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11.
Mehrdaad Ghorashi 《Nonlinear dynamics》2012,67(1):227-249
The general nonlinear intrinsic equations of motion of an elastic composite beam are solved in order to obtain the elasto-dynamic
response of a rotating articulated blade. The solution utilizes the linear Variational-Asymptotic Method (VAM) cross-sectional
analysis, together with an improved damped nonlinear model for the rigid-body motion analysis of helicopter blades in coupled
flap and lead-lag motions. The explicit (direct) integration algorithm implements the perturbation method in order to solve
the transient form of the nonlinear intrinsic differential equations of motion and obtain the elasto-dynamic behavior of an
accelerating composite blade. The specific problem considered is an accelerating articulated helicopter blade of which its
motion is analyzed since it starts rotating from rest until it reaches the steady-state condition. It is observed that the
steady-state solution obtained by this method compares very well with other available solutions. The resulting simulation
code is a powerful tool for analyzing the nonlinear response of composite rotor blades; and for serving the ultimate aim of
efficient noise and vibration control in helicopters. 相似文献
12.
Jahantigh Farhad Ghorashi Seyed Mohammad Bagher Mozaffari Samaneh 《Journal of Solid State Electrochemistry》2020,24(4):883-889
Journal of Solid State Electrochemistry - In this research, nanocoral (NC) film of TiO2 was decorated with nitrogen-doped graphene quantum dots (NGQDs, average size of ∼ 9 nm)... 相似文献
13.
Nonlinear Vibration Control of a System with Dry Friction and Viscous Damping Using the Saturation Phenomenon 总被引:1,自引:0,他引:1
Application of saturation to provide active nonlinear vibration control was introduced not long ago. Saturation occurs when two natural frequencies of a system with quadratic nonlinearities are in a ratio of around 2:1 and the system is excited at a frequency near its higher natural frequency. Under these conditions, there is a small upper limit for the high-frequency response and the rest of the input energy is channeled to the low-frequency mode. In this way, the vibration of one of the degrees of freedom of a coupled 2 degrees of freedom system is attenuated. In the present paper, the effect of dry friction on the response of a system that implements this vibration absorber is discussed. The system is basically a plant with a permanent magnet DC (PMDC) motor excited by a harmonic forcing term and coupled with a quadratic nonlinear controller. The absorber is built in electric circuitry and takes advantage of the saturation phenomenon. The method of multiple scales is used to find approximate solutions. Various response regimes of the closed-loop system as well as the stability of these regimes are studied and the stability boundaries are obtained. Especial attention is paid on the effect of dry friction on the stability boundaries. It is shown that while dry friction tends to shrink the stable region in some parts, it enlarges other parts of the stable region. To verify the theoretical results, they have been compared with numerical solution and good agreement between the two is observed.This work was done while the authors were associated with the Mechanical Engineering Department, Sharif University of Technology, Tehran, Iran. 相似文献
14.
Nonlinear dynamical systems, being more of a realistic representation of nature, could exhibit a somewhat complex behavior. Their analysis requires a thorough investigation into the solution of the governing differential equations. In this paper, a class of third order nonlinear differential equations has been analyzed. An attempt has been made to obtain sufficient conditions in order to guarantee the existence of periodic solutions. The results obtained from this analysis are shown to be beneficial when studying the steady-state response of nonlinear dynamical systems. In order to obtain the periodic solutions for any form of third order differential equations, a computer program has been developed on the basis of the fourth order Runge-Kutta method together with the Newton-Raphson algorithm. Results obtained from the computer simulation model confirmed the validity of the mathematical approach presented for these sufficient conditions. 相似文献