Temperature Dependence of Ductile Fracture in Structural Low-Carbon Steel

This study presents a temperature-dependent fracture model for predicting ductile crack initiation in low-carbon structural steel subjected to elevated temperatures. The continuum damage mechanics-based model is developed using data from twenty-five coupon tests on A572 Gr. 50 (345 MPa) steel on specimens with a wide range of stress triaxialities and Lode angle parameters over temperatures from 20°C to 700°C. Complementary finite element simulations replicate the stress–strain response up to fracture, while micromechanical void cell simulations provide insight into temperature-driven damage mechanisms. The experimental results show a systematic decrease in fracture strain with increasing temperature up to 600°C, attributed to diminished strain hardening leading to accelerated localization of plastic deformation at the microvoid scale. Void cell simulations corroborate these trends, demonstrating increased void growth rate and reduced localization strains at elevated temperatures. Based on these findings, the stress-weighted ductile fracture model (SWDFM) is extended to incorporate temperature dependence under varying stress triaxiality and Lode angle. The model is calibrated using the new experimental data, validated across multiple specimen geometries and stress states, and assessed for robustness through cross-validation.