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Composite material is widely used to maintain damaged structures of aircraft. The 3D finite element model of composite cement maintenance for aircraft is established by finite element method software ANSYS Workbench. The structural characteristics and usage status of the composite cement maintenance model is analyzed, and then the optimal structural parameters of the composite patch are obtained, including the length, width and thickness. The results show that the composite cement maintenance method could effectively restore the rigidity, and improve the strength of the structure. Furthermore, the optimal design for composite patch ensures safety of aircraft, economics of maintenance, and operability of repair methods.

The shell of scroll compressor was subjected to internal gas pressure during operation. In order to ensure the safety of the pressure shell, the structure parameters of the shell were determined initially by pressure vessel design method, and the strength of the shell was checked by finite element method. Because of the uncertainty of structural parameters, the reliability of the shell of scroll compressor was analyzed by finite element method and probability design system (PDS), and the reliability and probabilistic sensitivity of the shell were obtained. The results showed that the material’s strength, working pressure, thickness of head wall, thickness of cylinder wall, radius of cylinder and radius of head were the main factors to affect the reliability of the shell, and the reliability design method was better economic than the conventional design method. The above conclusions provide a scientific basis for the further optimal design of scroll compressor’s shell.

Generally, the welding HAZ is more sensitive to corrosion. In order to increase the corrosion resistance of the welding HAZ in aircraft structures, the laser surface treatment technology was used to treat the welding HAZ. In this study, the processing parameters of the laser surface treatment were optimized. According to our study, the laser quenching can increase the corrosion resistance property obviously. The laser surface treatment new technique has been used in the maintenance of the airplane structures, which has better application outlook.

In this paper, beam ends of beam-slab-column joints installed in reinforced concrete structures are simulated using ABAQUS FEM analysis software. The simulation work is carried out under the monotonic loading. The damage factor in the plastic-damage model is adopted for describing the damage state of concrete. The failure characteristics, the distribution of cracks on the top side of slab are discussed according to the simulation results. The stresses of longitudinal bars in the slab along with different distances between the longitudinal bar and the beam are given. In reliability assessment of the numerical model, the effects of slab thickness and slab reinforcement ratio on flexural behavior of beam-slab cooperative working are conducted further more.

To repair the damages of aero blades, laser cladding on GH710 substrate using NiCrMoNb powder by CO2 laser was carried out. The microstructure and microhardness of cladding layers were investigated. The property of dry sliding friction and wear in the air was tested. It was found that the cladding layer was well combined with the substrate. The white narrow metallurgical bonding zone was about 15~20μm. The microstructure transformed from coarse columnar grains to fine dendritic grains from bottom to top and the net-like grains were fabricated on the surface. The axis of columnar grains was perpendicular to the direction of the melting line. Columnar grains had the scale of 10~15μm on the width and 50~60μm in the axis direction. The area of the crystal lattice varied from 2μm×4μm to 5μm×9μm. The microhardness of cladding layer, metallurgical bonding zone and the substrate changed gradually. The microhardness was 450HV, 40%~50% higher than that of the substrate. The wearing capacity was 50%~55% of that of the substrate. The main form of abrasion was grain-abrasion and adhesion-abrasion.

To improve the wear-resistance of Ti600, and alleviate thermal stress as well under hyperthermal and excessive temperature difference condition, experiments of Ti-matrix FGM on Ti600 substrate by pulsed Nd:YAG had been carried out. The microstructures, microhardness and phase composition of FGM were investigated. And the friction wear properties of FGM, N-FGM and Ti600 substrate were examined in atmosphere. It was found that a rapidly solidified microstructure consisting of in situ synthesized TiC reinforced phase distributed on FGM substance evenly and dispersely in the form of globular grains had three main different shapes:bulky or imperfect arborescent crystal, fine or approximately equiaxial crystal and chopped fibriform crystal. With the increasing of original Cr3C2content, the number and size of arborescent crystal increased obviously. The distribution of main alloy components was gradient and continuous, presenting the same composition and regularity to the originally preset alloy powder. FGM and N-FGM had an average hardness of approximately 1450, 4.5-5 times of Ti600 substrate, attributed to TiC primary dendrites. With the reducing of weight percentage of TiC, microhardness decreased gradiently and continuously. Meanwhile, the wear resistance of FGM and N-FGM was improved obviously. Friction coefficient, wear loss and wear rate decreased significantly, 0.3-0.5 times of Ti600 substrate.

To explore reaction mechanisms and proper effects of aluminium in laser micro-molton pool, experiments of laser cladding (Ti+1-8%Al) on Ti-6Al-4V by pulsed Nd:YAG had been carried out. The microstructures, microhardness and phases of the cladding layers with different weight percentage of Al were investigated. The content of Al was quantitatively determinated when ordering α2 ceramic phase (Ti3Al matrix) were formed. And the friction and wear properties of the cladding layers were examined in atmosphere. It was found that the microstructure of the cladding layers included cellular crystals, columnar crystals, arborescent crystals and dispersive white granules. The α2 ceramic phase was formed when the content of Al was 6%wt. With the increasing of weight percentage of Al, the number and size of arborescent crystals increased obviously, as well as the microhardness, the maximum was 957.9Hv, 1.3-1.5 times of the layers with below 6%wt Al. Inversely, the wear resistance of the laser cladding layers was improved gradually. Friction coefficient, wear extent and wear rate decreased. 0.55-0.7 times of the layers with below 6%wt Al.

30CrMnSi is quenched and tempered steel with medium hardenability, and good mechanical properties. However, the anti-corrosion of the weld heat affected zone will be decreased, which will lead to the worse overall properties of parts. The anti-corrosion properties of heat affected zone will be improved by YAG laser treatment according optimized processing parameters. The microstructure of the modified heat affected zone was observed and analyzed in this paper. And the anti-corrosion property was studied also. The results showed that the anti-corrosion property of heat affected zone will be improved by laser remelting technology. The laser anti-corrosion is the effective method to enhance anti-corrosion property.

With the increase of the service time of shipborne aircraft, the overlarge impact load can affect the life of the hydraulic system accessories. At the same time, the vibration and the corrosion of the ser water will also affect negatively the accessories’ life. The accessories are the important composition of the hydraulic system. Therefore, it is necessary to study the possible faults and their rules. This paper aims to establish the suitable model to predict the faults by use of the FEM and experiments.

Hydrogen bondings in polyurethane urea elastomer, which reflect the microphase separation, have an important effect on the properties of the elastomer. The polyurethane urea elastomers, whose degree of microphase separation changed gradually, were prepared in the graded temperature field. Hydrogen bondings in them were investigated by FTIR technology. The discussions about C=O, NH, and -O- stretching vibration spectra were given. The percentage of hydrogen bonded carbonyl groups increases with the increase in the curing temperature in the thickness direction, which indicates the increase in the degree of microphase separation in it. The degree of hydrogen bonded ether oxygen atoms exhibits obvious difference in polyurethane urea with different crosslinking degree. It is this difference that leads to a contrast changing trend of the percentage of hydrogen bonded NH in different samples. Three-dimensional hydrogen bonding between urea carbonyl and NH is stronger than the hydrogen bonding between ether oxygen atoms and NH. The stretching vibration of hydrogen bonded ether group is at about 1 076 cm(-1).