Ultrasonic elliptical vibratory nanocutting mechanisms of Cu50Zr50 amorphous alloy: A molecular dynamics simulation

The mechanical properties of amorphous alloy have been proven to be unique and have a great application value. In this study, the deformation mechanism of Cu50Zr50 amorphous alloy during ultrasonic elliptical vibration cutting (UEVC) was revealed via molecular dynamics simulation in detail. It is founded that the amorphous alloy was more easily removed via repeated extrusion during UEVC. The reason is that the shear transition zone (STZ) can be activated and proliferated from the perspectives of the instantaneous change of cutting angle, the reversal of friction, the increase of free volume and the increase of atomic movement. The influences of the evolution laws of shear strain, cutting temperature, cutting forces, and material removal rate (MMR) under different ultrasonic frequency, amplitude ratio, and phase angle were also investigated. The results showed that the dynamic shear strain reactivation of amorphous alloy was realized from shear strain zone (ηMises>0.1) to shear strain zone (ηMises>1.0), following by the STZs and the formation of shear band. Simultaneously, UEVC increases the von Mises shear strain comparing with the conventional cutting, and the energy required for plastic deformation was reduced due to the special driving forces for atomic movement. In addition, the cutting temperatures in UEVC are higher than conventional cutting in all cases, and the UEVC provides a 47.49 % reduction in maximum cutting forces and a 14.22 % reduction in average cutting forces. What's more, the height of chip atomic piled-up increases from 12.5 Å to 21.0 Å due to the periodic changes of cutting depth, which improves the MMR effectively. The research is able to enrich the understanding of nanoscale deformation mechanisms in ultrasonic elliptical vibration nanocutting of Cu50Zr50 amorphous alloy.