Evaluation of elastic-plastic fracture toughness testing in the transition region through Japanese interlaboratory tests

International cooperative interlaboratory test programs on elastic fracture toughness in the transition region were carried out using thick compact tension (IT-CT) specimens at three temperatures to obtain basic information about the measurement of lower-bound fracture toughness of steels. Test results have provided some information regarding the standardization of a method for measuring the lower-bounded fracture toughness of steels. In particular, the guidelines on the measurement of Δa0, X and Δa0 + X were established and the tentative test procedure for the determination of the lower-bound fracture toughness was developed using a fractographic data analysis.