Nonlinear Normal Modes in a Two-Stage Isolator Using a Modified Finite-Element Galerkin Method

Figure 2

Top plots: displacement amplitude-frequency responses for the payloads in four types of two-stage isolators, for , , , , and . Bottom plots: magnitudes of the force transmissibility in four types of two-stage isolators. Black dashed lines, linear two-stage isolator (corresponding to a model as shown in Figure 1(a) with ; red dashed-dotted lines, type I; green dotted lines, type II; blue solid lines, type III. The responses and the force transmissibility of three nonlinear isolators are compared for different values of the upper lateral stiffness : , , , and (if reaches a value beyond 1.15 when and , the nonlinear isolator systems can easily become bi-stable for small changes of stiffness, which is undesirable and is not considered in this work).

(a)

(b)