Ductile fracture of dual-phase steel at elevated temperatures: Fid-Bau Portal

Ductile fracture of dual-phase steel at elevated temperatures

Ma, Chenzhi / Yan, Xia / Gernay, Thomas

Highlights • Fracture experiments were performed on dual-phase steel at temperatures from 20 to 700 °C. • Five specimen shapes were used to generate stress triaxialities from 0 to 0.51. • Finite element analyses with a plasticity-damage model were calibrated on the experiments. • The dependency of the damage and fracture initiation strains with stress state and temperature was identified. • The calibrated material model can be used to simulate fracture of steel members in fire.

Abstract 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 °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 °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.