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Analytical solution for large amplitude vibrations of microbeams actuated by an electro-static force
, Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1499-1507 ; 10263098 (ISSN) ; Asgarshamsi, A ; Goharkhah, M ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
An analytical study using Variational Iteration Method (VIM) is carried out in order to investigate the vibrations of electro-statically actuated double-clamped and simply-supported microbeams. Effects of applied voltage and residual axial load on the nonlinear natural frequency and deflection of the microbeams are studied. It shows that pre-compression in microbeams increases the amplitude of deflections for a specific applied voltage. Also, an increase in pre-tension motivates the microbeam to show more nonlinear behavior in an applied voltage. Predicted results are compared with the experimental data available in the literature and also with numerical results which shows a good agreement....
Shot peening coverage effect on residual stress profile by FE random impact analysis
, Article Surface Engineering ; Volume 32, Issue 11 , 2016 , Pages 861-870 ; 02670844 (ISSN) ; Hassani Gangaraj, S. M ; Mahmoudi, A. H ; Farrahi, G. H ; Guagliano, M ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
Shot peening is one of the most effective surface treatments for improving the fatigue strength of machine elements. In this paper, a new finite element-based model to predict the effect of coverage on the surface state is proposed and critically discussed. By this model, the effects of Rayleigh damping, mesh size, and target dimensions on residual stress profile are investigated using a random impingement simulation of shot peening. Moreover, the model enables the realistic simulation of shot peening process with an affordable computational time with respect of present approaches without reducing the number of impacts and analysis accuracy: the computational time was reduced by 25% in...
Endurance time method-application in nonlinear seismic analysis of single degree of freedom systems
, Article Journal of Applied Sciences ; Volume 9, Issue 10 , 2009 , Pages 1817-1832 ; 18125654 (ISSN) ; Ismail pour Estekanchi, H ; Vafai, A ; Sharif University of Technology
2009
Abstract
Endurance Time (ET) method has been introduced as a lime-history based dynamic analysis procedure. In this method, structures are subjected to a gradually intensifying acceleration function. Performance of the structures is assessed based on the length of the time interval that they can satisfy required performance objectives. In this study, some fundamental concepts of ET method are explained and the potentials and limitations of this procedure in nonlinear seismic analysis of SDOF structures are investigated. A numerical optimization procedure for generating ET acceleration functions that are compatible with ground motions are explained. Results of ET analysis for inelastic SDOF systems...
Isolated high step-up switched-boost DC/DC converter with modified control method
, Article IET Power Electronics ; Volume 12, Issue 14 , 2019 ; 17554535 (ISSN) ; Babaei, E ; Tarzamni, H ; Kolahian, P ; Sharif University of Technology
Institution of Engineering and Technology
2019
Abstract
In this study, a new isolated high-gain switched-boost DC/DC converter employing two symmetrical switched-boost networks along with a modified control algorithm based on the combination of the pulse-width modulation (PWM) and phase-shift modulation is proposed. Utilising symmetrical switched-boost networks increase the voltage gain of the proposed converter, significantly. Moreover, applying the proposed switching algorithm on the proposed isolated switched-boost DC/DC converter leads to the following advantages: (i) high-voltage gain, (ii) zero voltage switching (ZVS) turn-on of two switches, (iii) ZVS turnoff of two switches and (iv) appearing three controllable parameters (the...
Markerless human motion tracking using microsoft kinect SDK and inverse kinematics
, Article 12th Asian Control Conference, ASCC 2019, 9 June 2019 through 12 June 2019 ; 2019 , Pages 504-509 ; 9784888983006 (ISBN) ; Behzadipour, S ; Tsujita, T ; Komizunai, S ; Konno, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Motion capture systems are used to gauge the kinematic features of the motion in numerous fields of research. Despite superb accuracy performance, the commercial systems are costly and difficult to use. To solve these issues, Kinect has been proposed as a low-priced markerless motion capture sensor, and its accuracy has been assessed using previous motion capture systems. However, in many of these studies, the anatomical joint angles captured using the Kinect are compared to the 3D rotation angles reported by the gold standard motion capture systems. These incompatibilities in the determination of the human joint angles can lead to higher error estimation. To accomplish a valid accuracy...
Analytical approach to dynamic and vibration analysis of a spherical ball under contact stress
, Article Scientia Iranica ; Volume 18, Issue 6 , 2011 , Pages 1306-1312 ; 10263098 (ISSN) ; Hosseinzadeh, A ; Foumani, M. S ; Sharif University of Technology
2011
Abstract
This paper presents a nonlinear model to illustrate the effect of contact stress in the vibration behavior of mechanical components, especially rotating systems. The problem is considered in the case of the vertical vibration of a sphere on a plate. The Hertzian contact theory is used to obtain the relationship between contact force and the deflection of the mass center of the sphere. Modeling the system by a mass and a nonlinear spring, the vibration equation of the mass center of the sphere is derived. The method of LindstedtPoincar is implemented to solve the equation of motion, and obtain vibration characteristics under a compressive preload. The dependency of frequency on several...