In order to deeply reveal the chip formation mechanism of carbon fiber reinforced polymer (CFRP) helical milling at different fiber orientation angles (θ), for the complex oblique cutting characteristics reflected in the side edge milling process of CFRP helical milling, a microscopic finite element model of CFRP oblique cutting in matrix, fiber, and interfacial phases is constructed. The fiber failure mechanism of CFRP after machining at θ of 0°, 45°, 90°, and 135° was analyzed. The relationship between tool oblique angle (i) and chip size was explored, and the change law of residual stress with machining parameters was revealed, at the same time, the influence of the machining parameters and θ on the cutting force was elucidated. The results show that the fiber bending failure occurs at θ of 0° and 135°, shear failure occurs at 45°, and both bending failure and shear failure exist at 90°; Chip size at 0°, 45° and 90° are all positively correlated with i, and chip size at 135° is not correlated with i; Residual stress is positively correlated with cutting speed, not correlated with cutting depth; The cutting force shows the maximum value when θ=90° and the minimum value when θ=0°. When 0°<θ<90°, the cutting force tends to increase, when 90°<θ<135°, the cutting force tends to decrease. It can be seen that the cutting force is positively correlated with the cutting speed and depth, and the maximum error between the simulated and experimental cutting force values for different cutting speed and cutting depth is no more than 11% and 9%, which can predict cutting forces in CFRP helical milling.

Aiming at the lack of effective detection methods for micro-crack defects in the blades of coated single crystal superalloy turbines, the feasibility of eddy current detection method was explored and verified. A set of eddy current detection system was established to detect and identify defects at different depths of IC21 single crystal superalloy blades with thermal barrier coating, and the impedance amplitude variation was analyzed. Video microscope (DM), scanning electron microscope (SEM), metallographic microscope (OM), and energy dispersive spectrometer (EDS) were used to carry out the appearance inspection, anatomical analysis, metallographic examination, fracture analysis, and composition analysis of the defective blades to determine the nature and cause of the abnormal signals detected by eddy current. The developed eddy current probe has high sensitivity and can accurately detect prefabricated defects on complex curved surface single crystal superalloy turbine blades with thermal barrier coating. With the increase of defect depth, the amplitude of eddy current impedance signal increases. When the crack penetrates the blade matrix wall thickness, the amplitude of impedance signal reaches the maximum. The crack morphology of the IC21 single crystal superalloy high pressure turbine blade is similar to that of the original casting surface, and no obvious single crystal fracture characteristics were observed. The γ' phase of the blade matrix maintains a good cubed structure, indicating that the single crystal superalloy turbine blade has not experienced overtemperature during use. The eddy current testing platform can effectively detect about 2.3 mm×1.0 mm crack defects in turbine blades of single crystal superalloy with thermal barrier coating, and the research results effectively fill the gap in the detection method of micro-crack defects in the matrix under the thermal barrier coating. The failure analysis confirmed that the crack of the IC21 single crystal superalloy high pressure turbine blade was caused by the original recrystallization defect, and the process did not clearly require the conical convex of the cast to be repaired, which affected the detection and identification of recrystallization defect during corrosion inspection, which was the main reason for the cracking of the turbine blade. In view of this crack defect, it is suggested that proper casting and testing process optimization of the blade should be carried out to avoid missing detection of the original recrystallization defect.

Wire arc additive manufacturing (WAAM), as a novel rapid prototyping technology, can be applied to fabricate high-mechanical-property components with complex shape. Thin-walled components of GWZ932 alloy were fabricated by WAAM based on cold metal transfer (WAAM-CMT) with different deposition rates, and the microstructure evolution and mechanical properties were studied. The results show that as the deposition rate increases from 4.5 mm/s to 7.5 mm/s, the average height and width of deposition layers both decrease. The reduction of heat input also leads to significant grain refinement. At the deposition rate of 6 mm/s, the alloy shows the best mechanical properties, with the yield strength, tensile strength, and elongation of 161 MPa, 236 MPa, and 4.5%, respectively. The mechanical properties exhibit isotropy, and the fracture surface shows obvious characteristics of brittle fracture.

The high-speed laser deposition process can improve the corrosion problem of conventional cladding coatings. In order to study the effect of scanning speed on the microstructure and properties of cladding coatings, Inconel 625 coatings were prepared on 300M steel substrate with different laser scanning speed. The microstructure, phase composition, hardness and corrosion resistance of the coatings prepared at 40 m/min and 70 m/min were analyzed. The results show that the metallurgical morphology of Ni-based alloy coating prepared at different scanning speed is mainly cellular and columnar, and the phase composition is mainly composed of γ-Ni solid solution and Fe3Ni2. The hardness of high-speed laser cladding layer increases with the increase of line scanning speed, the corrosion potential increases and the corrosion current density decreases gradually. With the increase of scanning rate, the uniformity of the coating is improved, and the dilution ratio, grain size and heat input are significantly reduced, and the diffusion of interface elements is inhibited, so the corrosion performance of the material is significantly improved.

Lithium aluminum (Al–Li) alloy is a new-generation lightweight alloy material used in aerospace applications. In this study, arc additive manufacturing was used to fabricate aluminum–lithium–silicon alloy. A comparison was made between the microstructure and mechanical properties of the alloy in the as-deposited sample and the T6 heattreated sample. The experimental results show that the average size of the α–Al phase in the single-pass thin-walled deposited aluminum-lithium-silicon alloy was approximately 21.2 μm. SEM and XRD results revealed the presence of a large amount of micrometer-scale eutectic Si phase and eutectic phases containing Cu and Li in the microstructure. After T6 heat treatment, the coarse Al₂Cu phase and some eutectic silicon structures gradually dissolved into the matrix. The hardness of the additive sample increased from 96HV to 138HV, representing a relative increase of 43.8%. The tensile strength in the 0°, 45°, and 90° directions was 402 MPa, 350 MPa, and 330 MPa, respectively. The as-deposited samples exhibited tensile strengths of 160 MPa, 134 MPa, and 142 MPa in three directions, whereas the T6 heat-treated samples showed significantly improved mechanical properties.

In the process of laser deposition manufacturing, the complex thermal evolution such as heat accumulation and thermal cycle will lead to the overall bending deformation of the substrate and the parts. In order to avoid the decrease of dimensional accuracy of parts caused by excessive deformation, it is particularly important to measure the deformation caused by machining. In this thesis, a binocular vision deformation measurement system is built, and the image segmentation technology is used to extract the target area to filter out the interference of the additive manufacturing background. The combination of image segmentation and various stereo matching algorithms is studied, and the Census algorithm is used to obtain the disparity map of the segmented image. Finally, the singular value decomposition method is used to fit the reference plane to obtain the deformation value. Experiments show that the measurement system can realize the measurement of interlayer deformation. The method proposed in this paper improves the measurement efficiency while ensuring the measurement accuracy.

The microstructure and mechanical properties of forge + “wire arc additive manufacturing” (WAAM) hybrid manufactured TC11 titanium alloys were investigated by microscope observation, tensile test, SEM observation, microhardness measurement and statistical analysis in this paper. The results show that the hybrid manufactured samples can be divided into three parts: the WAAM region, the heat-affected region, and the forged region according to the structural characteristics. “Elongated equiaxed grains–fine equiaxed grains–columnar grains” distribution characteristic is presented from forging region to WAAM region in both as-deposited and heat-treated samples. The as-deposited microstructure changes from thick Widmanstatten structure in the forged region to fine basketweave in the WAAM region. After double annealing, basketweave transforms into a bimodal structure caused by the recrystallization in the forged region. The microstructure in the WAAM region remains basketweave with larger platelet α. The results of the mechanical properties test show that all fractures occur in the WAAM region because of the lower strength caused by dislocation and grain boundary. The comprehensive mechanical properties of hybrid manufactured TC11 samples are between WAAM samples and forged samples, which show the characteristics of low strength and high plasticity.

TB18 titanium alloy is a new type of near-β ultra-high strength titanium alloy, whose high specific strength and high specific stiffness are favored by the aerospace field. Three electron beam welding and heat treatment processes were used to obtain welded joints of TB18 titanium alloy, the relationship between the microstructure and mechanical properties of welded joints are researched through microstructure analysis, tensile and impact property testing, fracture analysis. Results show that TB18 titanium alloy electron beam welded joints consist of the base material, heataffected zone and fusion zone. In three electron beam welding and heat treatment processes, the fusion zone of solid solution+aging + welding state is composed of the softer β phase, resulting in its mechanical properties show lower strength and higher plasticity. The microstructure of the three regions of solid solution + welding + aging state, welding+solid solution + aging state are β-phase precipitated fine dispersed acicular α-phase. But the former in the fusion zone the ratio of length to diameter of acicular α phase is low, resulting in high strength, poor plasticity and brittle fracture. The ratio of length to diameter of welding + solid solution + aging state in three regions is uniform, so its high strength and good plasticity indicate strength and toughness matching characteristics, hence, it is the optimal electron beam welding and heat treatment process scheme.

Fuel regulator shell parts are the key components in aero-engine hydraulic products, characterized by numerous pore sizes, small aperture, large depth-diameter ratio, and so on. Considering the problems of a long processing cycle, a large number of cutting tools utilization, low efficiency, and high cost in the complex and high-precision hole machining of the fuel regulator shell, the personalized internal type composite forming cutting tools are designed and manufactured based on the structural characteristics and accuracy requirements of the hole. By improving the process plan and optimizing the cutting parameters and fulfilling the practical application in the product, the steady machining of the complex and high-precision hole can be efficiently achieved with high quality

In order to solve the laser peening eigenstrain inversely, based on the numerical theory of eigenstrain, an inverse method for eigenstrain based on geometric characteristics was established. Based on the finite element theory, the control equation between the eigenstrain and deformation of laser peening was established. On the basis of the control equation, an optimization model for inverse of eigenstrain was built by combining the deformation and the initial eigenstrain obtained by the dynamic analysis model. The eigenstrain was solved inversely from laser peening experiments carried out under different energies, and the results were verified based on the deformation and residual stress. The results show that the eigenstrain can be efficiently and accurately inversely solved by fusing of initial eigenstrain from dynamic model and the geometric characteristics of deformation.

The technology of cold extrusion strengthening holes with split sleeve is widely used in aviation manufacturing, maintenance and other fields to improve the fatigue life of aircraft structural holes. The residual stress distribution and fatigue life of cold extrusion strengthened hole of split sleeve were studied by simulation analysis method. Firstly, based on the finite element software ABAQUS, a finite element model of extrusion strengthening of 7050 aluminum alloy components was established, and the simulation results under different extrusion amounts were obtained, and the accuracy of the model was analyzed. Secondly, based on the results of the strengthened model, the fatigue life of the strengthened hole was predicted by using the fatigue analysis software Fe-Safe. Finally, a fatigue test comparison between the unextruded hole and the extrusion-strengthened hole with split sleeve was carried out. The results show that the most reasonable residual stress distribution can be obtained when the designed extrusion amount is 4.0% – 4.5%. When the extrusion amount exceeds 4.5%, the maximum residual compressive stress at the extrusion end basically remains unchanged. After extrusion, the hole diameter changes in a saddle shape along the axial direction, and the hole wall metal flows out toward both ends of the hole. This strengthening process has obvious effect on the fatigue gain of holes, and the fatigue life of strengthened holes is about 10 times that of unreinforced holes.

In the face of the shape measurement tasks of some large components in modern aircraft assembly and manufacturing process, problems such as difficulty in data fusion and large cumulative error may arise when using handheld 3D laser scanners alone. Therefore, a combined measurement method based on handheld 3D laser scanner and photogrammetry system is proposed. The photogrammetry system was used to establish the global measurement coordinate system, and the transformation relationship between the local visual angle measurement coordinate system and the global coordinate system was obtained by matching the same visual points to realize the automatic stitching of local scanning data of handheld 3D laser scanner. The quality analysis report of the large component shape was obtained by comparing the measurement data model with the design prototype. Under the condition of ensuring the measurement efficiency, the combined measurement method can improve the measurement accuracy of the profile surface. Taking the measurement and analysis of the contour accuracy of a certain type of the front frame component as an example, the measurement accuracy can reach 23.6 μm, which proves that the scheme is effective and feasible.

In order to explore the influence of processing parameters on delamination damage and control strategies in the drilling process of CFRP/Al interlayer structures, firstly, a test fixture is designed and a test platform is built. Different types and materials of drill bits are used to conduct drilling experiments on CFRP/Al interlayer structures, and high-quality drill bits are selected from them. Secondly, the optimal machining parameters were obtained through drilling and hole making experiments on high-quality drill bits under different process parameters. Finally, the variation of axial force and torque during the drilling process with process parameters was analyzed, and the hole making control strategy of CFRP/Al interlayer structure was analyzed. The research results show that the hard alloy double-edged step drill bit is the highest quality drill bit, with a speed greater than 4500 r/min and a feed time of 10 s as the optimal machining parameters, the maximum drilling axial force and torque decrease with the increase of feed time and speed, and the drilling quality of CFRP/Al interlayer structure can be improved by increasing the speed and feed time.