In the previous chapter, we considered the limitations of linear elastic fracture mechanics (LEFM) for testing materials in which fracture is accompanied by large-scale plastic deformation. These are high fracture toughness, low yield strength materials used in power generation, construction, and chemical industries. Because of the success in the use of LEFM for predicting fracture in high-strength, low toughness materials used in the aerospace applications, it is natural to address these limitations and extend fracture mechanics approach for predicting fracture in components made from “ductile” materials.