Potential and Limitation of a Nonlinear Modal Testing Method for Friction-Damped Systems
Experimental nonlinear modal analysis has been applied successfully, mainly on structures with stiffness nonlinearities. However, it remains a challenge to experimentally extract a nonlinear modal model of structures with nonlinear damping, such as friction. To systematically investigate a modal testing method for friction-damped structures, we introduce a new test specimen. The specimen is a beam that is clamped on one side and offers six possible locations to induce friction. Changing the friction location varies the significance of the non-linear effects, that is, frequency shift, increase in damping and change of mode shapes. We apply experimental modal analysis with one excitation point to track the properties of one mode from full stick to macro slip. To assess the quality and validity of the extracted modal model, we compare predicted steady-state vibrations with frequency response measurements close to resonance. Based on these results, we discuss the potential and limitation of the applied modal testing approach.
KeywordsNonlinear modes Modal analysis Force appropriation Jointed structures Nonlinear system identification
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