In-situ characterization method for tool ultrasonic vibration in rotary ultrasonic machining based on radiated acoustic pressure

In order to be used in the CNC machining center, one rotary ultrasonic machining (RUM) system needs to adapt to various cutting tools. Corresponding ultrasonic vibration units are often designed to work in a local resonant state rather than a full resonant state due to the diversity and complexity of tool shapes. Since the frequency at which the vibration of various cutting tools reaches the maximum is probably different, it is necessary and important to in-situ determine the working frequency of cutting tools in RUM. The key to determining working frequency is to characterize the tool vibration. Although the existing optical and electrical methods have been widely used for tool vibration characterization in some scenarios, they still have obvious limitations when applied to in-situ characterization in RUM systems. In this context, an in-situ characterization method for the tool ultrasonic vibration based on radiated acoustic pressure is presented in the paper. Firstly, characteristics of acoustic pressure distributions radiated from typical cutting tools in RUM are comprehensively studied based on analytical analysis, numerical simulation, and experimental measurement. Secondly, based on the relationship between the acoustic pressure and tool vibration, the measurement strategy and corresponding in-situ measurement system for acoustic pressure are developed to characterize the tool vibration in RUM. Finally, a series of experiments are conducted by using the measurement system, including determining the working frequency of cutting tools and quantitatively describing the vibration amplitude in RUM. It is shown that the proposed method is efficient and cost-effective for the in-situ characterization of the ultrasonic vibration of various cutting tools in RUM, especially for complexly shaped tools working in a local resonant state.