SU856772A1 - Method of strengthening part plane surfaces - Google Patents

Description

about t

The invention relates to mechanical engineering, in particular, to surface plastic deformation (FPD) of machine parts in order to increase their fatigue strength.

The known method of hardening the parts of the FPU by rolling them with rollers, when for given values of fff and hg Q the working load P for these rollers is preliminarily determined, and the profile radii of the rollers are chosen depending on P fl.

The purpose of the invention is to increase the hardening efficiency by increasing the fatigue strength of machine parts.

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This goal is achieved by performing a tensile test of a standard sample made from a material of a hardened part, and determining the limiting uniform distortion of the material of the part under stretching before rolling, and deforming the surface layer of the part, with a roller, until the deformation, equal to the measured, while the profile radius of the roller and 30

force P on it is chosen from the following ratios

-r / htl

 / | 1 „C - g

B.DpVxepHB

1tHD-fls p) b,. , ... Hei500E.r Y Dp-vDa 50 Dp4Т) where Op is the diameter of the roller in the running-in plane;

D is the diameter of the workpiece,

Qr yield strength of the material of the hardened part; .

ND is the plastic hardness of the material of the part;

fi- - the depth of the plastically deformed part layer,

fp - extreme uniform deformation of the material of the part under stretching /

X is the coefficient that takes into account; the influence of the eccentricity of the contact area on the depth of the de-normalized layer; RD is the conditional critical load at which plastic deformation arises at the center of contact of a ball 10 mm in diameter with a plane.

The method is carried out as follows.

 A standard tensile test is made from the material of the part. In the test, the limiting uniform strain p of this material is determined upon stretching. Then, according to available recommendations, the depth of the plastically deformed layer hg is determined.

Using the above formulas, the profile radius of the roller r and the rolling force R are calculated.

The run-in is made with the calculated parameters, and the plastic deformation of the surface layer is approximately equal to the maximum uniform deformation of this material.

Example. Several series of specimens with a diameter of 0–10 m are made from steel grades 30 and 30 “GSA. Samples of one series are subjected to rolling with rollers having profile radii G approximately equal to those calculated using the formula O), and the working loads calculated using formula (2) are used. Samples of the rest of the series made from the same material are rolled with rollers with profile radii different from the optimum npeflJiaraeNKJx. In this case, the force is selected in such a way that the hg depth of the hardened layer is the same for samples of the same series, the diameter of the roller Dp, measured in the section plane of the part, is also the same in all cases and is equal to twice the diameter of the part, i.e. 20 mm.

Samples of all series after rolling with rollers are tested for alternating bending on a UKI-YuM machine and their durability (by failure) is determined at a given level of operating voltage. The results of the tests for alternating bending of steel samples with a diameter of 10 mm DB, reinforced by rolling a roll w Dp 20 mm in various modes are shown in the table.

From the considered data of the table it is seen that the maximum durability of the samples is achieved under the condition when f p, i.e. when the values of r and P correspond to their optimal values (underlined in the table), calculated from the proposed 5 formulas. Thus, for samples of series a of steel 30 (Ep 0.15), the values of Gy will be optimal. 1.8 mm and RAPT 96 kg; for samples of the series (f from steel (p 0.09) - GORT, respectively, 3.45 mm and RAPT 138 kgf, etc. Deviation f. from tp (as well as g from g ,.) in any direction leads to a decrease in the durability of the sample details at all depths h.

Thus, the application of the proposed method of strengthening the rolling of cylindrical parts by means of surface plastic deformation allows to significantly increase their fatigue strength due to more complete realization of the resources of strengthening, as well as to ensure the selection of economically most advantageous processing modes that take into account the physical and mechanical properties of the material, its dimensions and requirements. imposed on the quality of the treated surface.

a) Steel 30; ND 170; ffy 34 kgf / mm; (Ep 0.15; h, (g 1.8 mm; P 96 kgf)

Claims (1)

1.05 mm b) Steel ZOx GSL: ND 286; 63.5 (h 3.45 mm; P Note. The advantage of the proposed method is that the use of calculated values in accordance with the proposed 1 dependencies and P in the process of rolling a part with a roller allows for a given depth of plastically deformed layer IV to provide in this layer the intensity of plastic deformation, which is equal to the maximum uniform deformation of the material when stretched, which brings to the limit the positive effect of the strengthening factors (i.e., work hardening and residual stresses) and thereby contributes substantially Improving hardening efficiency due to maximum increase at a given value of the fatigue strength of parts. Formula of the Invention A method for hardening parts by surface plastic deformation to a given depth, including running the surface of the part with a roller, the workload of which is determined by the mechanical properties of the part material, characterized in , in order to increase the hardening efficiency by increasing fatigue strength, extreme uniform deformation is measured before the run-in. material details when growing the same Continued table mm The number of cycles before the samples are eradicated from steel grades 20 and OXGSA, not subjected to rolling by rollers, is N 15000 and N 27000 cycles, respectively. kg / mm; p - 0.09; h 0.90 138 kgf) form a surface roller, to achieve the same measured, with the roller radius and usiny chosen from the following Y i -) exp (p diameter of the roller in the working plane of the diameter of the workpiece; yield strength of the material of the hardened part plastic the hardness of the material of the part is the depth of the plastically deformed layer of the part; the maximum uniform deformation is the material of the part under tension / coefficient f taking into account the real influence of the eccentricity. of the contact pad on the depth of the deformed layer; ll, p / 2, and P About ГРРРв 600tpV 50 roller diameter in the running-in planeJ Density of the workpiece. . plastic hardness of material) (GOST 18835-78) the depth of the plastically deflated part layer; extreme uniform deformation of the material of the part under stretching; coefficient taking into account the influence of the eccentricity of the contact pad on the depth of the deformed layer; PJJ - conditional critical load, at which plastic deformation is generated in the center of contact of a ball with a diameter of 10 mm with a plane. Sources of information taken into account in the examination I. Braslovsky V.I. Technologists running large parts with rollers. M., Mechanical Engineering,.