Modal Testing of Machinery Components

Abstract

In this paper attention is given to the practicalities of conducting tests according to the procedures outlined in the previous paper, with special reference to the components and subassemblies from rotating machines. First considered are problems associated with providing the appropriate excitation and of correctly measuring the resulting transducer signals of force and response. The question of extending these methods to rotating components is briefly discussed here (but is dealt with in more detail in other papers). Next, the modal analysis methods used to extract modal parameters from the measured FRF data are examined with particular reference to the question of their reliability in the presence of typical experimental errors in the data and of the possibility of non-linearity in the actual test structure. The questions of residual effects and of complex modes are discussed before considering the final stage of modelling and the difficulties which may be encountered here in practice.