The SED criterion is applied here assuming linear elastic behaviour,however the present tests were characterized by a nonlinear behaviour. Therefore some assumptions have been made in order to translate our modest non-linear behaviour to an elastic linear one for the evaluation of the parameters required for the definition of the control volume. It is worth mentioning that also Seweryn [7] applied successfully a linear elastic fracture criterion based on the critical value of the notch stress intensity factor although for duraluminum specimens some visible plastic deformations were present. Unnotched specimens often exhibit a nonlinear behaviour also under tensile loading whereas the overall behaviour of notched specimens remains linear as underlined