APPLICATION OF THE T-SCALING METHOD TO PREDICT FRACTURE TOUGHNESS UNDER COMPRESSIVE RESIDUAL STRESS IN THE TRANSITION TEMPERATURE REGION

摘要

The fracture toughness J_c of a material in the ductile-to-brittle transition temperature region shows a test specimen thickness (TST) effect and temperature dependence, and apparently increases when a compressive residual stress is applied. Many models to explain these phenomena have been proposed that can also consider the large scatter of J_c. On the contrary, the authors have focused on the mean J_c and have demonstrated that the TST effect on J_c and temperature dependence of J_c are due to "the loss of the one-to-one correspondence between J and the crack-tip stress distribution" and that the "scaled" crack-tip stress distribution at fracture is independent of the TST effect on J_c or temperature. The T-scaling method was proposed and validated for this purpose. In this study, the fracture prediction of a specimen with compressive residual stress was performed using the T-scaling method, and its validity was confirmed for high-strength steel of 780-MPa class and 0.45% carbon steel JIS S45C.