SU1754926A1 - Method of joining parts - Google Patents

Abstract

Usage: in mechanical engineering, in multi-shear bolted connections of parts. SUMMARY OF THE INVENTION: parts and gaskets are made with a series of holes. The distance between the outermost rows of holes and the adjacent ones in the gasket is made larger than the similar distance in the parts to be joined by a calculated value. At the same time laying make the set thickness. Connect the parts and gaskets in the package with the combination of all the holes, install the fastening elements in the latter and produce their axial tightening. 5 il.

Description

The invention relates to mechanical engineering and can be used in the manufacture of multi-cut shear bolted joints of increased resource. The fatigue life of known compounds is largely determined by the level of stresses on the walls of the extreme rows of bolt holes. To reduce the level of loading of the extreme holes, stepwise or short-shaped connections are used. However, the effectiveness of the known compounds is low. In order to reduce the stress level of smith, glueing is applied around the installation of extreme bolts of gaskets made of high-strength material; however, the known method is limited in efficiency, since it only reduces the smothering stress and does not completely eliminate it.

Closest to the present invention is a method of obtaining a joint of parts, which involves the installation of a high-strength gasket between the connected parts, which has a pre-bending before installation. When the bolts are axially tightened, the gasket is straightened and realizes a thrust opposite to the operational one on the wall of the extreme row of bolt holes. This contributes to increasing the durability of the joint. However, the known method does not imply the regulation of the size of this thrust, depending on the geometrical and mechanical characteristics of the parts and bolts being joined. Therefore, the probability of obtaining the required thrust by the criterion of fatigue life is low, which limits the technical effectiveness of this method, and hence its reliability.

The purpose of the invention is to increase the service life of the compound by increasing its fatigue life.

In order to achieve this goal in the method of obtaining the connection of parts, including the manufacture of pn parts with rows of holes, m high-strength gaskets with rows of holes between the outermost rows of holes and adjacent to them is greater than the same distance in the joint (L

WITH

VI JV

4 o

GO

her

details on the value of D etc. gaskets are manufactured with a thickness of 0.15-0.2 of the diameter of the fastening elements of the outermost row, and the value of D tn is determined depending on the geometrical and mechanical characteristics of the parts to be joined, the gasket and the connecting fasteners.

FIG. 1 shows the structure of a multi-part connection of parts, side view; in fig. 2 - a fragment of the design of the joining sheets and gasket prior to the installation of the connecting bolts, the geometrical parameters of the joint; in fig. 3 shows a fragment of the joint structure in the area of the installation of the extreme bolts before tightening them using callout 1 from FIG. one; in fig. 4 - a fragment of the design of the parts to be connected in the region of the installation of the extreme bolts and the parameters of the stress state in the joint after tightening the bolts; in fig. 5 shows the joint structure in the region of the installation of the extreme bolts and the parameters of the stress state in the joint after application of the operating load to the joint.

The developed method of obtaining parts joining involves performing the following technological operations:

- partial manufacture of the parts to be connected 1, 2 and high-strength gasket 3, the length and width of the gasket being equal to the length and width of the joint itself, and its thickness is determined from the ratio

5P (0.15-0.2) dBi. (1)

where dBi is the diameter of the extreme range of fasteners;

-connection of manufactured parts into a package, the gasket being placed between the parts to be connected, and making holes in the connection, and the distance between the extreme hole in the gasket and its adjacent is larger by the value of D tn than the same distance in the connected parts x:

D tn tin-ti, (2)

—the alignment of the axes of all the holes in the connected parts and the gasket and the installation of fasteners, for example bolts, in them (see fig. 3); The bolts are axially tightened with nuts, after having installed washers on them, and the bolts are tightened, starting from the point of the greatest deflection of the gasket.

When the bolts are axially tightened, the gasket at the site of the outer rows begins to straighten and burst the first with respect to the place where the load is applied to the part, a series of bolts in the direction of the load, and the second p d in the opposite direction. At the same time on the walls of the bolt holes occur

0

technological stresses see o ти, (see fig. 4), Fatigue failure, shown in fig. 1 of the connection occurs through the holes of the first relative to the place of application of a load of a number of bolt holes. So, for example, part 1 is destroyed along section AA, and part 2 through section BB. At the same time, on the walls of the holes under the extreme bolts, operating stresses occur about | m.1 (Fig. 5), but since the stresses on the walls of these holes are affected by technological stresses from the expansion of the bolts

OKI, then the total level of stresses in connection with the spacer will be less by the amount of previously created, i.e .:

Онн.1 0 см 1 -CU1 (3)

The technical efficiency of the developed- ® method will be greatest when

Ocv 1 - OKI. In this case, under the conditions of operational loading on the walls of the extreme holes, the magnitude of the stresses of cm 5 is zero and is close to it. Obviously, condition (3) is realizable provided

(four)

where Rtp is the thrust of the bolts;

Re is the magnitude of the load on the extreme bolt without the use of a gasket under operating loading conditions. The value of the EW can be determined from the expression

0

RB

(five)

 9-1 1 i

B m

N

where M is the number of rows of bolts of the joint;

Re - the value of the operational load on the connection.

The magnitude of the operational load Re is selected from the destructive of the condition of providing the connection with the required resource.

MVPpasp., (6)

where, 3-0,4 is typical for aircraft construction;

Rrazr - the value of destructive load on the connection. The magnitude of the breaking load on the joint is determined from the condition of providing the static strength of the joint to the shear

RRZER RB-gЈm N. (7)

where RB is the total cross-sectional area of the fasteners of one row; m is the number of cut planes of the joint;

t | - temporary resistance to shear of the material of connecting fasteners. Hence, the magnitude of the required thrust bolts in view of (5-7)

..m.N

 (0.33-0.44) RB-t6 -t. (8) From the condition of ensuring the minimum mass of the gasket, it follows that it should have the minimum possible thickness. We will determine it from the condition of its bearing capacity per cm of mercury.

GP

dp

(9)

 - Om.n.

where OMB is 1.1 oft, “n is the temporary resistance of the gasket material to compression.

Thus, the thickness of the gasket with regard to (8-9) is defined as

d (0.33 -0.44) RB-t | m

On

dBi On

7TdB1

(ten)

Considering that FB

, tЈ 0.65 On

the thickness of the gasket in the final expression is determined by the ratio

dp (0,15-0,2) dBi-m (11) The expansion of the gasket causes the following deformations in the joint:

stretching parts of connected parts;

the shift of the first and second rows of fasteners;

compression gasket,

Obviously, upon reaching the required magnitude of expansion of the bolts of the extreme range, these types of deformations must compensate for the difference in the steps of the extreme rows of holes in the gasket and the parts being joined, i.e.

. Atn Oa + OB-3B, (12) where yes, 5c, 5b are the deformations of the joint. The deformation of the extreme areas of the parts to be joined is determined by the expression

(-4-) 1

where, 2 - empirical coefficient;

ti is the pitch of rows of fasteners;

EI-modulus of elasticity of the material of the part 1;

tp is the pitch of the fasteners in one row.

The shear strain of the extreme rows of fasteners is determined by the expression

5c (Sv1 + Sv2) Rtp (14)

where CBL Sw2 is a cut on the first and second rows of fasteners.

Compression deformation of the gasket is determined by the expression

(13)

5B

yti rp

(15)

0 +

five

0

five

0

five

0

five

0

tp En Op

where En is the modulus of elasticity of the gasket material.

Thus, taking into account all types of deformations, the value of Atn is determined by the expression;

(Sv1 + Sva) +

Ыggg + -teg-t g N1b)

ip -i 1 t-i ui t-p wn

Or with (8)

Ati (о.зз- 0.44) FB -d | m

Ka + c + iiW + -sfc --- Efer i (17)

Thus, the obtained expressions (11) and (17) allow one to specify the geometrical parameters of the gasket in order to achieve the greatest technical effect by the developed method by the fatigue durability criterion.

An increase in the fatigue life of a compound as compared with the prototype makes it possible to increase its reliability, which will bring an economic effect during the operation of the product.

Claims (1)

The invention method of obtaining parts, including the manufacture of m-parts with rows of holes m high-strength gaskets with rows of holes with a distance between the outermost rows of holes and adjacent to them greater than the same distance in the connected parts x the Atn value, the connection of parts and gaskets into the package with the placement of gaskets between the parts and the alignment of all the holes, the installation of fasteners in the holes and their axial tightening, which differs from the fact that, in order to increase the service life by increasing fatigue life, gaskets made thick 5 (0.15-0.2) dBi, where del is the diameter of the fasteners of the outermost row, and the value of A tn is determined from the ratio At (0.33-0.44) FB TU m  № + «+ TiW + -ek - sfc-) b where FB is the total cross-sectional area of fasteners of the outermost row; SS TB - temporary resistance to shear material fasteners extreme range; m is the number of shims equal to the number of cut planes, CBI and Cb2 compliance of the first and WTO-EI and Ea - elastic moduli of the material relative to the place of application of the joining sheets, the load of a number of fasteners; En is the modulus of elasticity of the material of the pro 1.2-empirical coefficient; masonry; ti is the pitch of rows of fasteners; 5 (5i and & - thickness of the jointed fox-. tp - step fasteners in one. r du: L i Rz one  V five P R i P V: FIG. / I B Fig.Z