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This SAE Aerospace Standard (AS) defines the requirements for a polytetrafluoroethylene (PTFE) lined, para-aramid fiber reinforced, hose assembly suitable for use up to 4000 psi, and up to 275 °F, aircraft and missile hydraulic and pneumatic systems.
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
This specification covers a corrosion-resistant steel in the form of investment castings, solution and precipitation heat treated to 150 ksi (1034 MPa) tensile strength.
AMS F Corrosion and Heat Resistant Alloys Committee
To describe general guidelines for achieving selected levels of cleanliness in gas turbine engine fuel system components and to describe laboratory methods for measuring and reporting the contamination level of the wetted portion of fuel system components. As in SAE J1227 (covering hydraulic components), this practice includes guidelines for levels of acceptance but does not attempt to set those levels.
AE-5A Aerospace Fuel and Lubrication Systems Committee
This specification covers a premium aircraft-quality, low-alloy steel in the form of sheet, strip, and plate.
AMS E Carbon and Low Alloy Steels Committee
This specification covers spooling and packaging of bare welding wire to ensure cleanliness and freedom from corrosion, spool sizes and weights of spooled wire, and package weights of cut lengths.
AMS B Finishes Processes and Fluids Committee
This standard provides the recommended requirements for electrostatic spray application of AMS3143 powder coatings to aerospace components. Adherence to these requirements will facilitate satisfactory performance of the applied powder coating.
AMS G8 Aerospace Organic Coatings Committee
This SAE Aerospace Standard (AS) defines the requirements for a convoluted polytetrafluoroethylene (PTFE) lined, metallic reinforced, hose assembly suitable for use in aircraft fluid systems at temperatures of -65 to 400 °F and at operating pressures per Table 1.
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
This document aims to define the procurement requirements for galling-resistant, corrosion-resistant steel wire, with the chemical composition per UNS S21800 and AMS5848 and spring temper, used in the manufacture of helical coil threaded inserts. It will enable insert manufacturers to adhere to specific standards to meet the criteria outlined in this procurement specification.
E-25 General Standards for Aerospace and Propulsion Systems
This specification covers the requirements for shot peening of surfaces of parts by impingement of media, including metallic, glass, or ceramic shot.
AMS B Finishes Processes and Fluids Committee
Addressing the performance degradation bottleneck of conventional impact-resistant materials under complex operating conditions, and the limitation of existing research focusing primarily on enhancing single properties while neglecting material equilibrium, this study employs silicon carbide whiskers (SiCw) as the reinforcing phase. Through surface modification techniques, SiCw/celluloid and SiCw/polyimide dual-polymer composite systems were constructed and systematically investigated. Surface modification of SiCw was achieved using titanate and silane coupling agents. Through mechanical testing and X-ray photoelectron spectroscopy (XPS) characterisation, the effects of SiCw loading and modification treatments on composite mechanical properties and interfacial bonding were analysed. Results indicate that SiCw introduction significantly enhances the tensile, flexural, and impact strength of the polymer matrix, with optimal addition ratios identified: 6% for the celluloid system and 1.0% for the polyimide system. Surface modification further optimises toughening effects by reducing surface oxide layers and impurities on SiCw particles while strengthening interfacial bonding. This study provides practical guidance for the system design of high-performance impact-resistant composites. The resulting materials hold broad application prospects in sectors demanding high structural impact resistance, such as aerospace and transportation.
Xue, Kaiming
Aiming at the engineering problems of easy cracking and insufficient impact resistance of traditional airport concrete pavement under complex dynamic loads, this paper studies the application of functionally graded carbon fiber reinforced polymer ( FG-CFRP) in airport pavement. Based on the modified Halpin-Tsai model and the first-order shear deformation theory, the dynamic finite element control equation is established. Based on the COMSOL Multiphysics platform, the modal characteristics and transient impact response analysis are carried out, and the dynamic response of the aircraft under moving wheel load is simulated. The static bending test of FG- CFRP plate samples made in the laboratory was carried out, and the numerical model was calibrated. The relative error of test-simulation was controlled within 5 %, which verified the accuracy of predicting static response. The carbon fiber volume fraction gradient curve was parametrically studied to reveal the sensitivity of the gradient to impact and stress reduction. The key engineering factors such as long-term environmental durability and life cycle cost of FG-CFRP pavement are discussed, and targeted improvement and optimization strategies are proposed. The results show that the fundamental frequency of the gradient plate is about 1.93 % lower than that of the homogeneous plate, and the vibration mode characteristics are highly consistent. The peak displacement of transient impact is reduced by 9.4 %. Under the action of moving wheel load, the peak Von Mises stress decreased from 5.32 MPa to 2.15 MPa, with a decrease of 60 %. The gradient design realizes efficient load diffusion and impact hardening through the surface high modulus layer, and the gradual change of interlayer wave impedance promotes the dissipation of stress wave, which significantly improves the safety reserve and dynamic stability of pavement structure. This study verifies the application feasibility of FG-CFRP in high-performance airport pavement engineering, and provides innovative material solutions and theoretical support for the development of a new generation of long-life and high-reliability airport pavement.
Li, Zhenyue
Gas path faults in aero-engines are a major factor affecting flight safety and maintenance costs. To achieve the transition from time-based maintenance to condition-based maintenance and enhance fault prediction and health management capabilities, this paper conducts research on intelligent diagnostic methods based on performance parameters for engine gas path components. Firstly, a component-level nonlinear steady-state model of a dual-spool turbofan engine is established, employing a variable specific heat capacity method to improve computational accuracy and provide a healthy baseline for diagnosis. Secondly, addressing the strong nonlinearity and measurement underdeterminacy in fault diagnosis, a diagnostic framework integrating a multi-population genetic algorithm and multi-operating-point analysis is proposed. The multi-population genetic algorithm effectively enhances global optimization capability and solution stability through parallel evolution, migration operators, and an elite population strategy; multi-operating-point data increases information content and strengthens fault isolation capability. Finally, simulation experiments under ground test conditions are conducted to validate the diagnosis of single-component faults in the low-pressure compressor, high-pressure compressor, high-pressure turbine, and low-pressure turbine. The results show that the proposed method can accurately invert component performance degradation, with a high fault identification accuracy rate, verifying the effectiveness of the proposed model and algorithm. This research provides a feasible technical solution for intelligent condition monitoring and precise diagnosis of aero-engines.
Cai, Na, Li, Ming, Li, BianJiang, Yu, GuangHui, Ma, ZhongYuan
To provide auxiliary verification for the technical evaluation of low-altitude aircraft operation status and address the limited effectiveness of uncertainty handling, this paper proposes an evaluation method based on fuzzy reasoning and D-S evidence theory. Firstly, the relevant knowledge of D-S evidence theory and fuzzy reasoning is introduced. Secondly, the aircraft operation status levels are constructed, and an intuitionistic fuzzy reasoning system is established based on Gaussian membership functions. The initial basic probability assignments (BPA) are obtained through defuzzification using the intuitionistic fuzzy centroid method. The conflict between evidences is measured by the weighted average of Jensen-Shannon (J-S) evidence distance and conflict coefficient k, followed by multi-cycle discount correction and fusion. Finally, experimental verification proves the rationality of the proposed method, which can provide a reference for related research.
Niu, Xiaowei, Shen, Di, Yu, Fuping, Guo, Yiduo, An, Xiangyu, Xuan, Haoli
To improve the efficiency of airport surface operations involving multiple aircraft types and multiple flight-test aircraft at the same airport, this study investigates the taxi-route optimization problem for flight-test aircraft. First, a runway-exit-time optimization model is established by modeling the landing rollout process, with minimum runway-occupancy time as the objective, so as to determine the optimal rapid-exit taxiway. Second, a multi-aircraft taxi-route optimization model is formulated by incorporating taxi-conflict constraints and is solved using an improved wolf pack algorithm. The case study shows that the proposed method can effectively reduce the total taxi time of multiple flight-test aircraft and shorten the runway-occupancy time of arriving aircraft, thereby demonstrating good feasibility and practical engineering value.
Wang, Tong
In assessing lumbar spine injuries of civil aircraft occupants under vertical impact, existing anthropomorphic test devices cannot accurately capture the injury mechanisms. Digital human body models, such as THUMS, are primarily developed for automotive crashes, and their default seated posture differs from that of real civil aircraft occupants. Although the THUMS model can be adjusted to better represent civil aircraft occupants’ seating posture, the mechanical response of the lumbar spine after adjustment has not been sufficiently validated. This limits the model’s reliable use in assessing lumbar spine injuries of civil aircraft occupants. To address this limitation, the THUMS lumbar spine model was modified to reflect aircraft seating posture and physiological lumbar lordosis, and the stiffness of key lumbar ligaments was systematically optimized. Following optimization, the model’s mechanical response curves under flexion, anterior shear, tension, and compression all fell within the post-mortem human subject (PMHS) response corridors, with deviations from the mean PMHS curves significantly reduced. Under the typical 14 g vertical impact specified by FAR 25.562, the optimized lumbar spine exhibited lower peak flexion moments at all lumbar levels, while the axial compressive load and predicted injury risk became more concentrated in the upper lumbar spine. These findings indicate that directly using the original THUMS model may underestimate injury risk in the upper lumbar region while overestimating it in the lower lumbar segments. Posture adjustment, lumbar curvature correction, and ligament stiffness optimization enhance model biofidelity, providing a more reliable basis for the assessment of occupant lumbar injuries.
Shi, Xiaopeng, Jiang, Zihao
In transportation infrastructure constructed in mountainous and rocky regions, such as highway slopes, railway cuttings, bridge abutments, and tunnel portal slopes, uplift-resistant anchorage systems are widely required to ensure structural stability and service safety. To support anchorage design in such conditions, this study investigates the uplift bearing behavior, load-transfer mechanism, and key design parameters of pressure-type rock anchors in weathered rock strata through a combined field-and-numerical approach. A rock anchorage project in mountainous terrain in Shaoxing, Zhejiang Province, China, was adopted as the prototype case, and two representative anchors installed in strongly weathered and moderately weathered tuffaceous sandstone were selected for field pullout testing and three- dimensional finite element simulation. The failure characteristics, uplift load–displacement response, axial strain distribution of the grout body, and the effects of anchorage length and rock-socketed length were systematically examined. The results show that pressure- type rock anchors exhibit favorable uplift resistance in weathered rock strata. No overall pullout failure occurred during the tests, and no obvious cracking or significant ground deformation was observed. The uplift load–displacement curves exhibited a pronounced steep- transition pattern, and the axial strain of the grout body was mainly concentrated near the bearing plate and attenuated upward along the anchorage section. When the anchorage section extended into the moderately weathered rock stratum, strain attenuation became faster and interfacial load transfer became more efficient. Parametric analysis further indicates that the uplift bearing capacity increases approximately linearly with anchorage length before a critical anchorage length is reached, whereas the increase becomes much less significant beyond about 8 m. In addition, a proper increase in rock- socketed length can significantly improve the uplift bearing capacity. The findings provide useful reference for the design and optimization of uplift-resistant anchorage systems in transportation infrastructure founded in layered weathered rock.
Feng, Bing, Li, Panfeng, Zhou, Ji’an, Lv, Qing
In air-breathing hypersonic flight, when the flow conditions upstream and downstream are not appropriate, the air inlet is prone to failure to start, which can lead to engine stall or even flight failure. Therefore, real-time identification methods for air inlet flow modes must be developed. This paper takes the hypersonic inlet as the research object. In the wind tunnel experiment, the switching of the inlet unstarting/restarting was achieved by changing the Angle of attack, and the shadow images during the mode switching process and the pressure signals of multiple wall measurement points were obtained. The study shows that the traditional modal recognition method based on pressure amplitude, standard deviation, and power spectrum has a weak ability to recognize the starting/unstarting flow modes of the inlet in this paper. For this purpose, this paper proposes a flow mode recognition method based on pressure difference and standard deviation, which can achieve good recognition ability for each measurement point and has strong applicability. In addition, the method identifies the unstart point and the restart point separately instead of using a single detection threshold for judgment, significantly improving the accuracy of flow mode identification.
Si, Jinglin, Pi, Cuixuan, Xu, Shangcheng, Wang, Yunlong
Autonomous operations near space targets that do not cooperate present great challenges because position and attitude planning must be linked. A target of this type lacks navigation aids or communication systems, which makes relative motion planning much more difficult. Although methods based on convex optimization work well for problems with three degrees of freedom, like planetary landing, their use in integrated operations with six degrees of freedom is limited by constraints that are not convex. To solve this problem, this paper proposes a new framework for servicing spacecraft using sequential convex programming. The primary contribution is the extension of convex methods to high dimensional trajectory planning while adding a robust trust region constraint based on trajectory deviation. This mechanism reduces the chance of finding no solution during convex approximations. It improves reliability and convergence when solving complex problems. The approach first creates a continuous optimal control problem with an index that balances energy use and the angle of the line of sight. Nonlinear dynamics are simplified using first order Taylor expansions. Constraints for the field of view and collision avoidance are modeled using spherical and ellipsoidal regions. The non convex problem is changed into a sequence of discrete convex subproblems and solved through iterations. Numerical simulations show that the servicing spacecraft can safely approach the target with stable attitude while meeting all physical limits. The method using sequential convex programming with a trust region demonstrates great potential in optimizing computational efficiency alongside strong numerical stability, laying a solid foundation for future real-time autonomous trajectory generation in complex orbital environments.
Wang, Yuzhi, Yao, Zihao, Wang, Qian, Han, Ziwen, Zhang, Chao, Zhang, Yumei, Li, Shunli
Owing to their remarkable specific strength and stiffness, coupled with superior impact resistance and thermal/acoustic insulation, sandwich composite panels are extensively utilized in marine, aerospace, and transportation sectors. In contrast to conventional monolithic structures, the multi-layered architecture of sandwich panels introduces complex fatigue failure mechanisms that are not yet fully understood. This study experimentally investigates a U-shaped core sandwich panel featuring a rectangular hatch opening under uniaxial tensile fatigue loading, aiming to characterize its crack initiation and propagation behavior. Subsequently, a custom three- dimensional fatigue crack growth simulation code is developed, grounded in linear elastic fracture mechanics and the extended finite element method (XFEM). A comparison with experimental measurements reveals that the maximum relative error between the predicted and observed fatigue life is 15.7%. The findings offer a theoretical foundation and a technical reference for the fatigue design and life assessment of such sandwich structures.
Chen, Siyu, Xu, Yunze, Liu, Gang
This study constructs and validates a high-efficiency and high-fidelity adaptive Very Large Eddy Simulation (VLES) strategy based on user defined function(UDF) secondary development to investigate the complex and unsteady flow characteristics of civil aircraft intakes under crosswind conditions, conducting a comparative study of turbulence simulation methods across different hierarchies. Initially, the performance of traditional RANS turbulence models, including S-A, BSL k-ω, and SST k-ω, in simulating large-scale flow separation within intakes under crosswind conditions is evaluated, revealing that their applicability is limited. However, the predictive accuracy of RANS models can be improved to some extent by incorporating Explicit Algebraic Reynolds Stress Models (EARSM) and non-linear constitutive corrections. Under the maximum crosswind mass-flow condition, for complex flows dominated by shock and boundary-layer interaction, the SST model, high-resolution Large Eddy Simulation (LES), and the developed VLES model are compared. Furthermore, under variable crosswind mass-flow conditions, a comparative study on separation characteristics between the VLES and SST models is carried out. Finally, the simulation performance of the VLES model under installed nacelle conditions is verified. Research results indicate that the VLES model achieves superior near-wall boundary layer resolution while effectively mitigating the over-prediction of separation zone extent typically associated with LES, demonstrating higher accuracy without a significant increase in computational cost. Through verification via independent nacelle calculations, the VLES method shows a high degree of consistency with experimental data and non-linear SST model results in predicting separation characteristics under varying mass-flow rates, accurately reproducing the processes of shock-induced separation and boundary-layer reattachment. This research establishes the superiority of the VLES method in handling complex intake flow separation, laying a theoretical and technical foundation for its engineering application in the aerodynamic assessment of actual installed nacelles.
Jiang, Jintao, Han, Xingsi, Liu, Hao, Guo, Jin, Yu, Fan, Xu, Xiao
Spacecraft are now required to possess all-weather, zero-window, and support-independent launch capabilities. Consequently, research on spacecraft targeting must continue to focus on improving convenience and efficiency. In this paper, a spacecraft targeting method based on point cloud alignment is proposed. Firstly, external Triple Self-targeting Inertial Measurement Units are utilized to complete self-targeting. Secondly, the 3D point cloud of the spacecraft is obtained by binocular imaging technology, and an attitude transformation matrix is obtained by aligning the measured point cloud with the standard point cloud. Finally, the installation relationships between the binocular camera and the Triple Self-targeting Inertial Measurement Units, as well as between the guidance system and the spacecraft body, are determined. Combining these installation relationships with the attitude transformation matrix, the targeting results from the Triple Self-targeting Inertial Measurement Units are transferred to the spacecraft guidance system. In the simulation experiment, the maximum standard deviation of the three directions after multiple targetings is 9′9″, which can meet the requirements of spacecraft targeting. The method proposed in this paper fully retains the self-targeting advantages of the Triple Self-targeting Inertial Measurement Units without external support, while making spacecraft targeting more flexible and rapid. If applied to actual equipment, it will effectively enhance the adaptability of spacecraft equipment to environments.
Wu, Bingjie, Wang, Xiaozi, Zhang, Wei, Li, Mingrun
To improve the thermal shock resistance of the shell steel, a Cr coating was deposited on its surface using arc ion plating technology. The protective capability of the Cr coating on the shell steel at 900 °C following a water-cooling cycle was investigated. Automatic scratch tester, scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) were employed to characterize adhesion to the substrate, the microstructure, phase composition, and elemental composition of the shell steel and the Cr coating. The results indicate that the adhesion strength of the Cr coating is approximately 26.21 N, which is about 20.16% lower than the 32.83 N adhesion strength of the original Cr coating. At 900 °C, Fe₃O₄ and Fe₂O₄ form on the surface of the shell-and-tube steel. The oxide film exhibits cracking, peeling, and thermal fatigue, while oxidation defects accumulate within the steel, accompanied by significant precipitation of Ni. A dense Cr₂O₃ oxide film formed on the surface of the Cr coating, releasing thermal stress in the form of grid-like cracks. Under 10× magnification, no oxidation defects were observed within the Cr coating, and Fe from the substrate did not diffuse into the Cr coating; Under 100× magnification, the Cr coating exhibits fewer oxygen channels than the steel tube body. Oxygen is concentrated within these channels, and the Cr coating demonstrates significant resistance to thermal fatigue, providing markedly superior protection against thermal shock compared to the steel tube body.
Sun, Huixian, Lu, Xudong, Zhang, Rui, Guo, Cean