Landing gear is a key load-bearing structure of aircraft during ground operation, and the landing capacity of landing gear is determined by the performance of buffer. To solve the problem of buffer failure caused by insufficient static sealing of a rubber ring at groove side, a new structure of a butterfly rubber ring is proposed by analyzing the factors affecting sealing performance of the rubber ring. First, the constitutive equation of rubber material is derived based on the theory of hyper-elasticity, and the material parameters are obtained by fitting the experimental data. Then, by analyzing the simulation method of installation mode and installation stroke, the simulation method suitable for calculating the sealing performance of the rubber ring is established. The linear fitting formulas with Pearson coefficient greater than 0.92 are used to discuss the influence of pre-compression rate and hydraulic pressure on the sealing performance of the rubber ring. Compared with O-ring, the contact pressure of butterfly-ring is increased by 30% in assembly state and 14% in working state. The results show that the butterfly rubber ring has excellent static sealing performance. It is concluded that improving the configuration of the sealing ring can solve the insufficient unilateral sealing of the hydraulic buffer.

In view of the lack of image enhancement processing in the traditional methods in image preprocessing, which leads to a long detection time for internal cracks in the image and poor visual effects, an intelligent detection method for internal cracks in aircraft landing gear images under multimedia processing is proposed. A spatial index structure is established based on the multimedia database, and the aircraft landing gear images in the structure are enhanced and denoised. Image segmentation is performed according to the preprocessing results, the crack foreground and the road surface background in the image are separated, and the threshold value of each image is calculated. The threshold segmentation result is used to distinguish which pixels are the areas where the cracks may exist and which pixels belong to the image background, and the judgment result realizes crack detection. The experimental results show that the crack detection time of the proposed method is shorter, the visual effect of the detection results is better, and the average of the expert score reaches 93.6 points, which verifies the effectiveness of the proposed method from both the subjective and objective aspects.

The solidification experiment of Cu-25%Ag alloy used in high field magnet was carried out under high magnetic field,the precipitation of Ag in Cu-rich dendrites,the hardness and the electrical conductivity were investigated.It was found that the Ag phase precipitated exhibites continuous rod-like morphology in the larger Cu-rich dendrites,and exhibites discontinuous particlelike morphology in the smaller Cu-rich dendrites;the number of the Ag particles is more and the size is thinner in the sample solidified under 0 T than under 12 T high magnetic field.The hardness and electrical conductivity of the alloy have changed due to the size variance of Ag precipitates.

Crack closure model has been used in several applications on the prediction of fatigue crack growth life, with expression of crack opening stress often serving as milestones. A typical difficulty in calculating the crack opening stress is the phenomenon of crack closure caused by the compressive load effect. Compressive load effect, resulting in the change of residual stress status at the unloading stage and the decrease of crack opening stress, is a long‐term challenge for predicting fatigue crack growth life. We propose the expression of crack opening stress to predict fatigue crack growth life based on the analysis of compact tensile specimen with elastoplastic element method. It combines the characteristics of material and load to deal with the phenomenon of crack closure and uses stress ratio and normalized maximum applied load variable to construct the expression of crack opening stress. In the study of tensile‐compression fatigue crack growth experiments, the proposed expression is proved to improve, by comparative analysis, the predictive ability on the whole range of experiment data. The novel expression is accurate and simple. Consequently, it is conducive to calculate the crack opening stress under tension‐compression load.