Design optimization and experimental study of flexible hinge-type nonlinear energy sink

To address the difficulty of suppressing low-frequency line spectra in underwater vehicle radiated noise and the narrow operating bandwidth of conventional linear vibration absorbers with fixed tuning frequencies, this paper proposes a flexible hinge-type nonlinear energy sink (NES). First, a double-slotted flexible hinge-type NES structure is presented. Static mechanical analysis shows that the structure exhibits cubic stiffness characteristics near the static equilibrium position. Second, the IHB method is employed to characterize the periodic responses of the NES system. The effects of NES mass, stiffness, and damping on the amplitude-frequency response and vibration suppression performance are then investigated in detail. Subsequently, local optimization is performed to determine the optimal damping and stiffness parameters of the NES. The optimized NES shows strong robustness against variations in excitation frequency and amplitude. Finally, a prototype of the flexible hinge-type NES is fabricated, and a vibration test platform is established for experimental validation. Both simulation and experimental results show that the NES reduces the first-order resonance peak near 5.00 Hz by approximately 8.17 dB, decreases the average line-spectrum level over 4.43–5.82 Hz by about 3.74 dB, and broadens the vibration absorption bandwidth by approximately 27.8%. Compared with an equivalent linear dynamic vibration absorber, the NES provides better broadband vibration absorption performance. In addition, the NES can shift the resonance frequency of the coupled system and induce a strong modulation response.