Topic
Critical speed
About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.
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01 Jan 1995
TL;DR: In this paper, the authors explored the sliding speed at which the system is susceptible to frictionally-induced thermoelastic instability (TEI) in a simple system consisting of a rotating thin-walled cylinder whose end face slides against a rigid surface.
Abstract: In many sliding systems, the sliding surfaces are not coextensive, so that points on one surface experience alternating periods of contact and separation. This intermittent process can be expected to influence the sliding speed at which the system is susceptible to frictionally-induced thermoelastic instability (TEI). This question is explored in the context of a simple system consisting ofa rotating thin-walled cylinder whose end face slides against a rigid surface. The results show that at low Fourier number-i.e., when the frequency of the process is high compared with the thermal transient of the system-only the time-averaged frictional heat input is important and the critical speed is an inverse linear junction of the proportion of time in sliding contact. At higher Fourier number, lower critical speeds are obtained, but the dependence on Fourier number is relatively weak.
21 citations
TL;DR: In this article, a dynamic analysis model comprising track, embankment and layered ground was proposed based on the two-and-half-dimensional (2.5D) finite elements combining with thin-layer elements to predict vibrations generated by train moving loads.
21 citations
TL;DR: In this article, the problem of active stabilisation of a rigid rotor supported on journal bearings by application of piezoelectric actuators is addressed, where the actuators are capable of changing their size when subject to voltage.
Abstract: The paper is concerned with the problem of active stabilisation of a rigid rotor supported on journal bearings by application of piezoelectric actuators. The actuators are capable of changing their size when subject to voltage. In the considered system the piezoelectric elements move the bearing shell in order to protect the journal from excessive vibration. Motion of the journal is followed by inductive sensors, which transmit an electric signal to the control system. The signal is differentiated with respect to time and then sent to the actuators controlling current position and velocity of the mobile shell (state-based control). Such an approach endows the system with an increased inertia and damping, and both the quantities enhance stable working of the system. The stability is determined by analysing eigenvalues of the equations of motion linearised around a non-trivial equilibrium position. Carried out numerical simulations prove that the method is effective as it increases the critical speed twice or even more. The efficiency is confirmed for various loading conditions.
21 citations
TL;DR: An Advanced Influence Coefficient Method (AICM) is developed that utilizes the influence coefficients obtained at high speed and unbalances identified at the low speed to effectively estimate the balance masses required for the high-speed flexible rotor balancing.
21 citations
TL;DR: Recently, magnetic bearings have been applied to many rotating machines such as turbo-molecular pumps, cooling gas compressor, flywheel energy storage systems as discussed by the authors, and high-power density is the future.
Abstract: Recently, magnetic bearings have been applied to many rotating machines such as turbo-molecular pumps, cooling gas compressor, flywheel energy storage systems. And high-power density is the future ...
21 citations