Effect of temperature on fracture toughness in weld thermal simulated X80 pipeline steels

The aim of this paper is to study the effect of temperature on cleavage fracture toughness of weld thermal simulated X80 pipeline steels in ductile-to-brittle transition (DBT) regime. A large number of fracture toughness (as denoted by crack tip opening displacement-CTOD) tests together with finite element analyses are carried out by using deep-cracked single edge notched bending (SENB with a/W=0.5) specimens at various temperatures (-90℃, -60℃, -30℃ and 0℃). 3D finite element models of tested specimens have been used for the numerical simulation in this study. Coarse-grained heat-affected zone (CGHAZ) is considered as the material microstructure in preparation of weld thermal simulated fracture mechanics specimens. It has been found that the transferability of the true stress-strain curves obtained from weld thermal simulated round tensile bar to the fracture mechanics specimens works very well. Temperature shows only a slight effect on the material hardening behavior. As compared with experimental results, the 3D model can precisely predict the fracture toughness (CTOD-values) at different temperatures considered in this study.