On the stability of plastic flow in cutting of metals

We examine large-strain deformation and unsteady flow modes in cutting using high-speed imaging. For metals which exhibit large workability and strain hardening, the commonly assumed laminar flow is inherently unstable. Instead, the cutting is characterized by sinuous flow, with large-amplitude folding, that is triggered by a plastic buckling instability linked to the material microstructure. A microstructure basis is also suggested for shear band flow in high-speed cutting, with the band region showing a fluid-like characteristic with very small viscosity. Mechanochemical Rehbinder effects, long reported in cutting of metals, are found to be closely linked to the unsteady flow modes.