جستجوی مقالات مرتبط با کلیدواژه « mems » در نشریات گروه « مکانیک »

The electrical properties of nanostructured piezoelectric materials have attracted the attention of many researchers in the last decade. These features are used in piezoelectric micro-sensors. Mechanical propulsion is usually the result of contact between a piezoelectric surface and a foreign object. In this paper, the effect of mechanical propulsion using an air wave (sound) or vacuum on a silicon diaphragm is investigated. The local stresses created on the diaphragm due to the impact of an air wave have a significant effect on the peak-to-peak voltage of the piezoelectric sensor, which can be measured by measuring changes in this parameter. To investigate this, a micromachined diaphragm of silicon was examined and it was found that fabricating a piezoelectric sensor on a thin and patterned diaphragm could increase the peak-to-peak voltage by about 1.3 times. Detection of these stresses using piezoelectric material layered on the thin and formable diaphragm can act as a piezoelectric microphone or a barometer that the presence of microstructures on the diaphragm will increase their sensitivity.

Diaphragm pressure sensors are used in various industries. Much research has been done to optimize and improve the quality of these sensors. This paper investigates "sensitivity" as a critical variable in diaphragm pressure sensors based on MEMS technology. Aperture geometry is one of the most influential variables in the sensitivity of a diaphragm sphygmomanometer, which in addition to sensitivity, can affect other variables such as operating range, sensor accuracy, dimensions, and even price. To increase the performance and sensitivity of pressure sensors, the sensor aperture was simulated in AbaqusFEA software, and while validating the computational solver, different geometries were evaluated. The results showed that the circular diaphragm has the best performance. Then the effect of corrugations on the surface of the diaphragm was investigated, and different forms of waves were simulated. The results showed that creating a circular wave with a radius of 15 μm at the end of the diaphragm surface increases the sensor's sensitivity by 18%.

Regarding the necessity of obtaining high-quality resonators in micro electromechanical systems (MEMS), recognizing and investigating the parameters that effect on the quality factor are essential and inevitable. In micro electromechanical systems, microplates are used as resonators and RF filters and so on. In this paper, the effect of thermoelastic damping, which is one of the most important factors affecting the quality factor, has been investigated for rectangular microplates. Galerkin method has been used to simplify and solve the governing equations. The result is a nonlinear algebraic expression for the quality factors of microplates of general conditions due to thermoelastic damping. Unlike previous researches, the proposed model can directly calculate the quality factor. COMSOL Multiphysics software is used for finite element simulation. After verification of the proposed model, the effect of various parameters is investigated. The proposed model can also be used to calculate the pull-in instability voltage. The results of current paper can be used to design micro electro mechanical systems (MEMS) and another applications can be defined for that.

Sounding rockets provide a useful platform for the aerospace research activities in which carry out a research payload to the space and recover it in the ground. In the flight path, it does scientific experiments and acquire the result for more analysis in the ground. All of the well-known aerospace centers around the world use frequently the various forms of sounding rocket to test and evaluate their sensitive space components. Actually, space qualification process of a space module is completed sometimes through a real space flight using the sounding rocket. In this paper the performance of a MEMS based inertial measurement unit (IMU) is investigated. The investigation result shows that using appropriate filtering, MEMS based IMU can measure appropriately the dynamic behavior of the sounding rocket. These data may be used for further identification and validation tests.

The objective of the present paper is to investigate the static and dynamic responses of geometric non-linear micro-beams, which are made of functionally graded materials, in double-movable-electrode micro-electro-mechanical systems (MEMS). To do so, employing the non-linear strain-displacement relation in such structures based on the von Kármán theory, the governing equations of motion have been obtained by Hamilton’s principle and then solved through the Galerkin weighted residual method. The static and dynamic findings of the present work have been verified by those available in the literature for single-movable-electrode systems. The present static and dynamic results for double-movable-electrode systems have also been compared and successfully validated by those obtained through 3-D finite element simulations carried out in COMSOL commercial software. At the rest of the paper, aside from the influence of the movability of both electrodes, the inertia and material graduation effects on the non-linear response of the system have been investigated. The results reveal that the movability of both electrodes drastically reduces the pull-in voltage of the system.

Microelectromechanical systems (MEMS) are used in many elds of industry like automotive, aerospace and medical instruments. Among the various ways to operate the MEMS devices, the electrostatic actuator is the common mechanism, due to simplicity and fast response. Previous experiments have shown that the mechanical behavior of devices, which their sizes are in order of micron and submicron, are dependent to size dependency. They also have illustrated that by decreasing the dimension of structures, the size dependent eect is highlighted. In this case, the classical theories are not capable to predict the size dependent eects and mechanical behavior of the microstructures properly. Therefore, nonclassical theories such as modi ed couple stress and strain gradient theories have been introduced. It was shown that the modi ed couple stress theory can accurately predict the size dependent behavior of microstructures. There are some in uences observed in the MEMS, that they have notable eects on the mechanical behavior of microswitches, such as fringing elds and large de- ection. When the air gap is larger than the electrode's width of microswitches, the impacts of fringing elds and geometric nonlinearity signi cantly aect the mechanical behavior of the system. Therefore, neglecting the abovementioned eects leads to errors in the instability prediction of microswitches. Most of microswitches consist of a microcantilever with a proof mass and a xed substrate which there is an air gap between them. By applying voltage to the system, the microcantilever starts to de ect into the xed substrate. In this paper, pull-in instability and de ection of MEMS switches are investigated based on the size dependent model. The nonlinear model is introduced by considering modi ed couple stress theory and fringing eld eects as well as geometric nonlinearity. Utilizing the minimum total potential energy principle, the static equation of motion is derived in framework of the nonclassical theory. The eects of various parameters on static pull-in instability are studied and errors of considering the linear model or classical theories is calculated. The results show that the presented model is capable to predict the displacement and pull-in instability of the microswitches.