Critical undeformed chip thickness of brittle materials in single point diamond turning

In this work, the ultimate compression force that enables the plastic removal of brittle materials in diamond turning is initially modeled according to the theory of rigid-plastic mechanics. And subsequently, an independent oscillator model is reconstructed to calculate the microfriction force that appears at contact interface. As expected, a predictive model considering the ultimate compression force and microfriction force is finally established to calculate the critical undeformed chip thickness of brittle materials in diamond turning, in which a crack-free surface of brittle materials can be achieved as quickly as possible in a brittle-ductile coupled cutting mode. Based on the theoretical predictions and experimental observations, the “size effect” of the critical undeformed chip thickness is discovered, i.e., that the ratio of the critical undeformed chip thickness to tool cutting edge radius increases with the decrement of tool cutting edge radius. Such interesting variation law is attributed to the strengthening of the effect of the microfriction and concentration of the compressive stress under a small enough cutting edge radius, which produces more favorable conditions for the brittle-ductile coupled removal of brittle materials.