Ductile fracture of dual-phase steel at elevated temperatures

Structural steels can be subjected to a range of stress and temperature conditions, and accurate characterization of their limit states is a requirement for structural design. Yet data on ductile fracture at elevated temperatures remains relatively scarce especially for high-strength steel grades. This paper describes an experimental and numerical investigation of the ductile fracture of a high-strength dual-phase steel under multiaxial stress states at temperatures up to 700 degrees C. Experiments were carried out on five geometries of specimens and at four temperatures to identify the temperature-dependent fracture locus across a range of stress triaxialities. Finite element analyses of the experiments provided the equivalent strain at fracture initiation. It was found that the fracture initiation strain varies markedly with stress triaxiality and increases with temperature. The effect of strain rate become significant at 500 degrees C. A temperature-dependent plasticity-damage model was calibrated to predict ductile fracture initiation in the dual-phase steel. The proposed model can be used in finite element analyses to support performance-based design of steel structures at elevated temperatures resulting from accidental events such as fire.

Automated summary

This study investigates the ductile fracture of high-strength dual-phase steel under multiaxial stress states at elevated temperatures. Experimental results show that the fracture initiation strain varies with stress triaxiality and temperature. A temperature-dependent plasticity-damage model is calibrated to predict the ductile fracture initiation in the dual-phase steel. This research is important for supporting the performance-based design of steel structures at elevated temperatures resulting from accidental events such as fire.