GOST R 50708-94
(ISO 9649-90)
Group B79
STATE STANDARD OF THE RUSSIAN FEDERATION
WIRE
Test method for alternating twisting
Wire. reverse torsion test
MKS 77.040.10
77.140.65
OKP 12 0100
Introduction date 1996-01-01
Foreword
1 DEVELOPED AND INTRODUCED by the Technical Committee TC 146 "Hardware"
2 ADOPTED AND INTRODUCED BY Decree of the State Standard of Russia dated November 8, 1994 N 266
3 This standard contains the full authentic text of the international standard ISO 9649-90 "Metallic materials - Wire - Alternating twist test" with additional requirements reflecting the needs of the national economy
4 INTRODUCED FOR THE FIRST TIME
5 REVISION
1 area of use
1 area of use
This International Standard specifies a method for determining the ability of a metal wire with a diameter of 0.3 to 10 mm to undergo plastic deformation under alternating torsion. This test is carried out in order to detect surface and internal defects of the wire.
Additional requirements reflecting the needs of the national economy are typed in italics.
2 Normative references
GOST 1545-80 Wire. Torsion test method
3 Notation and definitions
Wire designations are shown in Figure 1 and Table 1.
Picture 1
Table 1
Designation | Definition | unit of measurement |
Round wire diameter | ||
Length of the part to be tested (grip distance) | ||
Number of twists in one direction |
4 Essence of the method
A wire sample is twisted a certain number of times through 360° around its axis in one direction and the same number of times through 360° in the opposite direction.
5 Test equipment
5.1 The grips shall be rigid for rigidity and abrasion resistance and shall be mounted on the machine in such a way that during the test they remain in one axis and do not subject the specimen to bending forces.
5.2 The machine must be designed in such a way as not to interfere with the change in the distance between the grips during the test.
5.3 One of the grips of the machine must rotate around an axis, the other must not have angular deviations, except in cases where such deviations are necessary for measuring torque.
5.4 The distance between the grips should be adjusted according to the length of the sample.
5.5 The testing machine shall be designed in such a way that the required tensile stress can be applied to the test piece in accordance with 7.2.
5.6 The machine must be able to change the direction of rotation.
6 Procedure for preparing specimens for testing
6.1 The piece of wire used as a sample should be straight.
6.2 If necessary, the sample is straightened manually, or, if this is not possible, with a hammer made of wood, plastic or copper on a flat surface of the same material.
6.3 When straightening, the surface of the wire shall not be damaged and the test specimen shall not be subjected to torsion.
6.4 A wire with a sharp local curvature shall not be used as a test specimen.
6.5 Unless otherwise specified in the relevant standard, the distance between grips (nominal) shall be as given in table 2.
table 2
In millimeters
Nominal wire diameter | Distance between grips (nominal) |
* 50 may be applied by special agreement. ** 30 may be applied by special agreement. A fixed distance between the grips can be set, which is specified in the relevant standard and recorded in the test report. |
|
7 Test procedure
7.1 Tests should be carried out at an ambient temperature of 10 to 35 °C.
Arbitration tests are carried out at a temperature of (25±5) °C.
7.2 The specimen is fixed in the grips in such a way that its longitudinal axis coincides with the axis of the grips and that it remains straight throughout the test. Unless otherwise specified in the relevant standard, this can be achieved by applying a constant tensile stress to the wire sample, sufficient to straighten the sample, the value of which should not exceed 2% of the nominal value of the tensile strength.
7.3 After fixing the test specimen in the machine, one of the grips shall be rotated at a speed not exceeding one revolution per second for wire diameters less than 5 mm and 0.5 revolutions per second for wire diameters of 5 mm or more. The number of turns in one and the opposite direction shall be specified in the relevant wire standard.
For one twist, they take a turn of 360 °.
After the end of the test, the surface of the specimen between the grips is checked visually, unless otherwise stated in the relevant standard.
7.4 The absence of visible defects is the basis for considering that the sample passed the test.
7.5 If the destruction of the sample occurred in the grip of the machine or near the grips (at a distance of less than 2) and the sample did not withstand the required number of twists, then the result of this test is not taken into account. The test must be repeated on another specimen taken from the same skein (coil) whose specimen failed.
8 Test report
8.1 The test report should contain:
a) the number of this standard;
b) characteristics of the test sample;
c) sample diameter;
d) method of editing the sample;
e) test conditions (e.g. length of the part to be tested, tensile stress);
e) test results.
Torsion is carried out by two different in magnitude and oppositely directed torques, which
supports (Fig. 7.b). Experimentally, the first scheme is easier to implement, and therefore it has found the greatest distribution, it should be taken into account that the second "pure bending" scheme in many cases provides more reliable results, since here the maximum bending moment occurs at a certain section of the sample length, and not in one section, as when using the first scheme.
Bend specimens do not have heads, which is another advantage over tensile test specimens, as the manufacture of samples with heads, especially from brittle materials, is much more difficult. To determine the properties of cast iron castings, cylindrical samples with a diameter of 30 ± 1 mm and a length of 340 or 650 mm are used (with a distance between the supports of 300 and 600 mm, respectively). To assess the characteristics of structural strength, it is recommended to use samples of large cross-section up to 30x30 mm.
Bend tests can be performed on any universal testing machine used for tensile testing. The sample is placed on the base plate in the lower grip and deformed with a bending knife fixed in the upper grip of the machine. The specimen bends when the lower grip is raised or the upper grip is lowered. At the same time, a bending diagram can be recorded on the chart tape in the coordinates load R- deflection arrow f. For a plastic material, the bending diagram looks as shown in Figure 8. If the material is brittle, then the diagram breaks at the point b. Knowing the magnitude of the loads R hc , R ex , R T , R b allows you to determine the limits of proportionality, elasticity, fluidity and flexural strength. Stresses at the stage of elastic deformation are calculated using the usual formulas for the resistance of materials.
In bending tests, as in the case of compression, sufficiently plastic materials do not fail. In this case, the sample is bent up to the parallelism of its parts located on both sides of the knife.
The simplicity of bending tests and the clarity of the resulting plasticity characteristics have led to the development of a number of technological samples that are used in the factory. The task of all these tests is to evaluate the plasticity of deformed semi-finished products, castings and products (sheets, wire, pipes, etc.). GOST 14019 - 80 "Bending test methods" provides for bending by concentrated force of flat specimens from rolled products, forgings and castings placed on two supports. The criterion for the suitability of products can be: 1) the specified bending angle of the samples ( β ) the appearance of the first crack when bending at an angle β , equal to or greater than the specified; 3) the possibility of bending the plate to parallelism or contact of the sides. There are also tests for bending a sheet, tape (GOST 13813 - 68) and wire (GOST 1579 - 80), in which a given number of bends is recorded, after which cracks appear or the sample collapses.
Torsional tests
Torsion is carried out by two different in magnitude and oppositely directed torques, which are applied to the ends of the sample in planes normal to its longitudinal axis.
Especially often these tests are used to evaluate the material properties of shafts and wires. The test procedure for samples of any materials with a diameter of at least 5 mm is standardized (GOST 3565 - 80). Samples should have a cylindrical working part and square heads. A sample with a working part diameter of 10 and a calculated length of 100 or 50 mm was taken as normal. It is allowed to use samples that are proportional, geometrically similar to normal, as well as tubular.
Torsional tests are carried out on special machines, which must ensure reliable centering of the sample, smooth loading and absence of bending forces, the possibility of sufficiently accurate setting and measurement of the torque. Machines with horizontal and vertical arrangement of the sample are used. The maximum torque varies from 60 Nm to 2 Nm.
As a measure of deformation during the test, the angle of twist is fixed φ .
During the test, each grip of the machine rotates through a certain angle (greater for the active grip). The sample twist angle is equal to the difference between these angles. Knowing the current values of the torque and the angle of twist, it is possible to construct a torsion diagram in the coordinates M kr - φ (Fig. 9). This diagram consists of an elastic section ( Or) and plastic deformation ( rk). Due to the absence of a significant local narrowing, there is no descending section in the torsion diagram, although after the formation of the first cracks, the deformation becomes uneven, concentrating near the fracture.
By analogy with other static torsion tests, the conditional limits of proportionality, elasticity, yield, strength, as well as the true tensile strength are determined. But all these properties are expressed not through normal, but through shear stresses.
Torsional proportional limit τ hc- this is the conditional shear stress at which the deviation from the tangential relationship between stresses and strains reaches such a value when the tangent of the angle formed by the tangent to the torsion diagram and the strain axis exceeds the original value by 50%.
Torsional elastic limit τ ex- conditional shear stress at which the sample is subjected to residual shear deformation by a given value:
The yield strength determined during torsion is usually conditional. This is the shear stress, which corresponds to a residual relative shift of 0.3% ( τ o,h), which is equivalent to an elongation of 0.2%.
Conditional torsion strength τ pch corresponds to the torsion moment before failure, it is calculated without taking into account plastic deformation.
The main characteristic of plasticity in torsion is the relative shear.
A variation of the torsion test is a test for twisting a wire with a diameter d less than 10 mm (GOST 1545 - 80). Sample length 100 d it is clamped in the hard jaws of the grippers and twisted when one of them is rotated at a constant speed (30 - 90 rpm). As a result of the test, the number of revolutions of the active grip until the wire breaks is determined. This number is considered a criterion of its quality (plasticity).
By the Decree of the USSR State Committee for Standards dated May 16, 1980 No. 2160, the introduction date was set
01.07.82
This International Standard specifies a test method for twisting at temperature of round metal and alloy wires with a diameter of 0.20 to 10 mm and shaped wires with cross-sectional areas corresponding to these diameters.
1. SAMPLING METHOD
1.1. The method of sampling for testing pa twisting is specified in the regulatory and technical documentation for the wire.
1.2. The length of the part to be tested, i.e. the distance between the grippers of the machine must correspond to that given in the table. one.
Table 1
It is allowed to use wire with a different sample length in accordance with the normative and technical documentation for the wire.
When testing for twisting shaped wire, the length of the sample should be equal to the length of the samples of round wire, equal in cross-sectional area.
It is allowed to test wire with a diameter of less than 0.20 mm according to the test conditions for a diameter of 0.20 mm.
(Changed edition, Rev. No. 1)
2. EQUIPMENT
2.1. Machines that meet the following requirements are used as test equipment.
2.1.1. The gripping jaws must have a hardness of at least 62 HRC e (61 HRC). On the jaws of the grips, a notch is allowed that does not cause destruction of the sample in the grips of the machine.
2.1.2. Machine grips must be aligned.
The misalignment should not exceed 1 mm with a distance between grips of 100 mm.
2.1.1.-2.1.2. (Changed edition, Rev. No. 1)
2.1.3. One of the grippers of the machine must rotate around the axis without moving along the center line, the other must have only longitudinal movement.
2.1.4. The gripper, which has longitudinal movement along the axis, must have a device for tensioning the test sample,
2.1.5. The machine must have a reading device for the number of revolutions of the active grip and a scale that allows you to set the desired distance between the grips.
2.1.6. The machine shall be capable of changing the direction of torsion six times when testing the specimen for torsion at a given rotational speed. The number of twists of the initial direction must be at least three.
3. PREPARATION FOR THE TEST
3.1. Before testing, it is allowed to edit the samples, which should not affect the surface condition and the shape of the wire section.
3.2. The sample must be fixed in the machine in such a way that its longitudinal axis coincides with the axis of the grips and that the sample does not rotate during the test.
4. CONDUCTING THE TEST
4.1. A pretension should be applied to the wire sample, the value of which should not exceed 2% of the breaking force.
4.2. During the test, the frequency of rotation of the gripper must comply with the requirements of Table. 2.
table 2
4.3. One twist is taken as one complete revolution of the machine's active grip.
4.4. If the destruction of the sample occurred in the grips of the machine or near the grips (at a distance of less than 2 d) and the specimen fails to withstand the required number of twists, the test shall be repeated on another specimen.
4.5. In accordance with the requirements of the normative and technical documentation for the wire, the following types of tests and control can be carried out:
twisting with a change in the direction of twisting;
twisting two adjacent folded samples (double twist);
twisting to determine the nature of the fracture and the state of the samples after the twisting test.
(Changed edition, Rev. No. 2)
4.6. It is allowed to test the wire in accordance with the requirements of Table. 3 until 07/01/98.
Table 3
For other lengths of the test piece, the rotational speed changes in direct proportion to the change in the length of the test piece.
(Changed edition, Rev. No. 1, 3).
5. PROCESSING THE RESULTS
5.1. The test result is taken as the number of twists that the sample can withstand before failure or without failure up to a specified number of twists.
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of Ferrous Metallurgy of the USSR
2 APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Standards No. 2160 of May 16, 1980
Change No. 3 was adopted by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 6 dated 10/21/94)
|
State name |
Name of the national standardization body |
|
The Republic of Azerbaijan |
Azgosstandart |
|
Republic of Armenia |
Armstate standard |
|
Republic of Belarus |
State Standard of Belarus |
|
Gruzstandard |
|
|
The Republic of Kazakhstan |
State Standard of the Republic of Kazakhstan |
|
Kyrgyz Republic |
Kyrgyzstandart |
|
The Republic of Moldova |
moldovostandart |
|
the Russian Federation |
Gosstandart of Russia |
|
The Republic of Uzbekistan |
Uzgosstandart |
|
State Standard of Ukraine |
4. The limitation of the validity period was removed according to protocol No. 7-95 of the Interstate Council for Standardization, Metrology and Certification (IUS 11-95)
5. EDITION with Amendments No. 1, 2, 3, approved in January 1987, November 1990, June 1996 (IUS 5-87, 2-91, 9-96)
By the Decree of the USSR State Committee for Standards dated May 16, 1980 No. 2160, the introduction date was set
01.07.82
This International Standard specifies a test method for twisting at temperature of round metal and alloy wires with a diameter of 0.20 to 10 mm and shaped wires with cross-sectional areas corresponding to these diameters.
1. SAMPLING METHOD
1.1. The method of sampling for testing pa twisting is specified in the regulatory and technical documentation for the wire.
1.2. The length of the part to be tested, i.e. the distance between the grippers of the machine must correspond to that given in the table. one.
Table 1
It is allowed to use wire with a different sample length in accordance with the normative and technical documentation for the wire.
When testing for twisting shaped wire, the length of the sample should be equal to the length of the samples of round wire, equal in cross-sectional area.
It is allowed to test wire with a diameter of less than 0.20 mm according to the test conditions for a diameter of 0.20 mm.
(Changed edition, Rev. No. 1)
2. EQUIPMENT
2.1. Machines that meet the following requirements are used as test equipment.
2.1.1. The gripping jaws must have a hardness of at least 62 HRC e (61 HRC). On the jaws of the grips, a notch is allowed that does not cause destruction of the sample in the grips of the machine.
2.1.2. Machine grips must be aligned.
The misalignment should not exceed 1 mm with a distance between grips of 100 mm.
2.1.1, 2.1.2. (Changed edition, Rev. No. 1)
2.1.3. One of the grippers of the machine must rotate around the axis without moving along the center line, the other must have only longitudinal movement.
2.1.4. The gripper, which has longitudinal movement along the axis, must have a device for tensioning the test sample,
2.1.5. The machine must have a reading device for the number of revolutions of the active grip and a scale that allows you to set the desired distance between the grips.
2.1.6. The machine shall be capable of changing the direction of torsion six times when testing the specimen for torsion at a given rotational speed. The number of twists of the initial direction must be at least three.
3. PREPARATION FOR THE TEST
3.1. Before testing, it is allowed to edit the samples, which should not affect the surface condition and the shape of the wire section.
3.2. The sample must be fixed in the machine in such a way that its longitudinal axis coincides with the axis of the grips and that the sample does not rotate during the test.
4. CONDUCTING THE TEST
4.1. A pretension should be applied to the wire sample, the value of which should not exceed 2% of the breaking force.
4.2. During the test, the frequency of rotation of the gripper must comply with the requirements of Table. 2.
table 2
4.3. One twist is taken as one complete revolution of the machine's active grip.
4.4. If the destruction of the sample occurred in the grips of the machine or near the grips (at a distance of less than 2 d) and the specimen fails to withstand the required number of twists, the test shall be repeated on another specimen.
4.5. In accordance with the requirements of the normative and technical documentation for the wire, the following types of tests and control can be carried out:
twisting with a change in the direction of twisting;
twisting two adjacent folded samples (double twist);
twisting to determine the nature of the fracture and the state of the samples after the twisting test.
(Changed edition, Rev. No. 2)
4.6. It is allowed to test the wire in accordance with the requirements of Table. 3 until 07/01/98.
Table 3
For other lengths of the test piece, the rotational speed changes in direct proportion to the change in the length of the test piece.
(Changed edition, Rev. No. 1, 3).
5. PROCESSING THE RESULTS
5.1. The test result is taken as the number of twists that the sample can withstand before failure or without failure up to a specified number of twists.
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of Ferrous Metallurgy of the USSR
2 APPROVED AND INTRODUCED BY Decree of the USSR State Committee for Standards No. 2160 of May 16, 1980
Change No. 3 was adopted by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 6 dated 10/21/94)
|
State name |
Name of the national standardization body |
|
The Republic of Azerbaijan |
Azgosstandart |
|
Republic of Armenia |
Armstate standard |
|
Republic of Belarus |
State Standard of Belarus |
|
Georgia |
Gruzstandard |
|
The Republic of Kazakhstan |
State Standard of the Republic of Kazakhstan |
|
Kyrgyz Republic |
Kyrgyzstandart |
|
The Republic of Moldova |
moldovostandart |
|
the Russian Federation |
Gosstandart of Russia |
|
The Republic of Uzbekistan |
Uzgosstandart |
|
Ukraine |
State Standard of Ukraine |
3. REPLACE GOST 1545-63
4. The limitation of the validity period was removed according to protocol No. 7-95 of the Interstate Council for Standardization, Metrology and Certification (IUS 11-95)
5. EDITION with Amendments No. 1, 2, 3, approved in January 1987, November 1990, June 1996 (IUS 5-87, 2-91, 9-96)
The torsion test is used to evaluate the metal of shafts or wires, and to determine the mechanical strength and ductility characteristics of high strength metals.
The essence of the method: one end of the sample is fixed motionless, and a couple of forces are applied to the other end in a plane perpendicular to the axis of the sample, which causes a torque M = F/d, where F- acting force, MPa (kgf/mm), d- sample diameter, mm.
During torsion, all cross sections of the sample are shifted (rotated) around a common axis with respect to the fixed section. This shift increases with increasing distance from the fixing point, and the lines parallel to the sample axis become helical.
Based on the results of testing specimens for torsion, the following characteristics are determined:
Shear modulus G , MPa (kgf / mm 2);
Torsional yield strength t 0.3, MPa (kgf / mm 2);
Conditional torsion strength t pc, MPa (kgf / mm 2);
True torsional strength t to, MPa (kgf / mm 2);
Maximum residual torsional shear gmax, glad;
The nature of the destruction during torsion: shear or tear.
Shear modulus - the ratio of shear stress to the conditional deformation caused by it.
Torsional yield strength - shear stress at which the sample receives a residual shear equal to 0.3%.
The conditional torsion strength is a tangential stress equal to the ratio of the largest torsional moment preceding destruction to the polar moment of resistance of the sample section.
The true torsional strength is the greatest true shear stress at sample failure.
The maximum residual torsional shear is the maximum angular deformation at a point on the sample surface at the moment of failure.
The nature of the fracture during torsion: shear - fracture from shear stresses, separation - fracture from tensile stresses.
For torsion testing, a testing machine can be used that provides:
Free torsion of samples;
Smoothness of static loading;
Free movement of one of the grips along the sample axis;
Load measurement with a force meter;
Torsion angle measurement.
Requirements for testing equipment, samples, preparation and testing of metals at room temperature are given in GOST 3565-80.
For torsion tests, cylindrical specimens with a working part diameter of 10 mm and a working part length of 50 and 100 mm with heads at the ends are used for fixing in the grips of the testing machine. It is allowed to test samples and products proportional to the standard ones, as well as tubular samples. The shape and dimensions of the sample heads depend on the method of fastening the samples in the grips of the testing machine.
For testing the torsion of metals at low and high temperatures, special devices are used that allow heating or cooling the samples. When heating the samples, it is necessary to hold at the test temperature, which ensures the stability of the structure.
24.12. Hardness measurement
The determination of hardness is one of the most commonly used methods of mechanical testing of metals, since they are relatively simple and labor-intensive. Most methods are based on the indentation of an indenter into the metal under test, and the resulting plastic or elastic deformation is considered as a measure of the hardness of the metal. Methods for determining hardness widely used in practice differ in the type of loading (static and dynamic) and the shape of the indenter pressed into the metal.
Hardness measurement under static loading
These methods differ in the shape of the indenter (ball, pyramid), its material (high-strength steels, hard alloys, diamond) and the magnitude of the applied load.
With a large print size (hardness determination according to Brinell, Rockwell, Vickers), averaged hardness values for metal macrovolumes are obtained. At small imprint sizes commensurate with the structural components (microhardness measurement method), the hardness of individual structural components is revealed.
