The effects of thermo-mechanical load on the vibrational characteristics of ultrasonic vibration system

The vibrational characteristics of ultrasonic vibration system play an important role in the stability and processing effect in ultrasonic machining. In this study, a theoretical analysis and experimental verification were employed to investigate the effect of the thermo-mechanical load on the vibrational characteristics of ultrasonic vibration system. Initially, a dynamic model was designed to analyze the influence of the thermo-mechanical load on the vibration characteristics. Based on the model, the single variable method was adopted to explore the effect of different mechanical loading and the rigidity coefficient of the tool on the vibrational characteristics. Then the experiment was conducted by imposing variable loads on the tool end face, and the amplitude, current, frequency and temperature of ultrasonic system were measured. Finally, the ultrasonic vibration drilling test was conducted to verify the experimental results. It was observed that the ultrasonic amplitude initially increased and later decreased with the increase in static load. In addition, with the increase in static load, the thermal effect was significant and the ultrasonic frequency presented a similar tendency, as the ultrasonic amplitude. Meanwhile, the variation of ultrasonic frequency was not significant under the thermo-mechanical load. The results of this study could provide a favorable reference in the design of an ultrasonic vibration system and selection the different tools in ultrasonic machining.