Identification of stiffness and damping in nonlinear systems

Abstract

Resonance nonlinearities in vibrating mechanical structures are either due to stiffness, damping, or a combination of both. A method is presented to detect the nonlinear distortions, determine and quantify the distortion levels. This is achieved by configuring a nonlinear device as a second-order, single-input-single-output (SISO) closed-loop feedback system such that static nonlinearities are confined to the feedback path, and the dynamic linear part is modeled as the forward gain. The closed-loop system is then subjected to random phase multisine excitations. This makes it possible to model the linear part by its frequency response function, thus facilitating the characterization of the nonlinear part. There is a good agreement between the estimated and experimental data. The results indicate distortion nonlinearities due to stiffness and damping with distinguishable levels. ©2010 Society for Experimental Mechanics Inc.