Accumulative plasticity analysis of hull structures with surface cracks under low-cycle fatigue loading

In fact, three-dimensional complex cracks and other defects are often contained by the components of marine engineering structures. In the early stage of fracture mechanics, for the sake of simplicity and convenience in mathematical processing, the actual cracks are often simplified as two-dimensional models, and ideal two-dimensional cracks almost do not exist. In addition, the hull structure not only has low cycle fatigue failure, but also has obvious accumulative plastic failure under the severe sea conditions accompanied by cyclic ultimate external loads. Therefore, it is particularly important to study the accumulative plasticity of hull structures with surface cracks under low-cycle fatigue loads. In this paper, the hull structure of AH32 steel with surface cracks is taken as the research object, combined with three-dimensional elastic-plastic fracture mechanics, and then the large nonlinear finite element software Abaqus is used to conduct numerical simulation, and the constitutive model of surface crack plate is established. The stress-strain relationship at the crack tip was analyzed by discussing different ellipse shape factors, crack depth and crack plate thickness, and based on this, the variation law of the accumulative plasticity at the crack tip is further discussed. It lays a sturdy foundation for the follow-up study of crack propagation fracture and life evaluation of hull structures with surface cracks.