RU2066859C1 - Process of determination of mechanical properties of material - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: tested sample is placed into device measuring Rockwell hardness number, ball indenter loaded in advance is indented into it. Then basic great load is applied. When it is removed readings of pointer of measurement instrument with unloaded indenter are recorded for usage while determining parameter characterizing mechanical properties of material. Readings of pointer of measurement instrument are also recorded when indenter is loaded. All operations are repeated with indentation of flat indenter of same material as ball one. Modulus E of elasticity which is found by formula

is used as parameter characterizing mechanical properties of material, where μ and m_i are Poison's ratios of material and indenter; E_i is modulus of normal elasticity of material of indenter; P is load; R is radius of ball indenter; W is elastic convergence of sample and indenter - W=((A-B)-(C-D)K, where A, B are readings of pointer of instrument under loaded and unloaded conditions of ball indenter; C and D are readings of pointer of instrument under loaded and unloaded state of flat indenter; K is scale factor of instrument. EFFECT: enhanced authenticity of determination of mechanical properties of material.

Description

 The invention relates to the study of materials by determining their mechanical properties and can be used to determine the modulus of normal elasticity of materials.

 A known method for determining the mechanical properties of materials, where as such are the characteristics of elasticity and dynamic hardness, consisting in the registration and analysis of ultrasonic vibrations of a sample excited by impact on it by any body [1] The disadvantages of this method include its complexity and need for implementation of special electronic equipment.

 The closest is the method of determining mechanical properties by measuring the Rockwell hardness, which consists in pressing a ball indenter into the test material, to which a load is first applied, and then the final heavy load is removed, this load is removed and the result is recorded [2] The disadvantage of this method is its low information content.

где W [(A-B)-(C-D)] K упругое сближение образца и индентора,
A и В показания стрелки в разгруженном и нагруженном состоянии соответственно с шаровым индентором,
С и D то же самое с плоским индентором,
K цена деления шкалы прибора,
μ,, μ_и коэффициенты Пуассона материалов образца и индентора,
E, E_и модули нормальной упругости материалов образца и индентора,
P нагрузка,
R радиус шарового индентора.The technical problem is to expand the capabilities of the method by additionally determining the modulus of normal elasticity. The problem is solved in that they additionally record the result under a larger load, and also repeat the same measurements with a flat indenter, and the modulus of normal elasticity is calculated using the converted well-known Hertz formula [3]
The method is carried out using a Rockwell hardness tester. A ball indenter is pressed into the test material, applying a preliminary load, combine the "Zero" scale with the end of the arrow, apply the main load. In contrast to the known method (determination of hardness), the readings of the device are recorded not only in the unloaded state, but also under load. In addition, the same procedure is done, changing the ball indenter to a flat one. The module is calculated by the formula obtained from the well-known Hertz formula (3):

where W [(AB) - (CD)] K is the elastic approximation of the sample and indenter,
A and B the readings of the arrow in the unloaded and loaded state, respectively, with a ball indenter,
C and D are the same with a flat indenter,
K the price of the division of the scale of the device,
μ ,, μ _and Poisson's ratios of the materials of the sample and indenter,
E, E _and normal elastic moduli of the materials of the sample and indenter,
P load
R is the radius of the ball indenter.

 The device is designed so that it shows the magnitude of the deformation that occurs when the main load is applied. However, this deformation includes elastic (reversible) and plastic (irreversible or residual). To determine the hardness, only the amount of plastic deformation is taken into account when the indenter is introduced into the test material and therefore the device reads after removing the main load. To determine the module by formula (1), it is necessary to know the elastic approach, i.e. from the reading of the device in the unloaded state (A) we subtract the reading in the loaded state (B), for which it is supposed to fix the latter. However, in addition to the desired approximation, the elastic deformation of the elements of the device itself contributes to the elastic strain obtained in this way. Therefore, it is proposed to determine the magnitude of this contribution to carry out the same procedure with a flat indenter and subtract the found value (C D) from the total value (A B).

Example. Sample steel plate with a hardness of LDC 45 units. brought into contact with a ball indenter with a 2.5 mm steel hardened ball, applied a preliminary load of 10 kg, combined the needle with the “zero” of the scale, then loaded with a load of P 40 kg, took readings B 66, unloaded and again readings A 95 then a flat indenter was installed and the same readings were taken in the loaded state D 79 and in the unloaded state C 99. μ Poisson's ratio of steel 0.3, E _and 20,000 kg / mm ² , the radius of the ball indenter 1.25 mm. The calculation showed (formula 1) that the desired elastic modulus E 20500 kg / mm ² , which is consistent with the tabular data [4] ie with the help of the Rockwell device it became possible to determine, besides hardness, the modulus of normal elasticity.

Literature
1. Baranov V.M. Ultrasonic measurements in atomic engineering. M. Atomizdat, 1975, p. 263.

 2. Testing of metals. M. Metallurgy, 1967, p. 45.

 3. Drozd M. S. Matlin M. M. Sidyakin Yu.N. Engineering calculations of elastoplastic contact deformation. M. Engineering, 1986, p. 220.

 4. Physical properties of steels and alloys used in energy. Directory. M.-L. Energy, 1967, p. 240.

Claims (1)

A method for determining the mechanical properties of a material by which a sample of the test material is placed in a Rockwell hardness measuring device, a ball indenter is applied to the sample to which a preliminary load is applied, then the main heavy load is removed, this load is removed, and the arrow reading of the device’s measuring device is recorded with the indenter unloaded and use these indications to determine the parameter characterizing the mechanical properties of the material, characterized in that I additionally fix the readings of the arrow of the measuring device with a loaded indenter, then the same operations are repeated when a flat indenter is pressed from the same material as the ball one, and the elastic modulus E, which is determined by the formula, is selected as a parameter characterizing the mechanical properties of the material

where μ and μ _{4 are} the Poisson ratios of the material and indenter;
E _{4 the} modulus of normal elasticity of the material of the indenter;
P load;
R is the radius of the ball indenter;
W elastic approximation of the sample and indenter;
W [(AB) (CD)] K,
where A, B are the readings of the arrow in the loaded and unloaded state of the ball indenter;
C, D readings of the arrow of the device in the loaded and unloaded state of a flat indenter;
K the price of the division of the scale of the device.