A modified micromechanics framework to predict shear involved ductile fracture in structural steels at intermediate and low-stress triaxialities

This paper employs a micromechanics framework to investigate the mechanisms and to predict the ductile fracture of structural steels at intermediate and low-stress triaxialities and under shear involved stress states. Unit cell-based micromechanical analyses are carried out to provide insights into the combined effects of triaxiality, Lode parameter, and shear stress component on the micro-mechanisms of ductile fracture. Based on the micromechanical analyses, an existing fracture model is modified to incorporate the influence of the shear stress component. Experimental investigations are carried out on three axisymmetric tension specimens, and a series of shear specimens made of Chinese Q460 steels to achieve uniaxial tension and shear dominated loading conditions, respectively. Finite element analyses are performed to evaluate the stress and strain fields in the tension and shear specimens. The modified model is calibrated by combining the experimental results with micromechanical analyses. Validation studies show that the predicted fracture initiation by the model agrees well with experimental results, implying a good performance of the proposed micromechanics framework for the prediction of the shear-dominated ductile fracture at intermediate and low-stress triaxialities.