Low Cycle Fatigue Reliability of Dissimilar Weldments Made by ZG18CrNiMoA Cast Steel and Q355D Structural Steel

Cast steel combines high strength and ductility, enabling flexible designs for heavily loaded structural components, yet the low‐cycle fatigue (LCF) performance of its welded component remains insufficiently understood. This study experimentally examines Q355D structural steel, ZG18CrNiMoA cast steel, and their dissimilar weldments under uniaxial strain‐controlled cyclic loading at multiple strain amplitudes. Cyclic stress–strain responses, hysteresis characteristics, failure modes, and fatigue lives were compared to reveal the effects of material mismatch and weld heterogeneity. Ramberg–Osgood relations and calibrated Chaboche models were employed to characterize monotonic and cyclic responses. Strain–life and energy–life correlations were then established to quantify fatigue resistance. An energy‐based model incorporating an appropriate fatigue parameter successfully correlated the fatigue lives of all three material systems within experimental scatter. The results identify their distinct low‐cycle fatigue characteristics and demonstrate that strain‐ and energy‐based approaches can support fatigue assessment and reliable design of welded cast‐steel components subjected to severe cyclic loading.