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Design and Fabricating of a High Speed Micro Spindle
, M.Sc. Thesis Sharif University of Technology ; Movahhedy, Mohammad Reza (Supervisor) ; Akbari, Javad (Supervisor)
Abstract
According to development of industry in every field such as nanotechnology and micro electro mechanical system (MEM) fabricating of high speed machining with micro dimension has been expanded. Micro spindles are such a device which is useful in many industries such as air space and electronic field. These machines can work in high speed and production rate with vast variety of features. Their dimensions are in millimeter range. So they can manufacture miniature features. Fabricating and technical science production of a high speed micro spindle with speed of more than 100000 RPM (micro macro milling) is purpose of this project. After to literature review according to science of micro...
Design and Prototyping of an Ultra High Speed Air Micro Spindle
,
M.Sc. Thesis
Sharif University of Technology
;
Movahhedi, Mohammad Reza
(Supervisor)
Abstract
Today, the need for high-speed machine tools, in areas such as defense, medical and electronic for producing parts with millimeter dimensions, and with features smaller than the millimeter, increased. To meet this need, the machine tool can be used with smaller dimensions and with high speed. These machines are able to produce these parts with high production rates.The project aims to improve technical design and construction of a micro spindle to achieve sustained speed about one hundred thousand RPM. In this project, the first step in understanding the fundamentals of the theory and the system components, and the whole operation was performed. The design is based on studies carried out in...
Design, Analysis and Manufacturing of Gas Foil Bearing
, M.Sc. Thesis Sharif University of Technology ; Akbari, Javad (Supervisor) ; Movahhedy, Mohammad Reza (Supervisor)
Abstract
Foil gas bearings are compliant surface, self-acting hydrodynamic bearings that use ambient gas as their working fluid. They do not require external pressurization and are typically constructed from several layers of sheet metal foils. In high-speed, high-temperature applications the GFB’s have the advantage of developing higher load capacities than with fixed geometry gas bearings. Since GFB’s have a complex structure consisting of a spring-like substructure with an overlying flexible surface, there exists a great variety of permutations on any given design. At current work presents a 1D model for GFB with couple solving Reynolds and Euler-Bernoulli beam equation. This mean top foil assume to...
Simulation and optimization of a semi spherical air bearing
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 7, Issue PARTS A, B, C, D , 2012 , Pages 153-159 ; 9780791845233 (ISBN) ; Shahiri, A ; Nikparto, A ; Sharif University of Technology
2012
Abstract
It is important to test the attitude control systems on satellites before they are launched in space. Traditionally this has been done by dropping the satellite, and firing the thrusters before the satellite makes a soft landing in a net. This method only allows a few seconds of testing and does not lend itself to the measurement of pointing accuracy. A better method is to mount the satellite on a spherical air bearing. In this paper behavior of a semi spherical air bearing is studied and analyzed in various conditions. These bearings are used in different applications such as simulation of approximately frictionless condition which is the satellite's situation in space. In this analysis...
Non-stationary Vibration of a Rotor with Foil Gas Bearings Passing Through Critical Speeds
, M.Sc. Thesis Sharif University of Technology ; Mohammad Navazi, Hossein (Supervisor)
Abstract
The use of air bearings was began the last decade. Oil-free air bearing technology is implemented in rotating machines such as turbines, Micro gas turbines and turbocharged, this technology has improved the efficiency of rotating systems. In rotating machines, at high speeds, passing through the critical speed happens. As a result, the natural frequency of the system is crossing the critical speed, which causes system instability and lack of system amplitude control. Instability causes damage to the system. The aim of this thesis is to investigate the nonstationary vibrations of a flexible rotor with air bearings in the passing critical speeds. Behavior of air bearings is also considered to...
Simulation of rarefied gas flows in MEMS/NEMS using a molecular method
, Article Proceedings of the ASME Fluids Engineering Division Summer Conference 2009, FEDSM2009, 2 August 2009 through 6 August 2009 ; Volume 1, Issue PART B , 2009 , Pages 1039-1044 ; 9780791843727 (ISBN) ; Ebrahimi, R ; Shams, A ; Sharif University of Technology
Abstract
In this work, the development of a two-dimensional Direct Simulation Monte Carlo (DSMC) Program for pressure boundaries using unstructured cells and its applications to typical micro-scale gas flows are described. For the molecular collision kinetics, variable hard sphere molecular model and no time counter collision sampling scheme have been used. Applications to micro-scale gas flows include micro-nozzel, nano channel and slider air bearing.The aim is to further test the treatment of pressure boundaries. For slider air bearing gas flows of the computer hard drive, the simulated gas pressures, at different rotating speeds, have a very good agreement with previous studies. The applicability...