Experimental coupling and decoupling of engineering structures using frequency-based substructuring

In many engineering application there are many instances in which it is convenient to be able to consider a complex engineering structure as an assembly of simpler components or substructures. Similarly, there exist applications in which, for model validation purposes, it might be important to identify the dynamic behavior of the structural subsystem starting from the known dynamic behavior of the coupled system and from information about the remaining part of the structural system. However, if the theoretical framework for Frequency Based Substructuring ( FBS) has been widely studied and demonstrated, measurement errors, ill-conditioning and difficulties in measuring all required degrees of freedom-in particular at the connections-lead to poor results when trying to apply these techniques to real structures. This paper will focus on the analysis of the results obtained by applying Experimental Frequency-Based Substructuring on a test structure, both for coupling and decoupling applications and under different boundary conditions. The paper will particularly discuss the effects of typical measurement errors on the final results and potential techniques that could be used to improve the robustness and applicability of this methodology.