GOST R 8.904-2015

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  ГОСТ Р 8.904-2015

GOST R 8.904−2015 (ISO 14577−2:2015) State system of ensuring unity of measurements (GSI). Hardness and other characteristics of materials at instrumental indentation test. Part 2. Verification and calibration of hardness testers

GOST R 8.904−2015
(ISO 14577−2:2015)

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

State system for ensuring the uniformity of measurements

HARDNESS AND OTHER CHARACTERISTICS OF MATERIALS AT INSTRUMENTAL INDENTATION TEST

Part 2

Verification and calibration of hardness testers

State system for ensuring the uniformity of measurements. Metallic materials. Instrumented indentation test for hardness and materials parameters. Part 2. Verification and calibration of testing machines

OKS 17.040.10*

_____________________

* According to the official website of Rosstandart OKS 17.020,

here and further. — Note the manufacturer’s database.

Date of introduction 2016−10−01

Preface

1 PREPARED by all-Russia research Institute of physicotechnical and radio engineering measurements of Federal Agency on technical regulation and Metrology on the basis of their own authentic translation into the Russian language the English language version of the international standard indicated in paragraph 4

2 SUBMITTED by the Technical Committee for standardization TC 206 «Standards and verification scheme», PC 206.2 «Standards and verification scheme in the field of measuring mechanical quantities"

3 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology of December 8, 2015 N 2114-St

4 this standard is modified in relation to the international standard ISO 14577−2:2015* «the metal Materials. Hardness and other material parameters, the method of instrumental indentation. Part 2. Verification and calibration of hardness testers» (ISO 14577−2:2015 «Metallic materials — Instrumented indentation test for hardness and materials parameters — Part 2: Verification and calibration of testing machines», MOD).

Additional words (phrase, indicators, their values) are included in the text of the standard to reflect the needs of the Russian economy and specifics of the Russian national standardization, which are underlined, solid horizontal line.

The name of this standard changed with respect to names specified international standard for compliance with GOST R 1.5−2012 (subsection 3.5)

5 INTRODUCED FOR THE FIRST TIME

Application rules of this standard are established in GOST R 1.0−2012 (section 8). Information about the changes to this standard is published in the annual (as of January 1 of the current year) reference index «National standards» and the official text changes and amendments — in monthly information index «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in the upcoming issue of the monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet (www.gost.ru)

Introduction

Under instrumental indentation refers to the process controlled by special test setting, in which there is a continuous introduction of a tip (diamond pyramid Berkovich, Vickers, carbide ball, etc.) in the test sample under the action of the smoothly increasing load, followed by its removal and registration according to movement of the tip load.

Hardness is usually defined as the resistance of a material to the penetration of another, harder material. The results obtained from the hardness test according to Rockwell, Vickers and Brinell hardness, determined after removing the test load. Therefore, the influence of elastic deformation of a material under the influence of the tip (indenter) is not taken into account.

This standard is prepared to allow the determination of hardness and other mechanical characteristics of the material by simultaneous measurements of load and displacement of the tip during indentation. Tracing a complete cycle of loading and removing test loads, one can determine the hardness values equivalent to the values measured by classical methods of hardness measurement. Also this method allows you to define additional material properties, such as its modulus of elasticity indentation hardness and elastic-plastic. These values can be calculated without optical measurement of the imprint.

The standard is designed to provide the possibility of obtaining material properties by conducting data analysis after the test.

1 Scope

This standard specifies the method of verification and calibration of hardness testers, is designed for measuring hardness scales Martens and scales of the indentation in accordance with GOST R 8.748.

It describes the method of item calibration and verification against reference measures of hardness. The requirement for the application of the method of testing measures hardness in addition to the item method of verification, as well as periodic control checks of hardness during operation.

This standard is also applicable to portable hardness testers.

2 Normative references

This standard uses the regulatory references to the following standards:

GOST R 8.748−2011 (ISO 14577−1:2002) State system for ensuring the uniformity of measurements. Metals and alloys. Hardness and other characteristics of materials at instrumental indentation test. Part 1. Test method

GOST R ISO 6507−1-2007 Metals and alloys. Measurement of hardness by Vickers. Part 1. Method of measurement

Note — When using this standard appropriate to test the effect of reference standards in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet or in the annual information index «National standards» published as on January 1 of the current year, and the editions of the monthly information index «National standards» for the current year. If replaced with a reference standard, which was given an undated reference, then it is recommended to use the current version of this standard, taking into account all enabled in this version modifications. If replaced with a reference standard, which is given a dated reference, it is recommended to use the version of this standard referred to above by year of approval (acceptance). If after approval of this standard in the reference standard, which is given a dated reference, a change affecting a provision to which reference, the provision is recommended to be applied without taking into account this change. If the reference standard is cancelled without replacement, the position in which reference is made to him, recommended to be used in part not affecting this link.

3 General conditions

3.1 Preparation

Hardness must be designed in such a way that it can be verified (calibrated). Before the verification (calibration) needed to verify compliance with the conditions set out in 3.2−3.4.

3.2 Hardness of

The hardness tester must be configured for operation in accordance with the requirements of this Manual and must be installed in environmental conditions that meet the requirements of this standard GOST R 8.748 and, where applicable, [1]. Hardness must be protected from vibrations. For tests in micro — and nanodiamond hardness must also be protected from air currents and temperature fluctuations.

The influence of environmental factors on the data can be evaluated by performing indentation at low load (e.g., equivalent to the normal load at initial contact) on the reference measure of toughness and analysis of movement of the tip over time. The variability of load is the stiffness of the contact (obtained from curve removing the load), multiplied by the average quadratic deviation (RMSE) of measurement of displacement, after subtracting any background drift in the average displacement. These uncertainties must then be included in the combined standard measurement uncertainty calculated in accordance with GOST R 8.748.

3.3 Tip

In order to obtain a good repeatability of the measurements, the probe must be rigidly mounted to the hardness tester.

The probe base should be designed in such a way that its contribution to the overall compliance were minimal (Appendix A). For correct measurements of hardness at depths of implementation is less than 6 microns it is necessary to determine the function of the surface area or cross sectional area of the tip (Appendix B).

3.4 Application of the test load

The application and removal of load should be done without shock or vibration that may significantly affect the measurement results. It must be possible to verify the device load application, exposure and removal of the test load.

3.5 Checking of hardness

Checking of hardness is conducted according to standard measures of hardness, for example, the test can be carried out in accordance with Annex C.

4 Elementwise calibration of hardness tester

4.1 General provisions

4.1.1 Elementwise calibration should be performed at constant temperature (23±5)°C. To determine the reliability of the calibration values as a function of temperature elementwise calibration should be carried out in suitable points of the range. If necessary, can be determined correction the calibration function or a set of calibration values, valid for certain values of the working temperature.

4.1.2 measuring instruments used for item calibration should be believed. The means of measurement used for item calibration must have traceability to national standards.

4.1.3 item-by-Item verification (calibration) includes:

a) confirmation of compliance with the applied and removed loads requirements 4.2 (definition of loads applied deflection from nominal);

b) confirmation of conformity of the readings of the device for measuring the displacement of the tip with the requirements of 4.3 (variance of the measured displacement from nominal);

C) proof of compliance with the compliance values of hardness requirements 4.4 (determination of compliance of hardness);

d) confirmation of compliance with the geometric parameters of the tip with the requirements of 4.5 (definition of geometrical parameters of the nozzle);

d) confirmation of compliance with the area function of the tip the requirements of 4.6, if the depth of the indentation is less than 6 microns;

e) determining the time intervals of the measurement cycle.

4.2 Confirmation of conformity of the applied and removed loads

4.2.1 the Load should be measured by the following methods, for example:

— through a device to measure the load of class 1 or higher by standard [2];

by balancing the load determined with an accuracy of ±0,2% attached with the help of attorneys (calibrated) of goods;

— by means of electronic scales with measurement accuracy of 0.1% of the maximum test load, or 10 microns to nanoscale.

4.2.2 Each used a range of loads must be verified (measured) in the whole range of loads as in the application, and when removing the test load. Should be checked (measured) at least 16 of the load values uniformly distributed in the range of application of the force, i.e., 16 values of the loads during the application of force, and 16 values of the loads during lifting force. This procedure should be repeated at least three times, then calculated the arithmetic average load value of three measurements for each point for loading and unloading.

When checking compliance apply and remove the load difference between the maximum and minimum values of the measured load must not exceed half the deviation limit specified in table 1.

For each series of three measurements of the load the difference between the average of the measured values of test load and the nominal load must be within the tolerance limits specified in table 1.

4.2.3 If the load is applied or film loading device of the hardness does not satisfy the requirements of table 1, the hardness is considered to be unserviceable.


Table 1 — Permissible deviations of the values of the test load

4.3 Confirmation of conformity of the device measure displacement of the probe hardness tester

4.3.1 the Required resolution of the system for measuring displacement of the tip depends on the value of the smallest measured depth of indentation. For microlepton it is 0.2 µm; for macrodiakonia 2 µm.

The scale of the instrument to measure displacement must be calibrated in such a way as to allow measuring the depth of indentation with a resolution shown in table 2.

4.3.2 Each measured range of motion should be checked with a suitable method and a corresponding measuring system. The device should be checked at least 16 points in each direction uniformly distributed in a check range of movement. This procedure should be repeated three times. For each point is calculated the arithmetic average of the three measured displacements.

For measuring the relative displacement of the tip recommended for the following measuring systems: laser interferometer, and inductive sensor, capacitive sensor and piezoelectric sensor.

For each series of three measurements, the difference between the average displacement and the nominal should be within the tolerances specified in table 2.


Table 2 — Solution and the tolerance limits of the device for measuring the displacement of the tip

4.3.3 temperature Changes are the most common source of drift. To minimize caused by the temperature drift, the temperature of the device needs to support so that the drift velocity remains constant during one measurement cycle. The drift velocity should be measured during, immediately before or after each measurement cycle, for example by tracking the movement of the tip over an appropriate exposure time. In the data verification (calibration) of displacement must be entered correction for temperature drift and changes in the rate of drift for the duration of one measurement cycle should be less than tolerances specified in table 2. The uncertainty of the results of the velocity measurements should be taken into account when calculating the uncertainty of measurement results of displacement tip.

4.3.4 If the deviations of the readings of the device for measuring the displacement of the tip do not satisfy the requirements of table 2, the hardness is considered to be unserviceable.

4.4 Determination of compliance of hardness

4.4.1 General provisions

Cm. Annex D of this standard and Annex C of the GOST R 8.748−2011.

Determination of compliance of hardness should be carried out after the test load and measurement system displacement was verified in accordance with 4.2 and 4.3.

4.4.2 Procedure

Definition give the hardness by measurement of indentation young’s modulus of at least at five different values of test load. Recommended method 3 described in Appendix D. Briefly, it consists in the following.

A standard measure of hardness needs to be fixed in the system for instrumental indentation in exactly the same way, what then will be to consolidate the samples. This is necessary in order to ensure faithful reproduction of the measure hardness values for total hardness compliance in each particular dimension. The yielding of hardness can influence the design and mounting of the tip, and the method of mounting the sample. For example, fastening of plastic (e.g., PVC) may provide additional flexibility in the measurement process. Determination of compliance of hardness should be performed using the tip which will be used in further measurements. For indentation depths of more than 6 microns is not necessary to take into account the real function of the square of the tip. To determine compliance of the hardness tester must be used, a standard measure of hardness, with the known value of elastic modulus during indentation, independent of the depth of indentation (for example, it is recommended that a material such as tungsten). Range test load is determined by the minimum test load, which corresponds to the depth of the indentation 6 µm, and the maximum test load hardness tester. The advantage of large depth of indentation is that the error of determining the area function of the tip will be less. However, you must ensure that the test results were not distorted due to SAG for material hardness. The measured value compliance with the indentation then can be compared with the calculated value of compliance with a sample with a known value of elastic modulus during indentation. To re — determine compliance of hardness was found the difference between the values of compliance apply to the movement of the tip in order to Refine the estimation of the depth of contact and, therefore, assessment of the compliance of hardness at each load. This procedure is repeated until then, until you have obtained a consistent value of compliance of hardness and depth of contact.

For indentation depths of less than 6 microns in the above-described method should be applied with the exception that for the calculation of the contact compliance using a reference hardness value of the elastic modulus during indentation should be used the actual contact area, calculated by a specific function of the square of the tip.

Many of the devices of nano — and microcapsule give the value of hardness does not depend on the load. However, if it is not, it is possible to determine the function of the compliance of hardness using the aforesaid procedure, but in a broader load range. The range of test loads is determined by the depth of indentation of more than 0.5 µm, maximum test load, the hardness or the maximum test load at which there was no unusual response of the material test sample (for example, influxes of metals or cracking of the ceramic or glass).

If the yielding of hardness is determined again, it should run the calibration of hardness reference measures of hardness.

The accuracy and repeatability of the hardness tester with the appropriate test loads shall not exceed the requirements specified in 5.2.5 (see tables 7 and 8). 5.1 shows the block diagram of actions taken when calibration of hardness reference measures of hardness. If after the application of the current actual value correction for the yielding of hardness and the area function of the tip the measured hardness does not satisfy the requirements of table 8, and as a result repeat the procedure using the newly tested (calibrated) tip and the actual value correction for the yielding of hardness corresponding to that tip to the nominal value of the action fails, it should be carried out maintenance of the hardness tester and automated verification. Current adjustment procedures compliance of hardness are given in [3].

For calibration procedures, described in Appendix D, you must use a standard measure of hardness (see [1]), which should be made of isotropic and homogeneous material. It is assumed that the elastic modulus during indentation and Poisson’s ratio do not depend on the depth of indentation.

4.5 Verification of compliance of the geometric parameters of the tip

4.5.1 General provisions

The geometrical parameters of the tips used in the measurements needs to be checked. Compliance with tip requirements of this part of the standard shall be certified by the certificate. The certificate must contain information about the function surface area and the cross sectional area of the tip. The latter should be provided using the methods described in Appendix B, and standard measures of hardness. The values of all geometrical parameters must be measured and reflected in the certificate.

If the angle of the tip is different from the nominal value of the perfect geometry of the tip, when the depth h more than 6 µm in all applicable calculations used shall be the average of the angles of the tip, measured during validation.

For bits used in nano — and microcapsule (depth of indentation of at least 6 µm) should be determined by a function of the square of the tip for the corresponding ranges of depths of indentation. The geometric parameters of lugs should be checked periodically (see section 7).

In the case of non-diamond bits have to be received value of the modulus of elasticity and Poisson’s ratio of the material of the tip and used in the relevant calculations instead of the values of the diamond.

Note — the Error in the determination of the apex angle of the Vickers tip, equal to 0.2°, leads to a systematic error in the determination of the area of 1%.

For pyramidal and conical tips, the angle should be measured in the range of indentation depths shown in table 3 and figure 1.

Table 3 — Values of the measuring range of the angle pyramidal and conical tips

Figure 1 — Illustration of the measuring ranges specified in table 3

Figure 1 — Illustration of the measuring ranges specified in table 3

4.5.2 The Tip Of The Vickers

4.5.2.1 the Four sides of the diamond right pyramid with a square base needs to be polished and not to have surface defects and impurities. Cm. notes for cleaning the surface of the tip Appendix D GOST R 8.748−2011.

The surface roughness of the tip affects the measurement uncertainty, similar to the effect of roughness of the test sample. When testing at the nanoscale should be considered the final surface treatment of the tip.

4.5.2.2 the Angle between opposite faces at the vertex of the diamond pyramid shall be 136°±0,3° (see figure 2).

The angle should be measured in the range between hand h(see table 3 and figure 1). Geometry and final processing of the probe should be monitored throughout the calibrated range of the indentation depths, i.e. from the top of the handpiece hto the maximum calibrated depth of indentation h.

4.5.2.3 the angle between the axis of the diamond pyramid and the axis of the probe (perpendicular to the landing surface) should not exceed 0.5°.

4.5.2.4 Four facets must meet at a point. The maximum allowable line length of the jumper between the opposite faces shown in the table 4 (see also figure 3).

4.5.2.5 the radius of the top of the tip should not exceed 0.5 µm to microcapsule (see figure 4).

4.5.2.6 Inspection of geometrical parameters of the probe should be conducted with a microscope or other suitable devices.

If the tip is used for testing in the micro — or the nanoscale, should be checked by an atomic force microscope with feedback. Such measurements strongly recommended to nanoscale.

Table 4 — Maximum allowable length of the line jumpers

Figure 2 — the angle of the diamond pyramid Vickers

Figure 2 — the angle of the diamond pyramid Vickers

Figure 3 — Line jumper at the top of the tip (schematically)

a — line jumper

Figure 3 — Line jumper at the top of the tip (schematically)

Figure 4 is the radius of the top of the tip

Figure 4 is the radius of the top of the tip

4.5.3 Tips Berkovich, modified Berkovich tips and tips «vertex cube»

4.5.3.1 usually there are two types of pyramidal diamond Berkovich tips. The tip of Berkovich (see [5]) are designed in such a way that at any given depth of indentation of its surface area was the same as that of the tip of Vickers. The modified tip of Berkovich (see [11]) are designed in such a way that at any given depth of indentation in its cross-sectional area was the same as that of the tip of Vickers.

4.5.3.2 the Four sides of the diamond right pyramid with a square base needs to be polished and not to have surface defects and impurities. Cm. notes for cleaning the surface of the tip Appendix D GOST R 8.748−2011.

The surface roughness of the tip influences the uncertainty of measurement results, similar to the effect of roughness of the test sample. When testing at the nanoscale, consider the finish surface of the tip.

4.5.3.3 the radius of the top of the tip should not exceed 0.5 µm to 0.2 µm and microlepton to nanoscale (see figure 4).

4.5.3.4 the angle between the axis of the diamond pyramid and three faces indicated . The angle between the edges of the triangular base diamond pyramid shall be 60°±0,3° (see figure 5).

Figure 5 — Angle handpieces Berkovich tip «vertex cube»

=65,03°±0,30° for Berkovich tip;

=65,27°±0,30° for a modified Berkovich tip;

=35,26°±0,30° tip «vertex cube».

Figure 5 — Angle handpieces Berkovich tip «vertex cube"

4.5.3.5 Verification of geometrical parameters of the probe should be conducted with a microscope or other suitable devices.

If the tip is used for testing in the micro — or the nanoscale, measurements should be made by means of an atomic force microscope with feedback. Such measurements strongly recommended to nanoscale.

4.5.4 Ball tip hard alloy

4.5.4.1 Balls of hard alloy should have the following characteristics:

— hardness: HV 10 is not less than 1500 in the determination in accordance with GOST R ISO 6507−1;