Modified transformation formulae between fracture toughness and CTOD of ductile metals considering pre-deformation effects

Strengthening action and degrading action are proposed to describe influences of plastic deformation on fracture toughness in ductile metals. Strengthening effect represents the shield operation of dislocation from crack and degrading effect displays the emergence of damage. In order to demonstrate two effects, the existing transform equation between fracture toughness and crack-tip opening displacement is modified based on a novel damage variable. The modified transform formulae can help to find the maximum of fracture toughness for metals and keep safer performance for structural components.