The mystery of rivets

Rivets are a type of fastener consisting of a head and a nail rod, mainly used to connect two nail-shaped objects with through holes and a cap at one end. With the needs of social needs, the scope of use of rivets is also very extensive, so that the most memorable thing is that the previous online circulation of "a rivet on the aircraft carrier can be replaced by an Audi car" and "Why don't the aircraft use welding, use rivets?"

Why is the price of rivets for small aircraft carriers tens of thousands of pieces?

We all know that one of the daily tasks of an aircraft carrier is to meet the take-off and landing requirements of carrier-based aircraft. When the carrier aircraft takes off, the temperature of the engine will rise rapidly, and the deck that takes off and land as a fighter needs to be specially designed and processed, which requires that the aircraft carrier deck must have the function of high temperature resistance and impact resistance. In order to protect the ship's surface from high temperature damage, a layer of high temperature resistant veneers need to be installed on the surface of the flight deck. The veneer material is special, which cannot be welded by existing technology, and finally can only choose rivet riveting fixing.

Rivets that can withstand high temperatures are made of special materials, all made of titanium alloys, titanium alloys with its unique high strength, high temperature resistance, corrosion resistance, light weight and other properties, become the best choice. These aircraft carrier deck rivets are naturally expensive because they are made of special materials, special processes, and small batches.

Of course, these rivets to fix the unfolded steel plate is not an easy task, each area of the pressure, load bearing, bite will be slowly changed due to take-off and landing operations, in order to manufacture strength and toughness to meet the requirements of rivets also need a high level of technology.

It can be seen that the technical requirements are high, the material is relatively special and the cost is high, of course, the rivets caused by the system will not be cheap to where to go, besides, the cost of an aircraft carrier is at least tens of billions of dollars, such as the total cost of the US Stennis aircraft carrier reached 33 billion US dollars, you can imagine where the parts on the aircraft carrier can be cheap.

Looking back, why is a lot of riveting used in aircraft manufacturing instead of welding?

In the manufacture of a large aircraft, the number of rivets used is as many as hundreds of thousands or even millions, and there are many ways to connect multiple parts, such as the use of rivets for connection, referred to as riveting; Joining metals by heating high temperature or high pressure, referred to as welding; The use of screw nuts for connection, referred to as screwing; So why choose riveting instead of welding, or other means when building aircraft? There are three main reasons for this:

1. Lightweight materials such as composite materials are not suitable for welding

There's a proverb in the aviation industry: "Fight to lose every gram of weight." In order to reduce the weight of the aircraft, the aircraft manufacturing will use as light as possible materials according to local conditions, and these materials are not suitable for welding in addition to steel structures, aluminum alloys are not suitable for welding, composite materials will also be damaged by welding, and the interconnection of different materials must be fixed in a physical way.

2. The weld seam is prone to metal fatigue problems

Civil aircraft usually have to serve for more than ten years, and welds are prone to metal fatigue problems, making the connection effect poor.

First of all, in the process of welding, the welding metal is affected by different heat dissipation rates, which will produce deformation and great internal stress, and the structure is easily damaged under complex load and force conditions; In addition, because welding is actually a metal reprocessing process, the mechanical properties of the metal near the weld seam will be significantly weakened with the base metal, becoming a weakness of the aircraft structure, and this change cannot be determined, so welding is rarely used on the aircraft.

3. Riveting is more reliable and stable

The reliability and consistency of riveting is much higher than that of welding or screwing, the quality of welding depends largely on the craftsmanship of the operators, and the connection strength of the riveting is relatively stable and reliable, the error of various parameters is extremely small, it is easy to carry out quality control and standardized production, if there is an operation error, the rivet can also be replaced.

Since riveting is suitable for metal structure connections subject to large shock or vibration loads, this high-efficiency connection method can enhance the stability of the structure, and the weight savings of millions of rivets are also considerable.

The role of aviation rivets in aircraft is like the soft tissue connecting human bones, if people do not have soft tissue, the skeleton is no longer strong and useless, the importance of aviation rivets can be seen.