ASTM E1426-98(2003)

Standard Test Method for Determining the Effective Elastic Parameter for X-Ray Diffraction Measurements of Residual Stress

SIGNIFICANCE AND USE
This test method provides standard procedures for experimentally determining the effective elastic parameter for X-ray diffraction measurement of residual and applied stresses. It also provides a standard means of reporting the precision of the parameter.
This test method is applicable to any crystalline material which exhibits a linear relationship between stress and strain in the elastic range.
This test method should be used whenever residual stresses are to be evaluated by an X-ray diffraction technique and the effective elastic parameter of the material is unknown.
SCOPE
1.1 This test method covers a procedure for experimentally determining the effective elastic parameter, Eeff, for the evaluation of residual and applied stresses by X-ray diffraction techniques. The effective elastic parameter relates macroscopic stress to the strain measured in a particular crystallographic direction in polycrystalline samples.  Eeff should not be confused with E, the modulus of elasticity. Rather, it is nominally equivalent to E/(1 + ν) for the particular crystallographic direction, where ν is Poisson's ratio. The effective elastic parameter is influenced by elastic anisotropy and preferred orientation of the sample material.
1.2 This test method is applicable to all X-ray diffraction instruments intended for measurements of macroscopic residual stress that use measurements of the positions of the diffraction peaks in the high back-reflection region to determine changes in lattice spacing.
1.3 This test method is applicable to all X-ray diffraction techniques for residual stress measurement, including single, double, and multiple exposure techniques.
1.4 The values stated in inch pound units are to be regarded as the standard. The SI units given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Apr-2003
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.13 - Residual Stress Measurement

Relations

• Replaces: ASTM E1426-98 - Standard Test Method for Determining the Effective Elastic Parameter for X-Ray Diffraction Measurements of Residual Stress
• Effective Date: 10-Apr-2003
• Replaced By: ASTM E1426-98(2009)e1 - Standard Test Method for Determining the Effective Elastic Parameter for X-Ray Diffraction Measurements of Residual Stress
• Effective Date: 01-Jun-2009
• Referred By: ASTM E2860-20 - Standard Test Method for Residual Stress Measurement by X-Ray Diffraction for Bearing Steels
• Effective Date: 10-Apr-2003
• Referred By: ASTM E915-21 - Standard Practice for Verifying the Alignment of X-Ray Diffraction Instruments for Residual Stress Measurement
• Effective Date: 10-Apr-2003
• Referred By: ASTM A729/A729M-17(2022) - Standard Specification for Carbon and Alloy Steel Axles, Heat-Treated, for Mass Transit and Electric Railway Service
• Effective Date: 10-Apr-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E1426–98 (Reapproved 2003)
Standard Test Method for
Determining the Effective Elastic Parameter for X-Ray
Diffraction Measurements of Residual Stress
This standard is issued under the fixed designation E 1426; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
When a crystalline material is strained the spacings between parallel planes of atoms, ions, or
moleculesinthelatticechange.X-raydiffractiontechniquescanmeasurethesechangesand,therefore,
they constitute a powerful means for studying the residual stress state in a body. To calculate
macroscopic stresses from lattice strains requires a material constant, E , called the effective elastic
eff
parameter,thatmustbeempiricallydeterminedbyX-raydiffractiontechniquesasdescribedinthistest
method.
1. Scope 2. Referenced Documents
1.1 This test method covers a procedure for experimentally 2.1 ASTM Standards:
determining the effective elastic parameter, E , for the evalu- E 4 Practices for Force Verification of Testing Machines
eff
ation of residual and applied stresses by X-ray diffraction E 6 Terminology Relating to Methods of Mechanical Test-
techniques.The effective elastic parameter relates macroscopic ing
stress to the strain measured in a particular crystallographic E 7 Terminology Relating to Metallography
direction in polycrystalline samples. E should not be con- E 1237 Guide for Installing Bonded Resistance Strain
eff
fused with E, the modulus of elasticity. Rather, it is nominally Gages
equivalent to E/(1 + n) for the particular crystallographic
3. Terminology
direction, where n is Poisson’s ratio. The effective elastic
parameter is influenced by elastic anisotropy and preferred 3.1 Definitions:
3.1.1 Many of the terms used in this test method are defined
orientation of the sample material.
1.2 This test method is applicable to all X-ray diffraction in Terminology E 6 and E 7.
3.2 Definitions of Terms Specific to This Standard:
instruments intended for measurements of macroscopic re-
sidual stress that use measurements of the positions of the 3.2.1 interplanar spacing—the perpendicular distance be-
tween adjacent parallel lattice planes.
diffraction peaks in the high back-reflection region to deter-
mine changes in lattice spacing. 3.2.2 macrostress—anaveragestressactingoveraregionof
the test specimen containing many crystals.
1.3 This test method is applicable to all X-ray diffraction
techniques for residual stress measurement, including single, 3.3 Symbols:
3.3.1 a = dummy parameter for Sum(a) and SD(a).
double, and multiple exposure techniques.
1.4 The values stated in inch pound units are to be regarded 3.3.2 c = ordinate intercept of a graph of Dd versus stress.
3.3.3 d = interplanar spacing between crystallographic
as the standard. The SI units given in parentheses are for
planes; also called d-spacing.
information only.
1.5 This standard does not purport to address all of the 3.3.4 d = interplanar spacing for unstressed material.
3.3.5 Dd = change in interplanar spacing caused by stress.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.3.6 E = modulus of elasticity.
3.3.7 E = effective elastic parameter for X-ray measure-
priate safety and health practices and determine the applica-
eff
bility of regulatory limitations prior to use. ments.
3.3.8 i = measurement index, 1# i# n.
3.3.9 m = slope of a graph of Dd versus stress.
3.3.10 n = number of measurements used to determine
This test method is under the jurisdiction of ASTM Committee E28 on
slope m.
Mechanical Testing and is the direct responsibility of Subcommittee E28.13 on
Residual Stress Measurement.
Current edition approved April 10, 2003. Published July 2003. Originally
approved in 1991. Last previous edition approved in 1998 as E 1426 – 98. Annual Book of ASTM Standards, Vol 03.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1426–98 (2003)
3.3.11 SD(a) = standard deviation of a set of quantities “a”. 6.2.2 The fixture shall maintain the irradiated surface of the
3.3.12 Sum(a) = sum of a set of quantities “a”. specimen at the exact center of rotation of the X-ray diffraction
3.3.13 T =X minus mean of all X values. instrument throughout the test with sufficient precision to
i i i
3.3.14 X = i-th value of applied stress. provide the desired levels of precision and bias in the mea-
i
3.3.15 Y = measurement of Dd corresponding to X. surements to be made.
i i
3.3.16 n = Poisson’s ratio. 6.2.3 The fixture may be designed to apply tensile or
3.3.17 c = angle between the specimen surface normal and bending loads. A four-point bending technique such as that
the normal to the diffracting crystallographic planes. described by Prevey is most commonly used.
6.3 Electrical resistance strain gages are mounted upon the
4. Summary of Test Method test specimen to enable it to be accurately stressed to known
levels.
4.1 A test specimen is prepared from a material that is
representative of that of the object in which residual stress
7. Test Specimens
measurements are to be made.
7.1 Test specimens should be fabricated from material with
NOTE 1—Ifasampleofthesamematerialisavailableitshouldbeused.
microstructure as nearly the same as possible as that in the
4.2 The test specimen is instrumented with an electrical
material in which residual stresses are to be evaluated.
resistance strain gage, mounted in a location that experiences
7.2 For use in tensile or four-point bending fixtures, speci-
the same stress as the region that will be subsequently
mens should be rectangular in shape.
irradiated with X-rays.
7.2.1 The length of tensile specimens, between grips, shall
4.3 The test specimen is calibrated by loading it in such a
be not less than four times the width, and the width-to-
manner that the stress, where the strain gage is mounted, is
thickness ratio shall not exceed eight.
directly calculable, and a calibration curve relating the strain
7.2.2 For use in four-point bending fixtures, specimens
gage reading to the stress is developed.
should have a length-to-width ratio of at least four. The
4.4 The test specimen is mounted in a loading fixture in an
specimen width should be sufficient to accommodate strain
X-ray diffraction apparatus, and sequentially loaded to several
gages (see 7.5) and the width-to-thickness ratio should be
load levels.
greater than one and consistent with the method used to
4.4.1 The change in interplanar spacing is measured for
calculate the applied stresses in 8.1.
each load level and related to the corresponding stress that is
NOTE 2—Nominal dimensions often used for specimens for four-point
determined from the strain gage reading and the calibration
bending fixtures are 4.0 3 0.75 3 0.06 in. (10.2 3 1.9 3 0.15 cm).
curve.
4.5 The effective elastic parameter and its standard devia- 7.3 Tapered specimens for use in cantilever bending fix-
tures, and split-ring samples, are also acceptable.
tion are calculated from the test results.
7.4 Specimen surfaces may be electropolished or as-rolled
5. Significance and Use sheet or plate.
7.5 One or more electrical resistance strain gages is affixed
5.1 This test method provides standard procedures for
to the test specimen in accordance with Guide E 1237. The
experimentally determining the effective elastic parameter for
gage(s)shouldbealignedparalleltothelongitudinalaxisofthe
X-ray diffraction measurement of residual and applied stresses.
specimen, and should be mounted on a region of the specimen
It also provides a standard means of reporting the precision of
that experiences the same strain as the region that is to be
the parameter.
irradiated. The gage(s) should be applied to the irradiated
5.2 Thistestmethodisapplicabletoanycrystallinematerial
surface of the beam either adjacent to, or on either side of, the
which exhibits a linear relationship between stress and strain in
irradiated area in order to minimize errors due to the absence
the elastic range.
of a pure tensile or bending load.
5.3 This test method should be used whenever residual
stresses are to be evaluated by an X-ray diffraction technique
NOTE 3—In the case of four-point bending fixtures the gage(s) should
and the effective elastic parameter of the material is unknown.
be placed well inside the inner span of the specimen in order to minimize
the stress concentration effects associated with the inner knife edges.
6. Apparatus
8. Calibration
6.1 Any X-ray diffraction instrument intended for measure-
8.1 Calibratetheinstrumentedspecimenusingloadsapplied
ments of residual macrostress that employs measurements of
by dead weights or by a testing machine that has been verified
the diffraction peaks in the high back-reflection region may be
according to Practices E 4. The loading configuration is such
used, including film camera types, diffractometers, and por-
that the applied stresses, in the region where the strain gages
table systems.
aremountedandwhereX-raydiffractionmeasurementswillbe
6.2 A loading fixture is required to apply loads to the test
specimen while it is being irradiated in the X-ray diffraction
instrument.
6.2.1 The fixture shall be designed such that the surface
Prevey, P. S., “A Method of Determining the Elastic Properties of Alloys in
stressappliedbythefixtureshallbeuniformovertheirradiated
Selected Cry
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