Plasticity Model for Structural Steel with Lode Angle Dependence

In recent years, the Lode angle was found to have a significant effect on plasticity and fracture strain of ductile metal under shear dominant loading, and the classical J2 plasticity theory generally overestimates the cases under shear dominant loading. In practice, shear dominant loading is common, that is, fillet-welded joints, partial-penetration welded joints, and metallic shear dampers. Therefore, it is important to study plasticity of structural steel under shear dominant loading and develop corresponding plasticity models for accurate evaluation of the plasticity and fracture of metallic structures. A plasticity model considering the effect of the Lode angle was simplified based on previous studies. Eight types of specimens with different configurations were designed to generate different initial stress states. Three different material tests were conducted to figure out little anisotropy in different locations of steel plate. The integration process for the simplified plasticity model were studied, and a user-defined subroutine in ABAQUS was developed for the model. A postnecking modification method for the true stress–true strain was recommended to evaluate the postnecking behaviors of structural steel through comparison of experimental and numerical simulation results. The simplified single parameter plasticity model proved to have high accuracy for specimens under various stress states, and a detailed calibration process for the material parameter was also introduced.