Effective Frequency Range and Jump Behavior of Horizontal Quasi-Zero Stiffness Isolator

Abstract

The quasi-zero stiffness (QZS) isolator shows excellent characteristics of low-frequency vibration isolation. However, the jump behavior caused by the strong nonlinearity is a primary reason for the failure of QZS isolators. In order to grasp the effective frequency range and failure mechanism of a horizontal QZS isolator comprehensively, the dynamics of the isolator were studied in the following two cases. In the first case, the isolator is subject to a base displacement excitation; in the second case, the isolator is installed on a linear structure that is subject to a harmonic force. The nonlinear algebraic equations describing the steady-state response of the two systems were derived via the complexification-averaging method, and the results obtained using the derived expressions were verified by comparing the results of the complexification-averaging method and the Runge–Kutta method. The effective frequency ranges of the isolator were then obtained, and the jump phenomena in the response amplitude induced by the strong nonlinearity of the isolator were analyzed. The results show that when the excitation amplitude is small, the vibration isolation system does not exhibit jumping behavior and the effective frequency range is relatively wide. With increases in the excitation amplitude, the system can exhibit jumping behavior when an additional impact load is considered, and this phenomenon leads to a narrowing of the effective frequency range. The characteristics of the jump phenomena produced in the two cases were analyzed, and the differences in the jump behaviors were elucidated. Furthermore, the effect of the isolator parameters on the effective frequency range was investigated.

Keywords

• vibration isolation
• strong nonlinearity
• additional impact
• lowest effective frequency