Vibration suppression performance of tunable parallel asymmetric nonlinear energy sinks with distinct stability characteristics under impulse excitation

• Parallel asymmetric NESs with three repulsive magnets (P-3ARMNESs) are proposed. • Impulse vibration suppression is studied numerically and experimentally. • Key parameters of P-3ARMNESs and counterparts are optimized via genetic algorithm. • P-3ARMNESs show superior performance over counterparts with equal mass. • Initial position and constraint-induced performance factors are discussed. Nonlinear energy sinks (NESs) are promising vibration absorbers known for their unique Targeted Energy Transfer (TET) mechanism and superior performance over linear vibration absorbers (LVAs) in terms of attenuation bandwidth and/or amplitude suppression. However, current research in NES lacks comprehensive studies on asymmetric multistable NES, even though the introduction of asymmetry fundamentally reshapes the potential landscape. Additionally, the limited research on multi-degree-of-freedom NESs has primarily focused on symmetric monostable systems, leaving the advantages of asymmetric parallel configurations largely unexplored. To overcome these challenges, this work explores the vibration attenuation capability of tunable parallel NESs incorporating three asymmetric repulsive magnets (P-3ARMNESs) across different impulse intensities, using theoretical modeling, numerical simulation, parameter tuning, and experimental validation. Taking into account the beam deflection and the tip magnet rotation, a dipole–dipole model is employed to characterize the magnetic force to enable dynamic system modeling for numerical simulation. For fair comparison, critical design parameters of the P-3ARMNESs and additional comparative configurations (single LVA, single symmetric NES (3RMNES), and single asymmetric NES (3ARMNES)) are optimized using genetic algorithm under varying excitation intensities. Numerical simulations and experimental validation reveal that the 3ARMNES outperforms the symmetric 3RMNES, confirming the benefit of asymmetry. Furthermore, maintaining identical equivalent mass, the optimized P-3ARMNESs achieves the best performance, demonstrating the advantage of parallel asymmetric configuration. Simulation and experimental results show that introducing asymmetry weakens the potential barriers of multistable NESs, thereby lowering the threshold for inter-well transitions. Meanwhile, the parallel configuration enriches dynamic responses, and the synergistic interaction of different modes enables efficient TET. These features—frequent inter-well transitions and efficient TET—are key to the superior vibration mitigation performance of the proposed structure. Additionally, the effect of initial positions on NES performance is investigated numerically and experimentally. Factors affecting P-3ARMNESs not addressed in experiments due to physical constraints are also numerically explored. These findings provide valuable insights for designing efficient, tunable parallel asymmetric NESs capable of mitigating impulse responses across a range of excitation amplitudes without increasing mass.

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