发展声隐身技术是提高舰船生存力和作战力的重要手段，抑制低频振动在结构中的传播是降低水噪声最有效的技术手段之一。然而，低频减振一直是振动控制领域的理论瓶颈和技术挑战。本项目将准零刚度方法拓展至局域共振超材料，提出基于准零刚度超材料的减振理论与方法，实现低频甚至超低频减振。研究内容包括：基于正负刚度并联原理和柔性机构理论，创新设计准零刚度超材料，研究其波动特性，揭示低频甚至超低频带隙产生机理；考虑超材料的非线性刚度，深入研究局域化、分岔和混沌等非线性动力学行为，揭示非线性对波动特性的影响与调控机制；利用惯性放大、彩虹效应、电磁或压电效应，探索拓宽带隙、提高减振效能以及主动调控带隙的理论与方法。最后，将本方法应用于舰船浮筏结构减振，通过模型实验验证其低频减振特性，为提高舰船声隐身性能提供新的理论支持和技术途径。

The radiated noises from underwater vehicles are fatal to their combat ability and survivability, and therefore it is essential to develop the acoustic stealth technology. In fact, one of the most effective methods to reduce the radiated noise is to prevent mechanical vibrations from propagating in the ship structures. However, the low-frequency vibration attenuation is still a bottleneck issue and a technology challenge in the field of vibration control. In order to solve such an issue, novel quasi-zero-stiffness (QZS) locally resonant metamaterials are proposed to attenuate low-frequency vibrations propagating from the on-board machines to the hull. The main contributions of this project can be listed as follow. Firstly, the QZS metamaterials are designed and constructed on the basis of both the principle of combining positive and negative stiffness and the theory of compliant mechanisms. Moreover, the dispersion relations are obtained by employing the plane wave expansion method to demonstrate the band structures and to reveal the mechanism of opening band gaps at low frequencies and even at very-low frequencies. Secondly, under large-amplitude excitations, the nonlinear stiffness of the QZS metamaterials should be considered, and the nonlinear dynamic behaviors, such as localization, bifurcation and chaos, are studied to discover the impact of the nonlinearity on the band structures and wave attenuations, which should be useful for tuning the band gaps by mean of the amplitude-related features. Thirdly, in order to broaden the band gap and to improve the wave attenuations, the inertial amplification mechanisms are used to enlarge the effective mass of the QZS resonator with the actual mass slightly changed, and the multi-degree-of-freedom QZS resonators are employed to create multiple desired band gaps. More importantly, when the central frequencies of the band gaps are designated to be close to each other, those band gaps would merge into one ultra-wide band gap due to the rainbow trapping effect. Furthermore, the electromagnetic springs and piezoelectric patches are utilized to regulate the stiffness of the QZS resonators based on the feedback responses, so that the band gap can be tuned actively and real time to accommodate to time-varying exciting conditions. Finally, this low-frequency vibration control method will be applied in the floating raft system to attenuate the mechanical vibrations propagating in the raft structures. The prototype of the raft will be built, and the experimental tests will be carried out to evaluate the vibration attenuation performances, and to verify this passive vibration control technology by using QZS metamaterials, which should be a promising solution of improving the acoustic stealth of the underwater vehicles.