Rotary ultrasonic machining of ceramics: Characterization and extensions

Advanced ceramics are attractive for many engineering applications due to their superior special properties. One of the reasons hindering their market expansion is the high cost of machining with current technology. There is a crucial need for the development of machining processes which are capable of achieving high material removal rate while maintaining the surface/subsurface damage to the machined parts at an acceptable level. Rotary Ultrasonic Machining (RUM), a hybrid machining process combining the material removal mechanisms of diamond grinding and ultrasonic machining, has the potential to do so.The objectives of this research are to investigate the material removal mechanisms involved in RUM, to model the RUM process, and based on this, to extend the process to face milling and characterize its performance.In this dissertation, the characterization of the RUM process will be discussed first. Experimental evidence has showed that, in RUM of ceramic materials, there exist two different material removal modes: brittle fracture and ductile flow. A mechanistic model based on the assumption that brittle fracture is the dominating material removal mode has been developed. This model, for the first time, makes it possible to predict MRR from the process control variables together with an experimentally determined model parameter. The predicted relations between MRR and the process variables agree fairly well with the experimental trends. An approach to modeling the ductile mode removal mechanism will also be discussed.Next, the extension of RUM to face milling of ceramics will be discussed. The limitation of commercial RUM equipment is that only circular holes can be efficiently machined. Attempts have been made by other researchers to extend RUM to machining flat surfaces or milling slots. However, these extensions either changed the involved material removal mechanisms or had some severe drawbacks. To overcome the shortcomings of the existing methods, a new approach to extend RUM to face milling of ceramics is proposed. The development of the experimental apparatus, the preliminary experimental results, and the results of a set of fractional factorial experiments will be presented. A Boolean germ-grain model has been developed to characterize the process.U of I OnlyETDs are only available to UIUC Users without author permissio