Experimental study on rotary ultrasonic machining (RUM) characteristics of Nomex honeycomb composites (NHCs) by circular knife cutting tools

Heterogeneous material properties and complex cellular hexagonal thin-walled lightweight structure of Nomex honeycomb composites (NHCs) pose significant challenges to achieve high quality processing in terms of low machinability, specialized cutting tools design, precision and influence of processing parameters on surface quality and cutting force. Surface defects have substantial impact on the functional performance and service life of sandwich structural components of NHCs used in aerospace, defense and automotive industries. In this paper, series of single factor and four-factors 4-levels orthogonal experiments were performed to study the effects of processing parameters on rotary ultrasonic machining (RUM) characteristics in terms of cutting force and surface quality by ultrasonic circular saw blade (UCSB) and ultrasonic circular knife (UCK) cutting tools. Furthermore, comparison of NHCs core workpiece cutting on RUM machine tool with ultrasonic vibration (UV) and without UV was conducted by both UCK and UCSB cutting tools. Experimental results proved that the cutting force increases with increase in feed rate and cutting depth whereas, it shows inverse relation with spindle speed and vibration amplitude. Cutting width has greater influence on cutting force among all processing parameters. UCK cutting tool generates less number of burr but length of burr is long and some tearing defects exists whereas, UCSB cutting tool produces large number of burr with very short burr length, no tearing defects and no uncut fibers. Moreover, NHCs core workpiece cutting on RUM machine tool with UV gives better surface quality and lower cutting force compared to without UV. The present study can be used as basis for comprehensive understanding of NHCs processing mechanism, cutting tools design and processing parameters optimization.