The theory of critical distances

The aim of this review article is to introduce the theory of critical distances, to which this special issue of the journal is devoted. The theory of critical distances (TCD) is the name which I have given to a group of theories used for predicting the effects of notches and other stress concentration features. The basic methodology is described, along with a number of variants which have developed over the years. After a brief history of the TCD, the predictive power of this group of theories is demonstrated, showing that they are capable of predicting experimental data on fracture and fatigue in a wide variety of circumstances. After some discussion regarding the fundamental scientific basis of the TCD, areas for future work in this field are suggested.