SU1317315A1 - Method of creep testing of specimens - Google Patents

Abstract

This invention relates to a testing technique, and specifically to methods for testing creep specimens. The purpose of the invention is to reduce the labor intensity of the tests by using three samples for determining the material characteristics. A series of three samples is heated to a predetermined temperature, loaded with a constant load at a constant speed, which for the first sample is chosen in the range 95-150 MPa / s, for the second - 20-60 MPa / s, and the third - 0.5-10 MPa / s, measure the magnitude of the deformation and determine its dependence on stress, which is judged on the characteristics of the material. 4 il. i (L 00 00

Description

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This invention relates to a testing technique, and specifically to methods for testing creep specimens.

The purpose of the invention is to reduce the labor intensity of the tests by using only three samples to determine the characteristics of the material.

FIG. Figure 1 shows diagrams of the stress-strain relationship for steel 40X at 20 ° C and loading at speeds corresponding to upper limits; in fig. 2 shows time warp diagrams plotted from FIG. one; Fig. 3 is the same when loaded at speeds corresponding to lower limits; FIG. 4 shows diagrams constructed according to FIG. 3

The method is carried out as follows.

At a given temperature, to determine the characteristics of the material, three samples are sequentially tested, which are loaded at a constant rate of -. tew. In this case, the loading rate of the first sample is chosen in the range of 95-150 MP / s, which contributes to instantaneous deformation. At a loading rate of less than 95 MPa / s, creep deformations occur in the sample, and at a loading rate of more than 150 MPa / s, no new data will be obtained on the physicomechanical properties of the material. In addition, the loading rate is greater. 150 MPa / s leads to the complexity of the design of test devices.

The loading rate of the second sample is chosen in the range of 20- 60 MPa / s, which ensures the occurrence in the sample of creep deformations, which have average values of maximum values. A sample with a speed below 20 MPa / s and above 60 MPa / s leads to a deviation of creep deformations in the sample from average values, which causes a decrease in the accuracy of determining the characteristics of the material.

. The loading rate of the third sample is chosen in the range of 0.5–10 MPa / s, which ensures the most accurate creeping diagrams. With this mode, the maximum possible airborne creep deformations occur in the sample. Loading the sample at a speed of less than 0.5 MPa / s causes the loading effect

52

Effort occurs for a long time, which increases the complexity of the test. Sample loading at a speed greater than 10 MPa / s

reduces the amount of creep deformation in the sample, which causes a decrease in the accuracy of determining the characteristics of the material.

In the process of loading all three

specimens register strain

specimens, determine the dependence of the strain on the stress, and on this dependence judge the characteristics of the material.

For other temperatures, the test cycle is repeated.

Example 1. A series of samples (4 pcs.) Of 40X steel with a diameter of 5.0 mm at 20 ° C was loaded at a constant speed of 150 MPa / s. The second and third series of samples at the same temperature were loaded with. speeds of 60 and TO MPa / s, respectively. The deformations of the specimens were measured, the test results were averaged. The diagrams of strain versus stress in samples are shown in FIG. 1. According to the test results, the creep characteristics of steel 40X were determined,

 which are shown in FIG. 2. Diagram 1 was obtained with a voltage in the sample equal to 300 MPa, diagram 2 - at 314 MPa, diagram 3 - at 320 MPa, diagram 4 - at 330 Mia

and diagram 5 at 340 MPa.

The dashed lines are diagrams of the dependence of strain on time, which are obtained experimentally by loading samples in accordance with the analogue. The discrepancy between the diagrams obtained by the proposed method and the basic one is less than 5%, which confirms the necessary degree of accuracy in determining the characteristics of the material.

Example 2. A series of samples (5 pcs.) Of 40X steel with a diameter of 5.0 mm at 20 C was loaded at a constant speed of 95 MPa / s. The second and third batches of the samples at the same temperature were loaded at speeds of 20 and 0.5 MPa / s, respectively.

Stress versus stress diagrams are shown in FIG. 3

According to the test results, the creep characteristics of steel 40X were determined, which are shown in FIG. 4. The procedure for determining rheological characteristics is similar to Example 1.

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Claims (1)

Invention Formula A method for testing creep specimens, according to which the specimens are heated to a predetermined temperature, is loaded with a constant load, the strain value is measured and the load is determined. (, MPa UOQ 05 20 tO 173154 the dependence of the strain on the stress by which the characteristics of the material are judged, characterized in that, in order to reduce the laboriousness of the tests, three samples are used, they are loaded at a constant speed, which for the first sample is chosen in the range of 95-150 MPa / s .dl second - 20-60 MPa / s, and the third - 0.5-10 MPa / s. 40 60 FIG. g 80 t.MUH. CTP / Zpar / Pius t so (rtsg.Z e-10 Compiled by M.Matyushin Editor V.Kovtun Tehred A.Kravchuk Proofreader S.Shekmar Order 2415/38 Circulation 776 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4