Failure Prediction of AISI 420 Martensitic Stainless Steel Using the Theory of Critical Distances

Abstract

This work aims to evaluate the capability of the theory of critical distances (TCD) to predict the static failure of U-notched AISI 420 martensitic stainless steel specimens with different geometric features under pure bending loading. Theoretical estimates of the stress intensity factor during fracture onset were calculated according to the line (LM) and point methods (PM), which consider the characteristic length L, inherent strength σ 0 , and notch tip radius ρ. Initially, L and σ 0 were determined on the basis of the material's properties (i.e., fracture toughness K Ic and ultimate tensile strength σ u,t ), resulting in imprecise estimates. Conversely, L and σ 0 determined using the appropriate analysis of linear-elastic stress fields ahead of notches with different sharpness provided highly accurate predictions. The microscopic study of fractured specimens ensured better comprehension of the results. Moreover, the accurate values of L and σ 0 were used to predict the failure of V-notched specimens.