In this study, a titanium alloy torsional spring used in aviation was taken as the research subject. Aiming at the fatigue life prediction problem of this spring, the life analysis of the titanium alloy torsional spring was performed using a customized UMAT subroutine based on the theory of continuous damage mechanics. Several sets of life prediction models and tests were compared. The fatigue lives of the springs at 60, 80, 100, and 120 degrees were 45,070, 65,067, 99,677, and 181,322 cycles, respectively. Compared with other fatigue life prediction methods, the fatigue life calculated by the customized subroutine was the most consistent with the fatigue life of the titanium alloy torsion spring tests. The average relative error between the measured experimental life value and the predicted value was 2.04%, which is less than 5%, meeting engineering measurement requirements. The effectiveness and applicability of the proposed model and method were verified, and the time and economic cost caused by excessively long experimental cycles were reduced. This helps improve the accuracy of fatigue life prediction for this titanium alloy torsional spring and provides analysis support for subsequent structural optimization and improvement.

The shock absorbers in the landing gear absorb and dissipate a significant amount of kinetic energy generated from impacts during the landing and taxiing phases to ensure the stability and safety of the aircraft. The nitrogen–oil binary system is a commonly used energy absorption medium in these shock absorbers. Nevertheless, the interplay of interfacial mass transfer dynamics, microscopic dissolution behavior, and pressure drop in the aviation hydraulic oil–N₂ system under landing conditions necessitates further elucidation. Thus, we investigated the interfacial mass transfer characteristics of the oil–gas mixing process using molecular dynamics (MD) for analyzing the dissolution mechanism of N₂ in the aviation hydraulic oil system. The results show that as system pressure and temperature increase, the degree of oil–gas mixing intensifies. Under conditions of 373 K, 35 MPa and 433 K, 20 MPa, the diffusion coefficient, interfacial thickness, and system energy reach their maximum values. An increase in system pressure facilitates the occurrence of oil–gas mixing until the interface disappears at the minimum miscibility pressure (MMP), with the obtained MMP value being 107 MPa. Finally, the solubility of N₂ molecules in aviation hydraulic oil under different conditions was statistically analyzed, which is identified as the root cause of the pressure drop in the shock absorber’s gas chamber. This study innovatively applies molecular dynamics simulations to unveil, for the first time, the dissolution mechanism of N₂ in aviation hydraulic oil at the molecular scale, overcoming experimental limitations in observing extreme pressure–temperature conditions. This research elucidates the behavior of aviation hydraulic oil and N₂ under different thermodynamic conditions, making it easier to capture the patterns of phenomena that are difficult to observe in extreme environments. The research findings not only enhance the microscopic understanding of oil–gas mixing within the shock absorber but also provide valuable guidance for optimizing energy dissipation efficiency, improving damping characteristics, and enhancing safety in aircraft landing gear systems.