Response Curves at the Critical Speeds of Sub-Harmonic and "Summed and Differential Harmonic" Oscillations

Abstract

Lateral vibrations of rotating shaft are recorded, and response curves of sub-harmonic and "summed and differential harmonic" oscillations are experimentally obtained. Summarizing, the amplitudes of sub-harmonic oscillation of 1/2 order increase with the magnitudes of eccentricity of rotating body. Shapes of response curves of sub-harmonic oscillations of forward precession are those of hard spring type, and the response curves of soft spring type are obtained for backward precessional whirling motions. For one critical speed of "summed and differential harmonic" oscillations, the height of peak decreases as eccentricity increases. The other critical speeds have a constant amplitude, even if the magnitude of eccentricity is changed. Shapes of response curves of "summed and differential harmonic" oscillations are either discontinuous response curves with jump phenomena or continuous, as the nonlinear spring characteristics of shaft are changed.