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), i.e., the vibro-impact damper, in the direction opposite to the barrier (which in this paper is called an obstacle) on its dynamics and efficiency in mitigating vibrations of the primary structure (PS) subjected to harmonic excitation. The barrier is rigidly connected to the PS. The primary structure is the heavy main construction, which must be protected from unwanted vibrations. It is a linear oscillator. The damper efficiency is assessed by the reduction in PS maximum mechanical energy. All damper parameters are optimized simultaneously. Optimization procedures are necessary, as only a damper with optimized parameters ensures high efficiency. Simultaneous optimization demonstrates a synergistic effect, providing the best parameter values that guarantee the highest damper efficiency and performance. 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, reducing the maximum PS energy by 3.5 times! 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.