Substructure decoupling on an experimental test bed

The paper considers the decoupling problem, i.e. the identification of the dynamic behaviour of a structural subsystem, starting from the known dynamic behaviour of both the coupled system and the remaining part of the structural system (residual subsystem). Substructure decoupling techniques can be classified as inverse coupling or direct decoupling techniques. Direct decoupling, that is used in this paper, consists in adding to the coupled system a fictitious subsystem that is the negative of the residual subsystem. Using simulated FRF data, it has been highlighted that the solution of decoupling problems is affected by ill-conditioning around a discrete number of frequencies, and is dependent on the choice of the measured DoFs. Using experimental data, additional problems can arise (systematic errors, inconsistencies, etc.) that are strictly connected with the use of measured FRFs, and require a specific approach. In this paper, experimental data, acquired on a test bed made by a plate and a rigid mass, are used to check the theoretical results and to look for additional issues that can not be observed from simulated data.