A new study published in Engineering delves into the material removal mechanisms in ultra-high-speed machining (UHSM), a key technology in advanced manufacturing.

High-performance engineering materials pose challenges in machining, such as low efficiency, poor surface integrity, and rapid tool wear. UHSM has been seen as a potential solution. However, the underlying material removal mechanisms remain unclear.

The researchers first reviewed the criteria for evaluating the ductile and brittle behaviors of materials during machining. They proposed the concept of the relativization of ductile-brittle property, emphasizing that there are no absolutely ductile or brittle materials. The ductility-brittleness transition can be induced by various factors, including machining conditions. For example, changing the machining environment or parameters can trigger this transition.

Three typical material removal mechanisms were summarized: ductile-mode removal based on shear stress, brittle-mode removal based on tensile stress, and extrusion removal based on compressive stress. The brittle-mode removal was found to have a broader range of applicability.

In UHSM, several important mechanisms were explored. High strain-rate-induced material embrittlement was analyzed from mechanical and stress wave perspectives. The thermal effect in UHSM was also investigated. Heat generation and transfer differ between ductile-mode and brittle-mode removals.

The study also focused on the ductile-brittle transition region (DBTR) under high-strain-rate conditions. Chip morphology in the DBTR becomes diverse, and the material removal mechanisms involve complex dislocation movements. A model based on dislocation mobility, modified by the dislocation bypass mechanism, can explain the material removal mechanisms in the DBTR.

Furthermore, the discussion section further standardizes the definition for UHSM, mainly exploring the transition of dislocation movement state at high strain rates, as well as the impact of the UHSM on crack propagation. Finally, the research hotspots and future perspectives of UHSM are prospected.

This research provides a comprehensive understanding of material removal mechanisms in UHSM, which is expected to promote the industrial application of UHSM technology. Future research directions include exploring the influence of UHSM on composite materials, the microstructure of the workpiece subsurface, and developing more suitable material constitutive models for brittle-mode removal in UHSM.

The paper “Material Removal Mechanisms in Ultra-High-Speed Machining,” authored by Hao Liu, Jianqiu Zhang, Qinghong Jiang, Bi Zhang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.12.033.