Application Analysis and Assessment of 34CrNiMo6 in Mooring Shackles

This study focuses on the mechanical properties of mooring shackles. Using a combined experimental and numerical simulation approach, a comprehensive analysis was conducted on the mechanical properties and structural reliability of 34CrNiMo6 alloy steel after different heat treatment processes. The optimized heat treatment process was experimentally validated: At −20 ℃, the mean impact energy ≥ 50 J, with a single minimum value ≥ 36 J, meeting toughness requirements. Crack Tip Opening Displacement （CTOD）values ≥ 0.24 mm, satisfying fracture resistance criteria and verifying compliance with the DNV-R4 certification standard.Finite element verification under Minimum Breaking Load （MBL）for shackle models （both pre- and post-corrosion） showed that the equivalent plastic strainwas consistently below the allowable threshold （10.92%）. Static load tests confirmed no permanent deformation, and fracture load tests demonstrated no structural failure, aligning with simulation results and validating structural strength. Conclusions:After optimized heat treatment, 34CrNiMo6 alloy steel achieves an excellent strength-toughness ratio. Simulation methods effectively determine structural reliability, providing a theoretical reference for engineering design.