Investigation of Inerter-based Vibration Absorbers for Machining Chatter Stability

Regenerative chatter, which is unstable vibration, is one of the most important issues that limit milling operations' productivity. One way to suppress the regenerative chatter is to utilise passive control methods such as tuned mass dampers (TMDs). However, the performance of passive control devices that use traditional elements (e.g. spring and dampers) is generally limited. The inerter, is a relatively new mechanical element, has been explored to improve dynamic performance of passive control systems in a wide range of engineering fields. However, it has not been examined for machining chatter stability as yet. Hence, this thesis investigates possible performance improvement using inerters in milling operations, develops an inerter design integrated into a passive device as a localised addition, and presents experimental validations of the effectiveness of the developed device. The potential benefits of using inerters are initially shown by numerical evaluations considering only simple inerter-based layouts. These layouts are considered localised additions to provide a more versatile solution similar to a traditional TMD. Optimal design parameters of the elements in the layouts are numerically determined by performing computations witht the self-adaptive differential evolution (SaDE) algorithm. The numerical simulation results indicate that the layouts can significantly improve milling stability by up to 40% in some cases. Milling operations generally need small-scale passive control applications due to the limited space. Furthermore, numerical evaluations indicate that the inerter requires producing small inertance due to the optimal inertance values obtained. Therefore, design studies are presented to meet the design criteria without performance loss. The developed inerter is capable of producing small inertance. Moreover, it allows the small adjustment of inertance for fine tuning by simply attaching additional lumped masses to the inerter. Using the developed inerter and a gel damper which provides hysteretic damping, an inerter-based passive device is proposed with the advantage of being applicable into small-scale applications without the need for a grounded connection like a traditional TMD. A prototype of the proposed device is manufactured for experimental validations. The dynamic behaviour of the prototype is initially tested by impact hammer tests. These initial tests also indicate the effectiveness of the prototype in a vibration suppression case. Finally, the functionality and stability improvement of the prototype are examined and validated under real cutting conditions.