Prediction of Fracture Toughness K_Ic of Steel from Charpy Impact Test Results

Abstract

This paper presents a method to predict the fracture toughness K_Ic and/or K_Id of steels using their Charpy impact test results and tensile properties. The fracture toughness, Charpy impact and tensile properties of 21/4Cr-1Mo, ASTM A508 Cl.1, A508 Cl.2, A508 Cl.3 and A533 Gr.B Cl.1 steels were measured and analysed on the basis of the excess temperature (test temperature minus FATT) and Rolfe-Novak correlation. The relationship between K_Ic/K_Ic-us and the excess temperature, where K_Ic-us is the upper-shelf fracture toughness K_Ic predicted by Rolfe-Novak correlation, discloses that the K_Ic transition curves of several steels are representable by only one trend curve of K_Ic/K_Ic-us or K_Id/K_Id-us versus excess temperature relation. This curve is denoted as a “master curve”. By using this curve, the fracture toughness of steel can be predicted using Charpy impact and tensile test results. By taking account of the scattering of both the fracture toughness and Charpy impact test results, the confidence limits of the master curve were also determined. Another approach to develop more general procedure of predicting the fracture toughness K_Ic is also discussed.