Fig. 4: Constitutive behavior on the cutting surface investigated with the computational model: unstable indentation-to-cutting transition and contact pressure behind the crack front.

a.1–3 Unstable indentation-to-cutting transition in a gelatin hydrogel at an indentation of the cutting tool where the strain energy of the continuum suffices to overcome the cohesive energy to create a new cutting surface. The onset of cutting occurs at the center of the sample beneath the center of the cutting tool. a.4-6 Detail of the transition with schematics of the cutting tool. a.7–9 Equivalent Von Misses stress (σ_VM) at the cutting surface driving the indentation-to-cutting transition. b.1–3 Decrease in the contact pressure t_N in a gelatin hydrogel at the cutting surface. A normal stress prevents the interpenetration of material and the cutting tool along the transition. b.4-6 Tangential contact stress t_T magnitude due to adhesion and wear along the transition. c.1,3,5 Contact pressure behind the crack front at a stage after the cutting tool has advanced in the cutting regime (a displacement of the cutting tool of 13 mm) for the gelatin hydrogel, elastomer, and meat-based food material. The contact pressure in the cutting surface is negligible behind the cutting front---at the sides of the blade. c.2,4,6 Binary field that represents the state of normal contact. Coulomb friction is zero in the areas where contact is inactive and minimal when contact occurs, but the contact pressure is negligible.