Effects of corrosion pits on the combined hardening behavior of low-carbon steel

This study utilizes artificial drilling to simulate corrosion pits and investigates their effect on the combined hardening behavior of low-carbon steel. The effects of the degree of pit volume loss (DOV), pit shape, pit diameter-to-depth ratio(d/h), pit quantity, and distribution on the elastic modulus, yield strength (initial yield surface radius), and yield plateau length of low-carbon steel are investigated through monotonic tensile and cyclic loading tests on steel plates with pits. Combined with the results of experimental and numerical simulations, the combined hardening behavior of steel plates with pits, including isotropic softening/hardening, kinematic hardening, and strain range memory effect is studied. It reveals the effect laws of pit characteristics on combined hardening behavior and proposes calculation formulas for the parameters of the full-range elasto-plastic combined hardening model. The formulas cover the plateau and hardening regions and apply to both single and multiple pitted steel. The results show that the DOV and d/h are the key factors affecting the combined hardening behavior of steel with pits, while the pit shape has negligible effect. When the number of pits exceeds 2×2, the quantity and distribution have a negligible effect on the combined hardening behavior for steel with multiple pits. Both isotropic softening and kinematic hardening behaviors exist in the plateau region; while within the hardening region, there are behaviors of isotropic hardening, kinematic hardening, and strain range memory effects for steel with pits. Pits reduce the saturation values of isotropic softening and kinematic hardening in the plateau region of steel and accelerate their saturation. In addition, the pits also lead to the weakening of isotropic hardening, kinematic hardening, and strain range memory effects within the hardening region of steel. However, multiple pits induce stress release, which mitigates the degradation of the combined hardening behavior of steel with pits.