GOST R 53568-2009

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  ГОСТ Р 53568-2009

GOST R 53568−2009 nondestructive testing. Determination of elasticity constants of the third order acoustic method. General requirements

GOST R 53568−2009
Group Т59

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

Nondestructive testing

DETERMINATION OF ELASTICITY CONSTANTS OF THE THIRD ORDER ACOUSTIC METHOD

General requirements

Non-destructive testing. The Evaluation of third order elasticity modulus by ultrasound method. General requirements

OKS 77.040.10

Date of introduction 2010−12−01

Preface

The objectives and principles of standardization in the Russian Federation established by the Federal law of 27 December 2002 N 184-FZ «On technical regulation», and rules for the application of national standards of the Russian Federation — GOST R 1.0−2004 «Standardization in the Russian Federation. The main provisions"
Data on standard

1 DEVELOPED by the Nizhny Novgorod branch of Institute of machines science named. A. A. Blagonravova of the Russian Academy of Sciences (NF IMASH), the independent nonprofit organization «Scientific-research center of control and diagnostics of technical systems» (ANO «nits KD»)

2 SUBMITTED by the Technical Committee for standardization TC 132 «Technical diagnostics"

3 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology dated 15 December 2009 N 861-St

4 INTRODUCED FOR THE FIRST TIME


Information about the changes to this standard is published in the annually issued reference index «National standards», and the text changes and amendments — in monthly indexes published information «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in a 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

Introduction

An objective assessment of the health and safety of operating the responsible technical objects in most practically important cases, is impossible without evaluation of the stress state, which is their material.

Among modern non-destructive methods of measurement of mechanical stresses and acoustic methods are among the most promising and increasingly used in the world.
In using acoustic methods for determining the stress state lies provocations effect — the linear dependence of the velocity of longitudinal and shear elastic waves from stresses in the material, a reliable experimental determination of which has become possible with the advent of modern ultrasonic and electronic measuring equipment.

The most important characteristics of the material, allowing to estimate its stress state, are it’s coefficients kostopoulou communication [1], determined by the constants of elasticity of the second and third orders. If the procedure of determining the constants of elasticity of the second order methodically worked for a long time, the determination of elasticity constants of the third order anything except [2], is not regulated. In this regard, it is urgent to develop a standard that meets modern requirements of the regulatory framework for developing NDT methods.

In addition to determining the stress state of solids on the basis of the phenomenon of customproperty, knowledge of the constants of nonlinear elasticity is important in determining the stress-strain state of plates and shells, in the study of the effects of interaction of fields and elastic strain fields of different nature (electrical, magnetic, etc.).

This standard is the methodical basis for the determination of elasticity constants of the third order in the application of acoustic methods for monitoring mechanical stress according to GOST R 52731, and can also be used for other practical applications of the nonlinear theory of elasticity, in particular, the analytical and numerical calculations of stress-strain state of materials and structures using nonlinear elastic material models.

1 Scope

This standard applies to laboratory acoustic method for determination of elasticity constants of the third order of solids and establishes the General requirements procedure for the determination of elasticity constants of the third order averaged over the thickness of the material and the volume of the ultrasonic beam, using bulk ultrasonic waves propagating in the direction perpendicular to the plane of the sample surface materials.

Knowledge of the elastic constants of the third order will allow for more accurate strength calculations of plates and shells considering nonlinear elastic properties of materials.

The physical basis of the method is provocateuse effect — the dependence of speed of longitudinal and shear elastic waves on the magnitude of uniaxial stresses in the material.

2 Normative references

This standard uses the regulatory references to the following standards:

GOST R 52731−2007 nondestructive testing. Acoustic method of control of mechanical stresses. General requirements

GOST 12.1.001−89 System safety standards. Ultrasound. General safety requirements

GOST 12.1.019−79 System of standards of occupational safety. Electrical safety. General requirements and nomenclature of types of protection

GOST 12.1.038−82 standards System of labor safety. Electrical safety. The maximum permissible values of the touch voltage and currents

GOST 12.2.013.0−91 (IEC 745−1-82) System of occupational safety standards. Machines manual electric. General safety requirements and test methods

GOST 1497−84 Metals. Test methods tensile

GOST 2768−84 Acetone. Specifications

GOST 2789−73 surface Roughness. Parameters and characteristics

GOST 6507−90 Micrometers. Specifications

GOST 10587−84 epoxy-Dianova uncured. Specifications

GOST 17299−78 ethyl Alcohol technical. Specifications

GOST 26266−90 nondestructive testing. The ultrasonic transducers. General technical requirements

GOST 28840−90 Machine for testing materials in tension, compression and bending. General technical requirements

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 published annually by the information sign «National standards» published as on January 1 of the current year and related information published monthly indexes published in the current year. If the reference standard is replaced (changed), when using this standard should be guided by replacing (amended) standard. If the reference standard is cancelled without replacement, then the situation in which the given link applies to the extent that does not affect this link.

3 Refer

3.1 this standard applies the following designations:

 — young’s modulus of the material of the test sample, MPa;

is the Poisson’s ratio of the material test sample;

 — bulk modulus of elasticity, MPa;

,  — Lamey coefficients of the second order, MPa;

elastic uniaxial stress in a test sample, MPa;

 — yield strength of material test specimen, MPa;

 — number of stages of elastic loading of the test sample;

 — the degree of elastic loading of the test sample 1, …, ;

 — load stage load ;

 — uniaxial tension test sample on the stage of loading, MPa;

 — the thickness of the test piece in the unloaded condition, mm;

the cross — sectional area of test specimen, mm, where the width of the working part of the specimen, mm;

 — delays of pulses of elastic waves on the stage of loading, ISS:

— 1 corresponds to elastic shear wave with the polarization vector parallel to the axis of the sample,

— 2 corresponds to elastic shear wave with the polarization vector perpendicular to the axis of the specimen,

— 3 represents a longitudinal elastic wave;

 — speed of propagation of elastic waves corresponding to the delays of pulses of elastic waves in the material , m/s;

 — coefficients kostopoulou communication, 1/MPa 1, 2, 3:

—  — relative change of the pulse delay of the shear wave, polarized along the direction of the uniaxial stress, if it is changed to 1 MPa;

—  — relative change of the pulse delay of the shear wave polarized transversely to the direction of the uniaxial stress, if it is changed to 1 MPa;

—  — relative change of the delay pulse longitudinal waves when the voltage of 1 MPa;

, ,  — elastic constants of the third order of Murnaghan, MPa.

4 General provisions

4.1 Determination of elasticity constants of the third order performed in accordance with the General requirements in [1].

4.2 Measurement and processing of results is performed in the laboratory.

4.3 Measurements carried out on test samples of material of the test object. Sample requirements are given in section 7.

4.4 To determine the constants of elasticity of the third order use of shear waves polarized along and across the axis of the specimen, as well as longitudinal waves.

4.5 diagram of the testing of the material corresponds to the echo method of ultrasonic testing [1]. Method of excitation of elastic vibrations — pin. The form of the emitted signal is a pulse with high frequency (ultrasonic) filling the envelope smooth and effective duration (at the level of 0.6 of the maximum amplitude) 2−4 period of the fundamental frequency.

4.6 For radiation and reception of acoustic signals used transceiver (combined) piezoelectric transducers (hereinafter — the converters) of longitudinal and shear waves according to GOST 26266.

4.7 elastic Constants of the third order are the volume average of the ultrasonic beam, determined by the transverse dimensions of the transducer and thickness of the sample material.

5 safety Requirements

5.1 measurements allow operators with skills in the operation of equipment of ultrasonic nondestructive testing, able to use national and industry normative and technical documents on the acoustic control techniques, trained to work with the applied measurement devices and certified for knowledge of regulations of safety in the relevant industries.

5.2 the Operator should be guided by GOST 12.1.001 and rules of technical safety for operation of electrical consumers according to GOST 12.1.019 and GOST 12.1.038.

6 Requirements for measuring instruments

6.1 as a means of measurement apply collected from production equipment, or specialized facilities (hereinafter — the devices) are certified and verified in the prescribed manner.

6.2 Acoustic instruments, must contain a set of probes with a nominal frequency of 5 MHz, enabling radiation and reception of shear and longitudinal elastic waves.

6.3 the Limits of permissible relative error of measurement of propagation time of pulses of elastic waves must not exceed ±10.

6.4 as the biasing devices use machines for testing materials in tension, compression and bending according to GOST 28840.

6.5 the Limits of permissible error of measurement of the direct load during the (in percent of the measured load) must not exceed ±0,5%, which corresponds to the testing machines group 0-according to GOST 28840.

6.6 To measure the sample thickness at the installation location of the Converter uses a micrometer according to GOST 6507 with a scale division of 0.001 mm.

6.7 Auxiliary devices and materials

6.7.1 Grinding tool for surface preparation — according to GOST 12.2.013.0.

6.7.2 For degreasing the surface of the sample used alcohol according to GOST 17299 or acetone GOST 2768.

6.7.3 To ensure acoustic contact of the transducer with the surface of the sample used epoxy resin according to GOST 10587, or other contact liquid. The viscosity of the contact liquid at the temperature of measurement should correspond to the viscosity of the epoxy resin at a temperature of 25 °C: 12−25 PA·s.

7 Requirements for test specimens

7.1 as the test specimens using flat specimens made of the material of the test object in accordance with GOST 1497.

7.2 Number of test specimens must be at least 5.

7.3 the Thickness of the test specimens shall not be less than 5 mm.

7.4 Width of the working part of the test samples should be 2−3 times larger than the geometric dimensions of the active elements of the transducers.

7.5 both sides of the working surface of the test samples in the center of the working part, prepare a square area with sides equal to the width of the sample, and a surface roughness of not more than 1,25 according to GOST 2789.

8 Preparation for measurement

8.1 each of the test sample before it is installed into the grips of the testing machine to measure the thickness at the installation location of the Converter.

8.2 Install the test sample in grips of testing machine.

8.3 put a layer of contact liquid on the prepared surface of the test piece.

8.4 In the center of the specimen install a transducer of shear waves by orienting its polarization vector parallel to the axis of the sample.

8.5 Above the axis of the sample set the transducer of shear waves by orienting its polarization vector perpendicular to the axis.

8.6 axis of the following sample installs the Converter for longitudinal waves.

8.7 turn on the device, display monitoring device timebase of the received signals.

8.8 Check the quality of acoustic contact, the screen monitor of the device must be observed repeatedly reflected pulses of the three types of waves during a scanning duration of not less than 50 µs for the shear and not less than 30 µs for longitudinal waves.

9 Order of measurements

9.1 Measurements are performed in normal climatic conditions

9.2 Test sample load strength , then 4−6 stages reduces its value .

9.3 the first stage of loading (1) choose the first echo pulse and a following second echo pulse, which is used for measuring pulse delay double the thickness of the specimen.

9.4 For the first echo impulse choose the point in time corresponding reference point of the profile of the pulse.

Note — as a reference choose one of the points where the signal has a zero value.

9.5 For the second echo pulse to determine the time corresponding to the same reference point of the profile of the pulse.

9.6 the difference In time determine the pulse delay on a double thickness of the specimen (1, 2, 3, respectively, for shear waves polarized along and across the test piece, longitudinal wave).

Note — If the error of determination does not meet the requirements of 6.5, the measured time interval between the first and -m echo pulses ( — sequence number of the echo-pulse) in accordance with GOST R 52371. In the future, as delays using the obtained value.

9.7 Measurement in accordance with 9.2−9.6 repeat each of the steps of loading the test piece.

9.8 Measurement in accordance with 9.2−9.6 repeat for all test samples of the material of the test object.

10 Processing of measurement results

10.1 the results of the measurements at all test samples for each wave type calculated correlation coefficients between the relative changes in the latency and voltage according to the formula

. (1)

The results of the measurements shall be considered satisfactory if the correlation coefficients for all types of waves is not less than 0.95. Otherwise, the experiment should be repeated with increased levels of loading until, until the condition of 0.95 (1,2, 3).

10.2 Factors kostopoulou connection is calculated by the formula

. (2)

10.3 elastic Constants of the third order of Murnaghan is calculated by formulas [3, 4]

, (3)

, (4)

, (5)

where

, (6)

, (7)

. (8)

Note — Instead of elasticity constants of the third order of Murnaghan allowed to use constants , a , [5], , , [6], , , [7].


Formula the connection between the constants shown in table 1.


Table 1 — Formulas of the link between the different constants of elasticity of the third order

11 Making measurements

The results of the measurements are fixed in the Protocol, the form of which is given in Appendix A.

Annex a (recommended). Form of measurement Protocol

Appendix A
(recommended)

PROTOCOL
determination of elasticity constants of the third order

Table 1 — measurement Results for the test sample N

9 Averaged values of elasticity constants of the third order are shown in table 2


Table 2 — the values of the constants of elasticity of the third order

Note — , ,  — relative error of determination of elasticity constants of the third order , , .