Welding is a widely used technology in modern manufacturing industry. It has the advantages of fast speed and good sealing. It is very important in the manufacturing of space, ship and automobile. Can the aircraft welding process be adopted in the manufacturing process? The answer is negative. The main reasons are as follows:
The first is the manufacturing material of the aircraft. Before Boeing 787 and Airbus A350XWB came out, the main manufacturing material of modern aircraft was aluminum alloy. This material has a prominent feature -- poor welding performance. After welding the traditional welding method, the local stress concentration in the welding area makes the metal brittle and easy to produce the defects such as sand, air bubble and micro crack, which makes the structure of the structure in these positions lower than the non welding area. This is unacceptable in aircraft manufacturing.
Although there are some special welding processes, such as friction stir welding and laser welding, the related technology is too complex, and it is difficult to ensure the stability of the process. For the same material, the thinner it is, the harder it is to weld. The thickness of the aircraft is generally only about 2 millimeters, even if it can be welded, the difficulty will be very large, not the ordinary operator can be competent, not conducive to the mass production of aircraft.
Boeing 787 and Airbus A350XWB are composed mainly of composite materials. These composites are made of a variety of single materials through a composite process, then made of a special process. The difficulty of welding is larger than that of aluminum alloy. The manufacturers almost do not use welding.
The next is the performance of the aircraft. When a plane flies at high speed, the body's skin is subjected to pulling force. The engine vibrates at work and the aircraft itself vibrates. All kinds of forces experienced by aircraft in every flight are constantly changing, and there will be fatigue problems. Tensile force, vibration and fatigue are the main reasons for the degradation of welding performance.
When a plane works in such an environment for a long time, tiny cracks may occur at the welding site. More frightening is that the next crack will continue to expand along the weld, and even lead to the disintegration of the aircraft in the air, the destruction of the machine crash. Riveting and screw connection have the characteristics of good resistance to vibration and fatigue, and because of the existence of connecting holes, they naturally have the ability to expand the crack resistance.
The last is the use of the aircraft. The service life of the aircraft is generally more than 20 years. There are many complicated and precise instruments in the body. In the process of long time use, all kinds of devices may be damaged in varying degrees. It is convenient for maintenance and replacement by riveting. If welding is used, all the skins of the aircraft must be replaced, which will increase the maintenance cost and the difficulty of single maintenance. Even if there is no equipment failure, it is necessary to check the aircraft regularly.