RU2384762C2 - Procedure for bolt connection of parts - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention refers to fixing devices. The procedure of bolt connection of parts consists in manufacturing a bolt, in installing the bolt into an opening of parts and in tightening with a nut. A head and body of the bolt are manufactured separately. The bolt body has a conic expansion at the end opposite to a threaded end. There is a conic through opening in the bolt head; cone angle of opening corresponds to the cone angle of expanded section of the body. Further, the body is inserted into the cone opening of the head and parts are connected by setting and nut tightening. Also the body has conic and cylinder sections conjugated with radius surface, while cone angle of the expanding section of the body is 6 - 15°.

EFFECT: increased fatigue strength and service life of connection and reduced prime cost.

2 cl, 2 dwg

Description

Technical field

The invention relates to technical physics, and more particularly to fasteners for parts and assemblies, and can be used in the manufacture of bolted joints using bolts, mainly from titanium alloys, operating under cyclic loads in aircraft, shipbuilding and other industries, to increase reliability and durability compounds.

State of the art

In the first years of the use of titanium, titanium fasteners were obtained by machining. This method of manufacturing fasteners is impractical due to the high complexity, low metal utilization rate and low production productivity, and hence the high cost of fasteners. In addition, the turning method does not provide sufficiently high mechanical properties of the bolts due to the unfavorable distribution of metal flow lines in the head area. In such bolts in the transition zone from the head to the rod, fatigue cracks easily propagate along the fibers, causing the destruction of parts.

In connection with the foregoing, the turning method was replaced by the technology of manufacturing fasteners with a hot head.

Hot planting is carried out with heating the planted part of the workpiece by the electric contact or induction method, the latter being preferred in view of a number of technological advantages. With these heating methods, the temperature of the workpiece required for the hot upsetting is at least (600-700 ° C).

However, the greatest productivity is provided by the technology of manufacturing fastening parts with cold heading. For this reason, cold heading has become a major operation, especially in the manufacture of small diameter fasteners. However, this method also has certain disadvantages: a) the need to ensure high quality of the surface of the workpieces and their geometric parameters; b) high specific upsetting pressures, which leads to rather rapid tool wear; c) the need to ensure a sufficiently high level of plastic and technological properties of the source material; d) the inevitability of the use of grease, the limited range of fasteners only with small-diameter bolts - up to 8-10 mm. These flaws are much less characteristic of hot landings. Therefore, the hot landing of the bolt heads was preserved, especially for large diameter parts, (see Auth. V.A. Volodin, I.A. Vorobyov, B.A. Kolachev, A.V. Mitin, A.V. Malkov, A. F. Korostelev, Manufacturing technology of titanium fasteners. - M.: Metallurgy, 1996, pp. 10 ÷ 14).

Known bolt according to the patent of the Russian Federation No. 2057255, IPC F16B 35/04. Publ. in 1996.

According to this patent, a bolt is manufactured as follows: a bolt is machined from a cylindrical blank, then an axial hole is drilled with a conical bottom in the bolt head and a solid plug is installed in it. The bolt provides a reduction in stress concentration coefficient and increases durability.

The disadvantage of this design in the case of the manufacture of titanium bolts is the low utilization of the material, which leads to an increase in the cost of bolted joints.

Known bolt according to the patent of the Russian Federation No.2019734, IPC F16B 35/04, 1994.

According to this patent, the manufacture of bolts is performed as follows: a rod and a head with a cylindrical hole are manufactured separately, the rod is partially inserted into the head hole and welded from the side of the rod end, the hole is filled with cement mortar to the height of the weld.

This method provides a good coefficient of use of the material, but it is complicated and time-consuming to manufacture, which leads to a significant increase in the cost of the bolt. In addition, a high percentage of marriage is not ruled out. These disadvantages also cause the high cost of bolted connections.

In the manufacture of various designs, various types of detachable connection and fastening of parts are widely used. The most common method of threaded connection by means of fastener parts such as bolt, screw, etc. At the same time, a bolt, a screw, etc. traditionally contain a monolithic rod and a bolt head (patent RU No. 2216658 and the technology for manufacturing titanium fasteners. M: Metallurgy, 1996. 143 pp.), Screw (OST 1.76508-86).

Typically, the method of bolting the parts includes: making a bolt, installing a bolt in the hole of the parts and tightening it with a nut.

Depending on the manufacturing accuracy of the parts to be joined and (or) violation of the orthogonality of the axis of the rod to the supporting surface of the head, the latter may not be combined with the surface of the complex part. In this case, a larger or smaller angle is formed between the contact surfaces of the part and the head of the bolt, causing bending stresses in the rod in the area of its interface with the head when tightening with a nut. This reduces the working resource. The disadvantage of these analogues can also be considered the high complexity of manufacturing a traditional monolithic bolt, especially from hard-to-work material, for example, titanium alloy, and the relatively low material utilization factor (CMM). A known method of manufacturing by friction welding of parts, mainly a type of bolt, consisting of a rod and a head (German patent No. 199717071, B23K, 20/12, 1999). According to this method, conical sections with outer and inner conical surfaces, respectively, on which the parts are mated and compressed with each other, are performed on the rod and head. When this rod is performed tapering to the end. When one of the parts rotates, frictional heating occurs before plasticization of the material in the friction zone and a welded joint is formed.

The main disadvantage of the prototype are:

- insufficiently smooth conjugation of the surfaces (fillets) of the rod and head, which negatively affects the connection resource;

- weakening of the rod at the interface made of a material sensitive to the thermal cycle of welding, which also reduces the strength of the connection.

SUMMARY OF THE INVENTION

The objective of the invention is to develop such a method of joining parts with bolts, which would increase the fatigue strength of the joint, performed mainly by bolts of titanium alloys, reduce the complexity, energy consumption while ensuring high CMM. In addition, the method should provide an increase in the resource of the compound and a decrease in its cost.

The problem is achieved in that in the method of bolting the parts, including manufacturing a bolt, installing the bolt in the hole of the parts and tightening with a nut, the bolt is made from the head and the rod separately, while the rod is made with conical expansion at the end opposite the end with standard thread, the head is made with a conical through hole, the cone angle of the hole in the head is made corresponding to the taper angle of the expanded portion of the rod, after which the rod is inserted into the conical opening tie heads and connect the parts.

In addition, in the method of bolting parts, the angle of the cone of the expanding section of the rod is equal to 6-16 °. This embodiment of the bolted connection allows to increase the resource of the connection of parts using bolts made of titanium alloys, to increase the CMM.

List of drawings

The invention is illustrated by drawings, in which:

Figure 1 - shows the elements of a bolt: a rod and a head made in accordance with the invention;

Figure 2 - shows a bolted connection of parts in section.

The implementation of the invention

The connection method according to this invention is as follows.

The bolt is made of two separate constituent elements:

- a rod made with a cylindrical section carrying a thread from one end, and with a conical extension at the other end, the opposite end with a standard thread applied

- heads with a tapered through hole, the cone angle of which corresponds to the taper angle of the expanding section of the rod.

The head 2 (see figure 1) is performed with a height h = (0.65-1) d _c (rod diameter). When h <0,65d _c - the strength of the head decreases; when h> 1d _c , the part of the head protruding beyond the end of the rod increases, not bearing the payload; reduced CMM. The smaller diameter of the conical hole of the head d _g perform equal to at least the diameter of the rod.

Rod 1 (see figure 1) is performed with a conical extension 4 with a cone angle of 6-20 °. When the cone angle is less than 6 °, a sufficiently strong connection of the rod with the head is not provided with the dimensional (or geometric) parameters of the heads of standard bolts. In addition, at smaller angles, the required quality of the parts is not ensured, since with the tolerances accepted, significant dropping of the conical portion of the rod into the head is possible. At taper angles greater than 20 °, the CMM sharply decreases, and the effect remains practically unchanged.

The conical and cylindrical sections of the rod are conjugated by a radius surface. The length of the conical portion L _{k of the} rod is 1.4-1.5 h, where h is the height of the standard head. With a shorter length L _{k, the} conical surface of the head does not fit entirely on the conical surface of the rod, and the part of the head protruding beyond the end of the rod does not carry a payload. With a greater length L _{k, the} excess part of the rod protrudes from the head, does not carry a payload, and the CMM is also reduced. There is a margin of the length of the conical section of the rod - 0.5 mm for possible when tightening the progress of the rod relative to the head.

With this bolt, standard nuts with a thread diameter corresponding to the diameter of the thread of the rod are used.

The head and the rod can be made of different materials depending on the working conditions of the connection: the working environment, temperature conditions and other special technical requirements. So, for example, combinations are possible: titanium with titanium; titanium with steel; titanium with copper or copper alloys.

The connection of parts with a bolt is as follows.

Pre-enter the rod with a threaded end into the conical hole of the head from the side of its larger diameter to align their conical surfaces; after that, a threaded end is inserted into the technological holes, onto which the nut is screwed and tightened to the stop, thereby fixing the head on the conical portion of the rod.

In the connected parts 5 and 5 ', a hole is drilled (better, assembled). The rod 1 is introduced with a cylindrical end into the conical hole of the head from the side of its larger diameter until the tapered surfaces of the rod 1 and the head 2 come into contact; introduce the rod 1 with a cylindrical section with a thread into the hole in the parts 5 and 5 'assembled for fastening and advance it until the contact surface of the head contacts the surface of the part. A standard nut 6 is screwed onto the threaded cylindrical part of the shaft 1 protruding from the part and tightened, while using, for example, a screwdriver, which is inserted into the slot 3 at the expanded end of the shaft, prevent it from rotating relative to the head and tighten the nut.

The advantages of the proposed method of fastening a package of two or more parts and fastening elements for it:

- increasing the fatigue strength of the joint by eliminating the causes of the weakening of the danger zone of the rod near the support surface of the head, such as stress concentration, and the possible appearance of bending stress in the rod;

- the possibility of using different structural materials for the rod and head, depending on the technical requirements in operating conditions;

- separate manufacture of the rod and the head improves the machining conditions and obtaining a higher purity of the surface of the rod in the danger zone of the interface between its cylindrical surface and the conical, which is especially important to increase strength and resource.

Claims (2)

1. The method of bolting the parts, including making a bolt, installing the bolt in the hole of the parts and tightening with a nut, the bolt is made from the head and the rod separately, the rod is made with conical expansion at the end opposite the end with the thread applied, the head is made with a conical through hole , the cone angle of the hole in the head is performed corresponding to the cone angle of the expanded portion of the rod, after which the rod is inserted into the conical hole of the head and the parts are connected by installing and tightening the nut, characterized in that the rod is made with conical and cylindrical sections of the rod mated with a radius surface, and the cone angle of the expanding section of the rod is 6-15 °. 2. The method of bolting the parts according to claim 1, characterized in that the tightening of the nut is carried out while holding it from rotation using a slot on the extended end of the rod.

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