Cryogenic machining is a cleaner processing technology which uses cryogenic coolants such as liquid nitrogen for cooling in material cutting process. It is widely used in the processing of difficult-to-machine metal materials in aerospace and other fields to solve problems such as insufficient cooling efficiency and poor machining quality during conventional cooling processing for these materials. In order to clarify the effect law of cryogenic machining on the surface integrity of difficult-to-machine metal materials, this paper particularly reviews the research progress in the analysis of surface roughness, micromorphology, microstructure, microhardness and residual stress of such materials under different cooling conditions. The results show that cryogenic coolant can take away a large amount of cutting heat and reduce tool wear, thus reducing the machined surface roughness, inhibiting surface defects, promoting grain refinement, improving microhardness and increasing residual compressive stress. Finally, researches on the surface integrity of cryogenic machining are summarized, and works which have not been carried out in relevant aspects are prospected.

The alternative energy technologies, the low energy consumption technologies, the supersonic flight technologies, and the integrated application of the three technologies are the main development directions of the future large airliner. The alternative energy for the large airliner mainly refers to the green and low carbon emission fuels, for example the normal temperature liquid SAF (Sustainable aviation fuels), the cryogenic liquid hydrogen and LNG (Liquid natural gas) fuels. The low energy consumption technologies for large airliner mainly refers to the energy-saving aerodynamic configurations, energy-saving propulsion technologies, and the integrated application of the two technologies, for example the BWB (Blended wing body) airliners and the airliners with large aspect ratio wings, the energy-saving propulsion technologies including extra-large BPR (Bypass ratio) or GTF (Gear transferred fan) turbofan engines, the low noise propfan engines, and the BLI (Boundary layer ingestion) and distributed propulsion methods for integrated configurations and propulsions. The supersonic flight technologies for large airliners mainly refers to the Mach 2–3 supersonic airliners and the future horizontal takeoff and landing hypersonic airliners, the sonic boom depression, the technologies to resolve the conflicts of the low speed states and the high speed states in both the aerodynamic configurations and the propulsion systems are the key design technologies. This article elaborates on the development trends and key technologies of alternative energy sources, low energy design, and supersonic technology for large passenger aircraft, providing new ideas for the future development of civil aviation.

Ceramic matrix composites have the characteristics of high hardness, high strength, anisotropy and heterogeneity, which lead to severe tool wear, poor processing quality and low processing efficiency during processing. The milling process of the laser ablation treated samples proved that almost no force and heat are generated when milling the powdery ablation products. Using finite element simulation and unidirectional ultrasonic vibration-assisted milling, it is found that the ultrasonic vibration-assisted milling process can achieve low-damage machining of ceramic matrix composites without reducing the processing efficiency. A combined processing technology of laser ablation and ultrasonic vibration assisted milling is proposed. Based on multi-dimensional indicators such as machining quality, machining efficiency, and tool cost, the milling machining strategy is comprehensively evaluated. The strategy of laser ablation+ultrasonic vibration assisted milling can obtain a better quality machined surface, and at the same time, the processing time is less, and the tool cost is low. In general, it is a process scheme that can realize high-efficiency and lowdamage milling of ceramic matrix composites

The mechanistic model of cutting force for the dedicated cutter was established by using the method of the equivalent cutting edge vector, in order to accurately predict the changing law of the instantaneous cutting forces generated by the complex multi-tooth dedicated cutter during helical milling. Firstly, the kinematic characteristics of helical milling was analyzed, and the mathematic description of the motion path of any cutting position was achieved. Then the undeformed chips and machining surfaces generated at stable cutting stage were simulated. Thirdly, the length of the equivalent cutting edge, the depth of cut and the width of cut for its corresponding undeformed chip were calculated. Simultaneously, the peripheral cutting edge was analyzed and the whole simulated cutting force model was created. Finally, the simulation value of cutting force was solved through identification experiment of cutting force coefficient. The results show that the values above can accurately predict the instantaneous cutting force change law of the dedicated cutter, and the equivalent edge vector method is an effective way to realize the cutting force modeling of helical milling process.

The key components applied in the aerial and aerospace fields are often made of high-performance materials that are always difficult to machine, which has become a bottle-neck problem hindering the development of related industries due to the lack of high-efficiency and high-quality machining methods for these materials. In this paper, high-speed grinding (HSG) is proposed to solve the problems with conventional machining of titanium alloys, nickel-based superalloys, reaction-bonded silicon carbide (RB–SiC), and aluminum silicon carbide metal matrix composite (SiCp/Al). The surface integrity of different materials after grinding at various conditions are characterized, analyzed, and discussed. The results show that HSG can increase the workpiece surface strain gradient and temperature gradient, reduce the depth of subsurface damage, as well as improve grindability and grinding efficiency for difficult-to-machine metals, ceramics, and composites. The exploratory research in this paper provides a feasible technical route for high-efficiency and high-quality machining of difficult-to-machine materials for broad application prospects in aerial and aerospace fields.

Ultrasonic longitudinal vibration assisted helical milling (ULVAHM) can significantly improve the machining quality. However, the complex kinematics can result in a more complex morphology of the surface machined by ULVAHM than that by a conventional helical milling. To predict the morphology and summarize the rules of the machined surface generated by ULVAHM, a morphology prediction model and its visualization method were proposed in this study, and a verification experiment was conducted to compare the three typical microscopic characteristics, namely, wave texture, sharp-like peak and segmented layer. A favorable agreement between experimental and simulation results was demonstrated. Afterwards, the effects of amplitude, rotational speed, revolution feed and tangential feed on the surface morphology were evaluated by using the model. The investigation results show that the amplitude in ultrasonic vibration leads to the formation of wavy patterns on sidewalls. As the spindle speed increases, the wavy pattern weave becomes sparser. Meanwhile, the height of oblique crest band, the spacing of split layers, and the height of shaped projection are determined by the circumferential feed per tooth, axial feed per tooth, and feed speed, respectively.

Aramid honeycomb core was a kind of lightweight material with excellent properties such as high axial specific strength, high axial specific stiffness, and strong axial compressive strength, which has been widely used in many advanced aircraft, satellites, and automobiles, especially as an important lightweight structural component, widely used in aircraft flaps, doors, floors, and other parts. After the material was formed, machining was an essential process to obtain high-precision contour dimensions and assembly features. However, the characteristics of soft, brittle, discontinuous and thin-walled cause poor machinability. In order to solve the extremely challenging machining problems, domestic and foreign research teams have carried out extensive and in-depth exploration to achieve high-quality and high-efficient machining of aramid honeycomb core. The analysis and overview of the machining mechanism of aramid honeycomb core has been summarized, the fixing methods, machining tools, machining equipment and machining processes of aramid honeycomb core have been systematically summarized, the application in the machining of typical structural components has been introduced, and the future development direction has been prospected

The machining quality of the casing is very important to the manufacturing and performance of the aeroengine. Due to the split structure, the machining process of the split casing is complicated and the machining quality is difficult to control. In this work, the two optimization indexes of high-precision and high-efficiency are taken as the focus to study the processing flow of the bypass duct split casing. Combined with the material characteristics and structural characteristics, the processing difficulties of the titanium alloy split casing are summarized and analyzed. The process scheme is designed for the key processing difficulties, including the selection of high-precision processing equipment, the selection of tooling fixtures in each process, the selection of tools and the setting of process parameters. On this basis, the milling process of the casing outer surface with complex features is focused on, and the processing area is divided to complete the determination of different milling methods and CNC tool paths. Finally, the cutting process was simulated and a complete and detailed machining process was obtained. Through the actual parts processing verification, the optimized process has improved the processing accuracy and processing efficiency. In this work, the research is carried out from the aspects of process route and cutting parameters, which effectively reduces the machining deformation of the parts, obtains the precise and efficient machining method of the bypass duct split casing processing, and provides some experience for the processing of large annular thin-walled parts.

The accurate placement of the ball head fixed to the aircraft structure into the ball socket at the end of numerical control locator is a prerequisite for attitude adjustment and docking of the aircraft structure. Aiming at the problem of locating large components accurately, a sliding mode control based ball adaptive positioning method was proposed. Firstly, perform amplitude limiting and FIR filtering on the output of the three-dimensional force sensor, and perform zero crossing linear regression on its calibration curve to improve the measurement accuracy of the force sensor; Secondly, a force guided locator driving model is constructed, and a force controller is designed based on sliding mode theory, of which design rationality is verified based on Lyapunov stability criteria; Then, a ball head dimming model based on sliding mode control is built in Simulink environment, and the simulation results show that the designed force feedback control system has no vibration and fast response speed; Finally, a simulation part of the fuselage is tested to verify that the test results meet the designed requirement of ball head low stress placement, which verifies the effectiveness of the method.

Due to the characteristics of light weight and high strength, weakly-rigid thin-walled workpieces are widely used in aerospace, automobile and other industrial fields, but they also have the disadvantages of small thickness, low rigidity and easily deformation during the manufacturing process. The fixture layout design is a very important factor to reduce the deformation and ensure the quality of thin-walled workpieces. Traditional fixture layout design of thinwalled workpieces depends on the intuitive judgment and experience accumulation of engineers, which is slow, high cost and large randomness of design. With the continuous improvement of computer technology, many scholars applied finite element simulation, mathematical programming method, intelligent optimization algorithm, surrogate model and so on to optimize the layout of thin-walled workpieces fixture components, and have obtained a lot of research results. According to the modeling method of objective function and the optimization algorithm, the related researches are systematically classified and discussed, and the merit and demerit of each modeling method and optimization algorithm are analyzed in detail. Finally, the related researches on the fixture layout optimization method of weakly-rigid thin-walled workpieces are summarized, and the corresponding research advice are put forward.

The wide variety of components and high degree of customization used in the aerospace industry make it difficult to develop positioning fixtures. Visual localization technology is a key part of intelligent manufacturing, which is based on machine vision to determine the position of the workpiece. It does not require a positioning fixture, and can be widely used in a wide variety of work conditions. However, the generality of common visual localization algorithms is not very high. Algorithms are usually only used to detect specific objects. In this paper, a novel visual localization algorithm based on YOLOv5s object detection network and Siamese network (YOLO–Siamese change detection network) was proposed. The network introduced the ConvDiff (Convolutional Difference) module to improve the effect of the feature extraction in the change detection network, and a semi-supervised learning method was used to train the model. Experiments show that without using the target artifact dataset, the algorithm reached 99.3% of the AP@0.5, 89.6% AP@0.5:0.95 on the validation set, and the single frame inference time was 16.13 ms. Without requiring target artifact data, the proposed algorithm achieved high localization accuracy and fast operation speed, thus improving the robustness and versatility of visual localization algorithms.

To solve the problem of uncertain position of camera and rotary milling cutter blade and improve the timeliness of image processing, a milling cutter wear detection method based on machine vision is proposed. According to the structure similarity index, the image quality of the tool was judged, and the image acquisition interval angle coefficient was introduced, and the image acquisition interval angle and spindle speed were determined. Features from accelerated segment test (FAST) algorithm was used to achieve fast and accurate adaptive cutting of tool wear area. Based on FAST feature points, an adaptive threshold segmentation method was proposed to effectively extract the edge of the wear region. Hough transform and minimum external rectangle method were used to correct the inclination angle of the main cutting edge, and then the average width of the wear zone B was extracted. Finally, the milling test was carried out. In 16 groups of tests, the maximum, minimum and average errors between the calculated value and the real value were 4.76%, 0.91% and 3.63% respectively. The experimental results show that the proposed method can obtain high-quality images of all milling cutter wear regions when the spindle is rotating, and then extract wear parameters efficiently and accurately.