SEM observations of grinding debris indicate material removal mostly by brittle fracture, except under extremely fine grinding conditions. In an attempt to account quantitatively for the magnitude of the specific grinding energy, the portion of energy associated with brittle fracture can be estimated as the product of the surface area generated by fracture and the fracture energy per unit area of surface generated [25]. For simplicity it is assumed that particles removed by grinding are cubes of dimension b. Approximating the fracture surface energy by half the critical energy release rate Gc (Gc = Kc2/E, where E is the elastic modulus and Kc the fracture toughness) for crack formation (two surfaces), the specific fracture energy for grinding is:
equation(3.1)
uf=3Gc/b