Energetic mode contributions in stochastic modal analysis: An application to mode classification

Complementary to classical modal analysis, usually performed on a test bench, identification of in-operation structures is more and more widely performed by the means of so-called “stochastic identification”. In this framework, modal information should be usefully completed by a criterion indicating the importance of each mode in the total structure response. In this paper, a mechanics-based energetic criterion is proposed in three forms: kinetic energy, potential energy and dissipated power. In the framework of stochastic subspace analysis, a method for the identification of these three quantities is developed. Two simulation test cases with two then five degrees of freedom confirm the method accuracy. Next an experimental test case is presented and analysed. Its validation requires the development of an independent approach. Globally the comparison of both methods shows satisfactory correlation. Finally a real-life case is used to illustrate some practical difficulties of the method.