Key fracture criteria for damage tolerance assessment of high-strength metallic materials in marine environments

Abstract

Abstract Marine corrosion and hydrogen-induced degradation significantly reduce the fracture toughness of high-strength metallic materials. Traditional safety assessments using air-measured toughness (KIC) often overlook coupled environmental effects, potentially overestimating performance and creating latent risks. This paper systematically reviews the definitions, engineering significance, and testing methodologies of key toughness parameters in fracture mechanics, including K IC, J IC, K ISCC, and K IEAC, and provides an in-depth analysis of their applicability in the damage tolerance assessment of high-strength materials within marine environments. Research on the fracture toughness of R6 grade anchor chain steel demonstrates that fracture toughness tests conducted under static immersion in corrosive media (3.5 % NaCl solution) do not align with actual service conditions. In contrast, fracture toughness values measured under low-rate loading in a hydrogen-saturated state (via pre-charging) are significantly lower than those obtained in air or simple corrosive environments. This experimental condition more effectively simulates the processes of hydrogen ingress, diffusion, and accumulation during long-term service. Therefore, this study proposes that new fracture toughness parameters, which fully reflect the synergistic influence of hydrogen-induced degradation and environmental corrosion, must be introduced into the damage tolerance assessment of high-strength metallic materials for marine engineering to ensure the reliability of structural fracture-prevention safety designs.