Charpy impact energy correlation with fracture toughness for low alloy structural steel welds

Abstract

This work addresses an experimental investigation of the cleavage fracture behavior for ASTM A572 Grade 50 steel welds fabricated by different welding processes. A primary purpose of this study is to examine a correlation approach to evaluate fracture toughness values of steel welds based on Charpy V-notch (CVN) impact energy data thereby enlarging existing relationships between fracture toughness and CVN energy. Fracture toughness testing conducted on three-point bend SE(B) specimens having a weld centerline notch provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc, for the steel welds, including the baseplate material. Conventional Charpy tests produce further experimental data which serve to characterize the ductile-to-brittle transition of the tested steel welds and the CVN energy correlation with fracture toughness data derived from conventional correlation formulas. A statistical analysis based on the Master Curve methodology conducted on the experimentally measured fracture toughness data provides the reference temperature for the tested materials from which estimates of fracture toughness based on CVN energy can be made. The results suggest that current correlations between T0 and the CVN energy may provide nonconservative fracture toughness estimates and, thus, should be modified when the primary purpose is to ensure adequate safety levels, as usually required in flaw assessment procedures.