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Author: Site Editor Publish Time: 2025-01-13 Origin: Site
Blind rivets, also known as blind rivets, are a type of rivet with great advantages in the field of single-sided riveting. With its many advantages such as high reliability, high connection strength, long service life and easy operation, it plays a key role in the connection of many materials, such as aluminum alloy, structural steel and composite materials. In the field of aircraft manufacturing and maintenance, especially in the riveting work of non-open parts of aircraft, blind rivets play an indispensable role.
Blind rivets are mainly composed of four parts, namely, nail rod, nail sleeve, locking ring and top plate. The specific structure is shown in Figure 1. The nail rod part is uniquely designed, with a serrated head and a broken neck groove and a shear ring. When the nail sleeve is riveted at the end, a tiny inner cavity will be formed on the head. This inner cavity is crucial in the subsequent riveting process. After the deformation of the locking ring, it will just enter and completely fill the inner cavity. The locking ring plays a key locking role in the entire riveting system. It is assembled in the broken neck groove. After the riveting is completed, it is clearly visible in the center of the nail head. During the riveting process, the lock ring will deform, effectively locking the nail rod and the nail sleeve tightly. The role of the top plate is to provide a reference surface for the riveting gun to bear the force when the riveting gun is working, ensuring the smooth progress of the riveting operation.
Abroad, the United States is the first country to produce and use blind rivets. The most commonly used products are CherryMax, Cher-ryMax ‘AB’ type, CherryLock type, and Alcoa’s Huck-Clinch type and HuckMax type.
At the beginning of the 21st century, China also successfully developed domestic blind rivets, compiled corresponding navigation standards, and used thousands of blind rivets of various specifications on a certain type of aircraft.
Blind rivets can replace solid rivets or bolts and other fasteners in many closed and closed structures to ensure the mechanical transmission effect and safety and reliability of the structure.
Preparation and insertion: First, insert the blind rivet accurately into the pre-punched rivet hole. Then, carefully place the nail rod into the pull head of the rivet gun to ensure that the position is correct. After fixing the rivet gun, prepare to start the operation of pulling the nail rod.
Initial pulling and deformation: When pulling the nail rod, since the nail sleeve is in a fixed state, there will be relative displacement between the nail rod and the nail sleeve. At this time, the shear ring on the nail rod will squeeze the nail sleeve, and then drill into the inner hole of the nail sleeve, gradually forming a blind end upsetting. At the same time, this process will cause the nail sleeve to expand and fit tightly with the surrounding structure, generating a strong clamping force.
Cutting and continued movement: The pull head continues to pull the nail rod until the shear ring is cut off and separated from the nail rod as a whole. At this time, the nail rod and the locking ring on it can continue to move through the nail sleeve. When the locking ring touches the top plate, it will be compressed and deformed, and finally form a "safety lock" that fills the groove at the end of the nail sleeve.
Final locking and connection completed: The "safety lock" locking ring tightly fills the groove at the end of the nail sleeve, and at this point, the nail rod and the nail sleeve are completely and firmly locked together. The pull head continues to pull the nail rod, so that the nail rod neck groove is pulled off at the head plane of the nail sleeve, thus forming a reliable and stable connection between the interlayers. It is worth noting that the main installation feature of the blind rivet is that the drilled hole must be slightly larger than the diameter of the nail rod, so as to ensure that the expanded part of the nail rod can be smoothly inserted.
The main installation feature of the blind rivet is that the hole must be slightly larger than the diameter of the nail rod so that the expanded part of the nail rod can be inserted. Loose holes are a common problem in the assembly process of blind rivets, which can be improved in two ways: one is to calculate the stacking thickness and the interlayer length so that the stacking thickness of the material falls exactly in the middle of the interlayer length range of the blind rivet; the second is to make sure that all gaps between parts have been eliminated before installing the blind rivet.
After the blind rivet is installed, the lock ring must be flush with the top surface of the nail head or below the top surface, and the maximum burr height of the lock ring is allowed to be 0.005″. The flushness of the nail head is measured from the top surface of the nail head to the smooth surface of the broken neck groove.
Diameter selection: Blind rivets provide a variety of diameter specifications for selection, the most common ones are 1/8″, 5/32″, 3/16″ and 1/4″. In some special maintenance and other application scenarios, you can also choose an enlarged piece with a diameter increase of 1/64″. For easy distinction and identification, the top sheet of the normal piece is designed in gold, while the top sheet of the enlarged piece is silver.
Clamping length determination: The clamping length of the blind rivet is not a fixed value, but a range. The difference between the maximum clamping length and the minimum clamping length is 1/16". There is a specific correspondence between the part number and the maximum clamping length, that is, the part number is equal to 16 times the maximum clamping length. For example, if the part number is "-04", then it can be calculated that the maximum clamping length is equal to 1/4", the minimum clamping length is equal to 3/16", and its clamping range is 3/16″~1/4″.
Other factors: Blind rivets have two types of head types: convex head and countersunk head. The materials include aluminum alloy, alloy steel, stainless steel, monel alloy and nickel alloy, and the surface treatment methods include cadmium plating or passivation. In the actual selection process, in order to select the blind rivet with the appropriate clamping length, the thickness of the interlayer can be accurately measured with the help of a professional ruler.
Specific parts of the aircraft: Blind rivets can be widely installed in many key parts of the aircraft, such as horizontal stabilizers, wings and engine nacelles. These parts have extremely high requirements for the reliability and stability of the connection, and the characteristics of blind rivets It just meets these needs.
Non-essential single-sided installation scenarios: Although blind rivets are mainly designed for single-sided connections, they can also play a role in some places where single-sided installation is not necessary. In many non-structural parts, such as aircraft interior devices, floors, de-icing equipment, etc., solid rivets are not necessarily required. At this time, the use of blind rivets can not only save installation time and reduce costs, but also reduce labor input, while reducing overall weight.
Application restricted areas: However, as shear-resistant fasteners, blind rivets also have some areas where they are not suitable for use. For example, in high-stress areas of aircraft, due to excessive stress, blind rivets may not be able to meet Sufficient strength requirements; in any area on or around the jet engine, loose blind rivet parts are at risk of being sucked into the engine air intake, causing serious accidents; wing connection devices, control panel hinge brackets, fixed tail surface connection devices or similar critical positions require extremely high reliability and stability of the connection, and blind rivets are difficult to meet; in areas where liquid sealing is required, blind rivets cannot provide good sealing performance; blind rivets are also not suitable for connections that are subject to tension and may pull out the nail head.
Blind rivets have significant advantages in industry, such as improving structural design, simplifying process installation, reducing assembly noise and production costs. Production, especially in the aviation field, has been widely used. Although China has achieved certain results in the research and development and production of blind rivets, it cannot be ignored that there is still a certain gap between domestic blind rivet products, especially blind rivets for composite materials, and foreign advanced products. There is room for further improvement in the richness of product types, the precision of processing and manufacturing, and the depth of theoretical research. In today's era of vigorously developing advanced aircraft, it is particularly important to strengthen the research and development of blind rivets in the application of composite material structures. Through continuous efforts, a complete and mature standard system has been gradually formed, thus laying a solid foundation for ensuring the advancement and quality level of aircraft.
