In-process measurement of vibrations in ultrasonic vibration superimposed turning using mechanical feedback signals

Performance of components or systems can be significantly enhanced by surface microstructuring. Ultrasonic vibration superimposed turning is a highly efficient method for this, including the microstructuring in finish machining. However, control of these processes under varying loads is difficult and requires constant regulation of the systems operating frequency and vibration amplitude. Applying sensors to measure mechanical vibrations and using them to control the system offers benefits over conventional approaches like phase-locked-loop (PLL) or autoresonant control. In the experimental investigations, two sonotrodes are designed to integrate a variety of sensors for vibration measurement. Strain gauges, fiber-optical sensors, an accelerometer, and a passive piezoelectric disk in the ultrasonic transducer have been chosen. The performance of the sensors is examined for a free vibration as well as in an ultrasonic vibration superimposed turning process. The sensors are evaluated at different operating frequencies and power levels as well as varied loads during manufacturing resulting from different feeds (0.05 mm and 0.1 mm). Furthermore, the cutting speed is varied (120 m/min and 480 m/min) to change the rotational frequency of the spindle. Results show that all of the sensors prove useful in measuring the vibrations and determining the resonance frequency of the system during operation. The research improves understanding of the benefits of measuring different mechanical properties (strain, acceleration) in ultrasonic vibration superimposed turning, allowing for a more accurate in-process monitoring of the ultrasonic vibration and the control of the system in the future.