Why do airplanes use rivets instead of welding?

Welding is a widely used process in modern manufacturing. It has the advantages of fast speed and good sealing. It is widely used in aerospace, shipbuilding and automobile manufacturing. So, can welding be used in the manufacturing process of aircraft? The answer is no.

Have you ever carefully observed the outer shell of an aircraft? If you look carefully enough, you will find that there are many rivets on its skin.

↓↓The dense rivets on the aircraft skin↓↓

Why do aircraft use rivets instead of welding? This has to do with the manufacturing materials, working characteristics and the characteristics of riveting...

 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 using traditional welding methods, there is local stress concentration in the welding area, which makes the metal brittle and prone to defects such as sand holes, bubbles and microcracks, making the performance of the structure in these locations lower than that of non-welded 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 more difficult 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 rarely use welding.

 The second reason is the working characteristics of the aircraft. 

When the aircraft is flying at high altitude and high speed, the fuselage skin is subjected to tension. The engine vibrates when it is 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.

↓↓The principle of riveting↓↓

If the aircraft works for a long time in such an environment, small cracks may appear at the welding points. What is more terrible is that the cracks will continue to expand along the welds, 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 easy to repair and replace. If welding is used, the skin of the aircraft must be replaced, which will increase the maintenance cost and the difficulty of a single repair. 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.

So, why is riveting mainly used in aircraft manufacturing, while welding is basically used for aircraft and shipbuilding?

Welding has the advantages of fast speed and good sealing, and is widely used in aerospace, shipbuilding and automobile manufacturing. Riveting and welding are both widely used processes in the manufacturing industry. Riveting has the characteristics of small connection deformation, low requirements for the connection environment, and is suitable for thin parts connection.

↓↓Welding and riveting↓↓

The use of welding in aircraft mainly considers the working environment and service life. The main consideration for aircraft is sealing. When entering the vacuum environment of the universe, the friction of the atmosphere does not need to be considered. Even sound is difficult to transmit, and resonance does not need to be considered. In addition, most spacecraft are recycled and discarded after a few times, so there is no need to consider the service life and replacement of original parts too much. Therefore, it is understandable that there is faster and more convenient welding.