The Influence of Free Movement in the Opposite Direction to the Obstacle on the Dynamics and Efficiency of a Single-Sided Vibro-Impact Nonlinear Energy Sink

This paper studies the effect of the movement of a single-sided vibro-impact nonlinear energy sink (SSVI NES) in the direction opposite to the obstacle on its dynamics and efficiency in mitigating vibrations of the primary structure (PS) subjected to the harmonic excitation. The damper efficiency is assessed by the reduction of PS maximum mechanical energy. All damper parameters are optimized simultaneously. The paper focuses on the SSVI NES with free movement in the direction opposite to the obstacle, without any constraints, which ensures its high efficiency. Its dynamics and efficiency are compared with those of other dampers, namely SSVI NES with limited motion away from the obstacle and the tuned mass damper (TMD). The preservation of damper tuning when changing the structural parameters such as the natural frequency of the PS, its damping and the intensity of the harmonic exciting force is also being studied. The dynamics of SSVI NES with free motion away from the obstacle is quite calm with periodic motion over almost the entire frequency range. Rapid alternation of modes with different periodicity and different numbers of impacts per cycle, as well as irregular modes, is observed only at high frequencies of the exciting force.