35 Identification of Dynamic Nonlinearities of Bolted Structures Using Strain Analysis 399 Fig. 35.14 Linearized FRFs formode 4 Fig. 35.15 Evolution of the Normalized Modal Damping as a function of the acceleration level (g) Fig. 35.16 Evolution of the Normalized Modal FRF peak levels as a function of the acceleration level (g) Table 35.2 Simulated and experimental ranking of nonlinear modes FEM prediction ranking Experimental ranking Mode Type 2 1 8 T4 3 2 7 B4 4 3 4 T2 1 4 6 T3 prediction criteria, those four most critical modes were captured. This means that the criticality ranking criteria can be partially validated. It is not an accurate technique but allows to identify the modes likely to show the most nonlinear behaviour. Another conclusion to this experimental analysis is the nature of nonlinearity that can be different for every mode. The influence of the bolted joint dynamics on the structure behaviour varies from one mode to another. That confirms
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