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    Finite Element Method and Analytical Approach Solutions for a Conical Axisymmetric Shell Structure Under Random Acoustic Loading

    , M.Sc. Thesis Sharif University of Technology Fallah, Mohsem (Author) ; Hosseini Kordkheili, Ali (Supervisor)
    Abstract
    When vibration of the structure is unrecognized we call it random vibrations which their analysis is very important in space structures because these structures are exposed to acoustic forces or forces produced by turbulence of the atmosphere when a spacecraft is launched. Also in the aviation field, the random vibration analysis use to examine the response of the aircraft and missile structures to atmospheric turbulence and gust. In this research dominated equations of a truncated conical axisymmetric shell structure with linearized approximation of Love’s equations under uniform pressure is utilized. Considering displacements in the form of Frobenius series expansion the frequencies and... 

    Robust Design Optimization for Fatigue Life with Geometric and Material Uncertainties of Mechanical Parts Under Random Loading Based on Maximizing Fatigue Life and Minimizing Uncertainty in Fatigue Llife Prediction

    , M.Sc. Thesis Sharif University of Technology Esfahani, Saeed (Author) ; Khodaygan, Saeed (Supervisor)
    Abstract
    Fatigue life prediction of a mechanical part is one of issues which a group of engineers are engaged with it and always they try to design the parts with the maximum of lifetime. Although many researches have been done in this field but yet we can see that predicted life are different from that happens in the reality because there are some uncertainties in the phenomena. Our effort in this project is creating an algorithm design so that the parts are designed by it, have the maximum fatigue life and the minimum uncertainty in prediction. In this project we have considered geometrical, material and random loading uncertainties as error resources. Older methods those are presented in this... 

    Geometrically Nonlinear Random Vibration of Structures Using Finite Element Method

    , M.Sc. Thesis Sharif University of Technology Dabouee Moshkabadi, Mehdi (Author) ; Hosseini Kordkheili, Ali (Supervisor)
    Abstract
    Indeterminate behavior of some forces in the aerospace industry due to flight at high speeds, gust, combustion, etc., has led to the exposure of structures to dynamic loads with random behavior in the nonlinear manner. To analyze problems in which the loading is random or the system parameters are random, the only possible way is to describe the system response in statistical values.Since most modern structures have complex geometry and the number of degrees of freedom is very high, advanced numerical solution methods are used to obtain the system response. In this study, the geometric nonlinear vibrations of structures under random loading are investigated by the finite element... 

    Effects of structural configuration on vibration control of smart laminated beams under random excitations

    , Article Journal of Mechanical Science and Technology ; Volume 24, Issue 5 , 2010 , Pages 1119-1125 ; 1738494X (ISSN) Zabihollah, A ; Sharif University of Technology
    Abstract
    The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation... 

    A finite element model for tapered laminated beams incorporated with magnetorheological fluid using a layerwise model under random excitations

    , Article Mechanics of Advanced Materials and Structures ; Apr , 2018 , Pages 1-8 ; 15376494 (ISSN) Momeni, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Taylor and Francis Inc  2018
    Abstract
    Laminated composite beams with variable thickness are being widely used in many engineering applications. To enhance the dynamic behavior of structures subject to random loading, tapered laminated beams incorporated with magnetorheological (MR) fluids (MR-tapered beam) are proposed. A finite element model has been developed for random vibration analysis of MR-tapered beam based on layerwise displacement theory. The effects of thickness ratios of tapered beam, magnetic fields, statistical properties, correlation and autocorrelation on dynamic behaviors of structures have been investigated. The proposed structural element significantly enhances the dynamic response of MR-tapered beam under... 

    A finite element model for tapered laminated beams incorporated with magnetorheological fluid using a layerwise model under random excitations

    , Article Mechanics of Advanced Materials and Structures ; Volume 27, Issue 1 , 2020 , Pages 12-19 Momeni, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Taylor and Francis Inc  2020
    Abstract
    Laminated composite beams with variable thickness are being widely used in many engineering applications. To enhance the dynamic behavior of structures subject to random loading, tapered laminated beams incorporated with magnetorheological (MR) fluids (MR-tapered beam) are proposed. A finite element model has been developed for random vibration analysis of MR-tapered beam based on layerwise displacement theory. The effects of thickness ratios of tapered beam, magnetic fields, statistical properties, correlation and autocorrelation on dynamic behaviors of structures have been investigated. The proposed structural element significantly enhances the dynamic response of MR-tapered beam under...