Mechanism (biology)

Quantum mechanics

Chip formation

Engineering

Metallurgy

Materials science

Shearing (physics)

Vibration

Acoustics

Silicon

Tool wear

Geology

Physics

Amplitude

Optics

Environmental science

Composite material

Machining

Strain rate

Extrusion

International Journal of Mechanical Sciences

Atomic force microscope (AFM) tip-based nanomilling has drawn significant attention because it can greatly improve the material removal rate. Previous studies have mainly focused on the machining process of two-dimensional (2D) nanomilling. However, the material removal mechanism and subsurface damage in three-dimensional (3D) ultrasonic vibration-assisted nanomilling (UVAN) are still unclear. Thus, by considering single-crystal silicon as the sample material, we investigate 3D-UVAN using experiments and molecular dynamics (MD) simulations. The material removal mechanisms for 3D-UVAN are uncovered first. We find that the material removal is dominated by shearing and extrusion, respectively, when the maximum undeformed chip thickness (UCT) is larger and smaller than a critical value. The strain rates generated by 3D-UVAN and 2D nanomilling are calculated by considering the machining velocity. It is higher for 3D-UVAN than for 2D nanomilling, which induces a fracture chip. The effects of vertical vibration amplitude and frequency in 3D-UVAN on the subsurface damage are investigated by MD simulation. Results show that the induced immobile dislocations lead to embrittlement of the material. Furthermore, a high strain rate occurs at a large vertical vibration amplitude and high frequency, which contributes to a shallow subsurface damage. This is also verified by TEM experiments. Thus, our findings enrich understanding of the material removal mechanism in 3D-UVAN and suggest a new route for suppressing subsurface damage.

Material removal mechanism and subsurface characteristics of silicon 3D nanomilling