On the shock performance of a nonlinear vibration isolator with high-static-low-dynamic-stiffness

• The shock characteristics of an isolator with geometric nonlinear stiffness are studied.
• Rounded step and versed sine displacements are used as base shock excitation.
• Closed-form solutions for a step or an impulse base excitation case are obtained.
• Increasing nonlinearity is beneficial when the shock input amplitude is small.
• The shock isolation performance of the quasi-zero stiffness system is the best.

The vibration isolation characteristics of a high-static-low-dynamic-stiffness (HSLDS) isolator, which has geometrically nonlinear stiffness, have been well established both theoretically and experimentally in the recent literature. However, the shock isolation characteristics of such an isolator subject to base excitation are not currently known. In this paper, these characteristics are determined for two illustrative inputs, which are a rounded step and a versed sine displacement, using a simple model of the isolator comprising a vertical spring coupled to two horizontal springs. The isolator is configured to reduce the dynamic stiffness of the isolator and hence increase the frequency range of isolation. The shock responses of the isolator are determined analytically for low levels of excitation, and numerically for high levels of excitation. It is found that when the shock amplitude is small, the nonlinearity is beneficial, and that the quasi-zero stiffness isolator has the best shock performance in terms of the smallest displacement and acceleration of the suspended mass.