SU1710877A1 - Shear bolt joint - Google Patents

Abstract

The invention relates to mechanical engineering, in particular to aircraft construction, and can be used in the manufacture of multi-shear bolted connections. The purpose of the invention is to increase the reliability; connections. In the bolted connection of parts, the threaded elements are made with load equalization elements in the form of threads of variable height decreasing from the end of the bolt to its head, from the side of the load applied to the part, and increasing to the head of the bolt from the diametrically opposite side of the bolt. The use of the invention makes it possible to reduce the level of stress seen along the wall of the bolt hole on the outer surface of the sheet. 5 il.

Description

The invention relates to mechanical engineering, in particular to aircraft construction, and can be used in the manufacture of multi-shear bolted connections.

The design of multi-shear bolts of connections is known. The fatigue life of known compounds is determined by the level of stresses on the walls of the extreme rows of bolt holes. To reduce the loading of the extreme rows of bolts and, accordingly, to reduce the magnitude of the stress of smiths, joints of variable stiffness or joints with a reduced diameter of the bolts of the first row are used. An effective way to reduce the stress level is the use of pre-stressed joints.

The closest in technical solution and the achieved result to the invention is the joining of parts by means of several rows of bolts, the first row of which is made in the form of an inclined bolt head. However, tilting the head requires the use of an additional washer under the bolt head, and high precision bolt manufacturing.

The purpose of the invention is to improve the reliability of the connection parts.

This goal is achieved by the fact that the bolted shear connection of parts contains a row of cylindrical bolts with nuts and washers placed on them installed in the holes of the parts to be joined. In this case, the bolts of the first row in the load direction are made with elements of load balancing. The elements of load balancing are made in the form of threads of variable height, decreasing from the end of the bolt to its head from the side of the load applied to the part and

(L

WITH

About 00

S xj

increasing to the bolt head from the diametrically opposite side of the bolt. The essential difference of the proposed technical solution is the design of the element for unloading the wall of the hole from the operating seepage stress, made in the form of thread turns of variable depth, which makes it possible to increase the reliability of a bolted joint according to the criterion of its fatigue life.

FIG. Figure 1 shows the construction of a multi-threaded single-shear bolted joint of sheet metal parts in a side view; in fig. 2 - the same, a fragment of the extreme p and bolts before their axial tightening; in fig. 3 - the same fragment and parameters of the stress state in the joined sheets after axial tightening of bolts of the extreme range; in fig. 4 - the same, after the load is applied to the connection; in fig. 5 shows the design of the bolt unloading element of the outermost row.

The proposed bolted shear connection of parts consists of joined sheets 1 and 2, as well as several rows of fasteners consisting of cylindrical bolts 3, washers 4 and nuts 5. The place of probable fatigue fracture of joined sheets are sections along the outer rows. bolt holes: section A-A for sheet 1 and section B-B for sheet 2. Bolts installed in these sections will be considered first with respect to the operating load applied to the sheet. Another source of probable fatigue failure of sheets is fretting corrosion, which occurs in places of increased contact stresses from bolt bending, for example, place B for sheet 1. The first, with respect to the load, a series of bolts has a stress leveling element on the wall of the hole, in which it is installed. The load leveling element is made in the form of threads of variable depth, the depth of the coils decreasing from the end of the bolt rod to its head from the side of the load applied to the part and increasing to the head of the bolt from the diametrically opposite side of the bolt (Fig. 5).

From the point of view of joining technology, it is advisable to initially install the inner bolt rows and tighten them, and then install the extreme bolt rows (Fig. 2). When the bolt is axially tightened with a nut, tension in the joined sheets occurs:

openings - oJM and see voltage on the sheet surface (cm - Direction of previously created see

(JCM is opposite to the direction of the presence of the operating voltage of see OCM (Fig. 3). After

the application on the connection of the operational load Re changes the parameters of the stress state at the place of fatigue failure. The resulting magnitude of stress on the walls

holes are reduced by the amount previously created. For example, in sheet 1:

  fl

Ccm1 - (7cm1 -WCM,

15

0

where is the magnitude of the seepage voltage in the joint without the use of unloading elements.

In sheet 2, the magnitude of the stresses is increased by the amount of the previously created, but this is not dangerous from the point of view of fatigue failure, since the sheet 2 in this place is not destroyed. Under the action of the operational load Re occurs

and more uniform distribution of the load on the outer surface of the sheet (k, which reduces both the magnitude and non-uniformity of contact stresses under the bolt head, reducing the damaging effect of fretting corrosion. Thus, the proposed technical solution compared to the prototype allows create prestress

see at the place of likely fatigue destruction of the sheet, reducing the operating stresses along the wall of the hole and reduce the damaging effect of fretting corrosion, which increases the fatigue

Q durability of joined sheets.

For aircraft construction, the use of duralumin alloys of the type D16T and B95 for joined sheets and steels of the type ZOHGSA, ZOHGSNA, 16ХСН for bolts is characteristic. With

5 of this, the ratio of the diameter of the bolts d to the thickness of the sheet to be joined S is in the range of 5-4. For this ratio, the angle of inclination of the thread profile on the bolt rod to the surface of the rod is recommended.

0 (/ p 8-15 °. More precisely, the angle 7p can be determined by calculation, the initial condition of which is that the extreme bolt occupies a vertical position in the loaded state.

The proposed technical solution allows reducing the level of stress on the outer surface of the sheet by 30–50% to see the bolt level on the outer surface of the sheet, increasing the fatigue life of the joint by 1.3–2.5 times and the compound life by 8–20%.

and its reliability, which will bring with the operation of the product economic effect.

Claims (1)

Claims Bolted shear connection of parts, containing a series of cylindrical bolts with nuts and washers placed on them in the apertures of connecting parts, while the bolts of the first row in the direction of the load applied to the part are made with load balancing elements, characterized in that In order to increase the reliability of the connection, the elements of the load balancing are made in the form of threads of variable height, decreasing from the end of the bolt to its head from the side of the load applied to the part and bolt head diametrically opposed side of the bolt. Phage.g CM.S FIG. 3 Fip. four