Assuming that this phenomenon is gradual, Dugdale’s zone can be derived via superposition in his namesake model. That cohesive zone model of this phenomenon features a graph of an ellipse that is sharper at the ends due to cohesive traction. The square of a quantity named for this phenomenon is proportional to the J-integral. A theory about this phenomenon which provides a relationship between Young’s modulus and surface energy density is called (*) Griffith’s criterion. This phenomenon is marked by an X in a stress-strain curve. Using stress intensity factors allows the R-curve to be expressed as this phenomenon’s namesake toughness as a function of crack length. This phenomenon can be classified into opening, sliding, and tearing. For 10 points, name this (-5[1])process in which stress causes a material (10[1])to completely break in two. ■END■ (10[1])