Table 7. Individual Beam Modal Properties from Test. 1 73.34 0.29 75.35 0.12 2 199.14 0.16 206.54 0.02 3 380.03 0.23 399.82 0.13 4 609.76 0.31 649.87 0.22 5 900.62 0.48 950.90 0.81 Frequency (Hz) Damping (% Critical) Beam A Beam B Mode Frequency (Hz) Damping (% Critical) Table 8. Two-Beam System Modal Properties from Test. 1 69.20 0.32 2 80.41 0.16 3 187.10 0.21 4 210.36 0.14 5 265.99 0.14 6 391.50 0.28 7 409.60 0.20 8 630.57 0.25 9 926.96 0.74 10 1108.11 0.59 Mode Damping (% Critical) System AB Frequency (Hz) The drive point measurements on system AB-TR and AB-TT at connection node 6 are shown in Figure 17 and Figure 18, respectively. Figure 17. Typical Drive Point Measurement on AB-TR at Connection DOF. Figure 18. Typical Drive Point Measurement on AB-TT at Connection DOF. Decoupling of System – Experimental Models As with the analytical models, many cases were studied to better understand the characteristics of each decoupling technique. For brevity, only the most promising results for each model will be presented. In all experimental cases, the Inverse FBS technique was excluded, as this technique was shown to produce extremely poor results with the perturbed synthesized FRF. While the measured FRF were of high quality, when used directly in the decoupling techniques the minimal noise contained in the FRF is magnified due to the matrix inversion performed in the computation. To remove this noise, modal parameter estimation was performed on all FRF in LMS Test.Lab, and new FRF were synthesized from the modal parameters using lower and upper residual compensation terms. The resulting FRF using the Mobility and Impedance approach with only connection DOF for system AB-TR and AB-TT are shown in Figure 19 and Figure 20, respectively. Three dominant peaks can be seen in the resulting FRF for both models; however, shifts in frequencies are present. For system AB-TT, an increase in damping is also present, and the antiresonance between the second and third peak is completely distorted. 182
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