大位移MEMS静电梳齿驱动器的设计及制作

文章提出了一种大位移低驱动电压的MEMS静电梳齿驱动器,对器件进行了设计、模拟、制作以及测试.梳齿驱动器的侧向不稳定性即侧向吸合现象限制了梳齿驱动器的最大驱动位移,发现侧向稳定因子S,随支撑梁刚度比ky/kx以及梳齿间隙g的增加而增加,随梳齿交叠长度的增加而减小;而驱动器的驱动电压随梳齿间隙的增加而升高.在以上研究的基础上,提出了一种采用小间隙无初始交叠、长度线性递增梳齿结构和高纵/横向刚度比的预弯曲支撑梁结构的梳齿驱动器.器件测试结果表明,驱动电压71V时,可以达到100μm的驱动位移,进一步测试表明,驱动器的基模共振频率为573Hz,Q值为35.88.     

一种新型MEMS开关微驱动器研究与仿真

介绍了一种基于光致形变聚合物材料的MEMS开关微驱动器。光致形变聚合物材料在光驱动型微执行器上的应用具有体积小、结构简单、易实现遥控等特点。根据MEMS的尺寸及性能要求建立开关及微驱动器模型,并得到所需最大驱动力。通过计算得出具有一定尺寸光致形变薄膜的等效弯曲行为,并将其应用到MEMS开关微驱动器上。运用ANSYS对微驱动器及闭锁机构仿真分析,根据仿真结果对结构进行改进,确定了采用多层薄板结构的方案,以满足最大驱动力要求。     

结构有限元模型的实验结果修正

本文在简要介绍了用实验模态分析结果修正结构有限元模型的全元素修正法后,结合一个算例演示了该方法的应用。计算和分析结果表明,经过修正的有限元模型与普通有限元模型相比能准确地反映结构的动态特性,说明了这种方法的可靠性和有限元动态模型修正的必要性。     

结构有限元动态模型修正方法综述

本文简要介绍和归纳了五种常用的动态模型修正方法。对每种方法,都给出了它的基本思路、目标函数和修正模型的求解过程,以及各阶段的主要计算公式。基于对各种方法的深入剖析,并结合作者本人的一些实际经验和应用体会,此文还揭示了各种修正方法之间的内在联系及实际使用中应注意的问题。     

基于有限元与块体元法的地下洞室变形及稳定分析

本文把有限元与块体无法结合起来,用来分析地下洞室围岩的变形及稳定性。此法在洞室附近使用块体元模型,以反映节理岩体变形的不连续性,而在远处使用连续的有限元模型,以减少计算工作量。文中推导了有限元与块体元法统一力学模型的支配方程,所编制的数值分析程序应用于某一实际工程问题,说明此法可行。     

基于位错密度的晶体塑性有限元方法的数值模拟及参数标定

运用ABAQUS有限元分析软件对基于位错密度的晶体塑性有限元方法(CPFEM)及其晶体塑性参数进行了深入的研究。结果表明,CPFEM晶体塑性本构可以准确地体现材料的力学性能。通过讨论不同晶体塑性参数,得到各个参数可以分别控制材料的屈服强度、硬化过程、剪切应变速率、极限强度等性能。此外,为了标定材料的晶体塑性参数引入多晶的代表体积单元(RVE)模型,并讨论了晶粒数以及晶粒规整度对于RVE模型的影响。结果表明,RVE模型的晶粒数达到临界值750个时能够体现等轴晶的宏观各向同性。结合晶体塑性RVE模拟和拉伸试验结果,对Inconel 718合金的晶体塑性参数进行标定,晶体塑性有限元的模拟结果和实验结果的误差小于5%。证明经过标定的晶体塑性参数可以准确反映Inconel 718的力学性能,也使得进一步研究该合金介观晶粒尺度的力学性能成为可能。     

一种新型热声制冷机声驱动器的设计与实验研究

为了满足热声制冷机声驱动器对高声强声源的需求,通过简化声驱动器驱动机构的各个零部件结构、连接方式,并考虑零部件的材质性降低驱动器运转时的惯性力,设计了一款强力且性能稳定的微型声驱动器,可应用于小型制冷机的实验研究.通过实验采集了驱动器在基频145 Hz、振幅0.5 mm下热声制冷机谐振腔内的声压、振速值,发现声压值最高...     

一种MEMS平板型同位素微电池的设计与制作

针对倒三角直槽型或倒金字塔型能量转换结构的同位素微电池难于加工以及放射性薄膜不均匀等缺陷,设计了一种较为简单的平板型能量转换结构.引入金属区这一结构,增强了放射源薄膜的接触稳定性.63Ni放射源电镀实验最终得到了一组理想的短路电流和开路电压数据.结果表明,该结构与传统的能量转换结构相比有更稳定的功率输出.     

坞式结构有限元仿真模拟及施工过程对底板受力影响分析

大型船闸底板表面经常会产生顺水流方向的纵向裂缝,常规设计方法无法解释.引入土体渗流固结理论,建立模拟船闸施工过程的有限元仿真模型,对比常规设计方法计算结果,从另一角度进一步分析底板开裂原因,认为常规设计方法是一种瞬态整体分析方法,既没有考虑船闸施工过程,也没有考虑土体沉降过程时间特性,对底板上表面应力计算存在较大偏差,建议设计时采用仿真方法进行计算分析.     

膜结构极小曲面找形的一种自适应有限元分析

找形分析是膜结构设计中的关键环节,但在数学上,膜结构的极小曲面找形分析是一个高度非线性问题,一般无法求得其解析解,因此数值方法成为重要工具。近年来,基于单元能量投影法（EEP法）的一维非线性有限元的自适应分析已经取得成功,基于EEP法的二维线性有限元自适应分析也被证实是有效、可靠的。在此基础上,该文提出一种基于EEP法的二维非线性有限元自适应方法,并成功将之应用于膜结构的找形分析。其主要思想是,通过将非线性问题用Newton法线性化,引入现有的二维线性问题的自适应求解技术,进而实现二维有限元自适应分析技术从线性到非线性的跨越,将非线性有限元的自适应分析求解从一维问题拓展到二维问题。该方法兼顾求解的精度和效率,对网格自适应地进行调整,最终得到优化的网格,其解答可按最大模度量逐点满足用户设定的误差限。该文综述介绍了这一进展,并给出数值算例用以表明该方法的可行性和可靠性。     

基于MEMS的静电微泵建模与仿真

对MEMS中应用广泛的静电微泵进行有限元建模分析．对于涉及多能量域下多场耦合的静电微泵建模,在仿真过程中进行了合理简化．其中在静态分析中,利用圆型薄板的小挠度变形理论和微机电系统中的静电力驱动理论来模拟静电-结构耦合过程;在泵膜的模态分析、谐响应分析以及非线性瞬态分析中,把腔内的流体当作附加质量作用在泵膜上,近似代替流场对泵膜的影响,从而减小计算量,提高了仿真效率．     

Optimal shape design of three‐dimensional MEMS with applications to electrostatic comb drives

A comb drive is one of the most important microactuators in Microelectromechanical (MEM) systems. In a standard comb drive, the capacitance varies linearly with displacement, resulting in an electrostatic driving force which is independent of the position of the moving fingers (relative to the fixed ones) except at the ends of the range of travel. It is of interest in some applications to have force profiles such as linear, quadratic or cubic. Such shaped comb drives could be useful, for example, for electrostatic tuning or to get actuators with longer ranges of travel than those of standard comb drives. This paper presents a methodology for solving three‐dimensional design (inverse) problems in MEM systems. Design of variable shape comb drives (shape motors) is presented as an application of the general methodology. It addresses issues of simulation, sensitivity analysis and then design of three‐dimensional comb drives. Direct simulation is carried out by the exterior, indirect boundary element method and shape sensitivities are obtained by the direct differentiation approach. The inverse problem determines the height profile of the moving fingers of a comb drive such that the driving force is a desired function of its travel distance. An available optimization code (‘E04UCF’ from the NAG package) is used to solve the inverse problem. Numerical results are presented for shape motors that produce linear or cubic force profiles as functions of travel of the moving fingers. Copyright © 1999 John Wiley & Sons, Ltd.     

磁致伸缩作动器的设计与性能分析

在分析超磁致伸缩材料特性的基础上设计了一种微位移作动器．通过有限元分析，对作动器的结构进行优化，得到均匀的偏置磁场和激励磁场；设计了预压力加栽结构和强制冷却结构．对该作动器的动、静态性能进行了测试，结果表明：作动器基本上工作在线性区域内，其位移伸缩量大，低频动态性能较好，高频谐波分量影响较小，相位延迟较小，同时也证明了对作动器的磁场分析和结构优化是正确的．     

拉曼抑制光频梳微腔的设计与仿真

为了解决回音壁模式下的微腔在产生光频梳时受拉曼效应的影响，尤其在重频GHz时难以产生平滑的光梳谱的问题。首先，设计并调节波导和微环的耦合长度；然后，优化耦合角度，调整微环与波导之间的匹配模式，降低在长波段的耦合Q值，增加拉曼产生的阈值，抑制拉曼效应。通过仿真分析得出，相较于一般的直波导微环耦合结构，设计的弯曲波导微环在短波长处拉曼阈值增加了3倍，且在短波长处产生的光频梳功率提高了20 dB。为回音壁模式微腔结构的设计提供了一定的参考价值。     

基于径向励磁和永磁-电磁联合驱动的主动平衡执行器

在线主动平衡系统因可实时抑制旋转设备运行过程中的不平衡振动,在高端机床和航空发动机等高端装备领域具有重要应用价值.平衡执行器作为主动平衡系统的终端执行机构,其性能参数决定了平衡系统的整体指标.对已有电磁滑环式平衡执行器的轴向励磁方法进行了改进研究,提出了一种基于径向励磁和永磁-电磁联合驱动方法的新型执行器结构,通过建立...     

A new fast finite element method for dislocations based on interior discontinuities

A new technique for the modelling of multiple dislocations based on introducing interior discontinuities is presented. In contrast to existing methods, the superposition of infinite domain solutions is avoided; interior discontinuities are specified on the dislocation slip surfaces and the resulting boundary value problem is solved by a finite element method. The accuracy of the proposed method is verified and its efficiency for multi‐dislocation problems is illustrated. Bounded core energies are incorporated into the method through regularization of the discontinuities at their edges. Though the method is applied to edge dislocations here, its extension to other types of dislocations is straightforward. Copyright © 2006 John Wiley & Sons, Ltd.     

A coupled FEM-MFS method for the vibro-acoustic simulation of laminated poro-elastic shells

A new simulation method for the vibro-acoustic simulation of poro-elastic shells is presented. The proposed methods can be used to investigate arbitrary curved layered panels, as well as their interaction with the surrounding air. We employ a high-order finite element method (FEM) for the discretization of the shell structure. We assume that the shell geometry is given parametrically or implicitly. For both cases the exact geometry is used in the simulation. In order to discretize the fluid surrounding the structure, a variational variant of the method of fundamental solutions (MFS) is developed. Thus, the meshing of the fluid domain can be avoided and in the case of unbounded domains the Sommerfeld radiation condition is fulfilled. In order to simulate coupled fluid-structure interaction problems, the FEM and the MFS are combined to a coupled method. The implementation of the uncoupled FEM for the shell and the uncoupled MFS is verified against numerical examples based on the method of manufactured solutions. For the verification of the coupled method an example with a known exact solution is considered. In order to show the potential of the method sound transmission from cavities to exterior half-spaces is simulated.     

Development of specimen and test method for strength analysis of MEMS micromirror

Specimens and fracture test methods for strength analysis of MEMS micromirrors were proposed. Bending and combined loading tests were performed, and torsion strength was estimated from those results. Two-parameter Weibull distribution was used to evaluate the fracture stresses estimated from the FEM model. The resulting scale and shape parameters were 787 MPa and 7.77 for the bending test and 517 MPa and 5.28 for the combined loading test. There was a difference in strength between the results of the bending and combined loading tests. From the load factor analysis, it was found that both geometry and stress distribution have to be considered to estimate the strength of MEMS since flaws are non-uniformly distributed. It was also found that torsional strength can be estimated on the safe side using the results of the combined loading test.     

A new mass lumping scheme for the mixed hybrid finite element method

Diffusion‐type partial differential equation is a common mathematical model in physics. Solved by mixed finite elements, it leads to a system matrix which is not always an M‐matrix. Therefore, the numerical solution may exhibit unphysical results due to oscillations. The criterion necessary to obtain an M‐matrix is discussed in details for triangular, rectangular and tetrahedral elements. It is shown that the system matrix is never an M‐matrix for rectangular elements and can be an M‐matrix for triangular an tetrahedral elements if criteria on the element's shape and on the time step length are fulfilled. A new mass lumping scheme is developed which leads to a less restrictive criterion: the discretization must be weakly acute (all angles less than π/2) and there is no constraint on the time step length. The lumped formulation of mixed hybrid finite element can be applied not only to triangular meshes but also to more general shape elements in two and three dimensions. Numerical experiments show that, compared to the standard mixed hybrid formulation, the lumping scheme avoids (or strongly reduce) oscillations and does not create additional numerical errors. Copyright © 2006 John Wiley & Sons, Ltd.     

Developing new enrichment functions for crack simulation in orthotropic media by the extended finite element method

New enrichment functions are proposed for crack modelling in orthotropic media using the extended finite element method (XFEM). In this method, Heaviside and near‐tip functions are utilized in the framework of the partition of unity method for modelling discontinuities in the classical finite element method. In this procedure, by using meshless based ideas, elements containing a crack are not required to conform to crack edges. Therefore, mesh generation is directly performed ignoring the existence of any crack while the method remains capable of extending the crack without any remeshing requirement. Furthermore, the type of elements around the crack‐tip remains the same as other parts of the finite element model and the number of nodes and consequently degrees of freedom are reduced considerably in comparison to the classical finite element method. Mixed‐mode stress intensity factors (SIFs) are evaluated to determine the fracture properties of domain and to compare the proposed approach with other available methods. In this paper, the interaction integral (M‐integral) is adopted, which is considered as one of the most accurate numerical methods for calculating stress intensity factors. Copyright © 2006 John Wiley & Sons, Ltd.