RU2626703C2 - Method of cylindrical parts parameters stabilization - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: part is put into rotation and applied the external load to it, causing the plastic deformation in it. One end of the part is fixed in the chuck of the machine and the part is given the multi-cycle uniform rotation about its axis, the external load in the form of the bending moment is applied to the other end.

EFFECT: geometric dimensions of the part are improved by eliminating the residual stresses along the axis of the part.

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Description

The invention relates to cold forming of metals, and in particular to methods for stabilizing the dimensions of long cylindrical parts such as shafts, axles, rods, rods, etc.

Known methods for static editing of long parts such as rods, shafts, sheets, carried out by applying an external load to a fixed part in one or two directions - in the transverse and longitudinal, causing plastic deformation in the part and correcting the curvature of the axis of the part described in the copyright certificates SU on invention No. 133812, No. 1148663, No. 410851, RU patents on the invention No. 2525023, No. 2140842.

The disadvantages of these methods is that after the external load is removed, residual stresses occur in the part, which change its shape and size over time. In addition, under the influence of external load, uneven stresses arise both in the cross section of the part and along the axis of the part, which does not provide uniform dressing and reduces the quality of processing.

Other editing methods include methods [RU patents for inventions No. 2478031, No. 2457100, No. 2380212], in the implementation of which the parts give rotation around the axis and load the part with shear force. Due to the rotation of the part in the cross section of the part, stress sections uniformly distributed along the circumference are formed, which helps to stabilize the position of the axis of the part.

The disadvantages of these methods include the fact that uneven stresses occur along the axis of the part, which reduces the quality of processing. In addition, the external load does not cause plastic deformation in the part, which does not provide a correction of the initial error in the location of the axis of the part.

The closest analogue in technical essence and the achieved effect to the claimed one is a method of stabilizing the parameters of cylindrical parts, in which the parts give rotation and apply an external load to it, causing plastic deformation in it, described in RU patent for invention No. 2116150. The rotation of the part is limited by its rotation around the axis. The external load is provided by static radial compression of the part by rolls until the part is straightened in the lower supporting and upper deforming elements arranged in a checkerboard pattern. In addition to radial compression, an axial compressive force is additionally applied to the part to a stress corresponding to the yield strength of the workpiece material, and it is also twisted relative to the longitudinal axis. Due to plastic deformation, the initial error in the location of the axis of the part is corrected, and due to the rotation of the part, an external load is applied to it from all sides, which helps to stabilize the position of the axis of the part.

The disadvantage of the closest analogue is the low quality of dimensional stabilization, since when the part is straightened from the convex side, elastic compression stresses are formed, and from the concavity, elastic tensile stresses are formed. Under the action of axial load, additional compression stresses arising are summed with elastic compression stresses on the part convexity side, plastic deformation is carried out in this part and residual stresses occur that are equal to the yield strength of the material. Tensile stresses, from the bulge side of the part, combined with the compressive stresses from the axial load, create a stress that is less than the yield strength. Elastic deformation is carried out in this part of the workpiece. Thus, after removing the external load, the part is only partially stabilized. But as a result of plastic deformation, residual stresses remain in it, which subsequently lead to its additional elastic deformation. The rotation of the straightened part between the rollers does not lead to its cyclic deformation, and therefore does not affect the stabilization of dimensions. The disadvantage of this method is that the deformation of the part in its various cross sections is different and due to this the correcting ability of the method is reduced. In addition, this method is difficult to implement, as it requires the presence of bulky power mechanisms.

The objective of the invention is to improve the quality of the process of stabilization of the geometric parameters of the part.

The problem is achieved by the fact that in the claimed method of stabilizing the parameters of cylindrical parts, in which the parts give rotation and apply an external load to it, causing plastic deformation in it, one end of the part is fixed in the machine cartridge and the part is given multi-cycle uniform rotation around its axis, to to the other end, an external load is applied in the form of a bending moment, determined by the formula:

M≥σ _T ⋅W,

where σ _T is the yield strength of the material of the part, MPa;

W is the moment of resistance to bending of the section of the part, mm ³ .

The technical result is the uniform removal of residual stresses along the axis of the part.

Since a bending moment is applied to the end of the part, the same bending stress arises in all cross sections of the part, which eliminates stress and uniformly stabilizes the part along its entire length. Since the parts give a multi-cycle uniform rotation, the same conditions of deformation and relaxation of residual stresses are created along the circumference of each section of the part, which also helps to stabilize the geometric parameters of the part. And since the bending moment is selected from the condition of creating plastic deformation along the entire length of the part, the initial error in the shape of the part is corrected uniformly along its entire length.

The invention is illustrated using the drawing, which shows a diagram of the processing of the part in accordance with the claimed method, and positions 1-2 are indicated:

1 - detail;

2 - cartridge.

The method is as follows. A cylindrical part 1 with an outer diameter d and a length L at one end is rigidly fixed in the cartridge 2. With the help of the cartridge 2 parts 1 give uniform rotation with a frequency of n. An external load is applied to the other end of part 1 in the form of a bending moment M of magnitude

where σ _T is the yield strength of the material of the part, MPa;

W is the moment of resistance to bending of the section of the part, mm ³ :

where d is the diameter of the part, mm

Under the action of the bending moment M in all sections of the part along its entire length, bending stresses equal to the yield strength of the material σ _T arise, as a result of which plastic deformation occurs. Due to plastic deformation, the initial error of the geometric shape of the part is corrected, and the axis of the part acquires a rectilinear shape. After about 20-30 revolutions of the part 1, the treatment is stopped - the bending moment M is removed from the part, the rotation of the part 1 is stopped and it is removed from the cartridge 2. The specified 20-30 revolutions of the part are usually enough to correct the shape error of the part in the form of an axis curvature and stabilize straightness axis.

Since the parts give rotation, the stresses in the part appear the same both along the circumference of each cross section of the part, and along its entire length. This allows you to fix all the errors in the location of the axis of the part, even if they do not lie in the same plane. In addition, the straightness of the axis of the part after processing is stabilized, since the residual stresses in the part are small and fully balanced.

- 265 мм. Материал детали - сталь 40Х, имеющая предел текучести σ_T=1175 МПа и предел прочности при изгибе σ_u=1520 МПа. Модуль упругости E=210000 МПа. Требовалось устранить кривизну оси детали, которая достигала на отдельных участках Δ=0,2 мм.Example. In accordance with the inventive method, the processing was subjected to a cylindrical part in the form of a rod with an outer diameter of d = 11 mm and a length

- 265 mm. The material of the part is steel 40X, having a yield strength σ _T = 1175 MPa and a flexural strength σ _u = 1520 MPa. Elastic modulus E = 210,000 MPa. It was necessary to eliminate the curvature of the axis of the part, which reached Δ = 0.2 mm in individual sections.

For a cylindrical part, the bending moment is equal to:

To realize dimensional stabilization, the part was installed at one end in a lathe chuck and gave it rotation with a frequency of n = 120 rpm. A higher rotational speed caused the part to heat up and vibrate in the process system. Too low speed reduced processing performance. A bending moment, determined by the formula (1), was applied to the other end of the part:

M≥1175-130.6 = 153 MPa.

Took M = 185 MPa. The moment close to the calculated value M = 153 MPa causes plastic deformation only in a thin surface layer of the part, which is not always enough to correct the position of the axis of the part. Too large a value of the bending moment, causing bending stress close to the tensile strength of the material of the part σ _u = 1850 MPa, can lead to its destruction.

The processing was carried out for 15 seconds, which at a speed of the part n = 120 rpm allows you to make 30 revolutions of the part. This is equivalent to 30 loading cycles of each section of the part.

After that, the processing was stopped and the error of the location of the axis of the part was measured, which did not exceed Δ <0.025 mm.

Thus, in a very short time by simple means, the error in the location of the axis of the cylindrical part is effectively corrected.

The technical and economic efficiency of the proposed processing method is as follows:

1. The quality of processing increases, since the error in the position of the axis of the part is eliminated and residual stresses that could lead to a loss of accuracy of the part over time are eliminated.

2. The simplicity of the method, there is no need to use powerful power devices.

Claims (3)

A method of editing cylindrical parts on a lathe, including fixing the part at one end in the lathe chuck, imparting rotation of the part around the axis with the help of a chuck, applying an external load to the part causing plastic deformation, characterized in that the parts impart uniform rotation with a frequency of 120 rpm min, an external load is applied to the other end of the part with the creation of a bending moment, causing in all sections of the part along its entire length, bending stresses equal to the yield strength of the material of the part, and rekraschayut editing after the 20-30 revolutions detail, the external load is defined as the bending moment by the formula: M≥σ _T ⋅W, where σ _T is the yield strength of the material of the part, MPa; W is the moment of resistance to bending of the section of the part, mm ³ .

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