Relation between various fracture transition temperatures and the Ksub(IC) fracture toughness transition curve

A plane strain transition temperature for a given specimen thickness is defined for ferritic steels as the temperature along the Ksub(IC) transition curve where the ASTM validity limit is reached. It corresponds to a ratio β of the thickness to (Ksub(IC)/σsub(y))2 proportional to the plastic zone, size, equal to 2.5. An empirical formula describing the Ksub(IC) transition curve yields a relation between the plane strain transition temperature, yield point and the thickness, which depends upon the chosen value of β. For a given steel transition, temperatures deduced from other tests such as the temperature corresponding to the initiation of stable tearing, the Charpy FATT, the NDT, the DWTT-FATT, were found to correspond to various characteristic values of the β ratio. This was checked using results found in the literature for different steels. This relation between a particular transition temperature and the thickness, which depends upon the shape of the Ksub(IC) transition curve, the yield stress and the corresponding value of the β ratio, is useful to make predictions about the thickness and the strain rate effects. It can be used to deduce transition temperatures of various tests from the knowledge of either the Ksub(IC) transition curve or from two other transition temperatures. (author)