Author
Zhao Guolong, Zhao Biao, Ding Wenfeng*, Xin Lianjia, Nian Zhiwen, Peng Jianhao, He Ning, Xu Jiuhua
* Corresponding author
Institutions
Nanjing University of Aeronautics and Astronautics
Citation
Zhao G L, Zhao B, Ding W F, Xin L J, Nian Z W, Peng J H, He N, Xu J H. 2024. Nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in aerospace community: a comparative analysis. Int. J. Extrem. Manuf. 6 022007.
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https://doi.org/10.1088/2631-7990/ad16d6
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Article guide
Lightweight, high reliability, and long life are the development trends of aerospace equipment, which promote the application of a large number of difficult-to-machine materials and structures. Traditional machining is the main material removal process for aerospace parts, but in the processing of difficult-to-machine materials such as high strength, high toughness, high hardness, anisotropy, heterogeneity, and difficult-to-machine structures such as thin walls and micro, a single traditional machining method faces problems such as low material removal efficiency and difficult to guarantee surface integrity. Therefore, there is an urgent need to innovate and develop machining technology to meet the challenges of efficient and high-quality machining of difficult-to-machine materials and structures in aerospace. In this context, a composite machining method for special energy field-assisted machining is proposed. In this method, special energy fields such as thermal energy, sound energy, electrical energy, magnetic energy, and chemical energy are used to improve the machinability of materials in the area to be processed, thereby reducing the difficulty of machining and realizing efficient and high-quality processing of difficult-to-machine materials and structures. Recently, Professor Zhao Guolong, associate researcher Zhao Biao, and Professor Ding Wenfeng (corresponding author) from the School of Mechanical and Electrical Engineering of Nanjing University of Aeronautics and Astronautics jointly published a review of "Special Energy Field-Assisted Machining of Aerospace Refractory Materials and Structures: A Comparative Analysis" in the SCI journal International Journal of Extreme Manufacturing (IJEM), systematically introducing the research background of special energy field-assisted machining. The latest developments and future prospects. Figure 1 illustrates several major special energy field-assisted machining processes, including vibration, laser, composite special energy fields, and other special energy fields (electrical, magnetic, chemical, and jet) assisted machining, as well as the advantages of this composite machining process and its applications in the aerospace field.
keyword
Difficult-to-machine materials, complex structures, special energy fields, machining, aerospace
Bright spots
- The method and principle of special energy field-assisted machining were systematically introduced.
- The advantages and limitations of various composite processing technologies are summarized.
- The forward design, equipment development and sustainability of composite processing technology are prospected.
Fig.1 Special energy field-assisted machining technology, advantages and applications.
Background:
Aerospace equipment has always been at the forefront of the scientific and technological innovation chain, and is of great significance to the development of the national economy and national defense construction. High performance, light weight, high reliability and long life are the eternal themes of the development of aerospace equipment such as aircraft, aero engines, satellites, and spacecraft, which promote the wide application of difficult-to-machine materials and structures, as shown in Figure 2. Difficult-to-machine materials in the aerospace field mainly include: high-strength and high-toughness materials, such as titanium alloys, high-temperature alloys, high-strength steels and ultra-high-strength steels, stainless steels, high-hardness and brittle materials, such as advanced ceramics and glass, and anisotropic and heterogeneous materials, such as metal-based/resin-based/ceramic matrix composites. Difficult-to-machine structures mainly include: microstructures, such as microgrooves, array micropores, thin-walled weak stiffness structures, such as wing wall panels, aero engine casings, and laminated and honeycomb structures, such as composite-metal laminates and aluminum honeycombs. However, difficult-to-machine materials and structures have brought great challenges to traditional machining such as cutting and grinding, and traditional single-field machining has problems such as large cutting force and high cutting temperature, low material removal rate, short tool life, and difficult to guarantee machining accuracy and surface quality. The composite processing technology of special energy field-assisted machining is a new way to solve the processing problems of difficult-to-machine materials and structures. By reducing the strength and hardness of the workpiece material in the area to be processed, inducing material deterioration, and changing the contact mode between the tool and the workpiece, the special energy field significantly improves the machinability of the material, reduces the difficulty of machining, and then improves the material removal rate, tool life and processing quality. In this paper, the process principles, characteristics, material removal mechanisms and applications of vibration, laser, electrical, magnetic, chemical, advanced jet and composite special energy field-assisted machining are reviewed, and the advantages and limitations of the above composite processing methods are compared and analyzed.
Fig.2. Difficult-to-machine materials and structures in the aerospace field.
Latest developments
Ultrasonic vibration-assisted machining technology is an important composite processing method for aerospace difficult-to-machine materials, including ultrasonic vibration-assisted turning, milling, drilling, grinding, etc., by applying sound energy to machining to improve the machining condition through high-frequency and micro-amplitude vibration vibration between workpieces or tools. In ultrasonic vibration-assisted machining, the relative reciprocating micro-amplitude vibration between the tool and the workpiece is superimposed with the original motion to produce the relative motion trajectory interference of the machining, so that the material removal mechanism is changed, so as to reduce the processing force and temperature, and improve the processing quality. The results show that compared with traditional grinding, ultrasonic vibration-assisted grinding can significantly improve the surface quality, reduce the surface roughness by about 20% on average, and increase the residual compressive stress of the machined surface by about 110%, as shown in Figure 3.
Fig.3. Ultrasonic vibration-assisted grinding process and characteristics. (a) Schematic diagram of ultrasonic vibration-assisted grinding process;(b) Comparison of surface morphology between ultrasonic vibration-assisted grinding and traditional grinding. (a-b) used with permission, Copyright (2022) Elsevier.
Laser-assisted machining uses laser irradiation to irradiate the workpiece material in the area to be processed, reducing the performance of the material or inducing the material to deteriorate into a free-cutting layer, improving the machinability of the material, and then using traditional machining methods to remove the material. The study shows that compared with traditional machining, the cutting force of composite machining is reduced by more than 60% and the tool life and machined surface quality are improved with the assistance of laser heating and softening, as shown in Figure 4. In laser-induced oxidation-assisted machining, the cutting force for removing the oxide layer is extremely low, which greatly improves the material removal rate and tool life, as shown in Figure 5. The synergy between laser and tool is a problem worthy of attention in the research of laser-assisted machining technology.
Fig.4. Laser heating-assisted turning composite processing technology and characteristics. (a) Schematic diagram of the process, (b) Trend of material strength with temperature, (c) Cutting force at different cutting speeds, (d) Tool wear at different cutting speeds. (a-b) used with permission, Copyright (2014) Elsevier. (c-d) used with permission, copyright (2010) Elsevier.
Fig.5. Laser-induced oxidation-assisted milling composite processing technology and characteristics. (a) Schematic diagram of the process, (b) Surface morphology of the material before and after laser irradiation, (c) Comparison of cutting force when milling oxide layer and matrix material, (d) Comparison of cutting force and tool life of composite machining and traditional milling process. (b) Used with permission, Copyright (2020) Elsevier. (c) Used with permission, Copyright (2023) Elsevier. (d) Used with permission, Copyright (2021) Elsevier.
Composite special energy field-assisted machining is a composite processing technology that uses two or more special energy fields to improve the machinability of workpiece materials, and then uses mechanical processing methods to remove materials. The composite special energy field effectively uses the advantages of each single special energy field, and at the same time makes up for the limitations of a single special energy field to achieve complementary advantages. The mechanism of the composite special energy field to improve the machinability of materials mainly includes changing the properties or deformation behavior of workpiece materials, inducing phase transformation or modification of materials, changing the interaction between tool and workpiece, and improving the chip forming process. As shown in Figure 6, compared with traditional machining, the cutting force of this process is reduced by more than 70%, the tool life is increased by more than 90%, and the machining surface roughness is greatly reduced.
Fig.6. Laser-ultrasonic vibration-assisted machining and its characteristics. (a) Schematic diagram of process principle;(b) Comparison of surface roughness between composite machining and traditional machining;(c) Comparison of cutting force of traditional machining, ultrasonic vibration-assisted machining, laser-ultrasonic vibration-assisted machining and laser-assisted machining;(d) Comparison of cutting force and tool life of composite machining and traditional milling process. (a-b) Used with permission, Copyright (2023) Elsevier. (d) Used with permission, Copyright (2020) Springer Nature.
The research of electrically-assisted machining mainly includes two processes: EDM-assisted machining and electric field-assisted machining. In EDM-assisted machining, the high temperature generated by the spark discharge causes the workpiece material to melt or even vaporize and be eroded, and at the same time produces a metamorphic layer, which is then removed by machining, as shown in Figure 7. Due to the high-temperature softening effect, the machinability of the metamorphic layer is improved. Studies have shown a 50% reduction in cutting forces and a 5-fold increase in material removal and tool life in EDM. The research of electric field-assisted machining is mainly focused on the field of polishing, under the action of electric field, the abrasive particles in the electrorheological fluid form a flexible polishing head, and the characteristics of the electrorheological fluid are controlled by adjusting the electric field intensity. Studies have shown that the polishing efficiency of this process is 5.6 times higher than that of the traditional polishing process.
Fig.7. EDM-assisted machining and its characteristics. (a) Schematic diagram of process principle, (b) Comparison of cutting force between composite machining and traditional machining, (c) Comparison of machining surface roughness, (d) Comparison of tool wear, (e) Comparison of tool wear morphology. (a-d) Used with permission, Copyright (2020) Elsevier, (2022) Elsevier. (e) Used with permission, Copyright (2022) Elsevier.
Magnetic field-assisted machining is a method of applying an external magnetic field in traditional machining to agglomerate the magnetic particles in the magnetorheological fluid to form a "small polishing head" with controllable shape and hardness, so as to achieve material polishing. By adjusting the strength of the applied magnetic field and other parameters, not only can the size and shape of the polishing area be controlled, but also the stability, contact stiffness and toughness of the polishing slurry can be ensured. Studies have shown that magnetic field-assisted polishing can greatly improve polishing efficiency and surface quality, as shown in Figure 8. There is also research on the use of external magnetic field to control the damping of tools or workpieces in machining, which effectively reduces the vibration in machining and improves the machining stability.
Fig.8. Magnetic field-assisted polishing technique. (a) Schematic diagram of process principle, (b) Schematic diagram of uniform polishing principle of complex surface, (c) Morphology and roughness of traditional polished surface, (d) Morphology and roughness of magnetic field-assisted polishing surface. (a) Used with permission, Copyright (2020) Elsevier. (b) Used with permission, Copyright (2014) Elsevier. (c-d) used with permission, Copyright (2017) Elsevier.
Chemical-assisted machining is a composite processing process that uses chemical solvents to improve the machinability of workpiece materials, and then uses mechanical processing methods to remove materials, and the current research mainly focuses on chemical-assisted mechanical polishing processes, as shown in Figure 9. In the process of chemically assisted mechanical polishing, there are usually two chemical reaction modes: solid-solid and solid-liquid. In the first mode, a chemical reaction occurs between the solid abrasive particles and the solid workpiece to form a soft layer that can be easily removed by the abrasive particles, while in the second mode, a chemical reaction occurs between the chemical reagent and the solid workpiece to form a soft layer. At present, this process has been widely used in the polishing of silicon wafers, sapphires, diamond films and metals.
Fig.9. Chemical-aided mechanical polishing technology. (a) Schematic diagram of the process, (b) Interface between polishing pad and workpiece, (c) Schematic diagram of abrasive removal of metamorphic layer, (d) Surface morphology of polishing pad.
Advanced Jet-Assisted Machining is a method of using advanced cooling lubricating media to reduce the cutting force and cutting temperature of the machining process, or to change the material properties of the workpiece (such as reducing the viscosity of the material), thereby improving machining efficiency, surface quality, and tool life. At present, the research mainly includes three aspects: low-temperature assisted machining, micro-quantity lubrication and low-temperature micro-quantity lubrication-assisted machining, and high-pressure jet-assisted machining. The results show that under the assistance of advanced jet, not only the cutting force and cutting temperature are greatly reduced, but also the stress state of the machining surface and the machining defects are improved, as shown in Figure 10.
Fig.10 Advanced jet-assisted machining technology. (a) Stress-strain curves of materials under different cooling and lubrication methods, (b) Chip morphology, (c) Schematic diagram of machined surface defects. (a-c) Used with permission, Copyright (2022) Elsevier.
Future outlook
With the rapid development of aerospace equipment, new difficult-to-machine materials and difficult-to-machine structures that can withstand extreme service environments are emerging. Although the special energy field-assisted machining methods reviewed in this paper have shown obvious advantages in processing difficult-to-machine materials and structures, there are still some problems worthy of further study. As shown in Figure 11, the future outlook mainly includes the following aspects: in order to obtain the optimal process matching to achieve the purpose of improving quality, efficiency and cost reduction, the forward design of special energy field-assisted machining technology is the focus of future research; in order to meet the needs of high-end, intelligent and green development of manufacturing industry, special energy field-assisted machining intelligent equipment needs to be developed urgently, and sustainable composite processing technology design is also a field worthy of future research.
Fig.11 Research prospect of special energy field-assisted machining of aerospace refractory materials and structures.
About the Author
Prof. Guolong Zhao
Nanjing University of Aeronautics and Astronautics
Zhao Guolong is a professor and doctoral supervisor of Nanjing University of Aeronautics and Astronautics. The main research areas are high-efficiency precision machining, composite machining, micro-machining technology and tool technology. He has presided over the National Natural Science Foundation of China, the Natural Science Foundation of Jiangsu Province, the Special Fund of Jiangsu Science and Technology Program, the National Defense Science and Technology Key Laboratory Fund, the Aeronautical Science Foundation and other projects, and participated in the National Key R&D Program, the Two Aircraft Special Project, the National Defense Foundation, the National Natural Science Foundation of China and other projects as the backbone of the project. The research results won the second prize of Beijing Science and Technology Progress Award and the first prize of Science and Technology Progress Award of China Aerospace Science and Technology Corporation. He has published more than 100 academic papers and authorized more than 20 invention patents. He served as the deputy secretary-general of the Cutting Advanced Technology Research Branch of the China Knife Association, a member of the first committee of the Extreme Manufacturing Branch of the Chinese Mechanical Engineering Society, a member of the youth editorial board of 5 journals, a member of the Huang Danian-style teaching team of "Aerospace Advanced Manufacturing" in national universities, a senior member of the Chinese Mechanical Engineering Society, and was selected into the "Six Talent Peaks" high-level talent plan in Jiangsu Province.
Zhao Biao is an associate researcher
Nanjing University of Aeronautics and Astronautics
Zhao Biao, associate researcher of the School of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, is mainly engaged in the research of efficient precision machining technology of aerospace difficult-to-machine materials and components. He was selected into the Young Talent Lifting Project of China Association for Science and Technology, won the second prize of Jiangsu Science and Technology Award, and the first excellent doctoral dissertation of the Chinese Society of Aeronautics and Astronautics. He has presided over more than 10 scientific research projects such as the key projects of the two basic science centers, the integrated projects/youth projects of the National Natural Science Foundation of China, the special funding of the postdoctoral station, and the Natural Science Foundation of Jiangsu Province. As the first author/corresponding author, he has published more than 50 SCI journal papers and applied for/authorized more than 10 invention patents
Prof. Wenfeng Ding
Nanjing University of Aeronautics and Astronautics
Ding Wenfeng, professor, doctoral supervisor and deputy dean of the School of Mechanical and Electrical Engineering of Nanjing University of Aeronautics and Astronautics, is mainly engaged in the research of efficient precision machining technology of aerospace difficult-to-machine materials. He has presided over more than 20 projects such as the National Natural Science Foundation of China, the National Key R&D Program, the two aircraft special projects, and the civil aircraft special projects. 24 invention patents have been authorized (ranked 1), and 160 journal papers have been published in one work/newsletter, including 142 SCI papers, 17 EI papers, 15 ESI highly cited papers, and 5 ESI hot papers. He has won 4 science and technology awards at or above the provincial and ministerial level, 2 first prizes of provincial teaching achievements, and 1 second prize of national teaching achievements. He has been selected as a Highly Cited Scholar in China by Elsevier, a young and middle-aged academic leader of the "Blue Project" of Jiangsu Universities, and a high-level talent of the "Six Talent Peaks" in Jiangsu Province. He has served as the editor-in-chief/editorial board member/youth editorial board member of 6 domestic and foreign SCI/EI indexed journals.
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