Wear at an incipient ploughing-cutting transition

Ductile wear is highly desirable in manufacturing and machining operations to achieve a high quality of finish. In a ductile regime of operation, a characteristic transition from ploughing to cutting is often observed in materials with different mechanical properties. We unveil the origin of this transition through a plastic, debris -free model of a tip causing wearing of a flat surface. The abraded volume depends on the equilibrium depth which is reached once the normal force is balanced by the lifting force during scratching. We show that the dependence of the equilibrium depth on the lifting force is highly non-linear and diverges above a threshold force that depends on the hardness, friction force and geometry of the tip. The threshold corresponds to a characteristic depth marking the ploughing-cutting transition. When this characteristic depth is below the ductile-brittle depth of cut, ploughing, cutting and brittle modes of operation are all possible. These abrasive wear modes are summarised in a unified mechanism map. The findings of this model, derived from theoretical considerations, are validated by DEM simulations and literature data from experiments.