Aviation metal structures often face the combined effect of Marine corrosion environment and repeated impact loads during service, which leads to corrosion damage on the material surface and significantly deteriorates its impact fatigue performance. In order to explore this phenomenon in depth, this paper systematically studied the impact fatigue life of AerMet100 steel and TC18 titanium alloy, the key structural materials in the aviation field, under different durations of neutral salt spray corrosion. The impact of corrosion duration on the impact fatigue life of two types of notched three-point bending specimens and the damage mechanism were systematically revealed by the neutral salt spray corrosion test, the dropping hammer impact fatigue life measurement test, and the scanning electron microscope (SEM) characterization technology. The results show: with the increase of salt spray corrosion time, the fatigue life of U/V-90° notched specimens of AerMet100 steel and TC18 titanium alloy U-notched specimens show a nearly linear decay trend, and the fatigue life of AerMet100 steel decreases to about 50% of that of non-corroded specimens after 240 h of corrosion. However, the U-notched specimen of TC18 titanium alloy decreases to about 50% of the uncorroded specimen after 480 h of corrosion. In contrast, the fatigue life of the V-90° notched specimen of TC18 titanium alloy is mainly affected by the stress state rather than the corrosion damage due to the high stress triaxial degree at the notch location. In addition, the SEM results show that with the extension of corrosion time, the number of corrosion products and pitting pits on the surface of AerMet100 steel samples increases significantly, accompanied by surface cracking, which promotes the initiation and propagation of fatigue cracks. Due to the shielding effect of the surface passivating film on the corrosive medium, the TC18 titanium alloy effectively prevents the in-depth erosion of the corrosive medium, limits the propagation path of the crack, and maintains a high fatigue life.

Prestressed concrete structures are subject to environmental corrosion during service, resulting in corrosion of the reinforcement and varying degrees of damage to the structure. This leads to a reduction in the structural load carrying capacity. To investigate the effect of the reinforcement corrosion on the flexural performance of prestressed concrete beams, corroded prestressed concrete beams were tested by a four-point bending test. It is shown that the corrosion of the ordinary reinforcement has a small effect on the cracking strength and ultimate strength of test beams. However, the effect of corrosion on the yield load is more obvious. When the corrosion rate of ordinary steel reinforcement is 3.8%, the yield load of the test beams decreases by 15.6%. Additionally, the corrosion rate of steel reinforcement has a smaller effect on the yield deflection of the test beams, but the effect on the ultimate deflection is more obvious. When the corrosion rate of steel reinforcement is 11.5%, the ultimate deflection decreases by 8.6%. The corrosion of the prestressed steel strand has a significant effect on the cracking load and yield load of the test beams, which is the main factor affecting the load carrying capacity and deformation capacity of the prestressed beams. The cracking load of the test specimen decreases by 32.9% when the strand corrosion rate is 7.6%.

Accurate prediction of the lifespan of lithium-ion batteries is crucial for ensuring the electrical safety of equipment. In the process of battery lifespan prediction, the selection of indirect parameters is a key link. However, at present, there are relatively few studies on the relationship between indirect parameters and the internal reaction mechanism of batteries. This paper conducts an experimental study on the relationship between indirect parameters in battery life prediction and the battery reaction mechanism, designs an integrated experimental scheme for battery charge and discharge cycles, electrochemical impedance and acoustic emission, and obtains the nonlinear evolution laws of capacity, impedance and mechanical damage with the number of cycles through experiments. By analyzing the evolution laws of charge transfer impedance (R_CT) and solid-state electrolyte interface film impedance (R_SEI), the mechanism by which R_CT and R_SEI affect the degradation of battery life by influencing the transmission and transfer of internal charges in the battery was discovered. Further, the intrinsic qualitative connection among battery capacity, impedance and damage was expounded. Subsequently, based on the qualitative connection between impedance and mechanical damage, the Pearson correlation coefficient was used to quantify the relationship between R_CT, R_SEI and the cumulative impact times of acoustic emission. The results show that the correlation coefficients of R_CT and R_SEI with the cumulative impact times of acoustic emission are both higher than 0.9, indicating that impedance is closely related to electrode mechanical damage. Impedance R_CT and R_SEI contain both electrochemical factors and electrode mechanical damage information. Moreover, the relationship between impedance and mechanical damage has been further verified through experiments with different charge and discharge rates and different electrode materials.