Below are excerpts from a practical guide for the American aviation mechanics for use aluminum rivets in the repair of aircraft. For beginners it will be helpful for the first acquaintance with aluminum rivets, experts-professionals can be compared with the American practice of domestic, including, the repair aluminum boats and boats.
Aluminum rivets "under the hammer"
Rivet with a solid core - rivets under the hammer - are a common type of rivets, which are used in aircraft structures. These rivets are the oldest and the most reliable of all types of fasteners. They are also widely used and the construction and repair of small river and sea vessels, such as motor boats and aluminum boats.
The advantages of the rivets are relatively low cost, and less complexity compared to screws and nuts. Moreover, for setting the rivets can be used automated high-performance tools and equipment.
Rivets are designed to work on a cut, however they are not used for joining thick materials or abraded material if subjected to tensile loads. The thing is, rivets that tensile strength is usually very low in comparison to their shear strength. The greater the total thickness of the joined sheets, the more difficult it is good to combine them with rivets.
Linked connections are in principle not sealed, if not riveting to use special sealants or gaskets. Since the rivets are put "on continuously", the order, to take them off their drill, which it is quite a difficult task.
SUMMARY rivet like fasteners
Before installation of the rivet consists of a smooth cylindrical rod with factory head at one end. To connect together two or more metal sheets, a rivet is placed in the hole diameter slightly larger, than the diameter of the rivet. After that, as a rivet installed in this pre-drilled hole, the rear end face down or deform one of several ways, by riveting hammer manual to pneumatic tools riveted. As a result of these actions the rivet shank expands to a diameter approximately one and a half times larger than the original. This forms a second head rivet, which firmly holds together the materials to be joined.
Head aluminum rivets
The solid rivet may have various shapes of heads, however, so-called universal head and the countersunk head with a cone 100 ° are the most common, at least, in American aircraft designs.
With universal head rivets have been specially designed for the aircraft as a replacement for conventional rivets with round head, and rivets with a low semicircular head ("brazier head").
The angle of the countersunk head may vary from 60 ° to 120 °, but an angle of 100 ° was adopted as the standard, since such a head with one hand, provides the necessary strength (tensile and shear), a, with another, minimally protrudes from the surface of the structure. This rivet is used there, where required aerodynamic surface smoothness, for example, on high-speed aircraft.
Aluminum alloys rivet
Typically, aluminum rivets are made of aluminum alloys such, how 2017 T4, 2024-T4, 2117-T4, 7050 and 5056.
Domestic alloy analogue 2017 It is the alloy D1, alloy 2024 - abortion D16, alloy 2117 - alloy D18. Aluminium alloy 5056 It has a complete analogue, but is close to the alloy AMg5. Aluminium alloy 7050 also has a full analog, but it refers to the type of alloy V94.
For repair of aircraft most commonly used aluminum alloy rivets 2117 (domestic analogue - alloy D18), so they can be installed in the state of delivery.
Some of the "rivets" aluminum alloys, e.g. 2024-T4 (D16) are too hard, to apply them directly to the delivery condition, and must be toughened before, how to install. Quenching consists in heating to a temperature of about 500 ° C and cooling in water. These rivets are used in the so-called state svezhezakalennom. Therefore, usually the rivets quenched and stored in the refrigerator, to delay the hardening of their aging. They were removed from the refrigerator just before installation. All this creates inconvenience for the production and therefore the majority of the alloy rivets 2024 was replaced by an alloy rivets 7050, which can be installed directly into the supply state.
Dimensions aluminum rivets
head type, when choosing the size and strength of the rivet depends on such factors, as a form of stress, that act in place of the rivets, the type and thickness of material, which rivet and rivet the location in the plane. Rivets countersunk head used therein, where required aerodynamic surface smoothness. Universal head can be used in most other places.
The size (or diameter) of the rivets is selected in accordance with the total thickness of the riveted sheets. If too thick rivet applied to a thin material, that effort, which occurs when you install the rivets, would lead to an undesirable swelling around the rivet head. On the other hand, if too small rivet apply for thick material, that its shear strength is insufficient, to carry the load in place of the compound.
The general rule when choosing the rivet diameter is the following: the rivet diameter should be, at least, c 2,5-3 times greater than the thickness of the thickest of the joined sheets. When repairing the aircraft most frequently used on the rivet diameter 2,5 to 9,5 mm (from 3/32 to 3/8 in). Rivets diameter less 2,5 mm is never used for structural elements, which carry the load.
Another way to determine the sizes of rivets, which can be used, is this: multiply the skin thickness by 3 and take the following size rivets. for instance, if the plating thickness is 1,0 mm, to 1.0 × 3 = 3.0 mm. Therefore, we must take the following after the rivet 3,0 mm, i.e 3,2 mm.
Usually, use rivets of the same or close aluminum alloy, that of the material, which will clinch. for instance, used alloy rivets 1100 (AD) and 3003 (AMts) for alloy parts 1100 and 3003 and alloy rivets 2117 (D18) for alloy parts 2017 (D1) and 2024 (D16).
Quality control rivets installation
Size riveted head is a visual control criterion for correct installation of the rivet. The usual size requirements otklepannoy head shown in Figure 2.
Design installation aluminum rivets
Installing rivets begins by clarifying the following questions:
- the required number of rivets;
- correct size and type of rivets;
- rivet material;
- rivet material condition and strength;
- the size of the rivet holes;
- distance between holes;
- the distance between the holes and the edge of the patch.
All these distances are measured in diameter rivets.
The length of the rivet
To determine the total length of the rivet, you want to install, You need to know the total thickness of the materials being joined, for example, sheets. Full length of the rivet equals the sum of the total thickness of the sheet and the length of the rod rivet, which is necessary for the correct formation of the rivet head. This part of the rivet length is one and a half of the rivet diameter (figure 2).
At repair of structural elements of the aircraft or boat has a strength of rivets installed central importance. If repairs are applied rivets, which have a lower strength, than the original, "relatives", rivets, they have a larger diameter, to compensate for this "deficiency" strength. for instance, rivets of alloy 2024-T4 may be replaced by rivets from alloys 2117-T4 or 2017-T4 only, If the rivets used to be larger than.
Rivets made of alloy 2117-T4 are used in common repair work plane, since they do not require pre-heat treatment, are very malleable, and at the same time strong enough. Moreover, these rivets have high corrosion resistance when used with most types of aluminum alloys.
Shear strength of various clinches
The strength of the established American rivet shear is shown in Figure 3.
American marking rivets
The strength of an aluminum rivet is recognized by the type of stamp on the head or the absence of a stamp (figure 4).
Source: The Aviation Maintenance Technician Handbook—Airframe, 2012