Influence of inertance and nonlinear damping on performance of NES based vibration absorber system

Abstract

Passive vibration control techniques such as dynamic vibration absorber (DVA) based on linear viscous dampers have been extensively studied and used in various applications. However, their efficiency is limited when applied to systems with uncertain modal parameters or systems with multiple natural frequencies. A transition from linear to nonlinear vibration absorption, based on the thought process of exploiting nonlinearity to enhance the performance of the systems, resulted in efficient techniques for vibration absorption. Among this, Nonlinear Energy Sink (NES) gained wide attention due to its effectiveness to reduce vibrations through targeted energy transfer (TET) mechanism. NES is a passive absorber with a mass, an essential nonlinear stiffness and damper. Being a nonlinear system it does not have a preferential natural frequency and can therefore interact with the primary system over wider range of frequencies to increase the performance. Despite its effectiveness, two critical drawbacks of NES are the mass of the NES and the threshold of external excitation needed to commence targeted energy transfer. In this thesis, a new NES design has been proposed to overcome these drawbacks, including an inerter and nonlinear damping. The coupling of linear systems to NES with nonlinear stiffness and linear damping has been extensively studied, but research on nonlinearly damped NES with inerter remains scarce. This thesis investigates two main directions for effective vibration suppression of mechanical systems using NES: (i) the effect of adding nonlinear damping to the NES, and (ii) the performance enhancement of the NES absorber system with the addition of inertance and nonlinear damping under low-intensity external excitation. This study can provide a broader perspective on the current vibration mitigation mechanisms and guidance for their improvement. To achieve this objective,we develop a general framework that allows us to understand the dynamics behind the proposed NES and address the significant drawbacks..