If we observe the aircraft closely, we will find that there are many nails on the skin of the aircraft. We often see such riveting technology in some large bridge buildings.
It is said that there are millions of such rivets on an aircraft – so why not directly weld the aircraft, but choose this seemingly troublesome rivet process?
Strive to reduce the weight of each gram
There is a proverb in the aviation industry: “strive to reduce the weight of each gram.” In order to reduce the weight of aircraft, materials as light as possible will be used in aircraft manufacturing according to local conditions.
In order to reduce weight, the skin of aircraft is usually made very thin. It is very difficult to weld such thin skins together. Moreover, the fuselage of the aircraft is made of aluminum alloy material, which has poor heat resistance, and the welding process will produce a lot of heat during welding, which is obviously not suitable for the aircraft with aluminum alloy fuselage.
The most advanced airliners in the world use a lot of composite materials, which will also be damaged by welding. The interconnection of different materials must be fixed by physical means.
Riveting is more stable and reliable
When I first took a plane, I sat near the wing window. When the plane bumped up and down in the air flow, the wing also shook obviously. At that time, the terrible Xiaobian was frightened
I believe many friends have seen such scenes. If the turbulence is serious, the wings of the aircraft will swing up and down greatly.
In this repeated swing process, the skin of the wing will be stretched or squeezed.
If the welding process is adopted, the strength of the welding will decrease significantly under this repeated stress change. Over time, these welding places are likely to produce some small cracks. If they are not found in time, it is a very big potential safety hazard.
Civil aircraft usually have to be in service for more than ten years. The weld is prone to metal fatigue, and the connection effect is not ideal. Riveting can reduce the vibration transmission between the joints, so as to reduce the risk of seismic cracking. For this repeated stress change, the firmness should be better and more reliable.
Rivets facilitate standardized mass production and reduce maintenance costs
The welding quality largely depends on the skill of operators. The welding is thin and thick, and the randomness is relatively large. It is still difficult to formulate a unified standard.
For these rivets used in riveting process, the error of various parameters is very small, which is easy to carry out quality control and standardized production. As we all know, there are high requirements for Standardization in aircraft manufacturing.
As like as two peas, the first rivet must be exactly the same as the tens of millions of rivets. This principle is similar to the large aircraft itself. It is not too difficult for a large country to manufacture an advanced large aircraft, but it is a great challenge to manufacture tens of thousands of the same products.
Rivets do not increase the aerodynamic resistance, but reduce it
Some people may wonder: will these seemingly protruding rivets increase the aerodynamic drag of the aircraft?
In fact, rivets used in the field of aviation manufacturing are mainly convex head and countersunk head rivets. In the interior of the aircraft, because there is no requirement for aerodynamic shape, the convex head rivet with low cost and easy processing is mainly used.
Countersunk rivets are mainly used for the smooth parts of the aircraft surface, which can effectively reduce the aircraft resistance. There are strict requirements for the tolerance of nail cap and nearby structures in the processing process. When you touch the aircraft surface, you can hardly feel the existence of rivets.
This application has brought remarkable results. According to the relevant data during World War II, the resistance of aircraft can be reduced by about 3% after using countersunk rivets.
The scattered parts are threaded through rivets, and finally become a large aircraft flying in the sky. Rivets are unknown in aircraft manufacturing, but they have made great contributions.