Material Removal Mechanisms in Ultrasonic Elliptical Vibration Cutting of Single-Crystal Tungsten: A Molecular Dynamics Study on Process Parameters

Single-crystal tungsten is used in high-temperature and radiation-related applications because of its high strength, hardness, and thermal stability. Its high hardness and brittleness make it prone to surface damage and tool wear during machining. Ultrasonic elliptical vibration cutting, as an efficient non-traditional machining technology, offers a new approach to improve the machining quality of single-crystal tungsten. However, the micro-mechanism of ultrasonic elliptical vibration cutting on single-crystal tungsten still requires further exploration. To simulate the processes of conventional cutting and ultrasonic elliptical vibration cutting, a nano cutting model targeting single-crystal tungsten was proposed in this study. By analyzing the energy distribution rules, cutting force fluctuations, stress concentration changes, and dislocation nucleation/evolution mechanisms during the processing process, an in-depth investigation was conducted on the cutting mechanism characteristics of single-crystal tungsten under different cutting parameters. The simulation results showed that, at a nominal cutting speed of 50 m/s and an ultrasonic frequency of 20 GHz, the average tangential and normal cutting forces under UEVC were 336 and 86 nN, respectively, representing reductions of 54.1% and 70.2% compared with the corresponding CC values of 732 and 289 nN. Despite these reductions in the average cutting forces, UEVC generated higher transient peak forces than CC. Within the simulated frequency range of 10–40 GHz, the average tangential force decreased by 32.1%, and the normal force showed a net decrease of 58.3%, whereas the average Newton-layer temperature increased from 400 to 555 K by 38.8%. Ultrasonic vibration alters the surface stress distribution and atomic shear deformation degree, while also influencing subsurface dislocation patterns.