Aiming to isolate disturbance vibration for heavy machines with low frequency, a novel hydro-pneumatic vibration isolator with high-static and low-dynamic (HSLD) stiffness is proposed, which contains bellows structure as elastic element and pressurized gas and incompressible liquid as working media. Due to that the natural frequency of isolation system with such isolator is close to zero and loading capacity can be adjusted by the gas pressure, the proposed device is termed as pneumatic near-zero frequency (NZF) vibration isolator. To obtain the mathematical model of isolator’s stiffness, the quasi-static derivation based on gas state equation is carried out first. Results prove that the presented isolator possesses ideal high-static and low-dynamic stiffness, which is also verified by the experimental data measured by a quasi-static test. The proportion of gas volume to total volume of gas and liquid media, respectively, in bellows and cylinder chambers are significant physical parameters, which dominate the nonlinearity extent of isolator’s stiffness. Different from most existing isolators, the proposed isolator includes fluidic damping and friction damping. The former is expressed by classic square-velocity-type nonlinear model, and the latter is modeled as Coulomb damping. To obtain dynamic response and vibration isolation transmissibility, the harmonic balance method is applied. A direct current term is added in the trial solution, which reflects the asymmetry of dynamic response. In respect of transmissibility analysis, square-velocity nonlinear damping brings a favorable advantage that it can ensure the fine force transmissibility in both resonance region and effective isolation band. This conclusion holds consistently under base motion excitation. Friction damping cannot give the same conclusion. Further comparison with a linear vibration isolator exhibits that the HSLD stiffness characteristics of the NZF isolator breaks through the trade-off between large loading capacity and small static deformation, and the square nonlinearity of fluid damping is able to overcome the dilemma that weak linear vicious damping is beneficial for isolation performance within the effective isolation frequency band, but cannot suppress resonance amplitude and transmissibility. And the experimental transmissibility is in good agreement with the analytical result. Besides, the influences of excitation variation on isolation performance are estimated theoretically. Due to the hardening stiffness, overload acceleration will cause the increase in linearized natural frequency of NZF isolator system, and thus, isolation effectiveness will be reduced.

为了隔离重型机械低频振动，提出了一种新型的具有高静态低动态刚度的液压气动隔振器，该系统以波纹管结构为弹性元件，以压缩气体和不可压缩液体为工作介质。 。由于带有这种隔离器的隔离系统的固有频率接近于零，并且可以通过气压来调节负载能力，因此该装置被称为气动近零频率（NZF）振动隔离器。为了获得隔振器刚度的数学模型，首先进行了基于气态方程的准静态推导。结果证明所提出的隔离器具有理想的高静态和低动态刚度，这也被准静态测试所测得的实验数据所证实。波纹管腔和气缸腔中的气体体积分别占气体和液体介质总体积的比例是重要的物理参数，它们决定了隔离器刚度的非线性程度。与大多数现有的隔离器不同，建议的隔离器包括流体阻尼和摩擦阻尼。前者用经典的方速度型非线性模型表示，后者用库仑阻尼建模。为了获得动态响应和隔振的可传递性，应用了谐波平衡法。在试验解决方案中添加了一个直流术语，它反映了动态响应的不对称性。关于透过率分析 平方速度非线性阻尼带来了一个有利的优势，即它可以确保在共振区域和有效隔离带中的精细力传递。该结论在基本运动激励下始终成立。摩擦阻尼不能给出相同的结论。与线性隔振器的进一步比较表明，NZF隔振器的HSLD刚度特性突破了大承载能力和小静态变形之间的折衷，并且流体阻尼的平方非线性能够克服弱线性恶性阻尼的困境。对于在有效隔离频带内的隔离性能有益，但不能抑制谐振幅度和透射率。实验透射率与分析结果吻合良好。除了，理论上估计了励磁变化对隔离性能的影响。由于硬化刚度，过载加速将导致NZF隔离器系统的线性固有频率增加，从而降低隔离效果。