An energy-based crack extension formulation for crack resistance characterization of ductile materials

Crack resistance behavior is an important property for reactor pressure vessel embrittlement evaluation as reactors operate in the upper shelf ductile regime. This property consists in evaluating the change of crack length with the applied loading expressed in terms of the J-integral. While J-integral formulation is available for standard geometries and it is relatively easy to determine, crack extension is either measured directly on the fracture surface of a number of specimens or estimated from one single specimen, necessitating sophisticated instrumentation. Based on a number of experimental observations, a simple procedure is presented which is based solely on the load-displacement test record and the initial and final crack length to determine the full crack resistance curve. The reliability of this new procedure for determining the crack resistance, the initiation toughness, and the tearing resistance is illustrated by several examples covering a wide range of materials and cracked specimen configurations.