Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.

Dynamic Loads on Spur Gear Teeth at High Speed : Influence of the Pressure Angle Errors and Comparison between the Reduction Gears and the Speed-up Gears

Abstract: Dynamic loads on spur gear teeth are measured by a high speed gear testing machine at a periphery velocity of 80 m/sec and below. The ground gears (some of them have pressure angleerrors) are tested as reduction gears and also as speed-up gears respectively. The maximum dynamic loads occur at a critical speed, at which the meshing frequency is equal to the natural frequency of the vibratory system consisting of a pinion, a gear and a combined tooth stiffness. At a speed over the critical one, the magnitude of the dynamic load approaches a certain constant which is determined by the tooth errors. When the errors are repeated in each meshing as in these cases, the dynamic loads of the gear tested as a follower are nearly equal to the ones tested as a driver.

Chaotic Vibration and Internal Resonance Phenomena in Rotor Systems

Abstract: Rotating machinery has effects of gyroscopic moments, but most of them are small. Then, many kinds of rotor systems satisfy the relation of I to (-1) type internal resonance approximately. In this paper, the dynamic characteristics of nonlinear phenomena, especially chaotic vibration, due to the 1 to (-1) type internal resonance at the major critical speed and twice the major critical speed are investigated. The following are clarified theoretically and experimentally: (a) the Hopf bifurcation and consecutive period doubling bifurcations possible route to chaos occur from harmonic resonance at the major critical speed and from subharmonic resonance at twice the major critical speed, (b) another chaotic vibration from the combination resonance occurs at twice the major critical speed. The results demonstrate that chaotic vibration may occur even in the rotor system with weak nonlinearity when the effect of the gyroscopic moment is small.

In-Plane Vibrations of a Thin Rotating Disk

Abstract: A model for the in-plane oscillations of a thin rotating disk has been derived using a nonlinear strain measure to calculate the disk energy. This accounts for the stiffening of the disk due to the radial expansion resulting from its rotation. The corresponding nondimensionalized natural frequencies are seen to depend only on the nondimensionalized rotation speed and have been calculated. The radially expanded disk configuration is linearly stable over the range of rotation speeds studied here. The sine and cosine modes for all nodal diameters couple to each other at all non-zero rotation speeds and the strength of this coupling increases with rotation speed. This coupling causes the reported frequencies of the stationary disk to split. The zero, one and two nodal diameter in-plane modes do not have a critical speed corresponding to the vanishing of the backward travelling wave frequency. The use of a linear strain measure in earlier work incorrectly predicts instability of the rotating equilibrium and the existence of critical speeds in these modes.