Effect of amplitude on material removal behavior and surface formation in ultrasonic elliptical vibration cutting of tungsten heavy alloys

Ultrasonic elliptical vibration cutting (UEVC) has the advantage of extending the tool life and improving the surface finish, which can realize the precision machining of hard and brittle tungsten heavy alloys (WHAs). Combined with finite element simulation and cutting experiments, this paper studies the effect of two-phase amplitude on the stress, strain, surface morphology, and residual stress distribution of the machined surface of WHAs by UEVC and draws the following conclusions: the material removal mode of WHAs in UEVC is the “Compression-Shear-Tension” composite process, and the tool cuts into the workpiece through extrusion and then forms chips through shearing and pulling. The variation of the two-phase amplitude causes the surface morphology and plastic deformation of the machined surface to exhibit up and down fluctuations, while the surface residual stress shows an alternating distribution of tensile and compressive stress, and the tensile stress is mostly distributed on the surface bulge. Increasing the amplitude A_a along the cutting direction promotes the flatness and deformation homogeneity of the surface, effectively reducing the residual tensile stress. Increasing the amplitude A_b along the cutting depth direction reduces the surface residual tensile stress but leads to the roughening and inhomogeneous deformation of the machined surface. Therefore, from the point of view of reducing the surface roughness and improving the fatigue life, the large A_a should be selected in UEVC of WHAs. In order to suppress the deterioration of the machined surface mass as large A_b is applied, it is necessary to ensure that A_a is larger than A_b.