A. Culla, W. D’Ambrogio, A. Fregolent and A. Schiavone Fig. 4 Benchmark: version 1 Fig. 5 Benchmark: version 2 Fig. 6 Subsystem B The nominal system parameters are shown in Table 1. Table 1 Mass values and spring constants of the benchmark i 1 2 3 4 5 6 m[kg] 0.822 0.414 0.407 0.867 0.443 0.452 k [N/m] 1046 2000 460 1411 709 1059 3.2 Tests The FRFs of both the coupled system and the subsystems need to be measured either to apply coupling procedure (FRF of the components) and to check the results (FRF of the coupled system), or to apply the decoupling procedure (FRF of the coupled system and FRF of the residual subsystem) and to check the results (FRFs of the ’unknown’ subsystem). The measured FRFs are curve fitted using a polyreference least square frequency domain identification technique in order to regenerate FRFs from a consistent modal model. The complete FRF matrix of the coupled system is measured. Figs. 7 and 8 show the measured raw and fitted point FRFs at the connections between the two subsystems. With regard to the subsystems, the used tension springs can not work in compression, so additional springs are needed to have a traction preload (Fig. 6). Therefore, the measured FRFs will be affected by the additional springs. The complete FRF matrix of both modified subsystems is measured. Figs. 9, 10, 11 and 12 show the measured raw and fitted point FRFs at the coupling DoFs. 98
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