71 Expansion of Nonlinear System Response Using Linear Transformation. . . 761 Beam A Beam B 0 3 4 5 6 7 8 9 10 11 12 12.5 13 14 15 16 17 17.5 18 21 23 25 28 Location (in.) -10 mV/g Accelerometer -100 mV/g Accelerometer -Force Gage -Impact Location 19 20 22 24 Fig. 71.19 Test bed with dimensioned schematic of impact and transducer locations 71.3.3 Experimental Case Study A modal survey was conducted to determine the characteristics of the two beams when mounted to the test fixture. Modal impacts were performed at 15 points on each component, where the impact and transducer locations are shown in a dimensioned schematic in Fig. 71.19 along with the actual tested structure. To characterize the dynamics of the beams, accelerometer measurements were acquired using LMS Test.Lab 10A [20] and 10 averages were taken for each impact point. Impacts were performed along the centerlines of the beams and only outof-plane direction motion (normal to beam surfaces) was measured. To extract the desired modal parameters of the tested components, the experimental data was curvefit using PolyMAX [21], which is an advanced modal parameter estimation algorithm implemented within LMS Test.Lab. This provided estimations of the natural frequency, mode shape, and damping characteristics for the system, where the natural frequencies and damping values are listed in Table 71.6. The experimentally measured mode shapes consisted of 15 ADOF per component and were expanded out to the full space FEM, which consisted of 146 DOF for Beam A and 130 DOF for Beam B. To perform this expansion, the full space
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