Experimental Investigation of Mode Shapes of Symmetric Structures

Abstract

Paper deals with experimental determination of modal parameters of symmetric structures which have so-called coupled mode shapes of vibration. These modes usually have almost the same frequencies. This is why it could be difficult to identify them from frequency response functions where their peaks overlap. Main attention is focused on the using of Complex Mode Indicator Function (CMIF) that is able to separate coupled and also closely spaced modes by using singular value decomposition of multiple reference FRF matrix. In the paper there is described a theoretical background of CMIF and its application in spatial domain parameter estimation. Its functionality is explained on an analytical model of mechanical system of six degrees of freedom. Its practical application is presented by experimental modal analysis of circular saw blade.