Rivets in aerospace industry

B737 horizontal stabilizer ribs

Rivets are one of the oldest types of fasteners in aviation industry.

The most important difference between rivets and screws/bolts is that rivets are such fasteners who's strength is increasing during installation. It can be explained with two reasons;

1. The material of the rivet during the plastic cold working (forging, stamping) experiences such structural transformation after which the strength (shear- and ultimate tensile strength) characteristics are improved. 
   
   
2. The diameter of the rivet and therefore its authoritative cross section of the main loading is increasing due to the upsetting.

Classification of rivets according to their usage:

• Solid shank rivets
• Hollow-end or semi-tubular rivets
• Blind rivets
• Rivet-like Special fasteners

The most commonly used type in aviation industry is the solid shank rivet. They are used to joint the load bearing elements of the airframe. On a modern passenger aircraft there can be about more than half a million pieces of rivets, from which 90% are of this kind.

The hollow-end/semi-tubular rivets, made from titanium alloys, are commonly used on composite structures, mainly on coal- and graphite fiber materials.

Blind rivets are used on such parts where the bilateral accessibility on the joining parts are not possible and therefore the traditional rivets can not be installed. Commonly used on the hermetic fuselage flush repairs, on the filler part.

The rivet-like fasteners can be classified further into three parts:

• Hi-shear rivet, which is in fact a high-strength bolt.
• CherryBUCK is a bi-metallic, one-piece fastener that combines a shear strength shank with a ductile titanium-alloy tail. It is the lightest weight shear pin, which has the characteristics of both a rivet and a bolt.
• Spacer rivets are in fact nor rivets, since they only fill the gap between the joining elements.

For further information on these types, please read in the appropriate blogs.

Resources: Imre Koncz, Balázs Gáti - Repülőgép szerkezetek, 2012

Classification of fasteners based on fastening methods

We can classify two types of fasteners based on their installation:

1. Removable fasteners - Those fasteners, which can be removed without the permanent damage or failure of either the fastened parts, or of the fastener, we call removable ones.
   
   They may be further installed after special and appropriate inspections.
   
2. Permanent fasteners - Those fasteners, which's either part is damages or fails during the dis-assembly, we call permanent ones.
   
   Some of the parts of the specific types (which have more parts) may be reused if they were not damaged during the dis-assembly.