Zones of material separation in simulations of cutting

• Atkins' variable-separable algebraic model well predicts the FEM simulation results
• Fracture toughness can be determined from the cutting force intercept.
• There exists a thin highly-damaged boundary layer in continuous chip cutting.
• The plastic work within the boundary layer measures the fracture toughness.
• The size of the boundary layer is possibly related with toughness-to-strength ratio.

FEM simulations of orthogonal cutting are reported in which both the Johnson–Cook (JC) constitutive relation and the Johnson–Cook separation (fracture or damage) criterion are used. Results demonstrate that the damaged regions, in which separation of material occurs at the tool tip, form thin boundary layers on the top of the machined surface and on the underside of the chip. Damage was calculated in terms of the parameters of the Johnson–Cook fracture criterion appropriate for A2024-T351 aluminium alloy. The size of the damaged layers is some 35 μm and appears to be independent of the uncut chip thickness t0t0 over the range investigated (50