Abstract
The characteristics of a passive nonlinear isolator are developed by combining a curved-mount-spring-roller mechanism as a negative stiffness corrector in parallel with a vertical linear spring. The static characteristics of the isolator are presented, and the configurative parameters are optimized to achieve a wider displacement range at the equilibrium position where the isolator has a low stiffness and the stiffness changes slightly. The restoring force of the isolator is approximated using a Taylor expansion to a cubic stiffness. Considering the overload and underload conditions, a dynamic equation is established as a Helmholtz-Duffing equation, and the resonance response of the nonlinear system is determined by employing the harmonic balance method (HBM). The frequency response curves (FRCs) are obtained for displacement excitations. The absolute displacement and acceleration transmissibility are defined and investigated to evaluate the performance of the nonlinear isolator, and they are compared with an equivalent linear isolator that can support the same mass with the same static deflection as the proposed isolator. The effects of the amplitude of the excitation, the offset displacement, and the damping ratio on the dynamic characteristics and the transmissibility performance are considered, and experiments are carried out to verify the above analysis. The results show that the overload and underload system can outperform the counterparts with the linear stiffness, softening stiffness, softening-hardening stiffness, and hardening stiffness with the magnitude of the excitation amplitude, and that its isolation performance is generally better than that of a linear system. The transmissibility, response, and resonance frequency of the system are affected by the excitation amplitude, offset displacement, cubic stiffness, and damping ratio. To obtain a better isolation performance, an appropriate mass, not-too-large amplitude, and larger damper are necessary for the proposed isolator.
Highlights
The purpose of vibration isolation is to avoid or reduce the undesirable effects of vibration with the aid of a device that isolates the vibration sources
Considering the overload and underload conditions, a dynamic equation is established as a Helmholtz-Duffing equation, and the resonance response of the nonlinear system is determined by employing the harmonic balance method (HBM)
A nonlinear isolator composed of a curved-mount-springroller mechanism as the negative stiffness element and a vertical spring is studied theoretically and experimentally
Summary
The purpose of vibration isolation is to avoid or reduce the undesirable effects of vibration with the aid of a device that isolates the vibration sources. Passive vibration isolation and control is the most prevalent vibration-isolating approach. The theory for both passive linear and nonlinear vibration isolation has been fully studied [1,2,3]. A linear vibration isolator is the simplest and most effective passive vibration isolator, but such an isolator has a fixed stiffness and can only isolate a vibration that is √2 times greater than the inherent frequency of the isolator, with a poor capability to isolate low-frequency vibrations [4]. A nonlinear vibration isolator can obtain a lower dynamic stiffness and a higher static-carrying capacity, leading to an outstanding low-frequency vibration isolation performance [5]. Theories and applications of nonlinear vibration isolators have gained popularity among scholars and have become a hot topic in research
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