THE CORRELATION BETWEEN CHARPY FRACTURE ENERGY AND FRACTURE TOUGHNESS FROM A THEORETICAL POINT OF VIEW

摘要

Empirical correlation formulas are often used to estimate fracture toughness from the Charpy fracture energy - although they are known to be in general of poor accuracy and valid only with restrictions to certain classes of materials. In the present paper these relations are dealt with from a theoretical point of view, by extending an approximate single specimen method to determine dynamic J-R-curves from impact bending tests to the case of a classical Charpy test. Surprisingly - since there seems to be no direct physical relationship between crack initiation and the ductile fracture energy - a mathematical relation was found to hold between these two parameters. As expected, this relation is not unique, but dependent on some material properties like tensile strength and uniform fracture strain. The relation turned out to be in good agreement with experimental data and the current empirical correlation formulas, giving some theoretical support to the latter and confirming the present model.