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RISS 인기검색어
- 검색키워드
- 저자 : Mansour Nikkhah-Bahrami (검색결과 6 건)
- 무료
- 기관 내 무료
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Mansour Nikkhah Bahrami,Aghil Yousefi-Koma,Hamed Raeisifard 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.1
In this paper, a comprehensive model of a micro-switch with both electrostatic and piezoelectric excitations, which accounts for thenonlinearities due to inertia, curvature, electrostatic forces and piezoelectric actuator is presented to demonstrate the mechanical characteristicsof such a micro-system. Dynamic equations of this model are derived by the Lagrange method. Static analysis of this model is performedwith five modes through the Galerkin method. The micro-switch beam is assumed as an elastic Euler-Bernoulli beam withclamped-free end conditions. The electrostatic actuation results are compared with other existing experimental and numerical results. Whereas the major drawback of electrostatically actuated micro-switches is the high driving voltage, using the piezoelectric actuator inthese systems can provide less driving voltage and control the pull-in voltage. The study demonstrates that when the ratio of electrostaticactuation distance to length of micro-switch is small, the nonlinear piezoelectric term has a significant effect on the pull-in phenomenon. There are three ways to influence the design and control of the mechanical characteristics of this micro-switch: the softening effect due toelectrostatic actuation, the hardening effect due to piezoelectric actuation, and varying the length and thickness of the piezoelectric actuator.
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Application of impulse damper in control of a chaotic friction-induced vibration
Mansour Ataei,Ali Asghar Atai,Sajjad Mirjavadi,Mohammad Sahebnasagh,Mansour Nikkhah-Bahrami 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.2
Friction-induced vibration is an important phenomenon with adverse effects on many dynamic systems involving friction. In this study,a very simple and well-known one-dimensional friction-induced dynamic system is considered in which the novel PZT stack impulse damper is incorporated into the system. It has been shown that by appropriately tuning the damping parameters, the chaotic behavior is removed quickly and efficiently. It has also been demonstrated that the system is sensitive to parameter change, and minimal modification of these parameters can revert the chaotic or periodic motion.
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Javad Mohammadi,Mansour Nikkhah Bahrami 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3
The stability of two rigid articulated pipes conveying fluid is considered. The velocity of fluid motion is harmonic. Parametric resonance for the second mode and 3:1 internal resonance in the presence of self-excited are considered. The method of multiple time scales has been applied for analysis. The effects of initial velocity 0 u , ratio fluid mass per total fluid mass and pipes mass g and flow frequency b on the frequency response for steady state and stability analyses are studied. Some comparative studies on the stability region of system are conducted with the results available in the open literature.
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Reza Poultangari,Mansour Nikkhah Bahrami 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7
The Vectorial-wave method (VWM) is developed to study free and forced vibrations of cylindrical shells in the presence of dampers at supports. In modeling the issue, a circular cylindrical shell is considered with two ended supports, including separate springs and viscous dampers in the possible directions. Accordingly, based on Flügge thin shell theory and by considering the wave vectors going in the opposite direction along with the shell axis, reflection and transmission matrices are determined to satisfy the shell continuity as well as the boundary conditions. The proposed method is verified through comparing its results with the available literature and the numerical results calculated by Finite element method (FEM). Employing VWM, the viscous characteristics of the applied supports on natural frequencies of the shell are investigated. Furthermore, frequency responses of the shell, which are affected by point-load excitation, are obtained. Finally, the results show that several tandem resonance picks can be eliminated via accurate setting of the support damping.
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Stability analysis of whirling composite shells partially filled with two liquid phases
Mohammad Sahebnasagh,Mansour Nikkhah-Bahrami,Roohollah Firouz-Abadi 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5
In this paper, the stability of whirling composite cylindrical shells partially filled with two liquid phases is studied. Using the first-order shear shell theory, the structural dynamics of the shell is modeled and based on the Navier-Stokes equations for ideal liquid, a 2D model is developed for liquid motion at each section of the cylinder. In steady state condition, liquids are supposed to locate according to mass density. In this study, the thick shells are investigated. Using boundary conditions between liquids, the model of coupled fluid-structure system is obtained. This coupled fluid-structure model is employed to determine the critical speed of the system. The effects of the main variables on the stability of the shell are studied and the results are investigated.
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Farshid Allahkarami,Mansour Nikkhah Bahrami,Ghassabzadeh Saryazdi 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.6
The main goal of this research is to examine the in-plane and out-of-plane forced vibration of a curved nanocomposite microbeam. The in-plane and out-of-plane displacements of the structure are considered based on the first order shear deformation theory (FSDT). The curved microbeam is reinforced by functionally graded carbon nanotubes (FG-CNTs) and thus the extended rule of mixture is employed to estimate the effective material properties of the structure. Also, the small scale effect is captured using the strain gradient theory. The structure is rested on a nonlinear orthotropic viscoelastic foundation and is subjected to concentrated transverse harmonic external force, thermal and magnetic loads. The derivation of the governing equations is performed using energy method and Hamilton's principle. Differential quadrature (DQ) method along with integral quadrature (IQ) and Newmark methods are employed to solve the problem. The effect of various parameters such as volume fraction and distribution type of CNTs, boundary conditions, elastic foundation, temperature changes, material length scale parameters, magnetic field, central angle and width to thickness ratio are studied on the frequency and force responses of the structure. The results indicate that the highest frequency and lowest vibration amplitude belongs to FGX distribution type while the inverse condition is observed for FGO distribution type. In addition, the hardening-type response of the structure with FGX distribution type is more intense with respect to the other distribution types.
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