Welding is a widely used process in modern manufacturing. It has the advantages of fast speed and good sealing. It is very useful in aerospace, shipbuilding and automobile manufacturing. So, can welding be used in the manufacturing process of aircraft? The answer is no. The main reasons are as follows:
First, it is caused by the manufacturing materials of the aircraft. Before the advent of Boeing 787 and Airbus A350XWB, the main manufacturing material of modern aircraft was aluminum alloy. This material has a prominent feature-extremely poor welding performance. After welding by traditional welding methods, stress concentration occurs locally in the welding area, making the metal brittle, and it is easy to produce defects such as sand holes, bubbles, and microcracks, making the performance of the structure in these locations lower than that of non-welding areas. This is unacceptable in aircraft manufacturing.
Although there are some special welding processes now, such as stir friction welding and laser welding, the relevant technologies are too complicated and it is difficult to ensure process stability. For the same material, the thinner it is, the harder it is to weld. The thickness of the aircraft skin is generally only about 2 mm. Even if it can be welded, it will be very difficult and not suitable for general operators, which is not conducive to mass production of aircraft.
The fuselage of Boeing 787 and Airbus A350XWB is mainly made of composite materials. These composite materials are made by combining multiple single materials and then undergoing special processes. The difficulty of welding is greater than that of aluminum alloy, and manufacturers almost do not use welding.
The second is caused by the working characteristics of the aircraft. When the aircraft flies at high altitude and high speed, the fuselage skin is subjected to tension. The engine vibrates when working, and the aircraft itself also vibrates. The various forces experienced by the aircraft in each flight are constantly changing, and there will be fatigue problems. Tension, vibration and fatigue are the main reasons for the degradation of welding performance.
If the aircraft works for a long time in such an environment, small cracks may appear at the welding point. What's more terrible is that the cracks will continue to expand along the weld, and even cause the aircraft to disintegrate in the air, resulting in the tragedy of aircraft destruction and death. Riveting and screwing have good anti-vibration and anti-fatigue characteristics, and because of the existence of connection holes, they naturally have the ability to resist the continued expansion of cracks.
Finally, it is caused by the use characteristics of the aircraft. The service life of an aircraft is generally more than 20 years. There are many complex and sophisticated instruments in the fuselage. During long-term use, various devices may be damaged to varying degrees. Riveting is convenient for maintenance and replacement. If welding is used, the aircraft's skin must be replaced, which will increase maintenance costs and the difficulty of single maintenance. Even if there is no equipment failure, the aircraft needs to be inspected and maintained regularly, including the need to disassemble the connected parts for inspection and maintenance. Welding is a non-detachable connection. Once disassembled, the structure is destroyed.
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