Shock isolation performance of a nonlinear isolator using Euler buckled beam as negative stiffness corrector: Theoretical and experimental study

Abstract

This paper concerns the shock isolation characteristics of a nonlinear isolator using Euler buckled beams as negative stiffness corrector. Both numerical and experimental studies are carried out. The non-dimensional dynamic equation of a single degree of freedom (sdof) nonlinear system composed by a loaded mass and the nonlinear isolator under shock excitation is established. The Runge–Kutta scheme is used for calculating the shock response for half-sine shock input. The performance of the nonlinear isolator is evaluated by the absolute acceleration response of the mass and the relative displacement of the isolator. The nonlinear isolator is assumed to work at three operating points, which are a quasi-zero stiffness (QZS), a Duffing-type non-zero stiffness and a Helmholtz–Duffing-type non-zero stiffness. It is shown that the dynamic stiffness characteristics in the working range is very important and will dominate the maximum response for shock isolation. The nonlinear isolator outperforms the linear one provided that the duration of the input shock is very small compared to the natural period of the linear system. The nonlinear isolator with QZS is not the optimized one for shock isolation. The nonlinear isolator with Duffing-type stiffness, which possesses a little positive stiffness, shows enhanced shock isolation capability. The performance of the nonlinear isolator with Helmholtz–Duffing-type stiffness will deteriorate as the overload increases. An experiment apparatus is built to test the shock isolation performance of the proposed nonlinear isolator that works at a Helmholtz–Duffing operating point. The comparative experiments for the nonlinear isolator and the linear isolator under half-sine shock excitation with different excitation levels are carried out. The experimental results validate the superior performance of the nonlinear isolator to the linear one and some interesting phenomena observed by theoretical study.