1990 Fiscal Year Final Research Report Summary
Nonstationary Vibrations of a Rotating Machinery Through Critical Speeds and Active Damping
Project/Area Number 
01550206

Research Category 
GrantinAid for General Scientific Research (C)

Allocation Type  Singleyear Grants 
Research Field 
機械力学・制御工学

Research Institution  Nagoya University 
Principal Investigator 
ISHIDA Yukio Nagoya University, Faculty of Engineering, Associate Professor > 名古屋大学, 工学部, 助教授 (10092991)

Project Period (FY) 
1989 – 1990

Keywords  Rotating Shaft / Critical Speed / Nonstationary Vibration / Nonlinear Oscillation / Subharmonic Oscillation / Combination Oscillation / FFT / Digital Signal Processing 
Research Abstract 
Rotating machinery has nonlinear spring characteristics for various reasons. In this research, nonstationary oscillations through critical speeds caused by nonlinear spring characteristics are investigated. 1. In an experimental apparatus in which a rotor was mounted on an elastic shaft, various kinds of subharmonic and summedanddifferential harmonic oscillations are observed. 2. In the theoretical and experimental analyses, we originated ComplexFFT method which utilizes a digital signal processing technique. By using ComplexFFT method, phase plane analyses, and the asymptotic methods, the following results are obtained : (1) In the case of the major critical speed, the maximum amplitude gamma max in nonstationary oscillation has only one value for a given angular acceleration. The rotor can pass the critical speed when the acceleration is higher than a certain value. The bigger the acceleration, the smaller the maximum amplitudes. (2) In the case of subharmonic oscillation of order 1/2, the maximum amplitude gamma max varies between 0 and (gamma max)_1 in randam even if the angular acceleration is the same. (3) In the case of summedanddifferential harmonic oscillation caused by unsymmetrical nonlinearity, the maximum amplitude gamma max varies between two values (gamma max)_1 and (gamma max)_2 in random for a given angular acceleration. (4) In the case of subharmonic oscillation of order 1/3, the rotor can pass the critical speed if the value of accelaration is very small or very large. Otherwise, the nonstationary amplitude is drawn toward stationary amplytude and the rotor cannot pass the critical speed. 3. The active damping technique is now under development and we could not obtain a completed results.

Research Products
(6 results)