Modulated ultrasonic elliptical vibration cutting for ductile-regime texturing of brittle materials with 2-D combined resonant and non-resonant vibrations

In this study, modulated ultrasonic elliptical vibration cutting (modulated UEVC) is proposed to generate micro-structured surfaces on brittle materials in ductile-regime. A novel tool is first developed to generate 2-D combined resonant and non-resonant vibrations in a single compact structure. The ultrasonic elliptical vibration is excited at the coupled resonant frequency of 20 kHz to enhance the ductile-to-brittle transition depth, while the simultaneously generated non-resonant modulation motion (up to 2 kHz) is used to adjust the tool center to generate surface structures dynamically. A theoretical model is established to analyze the instantaneous uncut chip thickness in modulated UEVC by considering a more general case of an inclined elliptical vibration trajectory. The analysis indicates that the orientation angle of 135° is optimal to achieve the maximal critical depth-of-cut in ductile-regime cutting. Experimental results are provided to demonstrate the process capability and to verify the proposed theoretical model. Micro dimple arrays have been successfully generated using the proposed modulated UEVC for a depth-of-cut up to 700 nm in ductile-regime, and an extended depth-of-cut up to 1 µm with minimal surface damage.