1、Designation: E 915 96 (Reapproved 2002)Standard Test Method forVerifying the Alignment of X-Ray Diffraction Instrumentationfor Residual Stress Measurement1This standard is issued under the fixed designation E 915; the number immediately following the designation indicates the year oforiginal adoptio
2、n or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the preparation and use of a flatstress-free test
3、specimen for the purpose of checking thesystematic error caused by instrument misalignment or samplepositioning in X-ray diffraction residual stress measurement, orboth.1.2 This test method is applicable to apparatus intended forX-ray diffraction macroscopic residual stress measurement inpolycrystal
4、line samples employing measurement of a diffrac-tion peak position in the high-back reflection region, and inwhich the u,2u, and c rotation axes can be made to coincide(see Fig. 1).1.3 This test method describes the use of iron powder whichhas been investigated in round-robin studies for the purpose
5、 ofverifying the alignment of instrumentation intended for stressmeasurement in ferritic or martensitic steels. To verify instru-ment alignment prior to stress measurement in other alloys,base metal powder having the same crystal structure as thealloy should be prepared in similar fashion and used t
6、o checkinstrument alignment at the appropriate diffraction angle.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the appl
7、ica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 11 Specification for Wire-Cloth Sieves for Testing Pur-poses23. Significance and Use3.1 This test method provides a means of verifying instru-ment alignment in order to quantify and minimize systematicexper
8、imental error in X-ray diffraction residual stress measure-ment. This method is suitable for application to conventionaldiffractometers or to X-ray diffraction instrumentation of eitherthe diverging or parallel beam types.3, 43.2 Application of this test method requires the use of a flatspecimen of
9、stress-free material that produces diffraction in theangular region of the diffraction peak to be used for stressmeasurement. The specimen must be sufficiently fine-grainedso that large numbers of individual crystals contribute to thediffraction peak produced. The crystals must provide intensediffra
10、ction at all angles of tilt, c, which will be employed (seeNote 1).NOTE 1Complete freedom from preferred orientation in the stressfreespecimen is, however, not critical in the application of the technique.4. Procedure4.1 Instrument Alignment:4.1.1 Align the X-ray diffraction instrumentation to be us
11、edfor residual stress measurement in accordance with the instruc-tions supplied by the manufacturer. In general, this alignmentmust achieve the following, whether the u,2u, and c axes arevariable or fixed (see Fig. 1):4.1.1.1 The u,2u, and c axes shall coincide.4.1.1.2 The incident X-ray beam shall
12、be centered on the cand 2u axes, within a focusing range, which will conform to thedesired error and precision tolerances (see sections 5 and 6).4.1.1.3 The X-ray tube focal spot, the c and 2u axes, and thereceiving slit positioned at 2u equals zero degrees shall be ona line in the plane of diffract
13、ion. Alternatively, for instrumen-tation limited to the back reflection region, the diffraction angle2u shall be calibrated.4.1.1.4 The proper sample position shall be established,using whatever means are provided with the instrument, suchthat the surface of the sample is positioned at the u and c a
14、xes, within the focal distance range which will conform to thedesired error and precision tolerances (see sections 5 and 6).4.1.1.5 The angle c must be determined accurately.1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Sub
15、committee E28.13 onResidual Stress Measurement.Current edition approved Apr. 10, 1996. Published June 1996. Originallypublished as E 915 83. Last previous edition E 915 90.2Annual Book of ASTM Standards, Vol 14.02.3Hilley, M. E., Larson, J. A., Jatczak, C. F., and Ricklefs, R. E., eds., ResidualStre
16、ss Measurement by X-ray Diffraction, SAE J784a, Society of AutomotiveEngrs., Inc., Warrendale, PA (1971).4“Standard Method for X-Ray Stress Measurement,” Committee on MechanicalBehavior of Materials, The Society of Materials Science, Japan, (20 April 1973).1Copyright ASTM International, 100 Barr Har
17、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2 X-Ray Optics:4.2.1 When the Ka characteristic radiation doublet is usedfor stress measurement, it is desirable to select incident andreceiving X-ray beam optics that will produce maximumseparation of the Ka1Ka2doublet. Perfo
18、rm stress measure-ments on the stress-free specimen employing the Ka1diffrac-tion peak at all c angles investigated. Because resolution of theKa doublet may vary with the angle c, and because someinstrumentation may be incapable (due to fixed X-ray optics) ofobtaining resolution of the doublet, care
19、 must be taken not toresolve the doublet at some c angles while blending thedoublet into a single peak at other c angles.4.3 Selection of Powder for a Stress-Free Iron Specimen:4.3.1 Use iron powder with a particle size greater than 1 m(4 3 105in.) (See Note 2.)NOTE 2Annealed armco iron powder of 45
20、 m (325 mesh) has beenfound suitable.4.3.2 Annealing of the powder in vacuum reduces diffrac-tion peak width, thereby increasing diffraction peak resolution.This is generally desirable (see Note 3). Powders in the form ofplastically deformed filings may be used, but will producebroader diffraction p
21、eaks. In the event that an instrumentincapable of resolution of the Ka1Ka2doublet is beingemployed, it may be desirable to deliberately obtain plasticallydeformed powders which insure that partial resolution of theKa doublet does not occur. Extremely fine powders have alsobeen shown to produce line
22、broadening, sufficient to suppressresolution of the Ka doublet.NOTE 3It may be advantageous to anneal an oxide-forming powder ina reducing atmosphere rather than in vacuum to avoid problems fromsurface contamination. It is not necessary to anneal ceramic powders sincethese materials do not tend to s
23、how line broadening from plasticdeformation.4.4 Stress-Free Specimen Preparation:4.4.1 A permanent stress-free specimen may be prepared bymounting the powder on the face of a microscope slide or in ashallow powder tray (of the type used for powder diffractionwork on a diffractometer) using a 10 % so
24、lution of nitrocellu-lose cement5diluted with acetone as a suitable amorphousbinder. Place several drops of the solution on a clean micro-scope slide or in a sample tray, and sprinkle the powder into thebinder. The powder may be spread and leveled with a secondmicroscope slide. When a uniform flat s
25、urface has beenproduced by alternately wetting with the binder solution andwiping with a second slide, set the specimen aside and allow itto dry for several hours. Excess amounts of the binder maycause it to peel away from the surface of the microscope slide.Rewetting of the surface with acetone and
26、 redrying mayeliminate this difficulty. Make the surface of the specimen asflat as possible so that the specimen surface is clearly defined.4.4.2 A temporary specimen may be rapidly prepared usingpetroleum jelly as an amorphous binder. Place a small quantityof petroleum jelly on the face of one micr
27、oscope slide andpress it against a second slide to extrude the petroleum jellyinto a uniform flat film. Remove the second microscope slidewith a wiping action taking care to keep the surface layer ofpetroleum jelly thin and flat. Holding the petroleum jelly-coated slide at a steep angle to a vertica
28、l line, sprinkle the ironpowder from a sufficient height above the slide so that thepowder strikes the coated surface and either adheres or isdeflected away. Do not allow the powder to pack and build upon the surface.5Duco Cement available from DuPont Co., Wilmington, DE 19898 has beenfound suitable
29、. Paraffin wax may also be used.FIG. 1 X-Ray Diffraction Stress Measurement Geometry and Angles DefinedE 915 96 (2002)24.4.3 The surface area of the powder must be of sufficientsize to intersect the entire incident X-ray beam at all c anglesto be used during stress measurement.4.5 Instrument Alignme
30、nt Check:4.5.1 Position the stress-free specimen on the X-ray diffrac-tion apparatus (see 4.1.1.4). In the event that a mechanical gagewhich contacts the surface of the specimen is used forspecimen positioning, a thin metal shim may be placed in frontof the powder surface to protect it. Place this g
31、age against theface of the metal shim, and adjust the positioning to account forthe inclusion of the shim in front of the gage such that thesurface of the powder is at the correct distance from thereference point of the gage for stress measurement.NOTE 4Failure to place the powder surface directly o
32、ver the center ofrotation of the c and 2u axes induces a systematic specimen displacementerror.4.5.2 Without adjusting the specimen position, perform fivesuccessive stress measurements using the method and correc-tion procedures normally employed for the instrument. Toavoid systematic error in the v
33、erification process when Karadiation is being used, care must be taken to either completelysplit or blend the Ka1Ka2doublet (see 4.2).NOTE 5Values for accuracy and precision of the various angles anddisplacements are not specified herein. These may be considered to be metcollectively when overall me
34、asurement errors and tolerances are withinthose specified in Sections 5 and 6.5. Calculations and Interpretation of Results5.1 Systematic Error:5.1.1 Reduce the X-ray diffraction data obtained from thefive measurements in whatever manner is normally employedfor the X-ray diffraction instrumentation
35、in use, and include allcorrections normally applied to raw X-ray diffraction data.Calculate the simple arithmetic mean and standard deviationabout the mean for the five measurements. If the mean value iswithin 14 MPa (2.0 ksi) of zero, the instrument and specimen-positioning gage can be considered t
36、o be properly aligned. Inthe event that the mean differs from zero by more than 14 MPa(2.0 ksi), repeat 4.1 and 4.5.5.2 Random Error:5.2.1 Experience has shown that the standard deviation ofthe five measurements should be within approximately 6.9MPa (1.0 ksi). In the event that the standard deviatio
37、n of thefive measurements exceeds 14 MPa (2.0 ksi), the stress-measurement technique employed and the instrumentationshould be investigated for sources of random error affecting themeasurement precision. Random error due to counting statis-tics may result from failure to take sufficient time during
38、themeasurement to obtain accurate intensity information, and thusto accurately determine the diffraction peak positions. Methodsare available3for estimating the standard deviation of themeasured stress due to the errors involved in counting andcurve fitting to determine peak positions. Mechanical so
39、urcesof error such as loose bearings and ways in the apparatus mayresult in significant random error.6. Precision and Bias6.1 The precision of this method will be dependent upon thetype of X-ray diffraction instrumentation employed and themethods of data reduction used in stress measurement. Theprel
40、iminary results of round-robin investigations using thismethod indicate that instrument alignment within 14 MPa (2.0ksi) (see 5.1) can be achieved for both standard diffractometersand two types of X-ray diffraction instrumentation designed forstress measurement in the back reflection region only. In
41、stru-mental precision measured by this method (see 5.2) has beenfound to be less than 66.9 MPa (1.0 ksi).6.2 The accuracy of this method is considered to be absolutebecause the specimen is stress-free. Deviation of resultsobtained in performing this method, provided the specimen hasbeen properly pre
42、pared and maintained, can be attributed to theinstrumentation under investigation.7. Keywords7.1 alignment; residual stress; x-ray diffractionASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of thi
43、s standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five yea
44、rs andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical commit
45、tee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E 915 96 (2002)3
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