Microstructural design strategy to maintain the brittle fracture toughness of hard-soft dual phase steel after cyclic plastic strain

Abstract Superstructures are seriously damaged because of plastic deformation when natural disasters, such as large earthquakes or unexpectedly large waves, occur. Therefore, there is a need to develop materials that are resistant to damage and fracture while maintaining a certain level of strength. In this paper, the difference in material toughness changes when cyclic prestrain occurs among different ferrite/pearlite two-phase microstructures were investigated. Synthetic analysis using strain gradient plasticity (SGP) theory, one of the crystal plasticity theories, was carried out, and conventional macroscopic material damage consideration rules were employed. Then, it was suggested that the amount of material damage changes among the different microstructures. In addition, a parametric study using SGP theory is performed to suggest directions for the microstructural design of steel with a lower risk of brittle fracture due to plastic deformation. As a result, damage-resistant materials with sufficient strength can be proposed.