loaded in tension (Fig. 3a), for example, the necked down process
region is located in-between the notches and is assumed to have
a height h < d, which should be similar to the thickness t of the
specimens (Hill, 1952).
Under these circumstances, the incremental work RdA dissipated
within an incremental volume hdA during crack nucleation
(or propagation) corresponds to the plastic work per unit of volume
at the onset of fracture (please refer to the volumes that are
schematically shown in the detail of Fig. 3a),