On the use of the Theory of Critical Distances to design notched metallic components against dynamic loading

The Theory of Critical Distances (TCD) is a well-known design method allowing the strength of notched/crack components to be estimated accurately by directly post-processing the entire linear elastic stress fields damaging the material in the vicinity of the stress raisers being designed. By taking full advantage of the TCD’s unique features, in this thesis, the TCD is reformulated to make it suitable for predicting the strength of notched metallic materials subjected to dynamic loading by post-processing both linear elastic and elastoplastic stress distributions. The accuracy and reliability of the proposed reformulation of the linear elastic TCD were checked against a number of experimental results generated by testing, under different loading/strain/displacement rates, notched cylindrical samples of aluminium alloy 6063-T5, titanium alloy Ti–6Al–4V, aluminium alloy AlMg6, and an AlMn alloy. To further validate the proposed design method also different data sets taken from the literature were considered. Such an extensive validation exercise allowed us to prove that the proposed reformulation of the TCD is successful in predicting the dynamic strength of notched metallic materials falling within an error interval of ±20%. Such a high level of accuracy is certainly remarkable, especially in light of the fact that it was reached without the need for explicitly modelling the stress vs. strain dynamic behaviour of the investigated ductile metals. Additionally, the FEM with Simplified-Johnson Cook elastoplastic material model was used to predict the dynamic strength of notched metallic material falling within an error interval of ±20%. Moreover, the elastoplastic TCD was also provided to be capable of predicting the dynamic strength of notched metallic materials falling within an error interval of ±6%.