Laser shock peening (LSP) is a new anti-fatigue life extension technology applied to the key parts of aeroengines. The existing offline detection methods have the problem of “quality blind spot”. To improve the consistency, reliability and stability of LSP processing quality, it is necessary to carry out accurate perception of multisource information of LSP process and online evaluation of target surface integrity. This paper starts with two kinds of important physical information released by the transient high-energy process of LSP. Namely, laser induced plasma shock wave (LIPSW) and laser induced plasma spectroscopy (LIPS). The status of monitoring and perception of two kinds of information in LSP dynamic process and the research progress of multi-source information fusion technology in LSP field are summarized. Finally, the urgent scientific problems and existing challenges are analyzed.
Composite materials had become one of the most important materials for aircraft structures. However, there is still a certain gap between the application of composite materials in China and the world’s advanced level. The typical feature is that the proportion of composite materials is relatively low. Compared with metal structures, the connection is the weak link in the assembly and manufacturing of composite structures. The riveting of composite structures has a positive effect on aircraft weight reduction and manufacturing cost control, but the riveting of composite materials is prone to damage, which limits its application in key connection parts. In this paper, the mechanical connection technology of aviation composite structure, especially the application of riveting technology, is systematically introduced, including riveting process and method, composite riveting structure and fasteners used in composite riveting. The damage of the composite material during riveting mainly includes three aspects: The damage in the hole making process, the impact damage on the surface of the composite material structure during riveting, and the extrusion damage to the composite material when the upsetting head is formed and the nail rod is expanded. This paper focuses on the impact damage to composite materials caused by the installation process and the extrusion damage to composite materials caused by the expansion of rivets, and puts forward corresponding solutions, mainly from reducing the extrusion degree of composite materials caused by the expansion of nail bars and taking protective measures for composite materials. Combining with the comparison of relevant research conclusions, it is concluded that formulating reasonable process specifications, adopting advanced riveting process methods and paying attention to the protection of gaskets can effectively suppress the riveting damage of composite materials and improve the riveting quality of composite materials. Finally, the development of composite riveting technology is prospected.
Electron beam physical vapor deposition (EB–PVD) is widely used in fabricating thermal barrier coatings (TBCs) onto aero-engine turbine blades. The process stability of EB–PVD determines the quality of TBCs and batch-tobatch consistency. In this work, two technologies including automatic evaporation of ceramic targets and multi-degreeof-freedom motion of blades were developed, in order to improve the EB–PVD coating performance. The results show that the ceramic targets can be automatically evaporated, yielding an even and smooth top surface. Coatings are obtained with a well-developed columnar structure. Two-layer coating system for ultra-high temperature applications can be further realized by the two-crucible configuration, which allows the deposition of two different targets within one coating process. The multi-degree-of-freedom motion enables the blades to rotate and tilt simultaneously, benefiting the tailoring of microstructure and thickness distribution of parts with complex geometries. Burner rig tests conducted for coating properties validation demonstrate that coatings deposited at the top surface of the platform exhibit excellent thermal cycling life compared with that at the outer surface of the blades.
The effect of oxygen doping content on the oxidation resistance of NiCrAlYN nano-cermet coatings at 1100 ℃ was investigated. Three coatings with different oxygen doping were prepared by multi-arc ion plating with O2 flow rates at 0, 10 sccm, and 20 sccm, respectively. After high-temperature at 1100 ℃ for 300 h, α–Al2O3 and NiAl2O4 were formed on the surface of three coatings. The thickness of the oxide scales was 8.78 μm, 7.9 μm, and 5.7 μm, respectively. The oxide scales of the coatings deposited at 0 and 10 sccm showed significant delamination with the upper layer of NiAl2O4 and the inner layer of α–Al2O3, while this was not observed on the coating deposited at 20 sccm. The increase of oxygen doping content in nano cermets could effectively inhibit the formation of large particles of Y–Al oxide contaminant in the oxide scales and thus decrease the growth rate of the oxide scales. After oxidation, the oxygen containing coatings degraded more slowly than that without oxygen doping, which is mainly attributed to the beneficial effect of dispersed oxide particles in oxygen containing coatings on inhibiting the degradation of the coatings.
Thermal/environmental barrier coating with optimized performance is critical for the application in advanced aero-engines. In this work, high-entropy rare-earth hafnates, （La0.2Gd0.2Ho0.2Er0.2Tm0.2）4Hf3O12 and（Yb0.2Lu0.2Ho0.2Er0.2Tm0.2）4Hf3O12, were prepared by a two-step sintering method. Mechanical properties, thermal properties and CMAS corrosion behavior of two materials were systematically investigated. （Yb0.2Lu0.2Ho0.2Er0.2Tm0.2）4Hf3O12exhibits higher hardness and fracture toughness than that of (La0.2Gd0.2Ho0.2Er0.2Tm0.2)4Hf3O12. High-entropy hafnates demonstrate reduced coefficient of thermal expansion and thermal conductivity. When corroded at 1300 ℃ , the reaction of（La0.2Gd0.2Ho0.2Er0.2Tm0.2）4Hf3O12 with molten CMAS is more severe and triggers the precipitation of apatite, which mitigates the infiltration of molten CMAS into thermal/environmental barrier coatings. The rare earth hafnate has been regarded as a promising thermal barrier coating material.
In order to explore the influence of Yb3+ and Er3+ doping at A position in Sm2Zr2O7 on its thermal conductivity, （Sm1–x–yYbxEry）2Zr2O7 (x=0.05, 0.1; y=0, 0.1) ceramic materials were prepared by solid-state synthesis, and their phase structure and thermal physical properties were tested. It is found that the modified（Sm1–x–yYbxEry）2Zr2O7 ceramic material has a cubic pyrochlore structure. Due to the change of mass difference and radius difference, phonon scattering increases, average free path decreases, and thermal conductivity decreases. At 600 ℃, the thermal conductivity of (Sm0.85Yb0.05Er0.1）2Zr2O7 is 1.3 W/(m·K). The co-doping of Yb3+ and Er3+ can effectively reduce the thermal diffusivity and thermal conductivity (RT–1000 ℃ ) of ceramic materials, which can be used as candidate materials for thermal barrier coatings.
Based on the orthogonal experiment, effects of power particle size, oxygen-fuel ratio, flow rate of carrier N2 and spray distance on microscopic structure and mechanical properties of D–gun sprayed NiCrAl coatings were investigated. The characterizations of microstructure of as-sprayed coatings were analyzed by SEM. The influence of four factors on the coating properties was studied by testing the porosity, microhardness and tensile bonding strength of the coating. The optimized process parameters of the D–gun sprayed NiCrAl coatings were particle size 13–45 μm, oxygenfuel ratio 1.25, flow rate of carrier N2 20 L/min and spray distance 170 mm. An NiCrAl coating for dimensional build-up application with uniform, dense microstructure, high hardness and adhesive strength was achieved through the D–gun spray process optimization.
To solve the springback and welding deformation problem of case shell, a new sizing method based on rubber fluid forming was proposed. Using a casing as the object of study, the pressure of case shell sizing is preliminarily determined by theoretical calculation. The dynamic explicit finite element method is adopted in the plastic deformation mechanism and circular alignment behavior of thin-walled welded cylindrical parts with the same basic characteristics as the casing is analyzed. And the results of finite element analysis show that the initial diameter, runout and wall thickness of the cylinder have influence on the runout orrection effect. The calibration effect of rubber fluid forming method was verified by a self-made calibration device.
In order to solve the problems of repetitive work, low design efficiency and difficulty in subsequent modification in the design procedure of framed-mold in autoclave processing for composites structures, the parametric design technology which is applied to the design of the mold, is divided into two aspects: the parametric design of dimensions and the parametric design of topological structures. In terms of parametric design of dimensions, based on the analysis of structural characteristics of the mold, the main design parameters of the mold are extracted, and the parametric design process is planned using the top-down design method. The concept of parameters tracing and the method of tracing main design parameters are proposed so as to modify the dimensions of the mold rapidly through parameters. In aspect of parametric design of topological structures, some topological structures of the mold can be modified parametrically by combining the knowledge engineering module of CATIA with object-oriented technology. Based on CATIA CAA secondary development platform, a parametric design system of mold in autoclave processing for composites structures is developed and verified with examples.
The assembly tools are the assembly process equipment for aircraft wings, fuselage, and other components. It has much higher assembly accuracy requirements than the aircraft components assembled on it. In this paper, the assembly tools of an aircraft component are the research object. According to the technical concepts of digital twin, a digital twin-based assembly process model is constructed to install assembly equipment accurately. And considering related elements such as personnel, tools, standards, and inspection requirements associated with the tools assembly process, the assembly process of the tools is planned and simulated. The visual assembly process orders are used to guide the actual assembly process, and the information interaction and feedback are realized by establishing the association between digital space and physical space.
In order to further improve the reliability of the turbofan engine rotor system assembly, this paper proposes a process failure mode influence analysis method for the rotor system assembly based on the assembly process characteristics of the turbofan engine rotor system. The PFMEA analysis process and PFMEA analysis objects of the rotor system assembly are given, and the PFMEA analysis is carried out with the nut assembly process and the rotor dynamic balance process as examples. The typical process failure modes are given, and the corresponding failure prevention measures are put forward to achieve the purpose of improving the process reliability of the rotor system. In order to improve the efficiency of PFMEA analysis and realize the effective management of the failure mode of the rotor system assembly process, the PFMEA analysis system is proposed, and the functional modules and implementation methods of the system are given.
