78 S. Richardson et al. Fig. 8.11 Modal frequency shapes Fig. 8.12 Modal damping shapes Both MAC and SDI were calculated between the EMA and FEA mode shapes of the Jim Beam. The MAC values shown in Fig. 8.5 indicate an acceptable level of correlation between the EMA and FEA mode shapes. The SDI values between the EMA and FEA shape pairs are shown in Fig. 8.8 and are all nearly zero, indicating that the EMA shapes have different values than the FEA shapes. A cursory comparison of the shape values in Figs. 8.3 and 8.4 verifies that the phases of the EMA shape components are approximately 90ı apart from the phases of the FEA shape components. MAC rightly indicates that the shapes are nearly the same, but SDI indicates that their component values are different. After the EMA shapes were rescaled to more closely match the FEA shapes [3], the MAC values in Fig. 8.7 and the SDI values in Fig. 8.9 both indicate a strong correlationbetween the EMA and FEA shape pairs. Next, the SDI calculation was used to classify the torque applied to one of the Allen screws used to hold the plates together on the Jim Beam. Five different torque values were applied to one Allen screw, as shown in Fig. 8.10. With each torque value applied to the screw, FRFs were acquired and curve fit to obtain the modal frequency and damping of the first six modes of the beam. Those values are listed as in Figs. 8.11 and 8.12.
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