Analysis of a Nonlinear vibration absorber for vibration control in a hand-held impact machine

Abstract

Hand-held impact machines (HIMs), such as jackhammers and chipping hammers, operate through the repetitive impacts of a percussive mechanism. Due to their widespread use, it is essential that these tools are designed for safe daily operation. This need is underscored by the fact that approximately 20% of operators risk developing vibration-related hand injuries, which can be career-ending. As a step toward improving the safety of these tools, this dissertation focuses on modeling their dynamic behavior to evaluate the effectiveness of vibration control strategies. The novelty of this work lies in the use of nonlinear mass– spring–damper models to describe tool dynamics, coupled with lumped-mass models of the hand–arm system. Traditionally, linear models have been employed for such evaluations; by contrast, this study introduces nonlinear modeling to capture the more realistic dynamics of HIMs. Furthermore, the role of a cubic nonlinear absorber in attenuating vibrations transmitted to the hand is systematically investigated through this framework. Key findings include the observation of nonlinear phenomena such as unstable periodic solutions, quasi- periodicity, chaos, and grazing. Frequency response analyses demonstrate the superiority of the cubic absorber over its linear counterpart, with notable improvements in performance when combined with an inerter. Parametric studies further reveal how the absorber can be tuned to enhance vibration attenuation across different nonlinear HIM models.