The characteristics of the fasteners used in the aircraft

The fastener market for aerospace aircraft fasteners is very extensive, and its performance requirements are very strict, which cannot be compared with ground machines. The main requirements are light weight, high strength, stable and reliable work performance and physical performance, vibration resistance, and relaxation performance. The detailed features are:

1. The amount of fasteners is very large. A medium-sized aircraft uses up to (2~3) million fasteners of various types. The total weight of the fasteners used in modern aircraft can account for 5 of the total weight of the aircraft. ~6%, the load capacity of the aircraft, that is, the effective load, is one of the important design indicators, generally 20~30% of the total weight of the aircraft. If the fastener connection can reduce the weight equivalent to 1% of the total weight of the aircraft, It will make a great contribution to the load capacity of the aircraft.

2. Very high requirements on the bearing capacity of the connection, especially the contradiction between high strength and weight is very sharp. Obviously, the weight problem raised by the first point can only be solved on the premise of improving the carrying capacity of the connection. In aerospace vehicles (including engines), there are many parts made of aluminum and magnesium alloys. Many connections have to withstand shock, vibration and variable load. Many connections have to work at high or low temperatures. This year, there are new materials, namely titanium alloys. The use of connected parts and connecting parts. All these have brought many new and special problems to improve the carrying capacity of the connection. The tensile strength of high-strength bolts used in aerospace machinery is about 50% higher than those used in general machinery or building steel structures. This is one of the examples of solving the problem of improving the load-bearing capacity. It is also for this purpose to develop fasteners with new structures and new materials, and to study new technological measures to improve the connection strength. More than 10 years ago, a large foreign aircraft used new materials and new structural bolts, nuts, and rivets, which reduced its structural weight by 4%. This is a fruitful example and also reflects an aerospace fastener connection. Features.

3. A variety of fastener structure forms are required to adapt to the structural form characteristics of the connected parts. The different characteristics of the various material components and the complex force and force transmission methods. There are many types and varieties of fasteners used in aerospace machinery. There are many, especially special structures, mainly because of this.

4. Adapt to the situation where the connection is not spacious or even difficult to access. The structure of the aerospacecraft and its engine is compact, and it must comply with the requirements of the shape. The available connection installation space is narrow, the openness is not enough, and individual is difficult to access. Some connections can only be installed from one side of it, which requires that the structure of the fastener can be adapted. Therefore, a variety of fasteners with special structures and corresponding installation tools have been researched and developed.

5. The general increase in the installation quality requirements of the connection requires that the installation of each connector in the connection is properly prepared and the force is uniform. For bolt connections, strict control of the pre-tightening force is required, and the inspection of the connection and installation quality is required to be convenient and reliable. Due to the large amount of fasteners, the installation speed is also a prominent problem. As aerospace vehicles have the characteristics of thin-walled structure and sheet metal structure, the connection position adjustment and compensation required to compensate for the accumulation of component size errors or deformation during installation is also a problem. Bring special problems.

6. The problem of connection loosening Many connections are subject to shock, vibration and variable load, and the mechanism of connection loosening is not exactly the same, which further complicates the problem.

7. A large number of shear bolt connections are used due to the mechanical characteristics and force transmission characteristics of the aerospace vehicle components, a large number of shear bolt connections are used, which is different from the large number of tension bolt connections used in general machinery, which leads to many Problems with connection structure details, connection installation and strengthening problems.

8. The service life of the spacecraft's fasteners is very short.

The above characteristics should be fully reflected in the research, design, manufacture, use and standardization of aerospace fastener connections.

The development of aerospace vehicle fastener connections is closely related to the development of general mechanical fastener connections. There are many types, varieties, and large amounts of fasteners for general machinery, which have played an important role in the development of fastener technology. There are many general mechanical fasteners on aerospace vehicles and their engines, and many fasteners specially developed for aerospace vehicles and their engines are also applied to general machinery. The exchange, collaboration, and mutual promotion of these two aspects of fastener technology have been the rich content and powerful factor in the development of fastener technology in the past, and it will be so in the future.