How are fighter jets "pieced together"? Originally, it all relied on this technology
2024-06-07
The "one nail, one rivet" fighter jet aircraft flies in harsh weather conditions, and the wings will experience severe shaking. At this time, some people may ask, "Will the wings break in the air?" In fact, the toughness of the wings is very good, and the safety factor is relatively high. In addition to selecting materials and designs, it also benefits from safe and reliable riveting processes. In addition, the large fuselage of fighter jets is not formed as a whole, and different sizes of skin and body structures are tightly "spliced" together through riveting technology. Riveting is the use of rivets to connect multiple workpieces, ranging from daily necessities such as scissors and pliers to the manufacturing of ships, spacecraft, and bridges, all of which use riveting technology. Since the birth of fighter jets, riveting technology has been widely used in the aviation industry manufacturing and maintenance fields. So, what are the unique advantages of riveting technology? How were the fighter jets "pieced together" again? Please refer to the interpretation of this article. In the Weapons Museum of the Chinese People's Revolutionary Military Museum, there is a MiG-15 fighter jet with the serial number 079 displayed, with rivets covering the fuselage. The riveting process provided by Zhou Le has many advantages. When the fighter jet flies at high altitude and high speed, it often experiences harsh environments such as low temperatures and strong winds, which pose great challenges to the aircraft structure. Unlike the overall die-casting of automobile bodies, the structural components of fighter jets are complex and need to meet the connection requirements of different structural components in terms of material, shape, and size, while ensuring the fastening of the body structure. The common connection methods for metal components in modern technology are mainly welding, riveting, and bolt connection. The choice of connection method depends on factors such as metal material, shape, thickness, force direction, and usage environment. Among them, riveting technology stands out with its unique advantages and has become the most widely used connection method on fighter jets. On the one hand, it is a lightweight choice. High speed and performance have always been the eternal pursuit of fighter jets. In order to be able to go on the battlefield with light equipment, generations of fighter jet manufacturers have almost competed for every gram, striving to "slim down". They not only use "lightweight" materials such as aluminum alloy and titanium alloy, but also have a skin thickness of 2 to 5 millimeters. This type of skin has poor weldability and is easily damaged and deformed due to welding heat, and can only be fixed by physical means. On the other hand, there are requirements for the flight environment. When a fighter jet flies at high speed, it will experience turbulence due to the influence of airflow, and the skin will be subjected to tensile and bending forces in various directions. This requires the connection process to be able to tighten various components, effectively disperse stress from all parties, and also have characteristics such as fatigue resistance, crack resistance, and resistance to repeated vibration. In addition, during the upgrade and maintenance process of the fighter jet, it is necessary to dismantle the skin and check for internal fault issues. Welding technology achieves permanent connections. Once cracks are found on the skin, it has to be replaced on a large area, which is not only time-consuming and laborious, but also increases maintenance costs. The riveting process allows for easy disassembly and assembly of parts of the skin, significantly improving maintenance efficiency. Nowadays, with the development of aviation industry technology, riveting technology has gradually evolved from the earliest single manual operation to new technologies such as hydraulic riveting and electromagnetic riveting to meet the connection needs of different materials and parts. Small rivets have high energy, and when we observe an aircraft up close, we will find countless nails sized rivets on the skin. It is understood that a medium-sized passenger plane is covered with millions of rivets throughout its body. The forms and types of aviation rivets are diverse, and commonly used ones include countersunk rivets, protruding rivets, etc. The selection of rivets varies depending on the installation environment, connection method, and size. In addition, the material and manufacturing quality of the rivets themselves are related to the reliability of the riveting process. Early rivets were mostly small wooden or bone bolts. In 1916, a scientist from the British aircraft manufacturing company obtained a patent for blind rivets that could be riveted on one side and were widely used in fields such as aerospace and shipbuilding. Later, with the upgrading of aircraft skin materials, rivet materials underwent changes from copper and aluminum to metal materials such as steel and nickel. One generation of materials, one generation of equipment. The application of new materials will inevitably promote the iterative upgrading of weapons and equipment. Currently, the emergence of stealth fighter jets and composite materials has raised higher requirements for rivets, with rivets represented by aluminum and titanium alloys gradually becoming the mainstream. Among them, aluminum alloy rivets are mainly used to connect skin, while titanium alloy has higher strength and better corrosion resistance, and is usually entrusted with the important task of connecting aircraft frames, landing gear and other components. Aviation products prioritize quality. The manufacturing quality of rivets is equally crucial. Rivets that appear to be only a few millimeters in size have machining accuracy even reaching the micrometer level. How to standardize the mass production of qualified rivets must be strictly controlled step by step from design, manufacturing to inspection. At present, different countries and industries adopt different manufacturing standards based on actual needs, such as ISO 15983 from the International Organization for Standardization and NAS from the American Aerospace Industry Association. In addition, some airlines also have their own rivet manufacturing standards, such as Boeing's BACR. Regardless of the standard, there are clear requirements for the material, size, integrity, mechanical properties, and corrosion resistance of rivets. In the actual processing stage, the production process of a rivet includes a series of processes such as material preparation, rivet rod drawing, forging, surface treatment, head processing, quenching and tempering, etc. The processing precision is extremely high, and the rivet is assigned with a "ID number number" through specific letters and numbers for identification and later traceability. Inspection is an important gateway to ensure quality compliance. At this stage, rivets need to be inspected in terms of appearance size, tensile strength, torque, etc. If necessary, some key indicators such as fracture load and salt spray resistance will also be tested. After layers of screening, rivets can only be put on duty. Strict manufacturing conditions endow rivets with powerful energy. According to calculations, the specific strength of rivets is as high as 1100 megapascals, which is equivalent to bearing the weight of 10 small cars per square centimeter of area. It can be said that small rivets, with their strong ability, have become an important guarantee for the safety of fighter jet flight. Each process involves learning that aircraft manufacturing is a complex project that requires a lot of working hours. Among them, the assembly process accounts for 40% to 50% of the total working hours, and more than 30% of the labor in the assembly process is spent on riveting. The reason for the long time consumption is due to the large number of rivets and the complex riveting process, which requires a lot of design and calculation. It can be said that every process is learned. Taking advanced fifth generation aircraft riveting as an example, in order to meet the requirements of stealth and aerodynamic shape, the skin of the fifth generation aircraft mostly uses countersunk rivets, which together with the skin form the entire smooth surface of the body to reduce aerodynamic resistance. This method has extremely high requirements for the riveting process. The first step is positioning. Before riveting, a series of preparatory work is required to arrange and layout the rivets according to the riveting position. Designers will use the principles of material mechanics to scientifically calculate the load distribution and transmission laws, and design reasonable rivet shapes and spacing. For key parts such as wings, a rivet array should be designed to ensure sufficient strength and hardness to support the connecting parts. The second step is to drill holes. Drill holes on the structural components positioned in the preliminary layout, and the drilling position must be accurate. Any deviation of less than 1 millimeter from a single hole can lead to the failure of the entire part processing. For this reason, the designer adopted a direct projection method on the skin, and even used AI technology for positioning to ensure the accuracy of the punching position. In practical operation, assembly workers need to machine a groove on the surface of the connecting piece, which is the same size as the nail cap, to fully embed the rivet into the skin, and then drill holes on the inner side of the structural part for later use. The third step is riveting and shaping. After preparing for positioning, drilling, and other work, the riveting process is officially entered. The assembly worker will insert suitable rivets into the previously drilled positions, use a riveting gun to tightly press the rivets into the connection, and shape the protruding parts on the surface of the riveted parts to make them connect smoothly with other components. After the riveting work is completed, the inspectors will also conduct a strict inspection of the appearance of the rivets to ensure that the nail heads are neat, the surface is beautiful, and there are no defects such as skewness, scratches, and cracks. At the same time, the riveted parts will be inspected to see if their strength meets the requirements and if there are any looseness issues, ensuring that their quality is qualified before final delivery. Is it okay after delivery? Of course not, "after-sales service" must also be complete. After a long period of exposure to wind and sun, a fighter jet inevitably experiences "metal fatigue", scratches and cracks on the skin are difficult to avoid, and rivets will also have a certain degree of wear and tear. During the maintenance phase, maintenance personnel need to systematically inspect the overall condition of the fighter jet, replace loose, broken, or damaged rivets, and perform riveting repairs on cracks and corrosion that appear on the fuselage. While ensuring the overall strength and aerodynamic appearance requirements of the fighter jet, the structural weight should be controlled as much as possible. The rapid development of aviation industry technology has brought about the increasingly mature riveting technology. I believe that with the emergence of advanced technologies such as automatic drilling and electromagnetic riveting, it will inevitably improve the efficiency of aircraft manufacturing and maintenance, providing reliable guarantees for the safety of aircraft flight. (Lai Xin She)
Edit：Luo yu Responsible editor：Wang er dong
Source：81.cn
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