Research on sensitivity of strain rate in ultrasonic elliptical vibration cutting of tungsten alloys

Abstract

Ultrasonic elliptical vibration cutting (UEVC) is represents an effective approach for achieving ultra-precision machining (UPM) of tungsten alloys, yet its underlying mechanisms remain incompletely understood. This study investigates the influence of strain rate effects on the material removal and surface formation of UEVC tungsten alloys. First, the strain-stress curves at varying temperatures are obtained by using Hopkinson bar test to verify the strain rate sensitivity of mechanical properties and fracture mechanisms. Then, the strain rate calculation model of UEVC zone is established basing on the dynamic vibration speed of the tool, and the nonlinear relationship between the strain rate and ultrasonic elliptical vibration parameters and cutting parameters is analyzed. The strain rate increases with the increase of two-phase amplitude and phase difference through FE simulation quantitative analysis, and the phase difference is the most sensitive factor. Finally, cutting experiments show that increasing the phase difference can improve the plastic removal mechanism of tungsten alloys and continuously reduce the surface roughness to 32 nm. Concurrently, the increase of phase difference significantly increases the dislocation density to 3 × 1017 m−2, the depth of the grain refinement layer is increased to 1300 nm, and the grain size is significantly reduced, which collectively exhibits potential performance optimization effects on the ion impact resistance of tungsten alloy components.