GOST R 52891-2007

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  ГОСТ Р 52891-2007

GOST R 52891−2007 Control of technological residual stresses by laser interferometry. General requirements

GOST R 52891−2007
Group Т59

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

CONTROL OF TECHNOLOGICAL RESIDUAL STRESSES BY LASER INTERFEROMETRY

General requirements

Control of technological residual stresses by laser interferometrical method. General requirements

OKS 77.040.10

Date of introduction 2010−01−01

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 Institute for problems in mechanics, Russian Academy of Sciences (IPM RAS)

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 December 27, 2007 No. 585-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

Residual technological stresses can be one of the causes of structural failure [1], which makes the actual methods and instrumental means of objective control.
The main difficulty of determination of residual stresses is that these stresses are balanced by material design. One way of breach of this balance and manifestations of residual stresses through the move is the creation of a non-through probe holes or annular grooves in [2], which make only a minor defect, usually commensurate with acceptable technological defects in the structure.
The size and depth of the probe holes that are acceptable for the products proposed for further exploitation, are determined by the user of this standard is engaged in such operation.
The most effective way to check movements in the vicinity of the probe holes is the method of laser interferometry. The basis of this method lies in the interferometric measurement of small displacements that occur in the neighborhood of the non-through holes drilled in the studied area of the object material with residual stress [3].

This standard will serve as a methodological basis of the method of laser interferometry in combination with drilling of the probe holes to determine the residual stresses in the solution of a wide class of engineering problems requiring rapid assessment of the stress state of the material in part responsible of technical objects.

1 Scope

This standard specifies the basic requirements for a procedure for the determination of residual technological stresses in the material technical features by probing the holes with use of laser interferometry both in laboratory and in field conditions when testing and control technologies of manufacturing products and structures for the assessment of a residual resource in the process of operation.

This standard applies to the laser-interferometric method of determining the principal stresses and their orientation in the surface layer of the material of construction, the depth of which is determined by the depth of the probe holes.

This standard describes two methods of measurement:

— full analysis with the stepwise drilling to determine the field of residual stresses in depth;

evaluation of rapid analysis, allowing a simplified procedure for the preparation of the surface of the test object, measurements and stress analysis.

This standard establishes the procedure for determining the stresses averaged over the drilling depth or the depth of the steps when step drilling.

This standard covers the determination of residual stresses resulting from welding, heat treatment, plastic deformation, fatigue damage accumulation, etc., and also stresses created by the external loads.

2 Normative references

This standard uses the regulatory references to the following standards:

GOST 12.1.004−91 System safety standards. Fire safety. General requirements

12.1.040 GOST-83 System of standards of occupational safety. Laser safety. General provisions

GOST 12.2.003−91 System safety standards. Equipment production. General safety requirements

GOST 12.3.002−75 System safety standards. The process of production. General safety requirements

GOST 2601−84 welding of metals. Terms and definitions of basic concepts

GOST 2789−73 surface Roughness. Parameters and characteristics

GOST 13344−79 emery Cloth abrasive cloth is water resistant. Specifications

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 Symbols and abbreviations

3.1 this standard applies the following designations:

 — the elasticity module (Yung), HPa;

 — the level of residual stress, MPa;

,  — the principal stresses, averaged over the probing depth of the hole, MPa;

 — absolute accuracy of measuring stress, MPa;

 — yield strength, MPa;

, the diameter and depth of the probe hole, mm;

, ,  — rectangular coordinate system;

, are angles of rotation of the main stress directions about the coordinate axes;

 — wavelength of laser radiation microns;

 — move edge of hole, mm;

the number of interference fringes;

 — arithmetic mean deviation of the profile, in microns.

3.2 this standard applies the following abbreviations:

NA — stress state;

OK — the object of control;

SI — measuring instruments.

4 Requirements to safety of works

4.1 the performance of the control allow persons trained in the method used and the equipment for the control of residual technological stresses.

4.2 When carrying out works on the determination of mechanical stress of the laser-interferometric method, the operator must be guided by the 12.1.040 GOST, GOST 12.2.003, GOST 12.3.002 and rules of technical safety for operation of electrical installations, approved by Gosenergonadzor.

4.3 Work is carried out in accordance with the safety requirements set out in the instruction manual of equipment, part of the used measuring instruments.

4.4 the methodology of interferometric measurements for a control a specific element of a technical system specify the requirements with which compliance is mandatory when working with control objects in the enterprise.

4.5 In the organization of works on control comply with fire safety requirements churchyard 12.1.004.

5 the requirements of the building control

5.1 Location of monitoring area and surface condition in the area should provide conditions for setting the optical unit of the interferometer and the ability to create probe holes.

5.2 Thickness OK in the drilling areas to avoid the growth of measurement error in excess in 9.3 shall not be less than the three maximum depths of probe holes.

5.3 Should be known the material is OK and its module of elasticity .

5.4 Surface OK in the area of measurement prepared in accordance with 7.3.

6 Requirements for measuring instruments

6.1 Composition of measuring instruments

SI include:

optical unit;

computer with the video input;

software;

— mechanical block.

6.2 the Appointment and the device of measuring

6.2.1 Optical unit is designed to monitor the micromovements of the investigated area of the surface is OK and is a remote module (interferometric sensor displacement field) located in the housing, adapted for fixing in different positions in different places OK, for example, plane, convex or concave cylindrical surface, about the speakers and the incoming angles etc.

The remote module contains a laser source, optical system and video camera.

6.2.2 the Computer input is suitable for receiving and processing, including real-time signal from a video camera of the remote module, using specialized software.

6.2.3 Software SI is designed to display the investigated area of the surface OK on the computer screen, and record images of the investigated area of the surface is OK before and after drilling the probe holes, creating an interferogram by processing the original images, determining the type of stress (tensile or compressive) in the observation of the interferogram in real time and calculate the magnitude and directions of principal residual stresses.

6.2.4 Mechanical unit intended for the education of the probing holes. As a mechanical unit can be used as special equipment and General purpose equipment.

Special-purpose equipment, for example, chemical etching, drilling core bits, abrasive machining, high speed drilling, etc., are used for the formation of holes in hard materials, including non-metallic, as well as for high-precision laboratory measurements, including speed of drilling.

For the Express analysis OK, made tractable structural materials, used metal cutting General purpose equipment, including hand drilling machine.

6.3 Requirements for methodological support of measuring instruments

6.3.1 Methodological support SI must contain the documents establishing:

— the purpose and scope SI;

— the composition and main characteristics of the hardware and software, including rules on measurement error;

— methods and means of achieving the compatibility of SI, including data, electrical, energy, software, development, and operational;

rules of aggregation of hardware and software and their interaction;

— a manual setting out the procedure for measuring voltages.

6.3.2 description of the functionality of SI in the operational, design and policy documents OK and C should reflect the specifications of the hardware and software.

6.4 Primary information for each zone of control must reside on external media, protected from unauthorized access.

7 preparation for measurement

7.1 Preparation for measurements includes the following main stages:

— analysis of technical documents and preparation of survey map;

— preparation of the object for measurement.

7.2 Analysis of technical documents and mapping surveys

7.2.1 based On the study of technical documentation analyze:

— materials of the object; the physical-mechanical characteristics, heat treatment;

— types of the national Assembly of the construction elements.

— operating conditions.

7.2.2 On the basis of the analysis carried out in accordance with 7.2.1, and subject to the requirements of 4.4 and 4.5 make a map of the characteristic areas of the control object, e.g. for welded joints — weld zone heat affected zone base metal (see GOST 2601).

7.2.3 Based on the types of HC and elastic characteristics of material in zones of control, select a location, number, diameter and depth of the probe holes in areas of measurement.

Note — to avoid increasing measurement error the centers of the probe holes should be located from each other at least by 4−5 their diameters. The maximum depth of the probe holes it is recommended that no more than 1/3 the thickness of the OK in the drilling areas to avoid distortion of the stress-strain state, and the growth of measurement error in excess of 9.3.

7.3 preparation of the object for measurement

7.3.1 Initial preparation consists of cleaning from dirt, rust, spatter from welding, washing and degreasing areas of measurements and locations for installing the device.

7.3.2 Secondary preparation includes the following steps:

— in control areas choose or prepare for each drill flat areas with characteristic dimensions of at least five probe diameters of holes;

— if necessary, smooth the areas by grinding or other machining; roughness of the prepared surface should be not more than 3.2 µm churchyard 2789.

Note — it Should be noted that the mechanical processing can alter the surface residual stress, and therefore it is unacceptable in the case of residual stresses in the surface layer thickness of 0.2−0.3 mm;

If the full analysis after machining it is recommended to remove the surface layer by etching to a depth of 0.2−0.3 mm.


— layout is carried out holes in the survey area (in typical cases it is recommended to prepare a template for placing the holes);

— when carrying out the Express analysis of the planned point to stake;

— after marking the study plot rubbed coarse calico or a cotton swab moistened with alcohol, acetone or gasoline purity Ч4.

Note — To enhance diffuse scattering surface in the scene, i.e. about the proposed holes can be further treated with sandpaper grit 4−8 H according to GOST 13344 or applied to it a thin coat of paint silverfish.

8 procedures for measuring

8.1 Conduct a single measurement

8.1.1 Optical unit installed in the survey area.

8.1.2 Start the program processing of the primary optical information.

8.1.3 Conduct the first exposure of the investigated area.

8.1.4 carry out the drilling of the probe holes at a selected depth.

8.1.5 carry out the second exposure.

8.2 the following measurements produce a repetition 8.1; when carrying out the step of drilling the probe holes for each stage, repeat steps 8.1.3 to 8.1.5.

Note — Between exposures is unacceptable:

— touch the housing of the optical unit;

— touch the area of measuring anything but drill and a special soft brush for chip removal.

The magnetic shavings are allowed to remove a magnetized object, without touching the surface.

9 Rules for processing results of measurements

9.1 Processing of results of measurements carried out using a specialized program for the creation and processing of electronic speckle interferograms.

Processed speckle interferogram is usually a symmetrical system bands, the number of which is proportional to the values of the principal stresses and has existed in this location prior to drilling the holes, and the orientation of the axes of symmetry of the fringe system coincides with the directions , the principal stresses relative to the selected coordinate system , , .

9.2 In the case of the measurement of normal movement the number of bands , regarded in any direction from the center of the hole, wave length , and moving the edges of the holes are related by the formula

. (1)

Move the edge of the hole associated with the level of residual stresses in the vicinity of probe holes, which is determined from the solution of the corresponding problem of elasticity theory inherent in the specialized program, or approximately (when ) for the purposes of proximate analysis according to the formula

, (2)

where and  — constant approximation: (30 MPa, 10 MPa·mm);

 — the reference diameter equal to 2 mm;

 — the modulus of elasticity of aluminum is 70 GPA.

9.3 Accuracy of measuring instruments

The error SI is determined by the accuracy of micromovements of the body surface in the vicinity of the probe holes.

When conducting Express-analysis number of lanes visually determined by the interferogram with an accuracy of ±0.5 bars. The resulting absolute error of definition of stress depends on the modulus of elasticity of the material of the object and the parameters of the hole and is defined by the approached formula

. (3)

Note — the Maximum error occurs when the minimum application of material, for example, at 1 mm, 4 mm measurement error is 10 MPa for aluminium and alloys on its base and 30 MPa for steels. With increasing depth and diameter of the probe holes measurement error by this method is reduced accordingly.

10 Rules for registration of measurement results

10.1 Probing the holes are numbered, their coordinates and sizes written in the card (Protocol) control (it is recommended to conduct in electronic form and in a special journal), plots of measurements photographed.

10.2 Description of each of the probe holes and the results of the measurements are fixed in the Protocol.

10.3 Additional information to be logged, the order of processing and storage protocols (or conclusion) set out in the technical documentation for the control.

10.4 If stress measurements are part of the research work, the results of measurements issued in accordance with the General requirements and rules of registration of reports on research work.

10.5 the results of the survey should be maintained until the next control OK.

Bibliography