Detection of localized nonlinearity in dynamical systems using base excitation experimental results

Nonlinear localization approaches are used not only for detecting the exact location of the nonlinear elements in mechanical structures, but they are also exploited in order to find any possible flaws such as cracks in Structural Health Monitoring (SHM) applications. This study aims to develop a localization method to determine the location of localized nonlinearities in dynamic structures utilizing the experimentally measured data obtained from the base excitation test. The nonlinear element in the experimental set-up is represented by a pair of permanent magnets placed on both sides on the free end of the cantilever, and a pair of electromagnets placed with equal distances on both sides of the permanent magnets. The combination of permanent and electromagnets create and apply nonlinear electromagnetic force on the free end of the cantilever beam. Hence, stepped-sine vibration tests are carried out using constant acceleration base excitation to measure the response of the nonlinear system. The linear response of the system obtained from the low amplitude test is used to update the Finite Element (FE) model of the underlying linear system of the structure. Then, the developed approach utilizes the updated linear model along with the measured nonlinear dynamics of the experimental set-up obtained using high-amplitude excitation to determine the location of nonlinearity. The results of the experimental study are demonstrated to show the performance of the presented method.