机电耦合中微开关悬臂梁的瞬态分析

在微机电开关梁的设计过程中,对其吸合过程的响应时间的分析具有重要的意义。对静电力驱动的微开关梁的瞬态分析用于确定设计中的结构或机器部件的响应时间是必要的。运用ANSYS软件对微梁模型进行机电耦合分析,采用Trans126换能器单元的直接耦合静电—结构分析模型,分析了微梁的瞬态特性,得出微梁的吸合时间随着厚度的增大而增大。     

机电耦合下两端固支微梁的静态分析

在微机电系统中,静电驱动两端固支微梁常作为驱动结构,因此对微梁结构的静态分析研究具有重要意义。采用ANASYS中直接耦合法Trans126降阶单元,建立微梁的机电耦合模型,分析几何结构参数与其最大挠度的关系,进一步揭示在微机电结构中微梁抗弯刚度与其厚度的关系。     

二维解耦微位移工作台的设计与有限元分析

微位移工作台在微机电系统、超精密加工和生物医学工程等领域有广泛的应用。设计了一种驱动器浮动的二维解耦微位移工作台。工作台采用双层柔性铰链杆对称一体化结构,消除了X、Y方向的耦合运动。推导了微位移工作台的理论刚度。为了验证此微位移工作台能够满足设计要求,采用有限元方法进行分析计算,有限元计算得到的微位移工作台刚度与微位移工作台的理论刚度吻合较好,并且通过有限元计算的结果验证了工作台在X、Y方向的运动无耦合。     

力电耦合下MEMS微梁变形行为的结构参数影响研究

MEMS和其它微系统产品中许多致动器利用静电力作为驱动力.在许多微型电动机和致动器的设计中,分析静电力作用下微梁结构参数如悬臂梁的厚度对微梁挠度的影响是必要的.基于物理环境法顺序耦合法来分析悬臂梁的力电耦合,运用ANSYS软件对微悬臂梁模型进行机电耦合分析,讨论了在其他结构参数不变的情况下,微梁厚度与最大变形量的变化关系,并通过拟合曲线进一步探讨了微梁厚度对结构驱动性能的影响.     

微机械电容式加速度计静力分析

本文根据微加速度计的结构特点,分析了单晶硅的力学特性,并且利用有限元方法对微电容式加速度计敏感芯片弹性梁的刚度、应力、应变进行了分析。     

微机电系统应用中的非线性力学问题分析

微机电系统（MEMS）中常作为和力有关的传感器使用的悬臂梁类型结构，在使用过程中经常会出现淖变形、大位移的情况，这时传统的线性分析方法会导致较大的系统误差。本文基于二次梁理论给出了该几何非线性问题的理论解，其正确性通过有限元的数值计算结果得到验证。这个通过非线性分析得到的理论解不但校正了线性分析方法的系统误差，提高了系统精度，而且扩大了系统的有效使用范围。     

微机电系统中基于模态展开和边界元法的静电-结构耦合高效分析方法

为了提高微机电系统中静电-结构耦合数值计算速度,提出了一种新的针对微结构小变形的静电-结构耦合高效率数值计算方法。该方法将用于结构分析的微梁线性方程与用于静电场分析的边界积分方程相结合,微梁方程部分用标准的模态分析法处理,静电边界元方程则采用边界元法处理,并且将边界元方程用Taylor级数在微梁未变形的位置展开,以使静电计算能在微梁未变形的位置进行。同以往的常规算法相比,当微结构变形微小时,使用该方法,微结构变形后的面电荷密度可以在微结构未变形中计算,从而大大提高了静电-结构耦合数值计算效率。将该方法的计算结果与已有的文献计算结果和ANSYS的计算结果做了对比,验证了本方法的正确性,并且计算效率有显著提高。     

具有不对称弹性梁的梳状微加速度计的结构变形分析

通常情况,梳状微加速度计具有对称结构.但是加工工艺的缺陷可能导致梳状微加速度计的弹性梁不对称,引起结构发生扭转运动.对于双端固定梁式结构,分析了弹性梁的不对称性对结构等效刚度的影响.在假设弹性梁长度相等,但弯曲刚度不相等的前提下,推导出了结构的等效刚度计算公式,并将其推广到任意不对称情况.最后用有限元仿真实例验证了理论...     

岸边集装箱起重机钢结构的有限元仿真计算

采用数值计算中的有限元理论和Ansys程序,对45 t-22 m岸边集装箱起重机整体钢结构进行建模,提出了大梁异形截面的仿真方法和偏轨梁的加载方法,求解有限元模型并得出各工况下的结构应力,证明钢结构设计满足要求。文中所述仿真计算研究也为结构优化设计提供参考。     

微旋转结构在薄膜应力测量中的应用

利用有限元仿真方法,研究了微旋转结构几何参数对结构应变响应的影响.结果表明,固定梁与旋转梁的长度以及这两种梁连接部分的宽度和连接中心距都对结构的应变响应具有较显著的影响,而梁的宽度及连接部分的长度对应变响应的影响可忽略,因此,需要综合考虑以达到结构的优化设计.给出了一组旋转结构的设计参数.     

Development and numerical validation of a finite element model of the muscle standardized femur

The human femur is one of the parts of the musculo-skeletal system most frequently analysed by means of the finite element (FE) method. Most FE studies of the human femur are based on computed tomography data sets of a particular femur. Since the geometry of the chosen sample anatomy influences the computed results, direct comparison across various models is often difficult or impossible. The aim of the present work was to develop and validate a novel three-dimensional FE model of the human femur based on the muscle standardized femur (MuscleSF) geometry. In the new MuscleSF FE model, the femoral attachment of each muscle was meshed separately on the external bone surface. The model was tested under simple load configurations and the results showed good agreement with the converged solution of a former study. In the future, using the validated MuscleSF FE model for numerical studies of the human femur will provide the following benefits: (a) the numerical accuracy of the model is known; (b) muscle attachment areas are incorporated in the model, therefore physiological loading conditions can be easily defined; (c) analyses of the femur under physiological load cases will be replicable; (d) results based on different load configurations could be compared across various studies.     

电镀铜薄膜疲劳性能与寿命预测

利用MMT-11N微机械疲劳试验系统对11.5 μm厚无基体支持的电镀铜薄膜试件的拉伸疲劳特性进行了试验研究。试件采用准LIGA工艺制作。试验在室温条件下进行,采用载荷控制、脉动循环加载,载荷频率为20 Hz,得到了铜薄膜光滑试件和缺口试件的S-N曲线,根据传统宏观疲劳理论确定了铜薄膜循环应力—应变曲线和应变—寿命曲线。利用修正局部应力—应变法对缺口试件的疲劳寿命进行了预测,预测寿命与试验寿命误差在3.2倍因子之内,预测结果较好地符合试验结果。试验表明,取半寿命周期的迟滞回线作为稳定迟滞回线在微机械疲劳中仍是可信的,局部应力—应变法亦可应用于微机电系统疲劳寿命预测,宏观疲劳理论在一定程度上也适合于描述微机械疲劳。     

Hybrid forging processes of micro-double gear using micro-forming technology

Micro-gear is an important actuating component used widely in micro-electromechanical systems (MEMS) devices. Forming and assembly technology of micro-parts are urgently needed to be developed. In this paper, novel hybrid processes combining isothermal enclosed forging process with two kinds of piercing methods have been presented to manufacture the micro-double gear. The metal flow and filling quality were studied with finite element (FE) simulation. The results show that the hybrid forging process with central piercing method can improve the defects (underfill and declining shaft) generated by double-ended piercing method. Based on FE analysis, the experiments of hybrid forging process was investigated with central piercing method and the micro-double gear was manufactured with good quality. The results show that central piercing method can solve the shortcoming of inclining shaft with double-ended piercing method. The hybrid forging process is an appropriate technology for manufacturing the micro-double gear.     

Comparative study of damped FE model updating methods

Most of finite element (FE) model updating techniques do not employ damping matrices and hence, cannot be used for accurate prediction of complex frequency response functions (FRFs) and complex mode shapes. In this paper, a detailed comparison of two approaches of obtaining damped FE model updating methods are evaluated with the objective that the FRFs obtained from damped updated FE models is able to predict the measured FRFs accurately. In the first method, damped updating FE model is obtained by complex parameter-based updating procedure, which is a single-step procedure. In the second method, damped updated model is obtained by the FE model updating with damping identification, which is a two-step procedure. In the first step, mass and stiffness matrices are updated and in the second step, damping matrix is identified using updated mass and stiffness matrices, which are obtained in the previous step. The effectiveness of both methods is evaluated by numerical examples as well as by actual experimental data. Firstly, a study is performed using a numerical simulation based on fixed–fixed beam structure with non-proportional viscous damping model. The numerical study is followed by a case involving actual measured data for the case of F-shaped test structure. The updated results have shown that the complex parameter-based FE model updating procedure gives better matching of complex FRFs with the experimental data.     

Stick–Slip Motion and Static Friction in a Nonlinear Deformable Substrate Potential

Nano-scale adhesive contact mediated by intermolecular van der Waals forces has become a typical fundamental problem in many areas. Interpretation and control of the strength and efficiency of the nano-scale adhesive contacts require a proper modeling considering the actual interfacial forces, the varying contact area, and clearance. In this article, the finite-element (FE) method is developed to model the nano-scale adhesive contact of elastic bodies with an adhesive pressure derived from the interatomic interaction Lennard-Jones potential, which permits numerical solutions for a variety of interface geometries. Compared with the analytical results from conventional Hertz, JKR, and DMT models, the validity of the FE model is verified. For nano-scale contact, the assumption of equivalent radius adopted in the Hertz model is initially investigated and proved to be improper for nano-scale adhesive contact due to the distribution variations of interfacial force caused by local contact geometry. Then adhesive contact behaviors of four typical nano-scale contact geometries inspired by tip shapes of bio-adhesive pads are investigated in detail, which are flat punch tip, sphere tip, mushroom tip, and empty cup tip. The simulation results indicate that the nano-scale tip geometry plays a dominant role on the pull-off strength. Within the investigated geometries, cup tip results in a highest adhesion efficiency followed by flat punch tip, sphere tip, and mushroom tip, respectively, which are highly geometry dependent and verified by former experimental results. The dominant effect is found coming from the contact area ratio of the adhesive area to the sticking area or the whole contact area. The FE modeling can serve a useful purpose in revealing the nano-scale geometry-based adhesion contact for surface topography design in MEMS to avoid stiction failure and for the artificial sticky feet in bionics to increase adhesion strength.     

Analysis of lateral extrusion of gear-like form parts

The analysis of lateral extrusion process was carried out. A three dimensional FE model was developed to analyze the effects of some important geometrical parameters such as initial billet dimensions, gap height and frictional condition on the required forging load, the material flow pattern and effective plastic strain distribution. The FE code of DEFORM-3D was employed. A series of experimental tests on commercial lead billets were carried out to verify the FE results. The simulation work has been performed by the rigid-plastic FE method. The results obtained using the numerical solutions have been compared with the experimental data for each case study in terms of required forming load and material flow pattern in different regions. Comparison between FE and experiment results showed good agreement. Both the simulation and experimental results highlight the major role of above mentioned parameters on the required forming load and material flow pattern. The results showed that the gap height has the greatest effect on the forming load and material flow. The results presented in this paper could be used as basic data in the design of the lateral extrusion process.     

MEMS耦合场分析与系统级仿真

微机电系统的计算机辅助设计是MEMS真正走向市场的重要基础。耦合场分析与系统级仿真是MEMSCAD中2个最关键的环节。概括了MEMSCAD的体系结构；综述了耦合场计算的常用数值方法及应用范围；着重介绍了适合于MEMS系统级仿真的2个基本模型的基本思想、构造方法，分析了各自的优缺点，指出今后有待继续研究的几个问题。     

Development and experimental validation of a three-dimensional finite element model of the human scapula

A new modelling approach, using a combination of shell and solid elements, has been adopted to develop a realistic three-dimensional finite element (FE) model of the human scapula. Shell elements were used to represent a part of the compact bone layer (i.e. the outer cortical layer) and the very thin and rather flat part of the scapula--infraspinous fossa and supraspinous fossa respectively. Solid elements were used to model the remaining part of the compact bone and the trabecular bone. The FE model results in proper element shapes without distortion. The geometry, material properties and thickness were taken from quantitative computed tomography (CT) data. A thorough experimental set-up for strain gauge measurement on a fresh bone serves as a reference to assess the accuracy of FE predictions. A fresh cadaveric scapula with 18 strain gauges fixed at various locations and orientations was loaded in a mechanical testing machine and supported at three locations by linkage mechanisms interconnected by ball joints. This new experimental set-up was developed to impose bending and deflection of the scapula in all directions unambiguously, in response to applied loads at various locations. The measured strains (experimental) were compared to numerical (FE) strains, corresponding to several load cases, to validate the proposed FE modelling approach. Linear regression analysis was used to assess the accuracy of the results. The percentage error in the regression slope varies between 9 and 23 per cent. It appears, as a whole, that the two variables (measured and calculated strains) strongly depend on each other with a confidence level of more than 95 per cent. Considering the complicated testing procedure on a fresh sample of scapula, the high correlation coefficients (0.89-0.97), the low standard errors (29-105 micro epsilon) and percentage errors in the regression slope, as compared to other studies, strongly suggest that the strains calculated by the FE model can be used as a valid predictor of the actual measured strain. The model is therefore an alternative to a rigorous three-dimensional model based on solid elements only, which might often be too expensive in terms of computing time.     

基于Krylov子空间法的MEMS降阶建模与仿真

获得系统的宏模型是MEMS系统级建模与仿真的关键。将Krylov子空间理论与方法应用于MEMS降阶建模,介绍了Krylov子空间的理论基础,针对MEMS中常见的静电—结构耦合系统,建立了有限元动力学方程,运用修正Arnoldi算法得到降阶模型。算例表明,经大幅度降阶得到的模型真实地反映了系统地运动状态,大大缩短了求解时间,降低了计算复杂度。