Study on Crack Identification with Responses Modulated by Nonlinear Energy Sink

Abstract

Owing to its vibration reduction and indirect signal amplification characteristics, a nonlinear energy sink (NES) is used for crack identification of structures. The equation of a cracked simply supported beam with an NES is derived and the influences of the crack properties on the dynamics of the system are investigated. A pixel method is applied to estimate phase diagram areas and crack parameters are identified based on the geometric features of the phase diagram. It is shown that the phase diagram of the NES varies significantly with crack parameters. This is because of the higher amplitudes generated by the absorbing NES with respect to the primary structure. In addition, the NES can reduce the amplitude of the cracked beam without hindering crack identification. Moreover, through introducing the NES, the system can produce a strongly modulated response, which can be utilized for convenient crack detection. Two sets of crack identification indices are defined for the system, generating a single-period response and a strongly modulated response. Contour maps of identification indices based on the area of phase diagrams are obtained by varying crack location and depth. The crack parameters are identified through the intersection of contour lines.