Experimental results on chatter reduction in turning through embedded piezoelectric material and passive shunt circuits

Chatter instability is an important drawback concerning high precision and accurate machining operations. Suitable strategies for chatter detection and reduction should be proposed and exploited in order to ultimately improve the final quality of machined parts. It is well known that chatter instability can be reduced by increasing damping since the later presents a proportional relationship with stability limits. The main idea in the present work is to address the issue of chatter instability by proposing a vibration reduction methodology through the use of embedded piezoelectric patches in the tool-holder connected to a passive shunt electrical circuit. This circuit is responsible for energy dissipation providing extra damping to the system. The strategy is numerically and experimentally tested in turning/boring operations. A simplified electro-mechanical distributed-parameter model is briefly described and numerically evaluated in order to assess the potentiality of the proposed technique. Actual measured frequency response functions of the tool-holder with different shunt strategies are compared demonstrating how damping can be modified. Moreover, two different shunt strategies are evaluated during a boring operation. Preliminary experimental results point to a considerable improvement in the quality of the surface finishing when the proposed passive shunt circuits associated to the piezoelectric elements are used, indicating that the proposed strategy can be a promising and feasible solution for chatter reduction. Nevertheless, there are still some technical difficulties that should be overcome towards the full practical implementation of the proposed methodology.