Ductile-to-brittle transition in high-strength steel: Experiments and damage-coupled constitutive modeling

This paper focuses on the experimental and numerical analysis of the ductile-to-brittle behavior of the high-strength low-alloy (HSLA) steel. Different uniaxial experiments, using samples manufactured from 2 mm thick sheet metal and covering a wide range of stress states, were conducted to identify the elastic, plastic, and ductile damage and fracture loci, and the details of the experimental–numerical hybrid identification strategy are discussed. In addition, a series of sub-sized V-notch Charpy tests from room temperature to -196°C were performed to investigate the ductile-to-brittle transition behavior. For numerical simulations, a modified Bai and Wierzbicki stress-state-dependent yield condition considering isotropic damage by incorporating a scalar damage variable is used to capture the elastic–plastic-damage behavior. The damage evolution is driven by energy dissipation. An extended stress-triaxiality-dependent Johnson–Cook-type damage and fracture model is developed by incorporating the Lode angle parameter to capture the initiation of ductile damage and fracture more accurately. Moreover, a novel temperature-dependent stress-based criterion is introduced to model brittle fracture. The proposed damage and fracture continuum framework accurately captures and predicts the ductile-to-brittle material behavior and can serve as an alternative to the traditional fracture toughness method for characterizing fracture behavior.