Chinese Journal of Aeronautics最新文献

The prolonged thermal exposure with centrifugal load results in microstructural degradation, which ultimately leads to a reduction in the fatigue and creep resistance of the turbine blades. The present work proposes a multi-scale framework to estimate the life reduction of turbine blades, which combines a microstructural degradation model, a two-phase constitutive model, and a microstructure-dependent fatigue and creep life reduction model. The framework with multi-scale models is validated by a Single Crystal (SC) Ni-based superalloy at the microstructural length-scale and is then applied to calculate the microstructural degradation and the fatigue and creep life reduction of turbine blades under two specific service conditions. The simulation results and quantitative analysis show that the microstructural degradation and fatigue and creep life reduction of the turbine blade are heavily influenced by the variations in the proportion of the intermediate state, namely, the maximum rotor speed status, in the two specific service conditions. The intermediate state accelerates the microstructural degradation and leads to a reduction of the life, especially the effective fatigue life reserve due to the higher temperature and rotational speed than that of the 93% maximum rotor speed status marked as the reference state. The proposed multi-scale framework provides a capable approach to analyze the reduction of the fatigue and creep life for turbine blade induced by microstructural degradation, which can assist to determine a reasonable Time Between Overhaul (TBO) of the engine.

The friction stir lap welding (FSLW) of metal to polymer is a challenging work due to the unavoidable polymer overflowing. Facing this problem, a novel seal-flow multi-vortex friction stir lap welding (SM-FSLW) technology based on the subversively-designed multi-step pin was put forward. Choosing 7075 aluminum alloy and short glass fiber-reinforced polyether ether ketone (PEEK) as research subjects, the welding temperature, material flow, formation and tensile shear strength of dissimilar materials lap joint under the SM-FSLW were studied and compared with those under traditional FSLW based on the conical pin. The multi-step pin rather than the conical pin effectively hindered the polymer overflowing due to the formation of vortexes by the step, thereby attaining a joint with a smooth surface. Compared with traditional FSLW, the SM-FSLW obtained the higher welding temperature, the more violent material flow and the larger area with high flow velocity, thereby producing the macro-mechanical and micro-mechanical interlockings and then heightening the joint loading capacity. The tensile shear strength of lap joint under SM-FSLW was 27.8% higher than that under traditional FSLW. The SM-FSLW technology using the multi-step pin provides an effective way on obtaining a heterogeneous lap joint of metal to polymer with the excellent formation and high strength.

Submerged abrasive waterjet peening (SAWJP) is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components. This study investigated the correlation of SAWJP process parameters on surface integrity and fatigue life of titanium alloy TA19. SAWJP with different water pressures and standoff distances (SoDs) was conducted on the TA19 specimens. The surface integrity of the specimens before and after SAWJP with different process parameters was experimentally studied, including microstructure, surface roughness, microhardness, and compressive residual stress (CRS). Finally, fatigue tests of the specimens before and after SAWJP treatment with different process parameters were carried out at room temperature. The results highlighted that the fatigue life of the TA19 specimen can be increased by 5.46, 5.98, and 6.28 times under relatively optimal process parameters, which is mainly due to the improved surface integrity of the specimen after SAWJP treatment. However, the fatigue life of specimens treated with improper process parameters is decreased by 0.55 to 0.69 times owing to the terrible surface roughness caused by the material erosion. This work verifies that SAWJP can effectively improve the surface integrity and fatigue life of workpieces, and reveals the relationship between process parameters, surface integrity, and fatigue life, which provides support for the promotion of SAWJP in the manufacturing fields.

Laser ablation is an important process during Laser-Assisted Grinding (LAG) of hard and brittle materials. To realize controllable material removal during laser ablation of RB-SiC composites, ablation experiments under different Laser Energy Density (LAED) and LAG experiments are conducted. Evolution rules and mechanism of physical phase, ablation morphology and crack characteristics caused by laser irradiation are investigated. The forces of LAG and Conventional Grinding (CG) are compared. The results show that ablation surface changes from slight oxidation to obvious material removal with LAED increasing, and ablation depth increases gradually. The ablation products change from submicron SiO₂ particles to nanoscale particles and floccule. High LAED promotes SiC decomposition and sublimation, which leads to the increase of C element. The SiC phase forms corrugated shape in recast layer and columnar shape in Heat Affected Zone (HAZ) at 56 J/mm². The cold and heat cycle leads to formation of fishbone crack. For ablation specimen under 30 J/mm², the grinding force can be reduced by a maximum of 39% and brittle damage region is reduced. The material removal and microcrack generated will significantly reduce the hardness and improve machinability, which can promote grinding efficiency.

For rough machining of a complex narrow cavity, e.g., a complex blisk channel on an aero-engine, the typically used cutting tools are the slender cylindrical cutter and conical cutter. Nevertheless, as neither of the two is particularly suited for rough machining, wherein the main purpose is to remove a large volume as quickly as possible, the machining efficiency is low, especially when the part materials are of hard-to-cut types (e.g., Titanium-alloy) for which it often takes days to rough machine a blisk. Fortunately, disc machining provides a new and efficient roughing solution, since a disc cutter with a large radius enables a much larger cutting speed and thus a larger material removal rate. However, due to the large radius of the disc cutter, its potential collision with narrow and twisted channels becomes a serious concern. In this paper, we propose a novel two-phase approach for efficiently machining a complex narrow cavity workpiece using a disc-shaped cutter, i.e., 3 + 2-axis disc-slotting of the channel by multiple layers (rough machining) + five-axis disc-milling of the freeform channel side surfaces (semi-finish machining). Both simulation and physical cutting experiments are conducted to assess the effectiveness and advantages of the proposed method. The experimental results show that, with respect to a same cusp-height threshold on the channel side surfaces, the total machining time of the tested part by the proposed method is about only 36% of that by the conventional approach of plunging-milling (for roughing) plus milling by a slender cylindrical cutter (for semi-finishing).

As a new addition to lightweight composite structures, the sandwich cylindrical shell with a metallic wire mesh core has emerged as a promising solution for thermodynamic performance analysis at elevated temperatures. The intricate interwoven cellular formations within the metallic wire mesh pose difficulties for thermo-mechanical modeling and property evaluation. First, the constitutive models employed to characterize hysteresis phenomena were presented, comprising isotropic elasticity, Bergstrom-Boyce model, Ogden hyper-elasticity, and parameter identification through mechanical examinations at varying temperatures. Second, the finite element modeling of cylindrical shell structures was determined for modal and steady-state dynamic analyses. Third, the experimental procedures were carried out, including the preparation of the sandwich cylindrical shell and the dynamic testing platform. The first-order natural frequency of the cylindrical shell structure is close to the resonance frequency of the dynamic test results, with a maximum error of 6.5%, demonstrating the accuracy of the simulation model. When compared to the solid-core cylindrical shell, the average insertion loss of the sandwich cylindrical shell structure within the frequency range of 10–1000 Hz at room temperature is up to 11.09 dB. Furthermore, at elevated temperatures, the average insertion loss of the sandwich cylindrical shell decreases but fluctuates as the temperature changes.

Composite Thin-walled Lenticular Tube (CTLT) is increasingly utilized in small satellites missions as a lightweight, foldable, and rollable structural material that facilitates the construction of large deployable systems. The CTLT is initially flattened and coiled around a central hub for storage before launch, during which elastic energy is stored as deformation energy, allowing it to be self-deployed on demand for use in orbit. This work presents a comprehensive investigation into the coiling, storage and deployment behaviors of CTLT that wraps around a central hub. A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigid-bodies mechanisms including the central hub and guide rollers, as well as the complex interactions among them. The coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the literature. Then, the dynamic deployment behaviors were analyzed in terms of two different deployment methods, namely, controlled deployment and free deployment. The effect of material property change during storage was also discussed through numerical experiments.

Disturbance-Free Payload (DFP) spacecraft can meet the requirements of ultra-high attitude pointing accuracy and stability for future space missions. However, as the main control actuators of DFP spacecraft, Linear Non-Contact Lorentz Actuators (LNCLAs) have control output problems with six-degree-of-freedom coupling and nonlinear effects, which will affect the attitude control performance of DFP spacecraft. To solve this problem, a novel concept for Non-Contact Annular Electromagnetic Stabilized Satellite Platform (NCAESSP) is proposed in this study. The concept is centered on replacing the LNCLAs with a non-contact annular electromagnetic actuator to solve the two problems mentioned above. Furthermore, for the different control requirements of the payload module and the support module of the NCAESSP, a high-precision attitude controller based on the robust model matching method and a dual quaternion-based adaptive sliding mode controller are proposed. Additionally, the simulation results verify the feasibility and effectiveness of the proposed approach.

Atmosphere-Breathing Electric Propulsion (ABEP) can compensate for lost momentum of spacecraft operating in Very Low Earth Orbit (VLEO) which has been widely concerned due to its excellent commercial potential. It is a key technology to improve the capture efficiency of intakes, which collect and compress the atmosphere for ABEP. In this paper, the mechanism of the capture section affecting capture efficiency is investigated by Test Particle Monte Carlo (TPMC) simulations with 3D intake models. The inner surface smoothness and average collision number are determined to be key factors affecting capture efficiency, and a negative effect growth model is accordingly established. When the inner surface smoothness is less than 0.2, the highest capture efficiency and its corresponding average collision number interval are independent of the capture section’s geometry and its mesh size. When the inner surface smoothness is higher than 0.2, the capture efficiency will decrease by installing any capture section. Based on the present results, the manufacturing process and material selection are suggested to be prioritized during the intake geometry design in engineering projects. Then, the highest capture efficiency can be achieved by adjusting the length and mesh size of the capture section.