On the plane-stress essential fracture work in plastic failure of ductile materials

In plane-stress ductile fracture, the irreversible work dissipated inside the fracture process zone (FPZ) is a material constant for a given sheet thickness and is called the specific essential fracture work (w_e). However, work dissipated elsewhere in the outer plastic zone is nonessential and is dependent on specimen geometry and size. In this paper, a theoretical basis for the essential fracture work is given and a simple but elegant experimental method is presented to separate the essential work from the total fracture work. In-plane mode I (opening) and mixed mode I/II (opening/sliding) as well as out-of-plane tearing mode III fractures are analysed. Experiments are conducted on a range of ductile engineering materials including metals, polymers and papers to illustrate the working principles of the theory.