Fig. 8 B 11 H and B 12 H with added masses of 70 grams in sub-structure B The results are clearly better. However, to recover the dynamic response of B, one has to uncouple the added masses. The results of such an operation are shown in figure 9. Fig. 9 B 11 H and B 12 H with and without the masses of 70 grams in sub-structure B Although the results are better than the initial ones (figure 5), they are worse than those of figure 6, when the masses were added to sub-structure A. The disturbances come up again in the same frequency range. 3.3 Coupling One of the main interests of the dynamic characterization of a sub-structure (like a joint) is to be able to predict the dynamic behavior of another structure (or a modified one), possibly a more complex one, inserting (coupling) the identified results from the uncoupling procedure. Whereas the uncoupling procedure tends to be unstable, as shown in this work, the coupling process is usually quite stable. Based on the results obtained for sub-structure B, a coupling procedure will be undertaken with similar components, two beams A1 and A2 but now with a length of 400 mm. Using the results initially obtained from figure 5, one obtains the behavior illustrated in figure 10. In figure 10 the disturbance in the area of 1000-1200 Hz remains. One can also observe the results of the coupling of B when the masses were added to A, i.e., when using the responses given in figure 6. Figure 11 illustrates this case. The results have improved and the disturbances have moved down, as expected. Most certainly, better solutions would have been obtained if one had performed a modal analysis identification to the results of figure 6, prior to the coupling procedure. 200 400 600 800 1000 1200 1400 1600 1800 2000 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 Receptance [dB] (ref. 1 m/N) Frequency [Hz] Hbjj11 Hb2jj11-1% 200 400 600 800 1000 1200 1400 1600 1800 2000 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 Receptance [dB] (ref. 1 m/N) Frequency [Hz] Hbjj12 Hb2jj12-1% 390
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