Switching and release dynamics of an electrostatically actuated MEMS switch under the influence of squeeze-film damping

This paper reports analytical modeling, simulation and experimental validation for switching and release times of an electrostatically actuated micromachined switch. Presented work is an extension of our earlier work [1] that analytically argued, and numerically and experimentally demonstrated, why pull-in time is larger that pull-up time when the actuation voltage is less than twice of the pull-in voltage. In this paper, switching dynamics is investigated under the influence of squeeze-film damping. Tests were performed on SOI (silicon-on-insulator) based parallel beams structures.Typical voltage requirement for actuation is in the range of 10-30 V. All the experiments were performed in normal atmospheric pressure. Measurement results confirm that the quality factor Q has appreciable effect on the release time compared to the switching time. The quality factor Q is extracted from the response measurement and compared with the ANSYS simulation result. In addition, the dynamic pull-in effect has also been studied and reported in this paper. A contribution of this work includes the effect of various phenomena such as squeeze-film damping, dynamic pull-in, and frequency pull-in effects on the switching dynamics of a MEMS switch.

Adsorption study of silica gel particle for improvement in design of adsorption beds used in solar driven cooling units

Simulations using Ansys Fluent 6.3.26 have been performed to look into the adsorption characteristics of a single silica gel particle exposed to saturated humid air streams at Re=108 & 216 and temperature of 300K. The adsorption of the particle has been modeled as a source term in the species and the energy equations using a Linear Driving Force (LDF) equation. The interdependence of the thermal and the water vapor concentration field has been analysed. This work is intended to aid in understanding the adsorption effects in silica gel beds and in their efficient design. (C) 2013 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Fabrication and Experimentation of a Cantilever Beam Based Piezoelectric Actuator and Sensor for Vibration Energy Harvesting

In the immediate surroundings of our daily life, we can find a lot of places where the energy in the form of vibration is being wasted. Therefore, we have enormous opportunities to utilize the same. Piezoelectric character of matter enables us to convert this mechanical vibration energy into electrical energy which can be stored and used to power other device, instead of being wasted. This work is done to realize both actuator and sensor in a cantilever beam based on piezoelectricity. The sensor part is called vibration energy harvester. The numerical analyses were performed for the cantilever beam using the commercial package ANSYS and MATLAB. The cantilever beam is realized by taking a plate and fixing its one end between two massive plates. Two PZT patches were glued to the beam on its two faces. Experiments were performed using data acquisition system (DAQ) and LABVIEW software for actuating and sensing the vibration of the cantilever beam.

Numerical Study of Counterflow Diffusion Flame and Water Spray Interaction

This paper reports numerical investigation concerning the interaction of a laminar methane-air counterflow diffusion flame with monodisperse and polydisperse water spray. Commercial code ANSYS FLUENT with reduced chemistry has been used for investigation. Effects of strain rate, Sauter mean diameter (SMD), and droplet size distribution on the temperature along stagnation streamline have been studied. Flame extinction using polydisperse water spray has also been explored. Comparison of monodisperse and polydisperse droplet distribution on flame properties reveals suitability of polydisperse spray in flame temperature reduction beyond a particular SMD. This study also provides a numerical framework to study flame-spray interaction and extinction.

DESIGN REQUIREMENTS FOR DIRECT SUPERCRITICAL CARBON DIOXIDE RECEIVER DEVELOPMENT AND TESTING

This paper establishes the design requirements for the development and testing of direct supercritical carbon dioxide (sCO2) solar receivers. Current design considerations are based on the ASME Boiler and Pressure Vessel Code (BPVC). Section I (BPVC) considers typical boilers/superheaters (i.e. fired pressure vessels) which work under a constant low heat flux. Section VIII (BPVC) considers pressure vessels with operating pressures above 15 psig 2 bar] (i.e. unfired pressure vessels). Section III, Division I - Subsection NH (BPVC) considers a more detailed stress calculation, compared to Section I and Section VIII, and requires a creep-fatigue analysis. The main drawback from using the BPVC exclusively is the large safety requirements developed for nuclear power applications. As a result, a new set of requirements is needed to perform detailed thermal-structural analyses of solar thermal receivers subjected to a spatially-varying, high-intensity heat flux. The last design requirements document of this kind was an interim Sandia report developed in 1979 (SAND79-8183), but it only addresses some of the technical challenges in early-stage steam and molten-salt solar receivers but not the use of sCO2 receivers. This paper presents a combination of the ASME BPVC and ASME B31.1 Code modified appropriately to achieve the reliability requirements in sCO(2) solar power systems. There are five main categories in this requirements document: Operation and Safety, Materials and Manufacturing, Instrumentation, Maintenance and Environmental, and General requirements. This paper also includes the modeling guidelines and input parameters required in computational fluid dynamics and structural analyses utilizing ANSYS Fluent, ANSYS Mechanical, and nCode Design Life. The main purpose of this document is to serve as a reference and guideline for design and testing requirements, as well as to address the technical challenges and provide initial parameters for the computational models that will be employed for the development of sCO(2) receivers.

连续移动三维瞬态激光熔池温度场数值模拟

详细介绍了在ANSYS软件平台上，建立连续移动三维瞬态激光熔池温度场计算模型的方法，计算模型中考虑了材料表面温度对激光吸收率的影响及材料相变过程对激光熔池温度场的影响。系统分析了连续移动三维激光熔池温度场随时间的变化规律。通过该计算模型，可以掌握激光加工过程中连续移动激光熔池的加热和冷却规律。计算结果表明，当激光沿45#钢基板表面由一端向另一端沿直线扫描时，由于热传导的作用，激光熔池温度随时间增加而升高，同时连续移动熔池表面温度最高点不在激光束中心，而是稍稍偏后于激光束中心。在相同激光工艺参数下，计算熔池横截面尺寸与实验所测熔池横截面尺寸相吻合，表明所建立的连续移动熔池温度场计算模型是正确和可靠的。

Application of laser cladding technology to improve the interface of thermal barrier coatings

The present study is focused on improvement of the adhesion properties of the interface between plasma-sprayed coatings and substrates by laser cladding technology (LCT), Within the laser-clad layer there is a gradient distribution in chemical composition and mechanical properties that has been confirmed by SEM observation and microhardness measurement. The residual stress due to mismatches in thermal and mechanical properties between coatings and substrates can be markedly reduced and smoothed out. To examine the changes of microstructure and crack propagation in the coating and interface during loading, the three-point bending test has been carried out in SEM with a loading device. Analysis of the distribution of shear stress near the interface under loading has been made using the FEM code ANSYS, The experimental results show clearly that the interface adhesion can be improved with LCT pretreatment, and the capability of the interface to withstand the shear stress as well as to resist microcracking has been enhanced.

钢包砼拱形防护门有限元模态分析

防护门是阵地工程中的薄弱环节,研究其在冲击载荷作用下的动态响应具有重要意义.作者利用ANSYS有限元分析软件,建立钢包混凝土拱形防护门的仿真模型.通过对模型进行模态分析,给出防护门的前10阶固有频率及相应的振型,对防护门的自振特性有了较为精确的认识,从而为进一步分析防护门的动力响应打下基础.

柱形杜瓦瓶端盖密封结构有限元分析

建立了针对柱形真空杜瓦容器端盖密封结构的轴对称模型.基于有限元软件ANSYS的结构非线性分析模块,分析了内、外密封圈与端盖的接触响应,得到了中心盖板的挠度、密封圈的变形与接触压力.求解了考虑密封圈的变形抗力时,螺栓需提供的压紧力附加值,其分析结果对类似结构杜瓦瓶的设计有一定的参考价值.

爆炸排淤填石法中淤泥的本构模型

以爆炸排淤填石法为背景,对不同应变率阶段淤泥的本构模型进行了分析,利用ANSYS/LS-DYNA动态有限元分析程序对所选择的模型进行验证和确认.计算和分析结果表明:在形成爆炸空腔的高应变率阶段,淤泥表现为理想不可压缩流体的性质;在小药量小抵抗线条件下,甚至在淤泥自重作用下的较低应变率变形阶段,其黏性效应也可以忽略不计.

热障涂层界面形貌尺寸与残余应力的关系

利用ANSYS有限元分析软件对热障涂层中的残余应力进行了模拟分析，得出了界面形貌尺寸与残余应力之间的关系。模拟结果表明，热障涂层中的残余应力是界面形貌尺寸的函数。这些结论为提高涂层界面结合强度的热障涂层界面造形提供了理论支持，也为热障涂层界面的优化提供了指导意见。

Squeeze-film Effects in MEMS Devices with Perforated Plates for Small Amplitude Vibration

Squeeze-film effects of perforated plates for small amplitude vibration are analyzed through modified Reynolds equation (MRE). The analytical analysis reckons in most important influential factors: compressibility of the air, border effects, and the resistance caused by vertical air flow passing through perforated holes. It is found that consideration of air compressibility is necessary for high operating frequency and small ratio of the plate width to the attenuation length. The analytical results presented in this paper agree with ANSYS simulation results better than that under the air incompressibility assumption. The analytical analysis can be used to estimate the squeeze-film effects causing damping and stiffness added to the system. Since the value of Reynolds number involved in this paper is low (< 1), inertial effects are neglected.

冷弯成型局部大变形测试装置的设计与研究

冷弯成型变形复杂,事先难以预测其变形效果.根据冷弯成型的特点和变形规律设计出基于万能实验机上的局部大变形测试装置,并应用此装置对冷弯成型过程进行回弹分析,为冷弯成型理论分析和使用ANSYS/LS-DYNA对冷弯成型分析提供科学依据.

Study of lateral mode SOI-MEMS resonators for reduced anchor loss

MEMS resonators fabricated in silicon-on-insulator (SOI) technology must be clamped to the substrate via anchoring stems connected either from within the resonator or through the sides, with the side-clamped solution often employed due to manufacturing constraints. This paper examines the effect of two types of commonly used side-clamped, anchoring-stem geometries on the quality factor of three different laterally-driven resonator topologies. This study employs an analytical framework which considers the relative distribution of strain energies between the resonating body and clamping stems. The ratios of the strain energies are computed using ANSYS FEA and used to provide an indicator of the expected anchor-limited quality factors. Three MEMS resonator topologies have been fabricated and characterized in moderate vacuum. The associated measured quality factors are compared against the computed strain energy ratios, and the trends are shown to agree well with the experimental data. © 2011 IOP Publishing Ltd.

Combination Of Cfd And Csd Packages For Fluid-Structure Interaction

In this article the UDF script file in the Fluent software was rewritten as the "connecting file" for the Fluent and the ANSYS/ABAQUS in order that the joined file can be used to do aero-elastic computations. In this way the fluid field is computed by solving the Navier-Stokes equations and the structure movement is integrated by the dynamics directly. An analysis of the computed results shows that this coupled method designed for simulating aero-elastic systems is workable and can be used for the other fluid-structure interaction problems.