A micromechanical approach to 3D damage modeling in structural steel based on unified mechanics theory

This study presents a polycrystalline plasticity model specifically designed for structural steel, emphasizing body-centered cubic (bcc) metals to simulate various mechanical loading states. The model is derived using unified mechanics theory, integrating micromechanics and thermodynamics principles, thereby eliminating the need for empirical curve fitting in damage modeling. Validation against monotonic tensile test data for S355J2 + N steel demonstrates a strong correlation with experimental stress-strain responses and fracture patterns. Numerical simulations across different geometric cross-sections indicate consistent failure patterns, with failure entropy of nearly 579.0 J/kg-K for S355J2 + N steel. Subsequent cyclic loading simulations affirm that the fatigue fracture entropy is independent of geometry and boundary conditions. Furthermore, comparative analyses with commonly used fatigue life prediction models are conducted, and potential directions for model improvement are discussed.