RU2304479C2 - Method for enhancing carrying capability of cylindrical tube at bending - Google Patents

Abstract

FIELD: plastic working of metals.

SUBSTANCE: method comprises steps of imparting oval profile to tube; heating cylindrical tube till rolling temperature and reducing it in stand by means of rolls at four sides while deforming it to oval shape having two mutually opposite arches joined by their foots one to other. One-piece oval tubular shape is formed at working; said shape has percentage height and main moment of inertia normalized by means of mathematical relations. Percentage height of shape corresponds to its maximum resistance momentum.

EFFECT: improved carrying capability and rigidity of products made with small material consumption, enlarged using range of tubes.

2 dwg, 1 ex, 2 tbl

Description

The present invention relates to the construction of bridge and crane structures, as well as when covering large spans of buildings.

Known I-beam profile that works well for bending [1, p. 260], [2, p. 52].

The beam section is selected according to the maximum bending moment M in it. The strength test of the beam in this section is carried out according to the formula

where W _X is the maximum moment of resistance of the beam relative to the main axis X of its section;

γ is the coefficient of the working conditions of structures [3, p. 12];

R _Y is the design resistance of steel, depending on the grade of steel and the thickness of the element;

σ are the maximum stresses at the upper and lower edge of the section.

From formula (1) it can be seen that for the same M, γ and the same strength of steel R, the bearing capacity of the beam depends on the moment of resistance W _X. The moment of resistance depends on the section profile.

The effectiveness of a particular section profile characterizes the radius of the section core

where A is the cross-sectional area.

Comparing the assortments of I-profiles [1, p. 260] of cylindrical pipes [2, p. 52], it is easy to see that, with the same material consumption, cylindrical pipes have lower moments of resistance and smaller radii of the core section than I-beams.

For a cylindrical pipe 3, the radius of the core section

⌀102 · 0.8 cm

or

I _X = A · r ² = 254 · 35.8 ² = 325536.6 cm ⁴

(see table 1 and table 2)

Currently, the I-beam profile is the best of the solid-walled when working on bending. That is, it has a maximum resistance moment W _X.

The maximum cross-sectional height of the currently rolled I-beams reaches 1 m [1, p. 260].

The maximum diameter of cylindrical pipes in accordance with GOST 10704-63 ^* reaches significantly larger values of 1420 mm [2, p.77].

Pipes of a larger diameter are known.

The rail and beam structure of the authors Nezhdanova K.K., Tumanova A.V., Nezhdanova A.K., Kareva M.A. [4, patent No. 2192381, 10.11.2002, Bull No. 31].

In the rail and beam construction, the crane beam is made of tubular elliptical in cross section. We accept this technical solution as an analogue.

In the analogue, a method for producing an elliptical pipe section is not described.

A cylindrical pipe is practically not used as a beam, since its bending strength, with the same material consumption, is less than that of an I-beam, and therefore the material consumption increases. This is a drawback of a beam from a cylindrical pipe.

The tubular beam has the following excellent properties:

- cushioning ability, mitigating dynamic effects;

- reduced corrosion resistance, since its outer surface is much smaller and there are no areas where dust and moisture accumulate;

- the stability of the pipe wall when bending is much higher compared to the I-beam due to the curvature of the wall;

The technical result of the invention is to increase the load-bearing capacity of a cylindrical pipe in bending and, as a result, to reduce its material consumption by deforming a circular cross-section of the pipe by rolls into an oval section from two mutually mirror arches connected by heels into a monolithic pipe; expanding the scope of beams with oval tubular profiles.

The technical result is realized in that the bearing capacity of a standard cylindrical pipe is increased. To do this, a cylindrical pipe is heated to a temperature of 600 ... 650 ° C, squeezed in a cage by rolls on four sides, deforming into an oval profile consisting of two mutually mirror arches joined together by heels, with the formation of a monolithic oval tubular profile with a relative tall

corresponding to the maximum moment of resistance determined from the cubic equation

where h is the height of the arch from the main axis X to the section profile of the midline;

b is the width of the arch in the midline;

t is the thickness of the wall, crimped by the rolls of the pipe,

A is the oval sectional area;

and the moment of inertia

A comparison of the developed method for producing a bending pipe with an oval profile with known methods of reinforcing structures shows the following significant differences, namely:

- a cylindrical pipe is heated and the section profile is oval, deformed by crimping it from four sides with rolling rolls;

- after deformation, a new oval profile is obtained, consisting of straight and mirror arches connected by their heels in a monolithic section.

As the basis of the oval profile of two mutually mirror arches connected by an heel in the oval, we take a parabolic arch of constant thickness t [5, p. 455]. Arches work perfectly in compression and have been known for a very long time (for example, arches of the Roman water supply). Arches are used in bridges [6, p.238].

The characteristics of the cross section of the arch can be easily determined by the formulas [7, p. 72].

Figure 1 shows an oval profile of two mutually mirror arches connected by heels in a monolithic pipe. Figure 2 - compression of the pipe rolls.

We introduce the following notation:

h is the height of each of the arches from the main axis X to the midline;

b is the width of both a straight and a mirror arch;

t is the thickness of the arch;

h + t / 2 - maximum height of the arch;

b + t is the maximum width of the arch;

2 (h-t) - the maximum size of the vertical oval cavity;

b-t is the maximum horizontal width of the cavity;

relative section height

The oval cross-sectional area from mutually mirror arches remains constant - const

from here

Denote the relative height of the oval profile, i.e., a larger diameter along the midline to a smaller

then

The main moment of inertia I _X oval profile relative to the X axis

Oval profile drag at midline

Substitute (9) into (11)

Find the extremum of the moment of resistance W _X depending on the height of the arch h with a constant cross-sectional area A const

To find the height of the arch h, at which the moment of resistance reaches an extremum, an equation of the third degree was obtained, which is easily solved [8, p.138]

After substituting (10) and (11) in (8), we obtain the value of the moment of resistance W _{X of the} new oval profile, depending on its relative height

Taking the derivative of (15)

we obtain the equation of the third degree to determine the relative height of the profile

at which its resistance moment W _X reaches a maximum

For example, for a pipe with a diameter of 1420

A = 443 t = 1

n ³ -3n ² + 2.7176114 · 10 ^-5 · n + 9.0587045 · 10 ^-6 = 0

n = 2.99999

For thin-walled profiles, we obtain the maximum moment of resistance W _X at n = 3.

For n = 3, we obtain from (10)

The main moment of inertia I _{X of the} oval profile is

Its maximum moment of resistance

Concrete implementation example

We increase the bearing capacity of the cylindrical pipe ⌀ 1320 · 11 mm for bending by compressing it in rolls oval profile.

At a cylindrical pipe

The main moment of inertia is D = 133.1 cm; d = 130.9 cm

Moment of resistance

The cross-sectional area of the pipe [2, p.77] according to assortment A = 452 cm ²

We specify the cross-sectional area

A = π · d _cp · t = π (132 -1.1) · 1.1 = 452.35791 cm ² .

The area in the assortment is less than actual by 0.079%. To calculate, we use the exact cross-sectional area. The cross-sectional area of the pipe after deformation remains unchanged A-const.

Define the relative height of the oval profile

according to clause 16

n ³ -3n ² + 3.8159226 · 10 ^-5 · n + 1.2719742 · 10 ^-5 = 0

n = 2,99999

For thin-walled section n = 3

Arch height

The main moment of inertia of the oval profile from two mutually mirror arches according to f. 18

I _XO = 2111651 cm ⁴ (2.125-fold increase)

The moment of his resistance according to f. 19

W _XO = 18012.51 cm ³ (1.197 times increase)

Table 1
Comparison of the moments of inertia I _X and the moments of resistance W _{X of the} cylindrical pipe and the oval profile of two mutually mirror arches after its deformation in the rolls. Dimensions, cm A cm ² t, cm I _X cm ⁴ W _X cm ³ width b, cm

I _cr , cm ⁴ ⌀102.88 254 0.8 325536.6 6383 59.53125 25,130 h = 89.296875 254 0.8 694,438.8 7742.1 30,481 485789 increases in 2.08 times 1,213 times 1,213 ⌀122 · 0.9 342 0.9 629420 10318.4 30,170 935963 h = 106.875 342 0.9 1339381.7 12479.7 71.25 36,490 increases in 2,087 times 1,209 times 1,209 ⌀1321.1 452.3579 1,1 993583.6 15054,3 77,045453 33,280 1449558 h = 115.56818 2111651 18012.5 39,819 increases in 2.125 times 1,197 times 1,197 ⌀142 · 2 443 2.0 1100877.3 15505.3 35,001 h = 124.59375 2357876.5 18848.9 83.06 42,548 1646407 increases in 2.14 times 1,216 times 1,216

Note: The moment of inertia for a cylindrical pipe is calculated

where r is the radius of inertia.

The moment of inertia I _X for a new section is calculated according to f. 18, and the moment of resistance

Output

Pipe deformation with respect to the relative height of the new oval profile

led to an increase in strength by 18.4 ... 21.6%, and rigidity in 2.08 ... 2.14 times. Data on increasing the strength and stiffness of pipes when they are deformed by rolls into an oval profile are given in Table 1.

For these pipes in Table 1 we will use the cross-sectional area given in the assortment.

Check the relation

for pipes ⌀102 · 0.8 cm ² ;

W _X = 6537.4 cm ³

n = 2,99999; I _X = 641808.7 cm ⁴ ; W _X = 10521.5 cm ³

⌀122 · 0.9 cm; A = 342 cm ²

n = 2,99999

⌀1321.1 cm; A = 355.1 cm ²

n = 2,99999

⌀1421 cm; A = 443 cm ² ; I _X = 1100877.3 cm ⁴ ; W _X = 15505 cm ³

n = 2,99999

For these pipes we take n = 3

We give the following comparison. Replace meter I-beams [8, p. 261] with equivalent pipes in area, and then we will compress these pipes into a new profile formed by two mutually mirror arches.

table 2
Comparison of the moments of inertia I _X and the moments of resistance W _{X of the} rolled I-beams and equivalent pipes before and after they are crimped by rolls into an oval profile Dimensions of I-beams and pipes, cm A cm ² t, cm I _X cm W _X cm ³ Width cm I _Y , cm ⁴ W _Y cm ³ I _KP cm ⁴

I 100B1 289 1.55 442460 8940 11510 720 312.3 30.93 0118.699 0.775 289 2 0.775 509004 8520.8 min 29,48 h = 101.879 289 2 0.775 1089929 10354 66,919 39588 1183 760098 max 35,827 increase in 2,413 1,158 3.44 1,64 2433.9 1,158 I 100B2 321 1.55 521600 10430 14250 890 545.2 32,49 0127.72183 0.8 321 20.8 654,579.3 10186.3 min 31.733 h = 112.85156 321 20.8 1401659 12376.5 75,234 53951.6 1627 1413902 max 38,556 increase in 2,687 1,186 3.76 1.42 2593 1,186 I 100B3 358 1.66 595560 11820 16610 1030 694.8 min 33,017 ⌀137.295 0.83 358 20.83 843563 12,214.5 34,119 h = 121.31024 358 20.83 1806340 14839.5 80,873 69527,4 1719.4 1258352 max 41.451 increase in 3,033 1,255 4,186 1,67 1811 1,255 I 100B4 397 1.84 662170 13060 18620 1150 936.3 min 32,897 ⌀137.3576.92 397 20.92 9363227 13542.6 34,112 h = 121.36549 397 20.92 2004 945.6 16463.6 80,910 77175.3 1907.7 1398749 max 41,470 increase in 3,028 1.26 4,145 1.66 1494 1.26

Note: attitude

Output:

1. After compression of the equivalent pipe into an oval profile, there was an increase in the moment of inertia I _X , a new profile compared to the I-beam of the same material consumption by 2.17 ... 3.03 times. The moment of resistance W _{X of the} new profile exceeded the moment of resistance of the I-beam by 15.8 ... 26% and, therefore, after compression in the rolls, the pipe acquired the best bending characteristics. Profile performance indicator - section core radius

increased in comparison with the radius of the core of the cross section of the I-beam 1.158 ... 1.26 times.

2. In view of the large diameters of pipes being rolled at present, 1420 mm and more, it became possible to abandon the use of unreliable trusses for coating industrial buildings and replace them with rolling profiles made of tube-rolled tubes.

The economic effect arose due to the following:

- a cylindrical pipe by deformation in the rolling rolls is transformed into a new oval profile of two mutually mirrored arches joined together by heels; material consumption has remained unchanged;

- the bearing capacity of the new profile has been increased in comparison with the material-intensive rolling double tee by 15.8 ... 26%, relative to the X axis;

- increased rigidity compared to the rolling I-beam I _X 2.17 ... 3.03 times relative to the X axis;

- increased moment of inertia during torsion I _X in 1427 ... 2498 times;

- increased moment of inertia I _Y 3.76 ... 4.186 times;

- increased moment of resistance W _X 1.42 ... 1.67 times;

- increased corrosion resistance of the structure.

Thus, all design performance indicators have improved.

Literature

1. Sakhnovsky M.M. Designer Handbook for Building Welded Structures, Dnepropetrovsk, "Promin", 1975

2. Vasilchenko V.T. Rutman AN, Handbook of the designer of metal structures Kiev: Budivelnik, 1980-288 p.

3. SNiP 11-23-81 ^* Steel structures. M.: TsITP Gosstroy USSR, 988.

4. Nezhdanov K.K. Tumanov V.A. Nezhdanov A.K. Karev M.A. Rail and beam construction. Patent of Russia No. 2192381, 10.11.2002, Bull, No. 31.

5. Reference designer of industrial, residential and public buildings and structures / Ed. A.A. Umansky - M .: Stroyizdat, 1960 .-- 1040 p.

6. Evgrafov G.K. "Bridges on the railways." - M., 1947

7. Pisarenko G.S., Yakovlev A.P., Matveev V.V. Handbook of resistance to materials: Naukova Dumka, Kiev - 1975. - 704 p.

8. Vygodsky M.Ya. Handbook of Higher Mathematics. M., 1977

Claims (1)

A method of producing a bending pipe with an oval profile, namely, that the cylindrical pipe is heated to a temperature of 600-650 ° C and squeezed into the cage by rolls on four sides, deforming into an oval profile consisting of two mutually mirror arches connected to each other heel, with the formation of a monolithic oval tubular profile with a relative height

corresponding to its maximum moment of resistance, determined from the cubic equation

where h is the height of the arch from the main axis X to the section profile of the midline; b is the width of the arch in the midline; t is the thickness of the wall, crimped by the rolls of the pipe; A is the oval sectional area; and the moment of inertia

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