Low-cycle fatigue testing and microstructure of high strength-ductility structural steel materials

The well-known tradeoff between strength and ductility is a key issue in the large-scale engineering application of steel materials to resist fatigue due to earthquakes and other vibrational excitations. The steel production industry provides a vast range of technologies to achieve the desired performances. Through experimental research, it was found that FeCrNi-based high-ductility steel (HD-S) can demonstrate remarkable hysteresis behavior due to extensive deformation capacity of strain-hardening until the ultimate fracture, compared to industrially manufactured high-strength steel (HS-S) with the level of 1 GPa in yield strength. The balance between strength and ductility can be realized by slightly adding the percentage of Ni by 5% to achieve a ductile hysteresis behavior. Moreover, the HD-S specimens exhibit greater resistance to low-cycle fatigue with large plastic amplitude. By developing a new damage evolution law based on instantaneous damage differential during nonstationary fatigue history, the fatigue life of materials is extended into the inelastic hinges of flexural beams/origami components. The proposed approach enables the fatigue design of steel structural components with desirable disaster-prevention capacities for complex steel structures.