13 Shock Response Fixture Developed from Analytical and Experimental Data... 147 0 200 400 600 800 1000 10-7 10-6 10-5 10-4 10-3 10-2 10-1 Frequency [Hz] Force [lbf] Log Fig. 13.9 Input force spectrum 0 200 400 600 800 1000 10-6 10-4 10-2 100 102 Frequency [Hz] Accelerance [G/lbf] Fig. 13.10 FRF with modal solution 0 0.05 0.1 0.15 0.2 -8 -6 -4 -2 0 2 4 6 Time [sec] Acceleration [G] Newmark method IFT method Fig. 13.11 Comparison of time response response signal will originally have length of 131,072 but only the first Fs 0.2 set of data will be used. The result is shown in Fig. 13.11 and the time response with the Newmark method is overlaid. Both of the signals compare well with less than 0.2 % difference on the peak point. Using the acceleration signals computed from the Newmark method or IFT method shown in Fig. 13.11, the SRS will be developed using 1/12 octave band shown in Eq. 13.17. For each additional SDOF system whose natural frequency is the
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