SU1453231A1 - Method of testing materials for tqo-axis tension - Google Patents

Abstract

The invention relates to methods for determining the strength properties of samples of sheet material by squeezing them out with hydrostatic pressure. The purpose of the invention is to increase the information content by providing a definition of local deformation and 5 5 5 7 sites of the occurrence of a crack. Sample 7 is installed in the matrix 5 and clamped by the piston 2. The pressure in the high pressure chamber 3 is raised to a value of 0.8-0.9 from the fracture pressure of the sample 7. The pressure in the chamber 3 is relieved. A dividing grid is applied to the sample in the bulge area and again install sample 7 into the test device. A pressure of 0.8-0.9 is applied to sample 7 from a pressure corresponding to the destruction of the sample simultaneously from two sides in chambers 3 and 6. Then, pressure in chamber 3 is increased until sample 7 is destroyed, the deformation rate of which is kept constant by adjusting pressure in chamber 3. The pressure in chamber 6 is kept constant during the loading process, as a result of which a localized deformation region is clearly manifested. 3 hp f-ly, 4 ill., 3 tables. J i (L sd soy 00 t Figure 1

Description

The invention relates to a testing technique and can be used to determine the strength properties of samples of sheet material by squeezing them out with hydrostatic pressure through matrices of round, elliptical, or other shapes.

The purpose of the invention is to increase the information content by ensuring the determination of local deformation and the place of occurrence,

Figure 1 shows the structural diagram of the device for implementing the method; FIG. 2 is a diagram of a signal converter of interlacing of the top of a deformable surface of a test sample; FIG. FIG. 3 shows the structure of a sensitive element of a signal transducer for moving the apex of a deformable sample surface; Fig. 4 is a graph of the dependence of the fracture toughness value K (the tested materials on the relative lengths of the localized deformation zone. The device for implementing the method comprises a first body 1 in which a pressure piston 2 is installed with a cavity forming the high pressure chamber 3 , a second body 4 in which a matrix 5 is installed with a cavity forming an additional high-pressure chamber 6. A test specimen 7 of a sheet material is mounted between the pressure piston 2 and the matrix 5. 7, the dies 5 and the pressure piston 2 are installed seals 8. The housings 1 and 4 are fastened with a lock 9. The high pressure source, made in the form of a pump 10 with an electric motor 11, is connected to chambers 3 and 6 via an adjusting unit 12, which electrically connects An additional chamber 6 is connected to a hydraulic accumulator 14 and a safety valve 15. A cavity 16 is formed between the pressure piston 2 and the first body 1 and connected to the regulator block 12. In the additional chamber 6. pin 17 of the sensor moving the tip of the bulge of the test specimen 7 is placed, pin 17 of the sensor is included in the transducer of the signal moving the vertex of the deformable surface of the test specimen 7 (Figures 2 and 3) and installed

the help of the sliding sleeve 18, the guide sleeve 19 and the guide rocker 20. The pin 17 is pressed against the roller 21 by the spring 22, and the movement signal generation unit 23 is electrically connected with the control unit 13.

The method of testing materials for biaxial stretching is carried out in the following manner.

Sample 7 is installed in the matrix 5 and clamped by the piston 2 by supplying the working medium pressure to the cavity 16. Then the working medium pressure is supplied to the high pressure chamber 3 to a value of 0.80-0.90 from the fracture pressure of the sample 7. Then the pressure in the chamber is relieved 3. Remove sample 7 with a bulge from the test device. Degrease the surface of the bulge. Apply a dividing grid on it from two sides. Sample 7 is reinstalled into the test apparatus and a pressure of 0.80-0.90 is applied to it from the pressure corresponding to the destruction of the sample and simultaneously in both chambers 3 and 6, then the pressure is increased only in chamber 3 until sample 7 is destroyed. With such loading of the samples, all tested materials clearly show a localized deformation region - the neck area. To ensure the stability of localized deformation, the deformation rate of specimens 7 is ensured as follows. The signal proportional to the amount of deformation of the sample 7, produced by the node 23, goes to the control unit 13, which, controlled by the organ regulator unit 12, maintains the pressure in chamber 3, ensuring the constant deformation rate of the sample 7 ° C, the additional chamber 6 is maintained at a constant pressure hydroaccumulator 14 and safety valve 15. The tests are carried out in automatic mode

Materials for the manufacture of samples 7 are sheet alloys of the aluminum grade AMGB and 1201, as well as titanium alloy of the grade OT4-1 and sheet steel of the type 18-8. The thickness of the sheets is 1.2-3.05 mm. The main series of experiments conducted on. Samples Alloy AMgbo The tests of samples of other materials were carried out only for the purpose of confirming the results obtained from tests of specimens of aluminum alloy AMgb. The free size of the circular die is 140 mm.

In Table 1, the values of standard mechanical properties of AMgb alloy specimens 1.5-2.0 mm thick, determined at a single static stretch, and e is the corresponding ultimate ductility, Ggj is the yield strength, (Jg is the tensile strength, o is the elongation (on a tenfold sample), C is the narrowing of the cross sectional area, (p is the failure stress, final deformation, corresponding to the failure.

As follows from the data presented in Table 1, all the mechanical characteristics of the alloys change quite naturally with a change in the hardening size (the value of the preliminary deformation of the AP), which corresponds to the currently existing representations.

Standard and nonstandard mechanical characteristics of flat standard 10-fold specimens in the form of a double oar were determined experimentally with a single uniaxial static discontinuity. The results of the experiments are presented in the table2, where the ratios between the length of the local deformation zone -A (neck length) and uniform elongation on the one hand and the standard ductility characteristics under uniaxial and t and biaxial (e) stretching (in - sample thickness).

From the data presented in table. 2, it follows that there is no clear correlation between standardized and non-standardized mechanical characteristics.

Table 3 presents the values of the ratios between the strength characteristics under uniaxial and biaxial static single loading of samples of AMgb alloy of varying degrees of loading of PD.

From Table 3 it follows that the m between the strength characteristics, determined during uniaxial and biaxial loading, is observed

ten

AND)

20

thirty

35

40

45

50

55

31

l qi depending on the pebbles PD - the degree of hardening.

It follows that the characteristic of local, concentrated deformation cannot be determined by calculation, based on the ratio of the usual standardized characteristics. It should be determined experimentally.

Fig. 4 shows a graph with a correlation curve relating the values of fracture viscosity K, C to values of relative localized, concentrated plastic deformation.

As follows from the review and analysis of the data presented in Fig. 4, a direct, although not linear, correlation is observed between the quantities.

Thus, the method makes it possible to estimate the magnitude of the fracture viscosity. The method makes it possible to evaluate the material's material resistance on samples of small thickness, i.e. realizes the condition of plane deformation.

Claims (2)

Invention Formula one-. The method of testing materials for biaxial stretching by means of: one loading a flat sample with an internal hydraulic pressure, measuring the pressure of the medium and the deformation of the sample during loading and at the moment of rupture and determining the strength properties of the material, so that that, in order to increase the information content of ensuring the determination of local deformation and the site of the occurrence of a crack, loading the sample is carried out before detecting the localized deformation region, the pressure of the medium corresponding to this rmatsii is applied to the sample equal to the pressure on the other side and maintained constant during Vromi further the stress and the deformation is measured in the region of the local deformation, 2. The method according to claim 1, characterized in that after detecting the local deformation zone in this zone, a mesh is applied to the surface of the sample, and strain measurement is performed by measuring the dimensions of the mesh dimensions. 3, the method according to claim 1, characterized in that at the time of detection of the localized deformation region, the loading moment of the sample is taken to a pressure of 0.8-0.9 from the value of the fracture pressure, A. Method of pop, 1, characterized in that the loading is about 14532316 The specimen is placed at a uniform rate of deformation by measuring the movement of the tip of the deformable surface and changing the pressure of the medium in accordance with it. Table 1 About 1.85 0.71 0.546 0.376 2.61 10 1.25 0.74 0.667 0.157 1.70 20 1.15 0.81 0.757 0.109 1.42 Table3 30, 1, 13 0.84 0.100 1.35 40 1.13 0.86 0.810 1.00 1.32 5f. Jw Fig.Z l tCpl rftft A // nineteen