Semiactive Magnetorheological Damper for High Aspect Ratio Boring Process

This paper aims to develop a new semiactive damper to attenuate chatter vibration of a high aspect ratio boring bar. Design of the damper utilizes magnetorheological (MR) fluid and an electromagnet to control a damping force by a current input during machining process so as to effectively attenuate the chatter vibration. Various aspects of research on MR fluid and dynamic characteristics of boring operation and the MR damper have been investigated; First of all, effectiveness of MR fluid on attenuating vibration has been investigated by various designs of the damper and magnetic field. Then, the behavior of the MR fluid is simulated and its result is utilized to estimate dynamic motion of the MR actuator. Furthermore, simulation of the boring tool, force, and stability model shows significant improvement in machine chatter particularly for a high aspect ratio boring bar. The results provide a fundamental understanding to estimate dynamic vibration of the boring bar and offers optimal conditions for effectively attenuating chatter vibration. Finally, various experiments have been demonstrated to identify parameters of the MR damper and the results of boring machining show damper attenuation capability for wide frequency band by various cutting conditions corresponding to chatter frequencies.