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The importance of good riveting in aeronautics

A flying aeroplane produces a great deal of vibrations on its structure due to the action of the forces exerted by the air that provides it with lift. In aeronautical engineering design, the action of vibrations is a highly serious study which requires a great deal of attention and calculations, a lot of calculations. One of the most feared effects of vibrations on an aircraft structure is flutter.

A joint of two parts using a solid-shaft riveting system provides them with the flexibility and strength needed to withstand the forces and frequencies exerted on the aeronautical structure during flight.

Due to this action of vibrations, the joints of an aeroplane structure’s parts cannot be welded together, since the strength of the joint between two welded parts (either by electric or thermal systems) makes that weld a rigid weak point that is not very flexible in the face of vibrations at a much lower frequency than the ones generated in flight. The points where parts are welded together would therefore become breakage points at certain frequencies. If we wanted to weld together aircraft parts, we would have to lower its flight speed to prevent vibrations from reaching the joints’ resonance point.

Before arc, plasma or any other kind of welding existed, industry joined parts by means of a system known as “latticework”, which consists of riveting the parts together. In shipbuilding, thick steel plates were riveted together with solid‑shaft rivets that were heated to almost melting point (red hot) and hit by a riveter and fastener.

This system is used in aeronautics today to join parts together, but the rivet is of course not heated up. Riveting ensures that neither of the parts is excessively heated (as is the case in welding, which leads to an atomic reordering in the affected area due to the heating), thereby ensuring that the material’s properties concerning its ability to withstand vibrations and its flexibility remain intact. The only damage suffered by the material results from the drilling and the forces exerted on the riveting.

As far as the riveting force mentioned above is concerned, the workers responsible for riveting and fastening are the ones who calculate and apply them to close the rivet. The riveter is responsible for hitting the rivet with the necessary accuracy and force to ensure it is not damaged, while the fastener ensures the fastening’s force and angle are as perfect as possible, so the rivet’s closure head is suitable. This operation requires a certain degree of precision, in addition to the workers’ touch and experience. A riveting team tends to find the rivet’s hitting and fastening point through its sound or simply by sight, ensuring that the closures are suitable once they have been checked with the appropriate templates.

To design the areas where rivets are to be placed, the distance between rivets is calculated to avoid any possible cracking in assembly processes or in the case of the forces which are generated in flight. There is a very direct relationship between the thickness of the material to be riveted, the length of the rivet to be placed and the material’s own characteristics. Riveting lines are not usually visible at first sight, especially when the structure is painted over. This is due to the fact that, if the riveting work is done properly, the forces applied to the parts are in keeping with the work needed to close the rivet, but without deforming the material of the parts to be joined. A properly riveted structure is totally smooth if we pass our hands over it. Any deformation we notice on riveted parts is a point where excessive forces have been exerted and could lead to a possible breakage during flight.

As we mentioned above, a joint of two parts using a solid-shaft riveting system provides them with the flexibility and strength needed to withstand the forces and frequencies exerted on the aeronautical structure during flight. It is the only way to clad aircraft to date. A way will perhaps be found in the not so distant future to join two parts at an atomic level that coverts the two parts into a single one, while conserving all the material’s properties, especially with regard to vibrations, thus allowing aeroplanes to be even safer and more responsive.

 

 

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12/03/2018

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