nanoplates.     

Buckling of a composite cantilever circular cylindrical shell subjected to uniform external lateral pressure

In this paper a solution is presented for a buckling problem formulated for the cantilever circular cylindrical composite shell subjected to uniform external lateral pressure. The edge of the shell is fully clamped at one end of the cylinder and is free at the open section of the other end. An analytical formula for critical pressure has been derived using the generalised Galerkin method. The approach is illustrated by the buckling analyses of composite, orthotropic and isotropic shells. The results are verified using the finite-element method. It has been shown that the analytical solution provides an accurate estimate of the critical load and does not involve any computationally expensive procedures. This is particularly useful in the design optimisation of composite structures.     

Nanodielectrics with giant permittivity

Nanodielectrics is an emerging area of research because of its potential application in energy storage and transducers. One-dimensional metallic nanostructures with localized electronic wave functions show giant dielectric constant. Following the prediction, during the last couple of years we have investigated the effect of giant permittivity in one-dimensional systems of conventional metals and conjugated polymer chains. In this article, we have tried to summarize the works on giant permittivity and finally the fabrication of nanocapacitor using metal nanowires, which shows giant permittivity is also discussed.