Dry friction damper for supercritical drive shaft

Abstract

In this article the construction and mathematical model of a dry friction damper with radial gap, designed for dumping flexural vibrations of a supercritical propulsion shaft (developed previously during design works made in Institute of Aviation on propulsion system for an ultralight IS-2 helicopter), while passing through the resonance is presented. Some results of mathematical and numerical analyses of such a system (supercritical shaft + damper) behaviour are also presented – among other things, very distinctive behaviour of the shaft, while passing through resonance, is shown. From a theoretical point of view, it is interesting that certain range of damper parameters, obtained in the course of numerical analysis, lead to chaotic vibrations of the system (they were also observed in practice). From a practical point of view, it will be interesting that the article shows a way how to create a dimensionless (and therefore general) parameters of the system: supercritical shaft and friction damper and also simple engineering methodology for selection of suitable (for the correct operation of the shaft) damper parameters depending on the parameters of the shaft, developed during series of analyses. The practical aspect of the problem seems to be particularly important, as the supercritical propulsion shaft equipped with a friction damper can be very structurally simple, light and inexpensive, and still it is not widely used, probably because of certain doubts aroused in the constructors by the term: “resonant vibrations”.