Improvement of machining stability using a tunable-stiffness boring bar containing an electrorheological fluid

In boring, cantilever structural boring bars limit machining regimes due to the development of chatter vibration. In this paper a new method based on a variable-stiffness boring bar containing an electrorheological (ER) fluid is proposed to suppress chatter in boring. ER fluids undergo a phase change when subjected to an external electrical field, the deformation modes of which are dependent on applied electrical field strength and strain amplitude. This phenomenon permits the global stiffness and energy-dissipation properties of the bar to be tuned on line by varying the electrical field strength. It is shown experimentally that chatter can be suppressed by continuously varying the stiffness of the bar in processes.