To address the poor meshing performance of helical cylindrical gears under variable center distances in high-speed rolling mills, this study establishes a finite element meshing model in Abaqus, considering gear meshing misalignment. Under typical operating conditions, simulation analyses of gear tooth contact are carried out to study the influence of center distance variation on key meshing performance parameters. Based on these results, comprehensive tooth surface modifications are proposed, including linear and crowning reliefs along the tooth lead direction and tip reliefs along the profile direction. A comparative analysis of gear meshing performance before and after modification is then performed. The results show that, prior to modification, the tooth surface exhibits significant load bias. Increases in center distance lead to a considerable decrease in contact ratio and contact area percentage, along with notable increases in maximum contact stress, maximum root bending stress, and the peak-to-peak transmission error - resulting in a substantial decline in overall meshing performance. Following surface optimization, load bias is significantly reduced, and improvements are observed across all key indicators, including reductions in maximum contact stress, bending stress and transmission error. The optimized gear surface exhibit enhanced adaptability to center distance variations, leading to a marked improvement in meshing performance.

This study addresses the vibration problems in high-speed long-shaft rotor system of an aerial UAV by developing a computational model that incorporates various forms of bearing support and damping. Using Ansys Workbench, the effects of bearing support forms and bearing damping on the critical speed of the rotor system are analyzed. Results indicate that the critical speed is significantly higher with rigid support than with flexible support. When rigid support is combined with bearing damping, the critical speed decreases with the increase of damping, and the influence of bearing damping decreases in higher-order modes. Additionally, the harmonic responses of the system are consistent across different positions, with the response amplitude increasing as the unbalanced load rises. Furthermore, the response amplitude shows an upward trend with increased damping.

To solve the resonance problem of an aviation parallel casing, the finite element method is used to analyze the constrained modal frequencies, considering typical working conditions and the elastic support stiffness of the aircraft frame. This study investigates the influence of casing structural parameters on the constrained modal frequencies. The results show that optimizing the constraint position is the most effective way to significantly change the natural frequencies. When the natural frequency is at the edge of the resonance intervals, it can be adjusted slightly by optimizing the wall thickness and stiffener parameters. When the two constraint positions are located on the symmetry axis of the casing plane, the natural frequencies reach their minimum and decrease obviously with a reduction in the constraint distance. With an increase of the thin-wall thickness, the 1^st, 3^rd, 5^th and 6^th modal frequencies decrease, while the 2^nd and 4^th modal frequencies increase. The 1^st and 3^rd modal frequencies are almost unaffected by the stiffener parameters. The 2^nd and 4^th modal frequencies increase with the increasing width and height of the stiffener and decreasing stiffener aspect ratio. In addition, the 4^th modal frequency increases with the increasing angle of the stiffener. The 5^th and 6^th modal frequencies increase with an increasing stiffener angle and decreasing stiffener width. Based on these findings, the aviation elastic parallel casing was optimized to ensure the natural frequencies avoid the resonance intervals, thus improving the vibration resistance of the casing.