Power flow techniques in the study of machinery installations for the purpose of vibration control

Abstract

A typical machine installation consists of a source of vibration mounted on resilient isolators attached to a flexible substructure. There are usually also other vibration transmission paths, such a pipework, shafts, etc., which act as short‐circuit elements across the isolators. It can thus be seen that there are a variety of mechanisms by which vibration is transmitted from the source to the point of interest on the substructure. The power flow approach to this type of problem is a basic concept which enables the relative importance of the various transmission paths to be critically assessed. Work has been carried out on the estimation of vibrational power flows between coupled systems, using approximate mobility methods, and this has led to the establishment of design rules for machinery seatings, together with simple formulas for estimating point mobilities of structures. Experimental techniques have also been developed. One development concerns measurement of vibrational power flow through isolators so that, for one machine mounted on a set of isolators or even an array of machines, the power inputs to the substructure at each isolator connecting point can be determined. The other, most recent development is the structural intensity meter which enables one‐ and two‐dimensional power flows to be measured in beams and plates. Intensity maps can be plotted for plate‐type structures, for example. The paper outlines the power flow approach to the machinery installation problem, with the objective of vibration control, and reviews the developments noted above.