Dynamic analysis of a microbeam fixed in a closed chamber containing an incompressible fluid

Dissertation for Master's Degree in Mechanical Engineering

Applied Design Orientation

Abstract

Microwires are used as the main element in most sensors and actuators. In some cases, such as micro switches, this member may also be used in an environment containing fluid. Therefore, in this article, we analyzed the dynamic behavior and frequency analysis of a micro beam that is located in a closed chamber containing fluid. . Assuming Euler-Bernoulli beam and incompressible and non-viscous fluid, fluid-solid coupled equations were extracted using Fourier-Bessel method and then the corresponding eigenvalue problem was analyzed and the effect of fluid appeared as added mass in the equations. Next, the dependence of the natural frequencies of the beam on the characteristics of the fluid and the geometric dimensions of the chamber has been investigated and it has been shown that changes in the length of the beam and the location of the beam in the chamber as well as the use of different fluids with different properties have a significant effect on the change of system frequencies. In the following figure, the modes of the beam in two wet and dry states have been compared and the effect of fluid characteristics on the system modes has been shown and also the patterns of fluid movement following the behavior of the beam have been investigated. As a result, it can be concluded that the presence of fluid greatly affects the above modes. In addition to examining the free vibrations of the coupling system, the behavior of the beam due to electrostatic excitation in the form of step voltage has also been investigated and the effects of fluid characteristics and system geometry on The transient response and instability time of the system have been analyzed, also by applying different step voltages, the dynamic response and instability of the microbeam are studied. Statics, instability, geometric and material changes, incompressible and non-viscous fluid, concepts and general concepts, electromechanical microsystems [1] It is known as one of the most promising technologies in the 21st century, which is able to bring about a tremendous transformation in the industry and consumer products such as the automotive industry, medicine, electronics, communications, etc., with the integration of microelectronics and micromachining technology.

MEMS technology is the manufacturing of integrated parts and systems consisting of electrical and mechanical components that uses group production methods. The word MEMS, which stands for electromechanical microsystems, is common in America, while microsystem technology is common in Europe, and micromachines are common in Japan. Volumetric and surface micromachining processes are used to remove and/or deposit layers of silicon or other materials to produce mechanical and electromechanical components. Micro optical devices and structures and radiant energy, sensor/actuator circuits, integrated circuits (IC) [2] processor/controller) that are non-mass produced and:

converts physical parameters and stimulations into electrical, mechanical and optical signals and vice versa.

The tasks of sensing, operating and.

Includes control parts (intelligence, decision-making, gradual learning, adaptation, self-oriented organization, etc.), detection, signal processing and information collection.

Basically, MEMS is a system consisting of structure, sensor, electronic circuit and micro device (Figure 2-1). The micro structure forms the framework of the system; The sensor searches for micro-signals; The micro electronic circuit processes the received signals and gives commands to the micro actuator to respond to the signals.

Using the technology of manufacturing integrated circuits and in order to produce mechanical and electromechanical devices, MEMS is usually built on a silicon substrate, parts of which are separated by selective etching or new layers are added to it. knew As the name suggests, "Micro" refers to size, "Electro" refers to electricity or electronics, and "Mechanical" includes moving parts. From the physics point of view, MEMS is usually a set of mechanical and electronic elements that are mounted on a normal silicon wafer using micro manufacturing technology. Electronics can be made by the IC process (such as CMOS [3]) and mechanical elements by micromachine methods that are compatible with the IC manufacturing process. Figure (1-3) shows a schematic view of the MEMS chip. Sensors and actuators can be made from mechanical elements and signal processing and control units can be made using electronic circuits

So the whole system can be assembled on a single chip without any external social process. Collecting the whole system on a single chip with a miniaturization process leads to the creation of a low-cost and high-quality structure. The applications of this technology are so wide that it can be said that it is used in almost all different industrial fields, including mechanical, electrical, optical, and chemical systems, or it is in the research and sample making phase. Placing the sensor along with intermediate circuits on one circuit has the advantage of reducing disturbing noises and increasing the speed of assembly and commissioning. The similarity of characteristics of similar products causes more reliability due to the reduction of effective parameters. The precise arrangement of elements, which is essential for the system to reduce errors, is easier in the micro space.

In the early 1990s, with the advancement of IC manufacturing technology, MEMS emerged, where sensors, actuators and control functions were made in silicon. With government and industrial financial support, MEMS researchers have made significant progress and proved their superior and revolutionary abilities in many different fields. Many examples of MEMS are used in commerce and industry, such as micro-accelerometers [4], micro-sensors [5], ink-jet printers [6], micro-mirrors [7], etc.

In addition to these simple devices, more complex designs of MEMS have been proposed and proven. Because of their concept and possibilities in various fields such as biomedicine, chemistry, fluids, information storage, wireless optical communication, etc. With more effort and energy, new branches of MEMS technology have emerged, including [8] MOEMS and [9] µTAS, which are important because of their application potential in the market. rtl;">Micro-beams as the main components used in most of the sensors and actuators. In some cases, such as micro switches, these members may also be used in environments containing fluid. Therefore this paper analyzes the dynamic behavior and frequency analysis of a micro-beam in bounded fluid domain. With assumption oyler Bernoulli's beam and considering incompressible and inviscid liquid, the fluid-solid's coupled equations extracted from Fourier-Bessel series Then the corresponding eigenvalue problem has been analyzed the effect of fluid added mass has been appearing in the equations. Dependence on natural frequencies of fluid properties and geometry of the beam and cavity have been investigated. And demonstrated that beam's length and off-center's variation and also use of difference fluids has a visible changes on natural frequency. In continuous micro beam mode shape compared at wet and dry condition and effect of fluid properties shown on the various modes. And fluid's pattern movement investigated consequently of beam's behavior. The result can be inferred that the fluid will seriously affect the above modes.