Design and optimization of nonlinear vibration isolator in two degrees of freedom

Mechanical vibrations affect all manner of structures and systems. Vibration effects are usually not desired; they might cause fatigue, sudden failure, or affect sensitive sensors. Vibration isolators are essential components that suppress or eliminate vibration effects. Towards this goal, many types of active and passive vibration isolators exist. Passive isolators have two main categories, which are linear and nonlinear. The type which is being discussed throughout this thesis is of the passive nonlinear type. More specifically, it is a type of high-static-low-dynamic-stiffness, hardening, and nonlinear due to geometry vibration isolator in two degrees of freedom. Single degree of freedom quasi zero stiffness (SDOF QZS) isolators are also a part of this type. The optimization and performance of SDOF QZS isolators are well established. However, they are not suited to handle excitation on two axes. Therefore optimization and performance of a more general type in two degrees of freedom isolator is investigated. The isolator is considered with simple linear springs, but the geometry of the springs causes inherent nonlinearities. Optimization is carried out using genetic algorithms in conjunction with a Runge-Kutta numeric solver because of the nonlinear nature of the isolator. The algorithm of the optimization process is laid out and benchmarked against an equivalent QZS isolator.