Mathematical model of thrust force for rotary ultrasonic drilling of brittle materials based on the ductile-to-brittle transition phenomenon

Modelling the thrust force of rotary ultrasonic drilling (RUD) is an important aspect for optimizing the process parameters and predicting the material cracking and edge chipping. Mainly, the material removal of brittle material occurs mainly through the brittle mode, while the ductile mode occurs in case of micro or nano-depth of cut. This paper introduces a mathematical model for thrust force based on the two material removal modes. The mathematical model correlates the thrust force with the material characteristics and the machining parameters as feed rate, spindle speed, ultrasonic amplitude, frequency and tool abrasive size, tip angle, and concentration. Complete hole drilling and scratch-drilling with depth of 10-m experiments are conducted in soda glass to verify the model. Thrust force measurement and microstructure features are used to verify the model. The predicted model results agree with the experimental results. The model predicts that the range of feed rate and spindle speed produce the ductile mode cutting.