This PhD research work aims to reformulate the so-called Theory of Critical Distances (TCD) to make it suitable for predicting failures in notched metallic materials as the rate of the applied loading increases. Over the last 80 years, such a theory has been successfully employed to predict both static and fatigue failures in notched components, exploring its accuracy and its reliability in different ambits of the structural integrity field. In most of these previous applications, the stress fields in the relevant region close to the notch could be assumed to be linear-elastic without much loss of accuracy. In this context, the aim of this research activity is to investigate whether this linear-elastic TCD can also be successful in predicting failures in notched metallic components when the final breakage is preceded by large-scale plastic deformations, the local plastic behaviour depending on the rate of the applied loading. Notched specimens containing different geometrical features will be tested under tensile loading, by subsequently attempting to predict failures by directly post-processing the results of linear-elastic Finite Element Analysis (FEA).