BS EN 15305:2008

Foreword
Introduction
1 Scope
2 Normative references
3 Terms, definitions and symbols
   3.1 Terms and definitions
   3.2 Symbols and abbreviations
4 Principles
   4.1 General principles of the measurement
   4.2 Biaxial stress analysis
   4.3 Triaxial stress analysis
5 Specimen
   5.1 Material characteristics
        5.1.1 General
        5.1.2 Shape, dimensions and weight
        5.1.3 Specimen composition/homogeneity
        5.1.4 Grain size and diffracting domains
        5.1.5 Specimen X-ray transparency
        5.1.6 Coatings and thin layers
   5.2 Preparation of specimen
        5.2.1 Surface preparation
        5.2.2 Stress depth profiling
        5.2.3 Large specimen or complex geometry
6 Equipment
   6.1 General
   6.2 Choice of equipment
        6.2.1 General
        6.2.2 The omega-method
        6.2.3 The chi-method
        6.2.4 The modified chi-method
        6.2.5 Other geometries
   6.3 Choice of radiation
   6.4 Choice of the detector
   6.5 Performance of the equipment
        6.5.1 Alignment
        6.5.2 Performance of the goniometer
   6.6 Qualification and verification of the equipment
        6.6.1 General
        6.6.2 Qualification
        6.6.3 Verification of the performance of the
               qualified equipment
7 Experimental Method
   7.1 General
   7.2 Specimen positioning
   7.3 Diffraction conditions
   7.4 Data collection
8 Treatment of the data
   8.1 General
   8.2 Treatment of the diffraction data
        8.2.1 General
        8.2.2 Intensity corrections
        8.2.3 Determination of the diffraction line position
        8.2.4 Correction on the diffraction line position
   8.3 Stress calculation
        8.3.1 Calculation of strains and stresses
        8.3.2 Errors and uncertainties [16], [17]
   8.4 Critical assessment of the results
        8.4.1 General
        8.4.2 Visual inspection
        8.4.3 Quantitative inspection
9 Report
10 Experimental determination of XECs
   10.1 Introduction
   10.2 Loading device
   10.3 Specimen
   10.4 Loading device calibration and specimen accommodation
   10.5 Diffractometer measurements
   10.6 Calculation of XECs
11 Reference specimens
   11.1 Introduction
   11.2 Stress-free reference specimen
        11.2.1 General
        11.2.2 Preparation of the stress-free specimen
        11.2.3 Method of measurement
   11.3 Stress-reference specimen
        11.3.1 Laboratory qualified (LQ) stress-reference
               specimen
        11.3.2 Inter-laboratory qualified (ILQ) stress-reference
               specimen
12 Limiting cases
   12.1 Introduction
   12.2 Presence of a subsurface stress gradient
   12.3 Surface stress gradient
   12.4 Surface roughness
   12.5 Non-flat surfaces
   12.6 Effects of specimen microstructure
        12.6.1 Textured materials
        12.6.2 Multiphase materials
   12.7 Broad diffraction lines
Annex A (informative) - Schematic representation of the European
        XRPD Standardisation Project
Annex B (informative) - Sources of Residual Stress
   B.1 General
   B.2 Mechanical processes
   B.3 Thermal processes
   B.4 Chemical processes
Annex C (normative) - Determination of the stress state - General
        Procedure
   C.1 General
   C.2 Using the exact definition of the deformation
        C.2.1 General
        C.2.2 Determination of the stress tensor components
        C.2.3 Determination of theta and d[0]
   C.3 Using an approximation of the definition of the
        deformation
        C.3.1 General
        C.3.2 Determination of the stress tensor components
        C.3.3 Determination of theta[0] and d[0]
Annex D (informative) - Recent developments
   D.1 Stress measurement using two-dimensional diffraction
        data
   D.2 Depth resolved evaluation of near surface residual
        stress - The Scattering Vector Method
   D.3 Accuracy improvement through the use of equilibrium
        conditions for determination of stress profile
Annex E (informative) - Details of treatment of the measured
        data
   E.1 Intensity correction on the scan
        E.1.1 General
        E.1.2 Divergence slit conversion
        E.1.3 Absorption correction
        E.1.4 Background correction
        E.1.5 Lorentz-polarisation correction
        E.1.6 K-Alpha2 stripping
   E.2 Diffraction line position determination
        E.2.1 Centre of Gravity methods
        E.2.2 Parabola Fit
        E.2.3 Profile Function Fit
        E.2.4 Middle of width at x% height method
        E.2.5 Cross-correlation method
   E.3 Correction on the diffraction line position
        E.3.1 General
        E.3.2 Remaining misalignments
        E.3.3 Transparency correction
Annex F (informative) - General description of acquisition
        methods
   F.1 Introduction
   F.2 Definitions
   F.3 Description of the various acquisition methods
        F.3.1 General method
        F.3.2 Omega method
        F.3.3 Chi method
        F.3.4 Combined tilt method (also called scattering
               vector method)
        F.3.5 Modified chi method
        F.3.6 Low incidence method
        F.3.7 Modified omega method
        F.3.8 Use of a 2D (area) detector
   F.4 Choice of Phi and Psi angles
   F.5 The stereographic projection
Annex G (informative) - Normal Stress Measurement Procedure" and
        "Dedicated Stress Measurement Procedure
   G.1 Introduction
   G.2 General
        G.2.1 Introduction
        G.2.2 Normal stress measurement procedure for a
               single specimen
        G.2.3 Dedicated Stress Measurement Procedure for
               very similar specimens
Bibliography

Specifies the test method for the determination of macroscopic residual or applied stresses non destructively by X-ray diffraction analysis in the near-surface region of a polycrystalline specimen or component.

This European Standard describes the test method for the determination of macroscopic residual or applied stresses non-destructively by X-ray diffraction analysis in the near-surface region of a polycrystalline specimen or component.

All materials with a sufficient degree of crystallinity can be analysed, but limitations may arise in the following cases (brief indications are given in Clause 12):

• Stress gradients;

• Lattice constants gradient ;

• Surface roughness;

• Non-flat surfaces (see 5.1.2);

• Highly textured materials;

• Coarse grained material (see 5.1.4);

• Multiphase materials;

• Overlapping diffraction lines;

• Broad diffraction lines.

The specific procedures developed for the determination of residual stresses in the cases listed above are not included in this document.

The method described is based on the angular dispersive technique with reflection geometry as defined by EN 13925-1.

The recommendations in this document are meant for stress analysis where only the diffraction line shift is determined.

This European Standard does not cover methods for residual stress analyses based on synchrotron X-ray radiation and it does not exhaustively consider all possible areas of application.

Radiation Protection. Exposure of any part of the human body to X-rays can be injurious to health. It is therefore essential that whenever X-ray equipment is used, adequate precautions should be taken to protect the operator and any other person in the vicinity. Recommended practice for radiation protection as well as limits for the levels of X-radiation exposure are those established by national legislation in each country. If there are no official regulations or recommendations in a country, the latest recommendations of the International Commission on Radiological Protection should be applied.