PSI - Issue 19

Giovanni M. Teixeira et al. / Procedia Structural Integrity 19 (2019) 175–193 Author name / Structural Integrity Procedia 00 (2019) 000–000

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The dynamic analyses in this study are based on the modal superposition technique, which fundamentally combine modal results with modal coordinates (scale factors) in order to represent the full response spectrum in the time and frequency domains. A detailed discussion about linear dynamics can be found in Teixeira et al. (2014), Teixeira et al. (2015) and Thorby (2008). The frequency extraction analysis reveals the first 10 resonant frequencies of this system are: 41.6Hz, 46.2Hz, 52Hz, 64.7Hz, 76.3Hz, 82.8Hz, 83.7Hz, 94.6Hz, 96Hz and 96.4Hz. Fig. 23 shows the von Mises stress fields associated with the first 3 vibration modes.

Fig. 23. The first 3 modal stresses of the structure from the frequency extraction analysis.

The modal dynamic analysis transforms the acceleration inputs (Fig. 20-22) into the generalized displacements shown below (Fig. 24). These signals scale the modal stresses in order to obtain the stress histories at every node in the structure, followed by rainflow counting and damage evaluation as described on section 2.

Fig. 24. Generalized displacements for the first 10 vibration modes from the modal dynamics analysis (time domain).