1、Designation: E 8/E 8M 08American Association StateHighway and Transportation Officials StandardAASHTO No.: T68An American National StandardStandard Test Methods forTension Testing of Metallic Materials1This standard is issued under the fixed designation E 8/E 8M; the number immediately following the
2、 designation indicates the year oforiginal adoption 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.This standard has been approved for
3、use by agencies of the Department of Defense.1. Scope*1.1 These test methods cover the tension testing of metallicmaterials in any form at room temperature, specifically, themethods of determination of yield strength, yield point elon-gation, tensile strength, elongation, and reduction of area.1.2 T
4、he gage lengths for most round specimens are requiredto be 4D for E 8 and 5D for E 8M. The gage length is the mostsignificant difference between E 8 and E 8M Test SpecimensTest specimens made from powder metallurgy (P/M) materialsare exempt from this requirement by industry-wide agreementto keep the
5、 pressing of the material to a specific projected areaand density.1.3 Exceptions to the provisions of these test methods mayneed to be made in individual specifications or test methods fora particular material. For examples, see Test Methods andDefinitions A 370 and Test Methods B 557, B 557M.1.4 Ro
6、om temperature shall be considered to be 10 to 38C50 to 100F unless otherwise specified.1.5 The values stated in SI units are to be regarded asseparate from inch/pound units. The values stated in eachsystem are not exact equivalents; therefore each system mustbe used independently of the other. Comb
7、ining values from thetwo systems may result in non-conformance with the standard.1.6 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 de
8、termine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 356/A 356M Specification for Steel Castings, Carbon,Low Alloy, and Stainless Steel, Heavy-Walled for SteamTurbinesA 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsB
9、 557 Test Methods for Tension Testing Wrought and CastAluminum- and Magnesium-Alloy ProductsB 557M Test Methods for Tension Testing Wrought andCast Aluminum- and Magnesium-Alloy Products MetricE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Tes
10、t-ingE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE83 Practice for Verification and Classification of Exten-someter SystemsE 345 Test Methods of Tension Testing of Metallic FoilE 691 Practice for Conducting an Interlaboratory Study toDetermine the
11、 Precision of a Test MethodE 1012 Practice for Verification of Test Frame and Speci-men Alignment Under Tensile and Compressive AxialForce ApplicationE 1856 Guide for Evaluating Computerized Data Acquisi-tion Systems Used to Acquire Data from Universal TestingMachines3. Terminology3.1 DefinitionsThe
12、 definitions of terms relating to tensiontesting appearing in Terminology E6shall be considered asapplying to the terms used in these test methods of tensiontesting. Additional terms being defined are as follows:3.1.1 discontinuous yieldingin a uniaxial test, a hesitationor fluctuation of force obse
13、rved at the onset of plastic defor-mation, due to localized yielding. (The stress-strain curve neednot appear to be discontinuous.)3.1.2 elongation at fracturethe elongation measured justprior to the sudden decrease in force associated with fracture.For many materials not exhibiting a sudden decreas
14、e in force,the elongation at fracture can be taken as the strain measuredjust prior to when the force falls below 10 % of the maximumforce encountered during the test.1These test methods are under the jurisdiction of ASTM Committee E28 onMechanical Testing and are the direct responsibility of Subcom
15、mittee E28.04 onUniaxial Testing.Current edition approved Feb. 1, 2008. Published March 2008. Originallyapproved in 1924. Last previous edition approved 2004 as E804.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B
16、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3 lower yi
17、eld strength, LYS FL-2in a uniaxial test,the minimum stress recorded during discontinuous yielding,ignoring transient effects.3.1.4 uniform elongation, Elu, %the elongation deter-mined at the maximum force sustained by the test piece justprior to necking or fracture, or both.3.1.4.1 DiscussionUnifor
18、m elongation includes both elas-tic and plastic elongation.3.1.5 upper yield strength, UYS FL-2in a uniaxial test,the first stress maximum (stress at first zero slope) associatedwith discontinuous yielding at or near the onset of plasticdeformation.3.1.6 yield point elongation, YPEin a uniaxial test
19、, thestrain (expressed in percent) separating the stress-strain curvesfirst point of zero slope from the point of transition fromdiscontinuous yielding to uniform strain hardening. If thetransition occurs over a range of strain, the YPE end point isthe intersection between (a) a horizontal line draw
20、n tangent tothe curve at the last zero slope and (b) a line drawn tangent tothe strain hardening portion of the stress-strain curve at thepoint of inflection. If there is no point at or near the onset ofyielding at which the slope reaches zero, the material has 0 %YPE.4. Significance and Use4.1 Tens
21、ion tests provide information on the strength andductility of materials under uniaxial tensile stresses. Thisinformation may be useful in comparisons of materials, alloydevelopment, quality control, and design under certain circum-stances.4.2 The results of tension tests of specimens machined tostan
22、dardized dimensions from selected portions of a part ormaterial may not totally represent the strength and ductilityproperties of the entire end product or its in-service behavior indifferent environments.4.3 These test methods are considered satisfactory for ac-ceptance testing of commercial shipme
23、nts. The test methodshave been used extensively in the trade for this purpose.5. Apparatus5.1 Testing MachinesMachines used for tension testingshall conform to the requirements of Practices E4. The forcesused in determining tensile strength and yield strength shall bewithin the verified force applic
24、ation range of the testingmachine as defined in Practices E 4.5.2 Gripping Devices:5.2.1 GeneralVarious types of gripping devices may beused to transmit the measured force applied by the testingmachine to the test specimens. To ensure axial tensile stresswithin the gage length, the axis of the test
25、specimen shouldcoincide with the center line of the heads of the testingmachine. Any departure from this requirement may introducebending stresses that are not included in the usual stresscomputation (force divided by cross-sectional area).NOTE 1The effect of this eccentric force application may be
26、illus-trated by calculating the bending moment and stress thus added. For astandard 12.5-mm 0.500-in. diameter specimen, the stress increase is 1.5percentage points for each 0.025 mm 0.001 in. of eccentricity. This errorincreases to 2.5 percentage points/ 0.025 mm 0.001 in. fora9mm0.350-in. diameter
27、 specimen and to 3.2 percentage points/ 0.025 mm0.001 in. for a 6-mm 0.250-in. diameter specimen.NOTE 2Alignment methods are given in Practice E 1012.5.2.2 Wedge GripsTesting machines usually are equippedwith wedge grips. These wedge grips generally furnish asatisfactory means of gripping long speci
28、mens of ductile metaland flat plate test specimens such as those shown in Fig. 1. If,however, for any reason, one grip of a pair advances fartherthan the other as the grips tighten, an undesirable bendingstress may be introduced. When liners are used behind thewedges, they must be of the same thickn
29、ess and their facesmust be flat and parallel. For best results, the wedges should besupported over their entire lengths by the heads of the testingmachine. This requires that liners of several thicknesses beavailable to cover the range of specimen thickness. For propergripping, it is desirable that
30、the entire length of the serratedface of each wedge be in contact with the specimen. Properalignment of wedge grips and liners is illustrated in Fig. 2. Forshort specimens and for specimens of many materials it isgenerally necessary to use machined test specimens and to usea special means of grippin
31、g to ensure that the specimens, whenunder load, shall be as nearly as possible in uniformlydistributed pure axial tension (see 5.2.3, 5.2.4, and 5.2.5).5.2.3 Grips for Threaded and Shouldered Specimens andBrittle MaterialsA schematic diagram of a gripping devicefor threaded-end specimens is shown in
32、 Fig. 3, while Fig. 4shows a device for gripping specimens with shouldered ends.Both of these gripping devices should be attached to the headsof the testing machine through properly lubricated spherical-seated bearings. The distance between spherical bearingsshould be as great as feasible.5.2.4 Grip
33、s for Sheet MaterialsThe self-adjusting gripsshown in Fig. 5 have proven satisfactory for testing sheetmaterials that cannot be tested satisfactorily in the usual type ofwedge grips.5.2.5 Grips for WireGrips of either the wedge or snubbingtypes as shown in Figs. 5 and 6 or flat wedge grips may beuse
34、d.5.3 Dimension-Measuring DevicesMicrometers and otherdevices used for measuring linear dimensions shall be accurateand precise to at least one half the smallest unit to which theindividual dimension is required to be measured.5.4 ExtensometersExtensometers used in tension testingshall conform to th
35、e requirements of Practice E83 for theclassifications specified by the procedure section of this testmethod. Extensometers shall be used and verified to includethe strains corresponding to the yield strength and elongation atfracture (if determined).5.4.1 Extensometers with gage lengths equal to or
36、shorterthan the nominal gage length of the specimen (dimensionshown as “G-Gage Length” in the accompanying figures) maybe used to determine the yield behavior. For specimens withouta reduced section (for example, full cross sectional areaspecimens of wire, rod, or bar), the extensometer gage lengthf
37、or the determination of yield behavior shall not exceed 80 %of the distance between grips. For measuring elongation atfracture with an appropriate extensometer, the gage length ofE 8/E 8M 082DimensionsStandard Specimens Subsize SpecimenPlate-Type, 40 mm1.500 in. WideSheet-Type, 12.5 mm0.500 in. Wide
38、6mm0.250 in. Widemm in. mm in. mm in.GGage length (Note 1 and Note 2) 200.0 6 0.28.00 6 0.0150.0 6 0.12.000 6 0.00525.0 6 0.11.000 6 0.003WWidth (Note 3 and Note 4) 40.0 6 2.01.500 6 0.125, -0.25012.5 6 0.20.500 6 0.0106.0 6 0.10.250 6 0.005TThickness (Note 5) thickness of materialRRadius of fillet,
39、 min (Note 6) 25 1 12.5 0.500 6 0.250LOverall length, (Note 2, Note 7, and Note 8) 450 18 200 8 100 4ALength of reduced section, min 225 9 57 2.25 32 1.25BLength of grip section (Note 8) 75 3 50 2 30 1.25CWidth of grip section, approximate (Note 4 and Note 9) 50 2 20 0.750 10 0.375NOTE 1For the 40 m
40、m 1.500 in. wide specimen, punch marks for measuring elongation after fracture shall be made on the flat or on the edge ofthe specimen and within the reduced section. Either a set of nine or more punch marks 25 mm 1 in. apart, or one or more pairs of punch marks 200mm 8 in. apart may be used.NOTE 2W
41、hen elongation measurements of 40 mm 1.500 in. wide specimens are not required, a minimum length of reduced section (A)of75mm2.25 in. may be used with all other dimensions similar to those of the plate-type specimen.NOTE 3For the three sizes of specimens, the ends of the reduced section shall not di
42、ffer in width by more than 0.10, 0.05 or 0.02 mm 0.004, 0.002or 0.001 in., respectively. Also, there may be a gradual decrease in width from the ends to the center, but the width at each end shall not be more than1 % larger than the width at the center.NOTE 4For each of the three sizes of specimens,
43、 narrower widths (W and C) may be used when necessary. In such cases the width of the reducedsection should be as large as the width of the material being tested permits; however, unless stated specifically, the requirements for elongation in a productspecification shall not apply when these narrowe
44、r specimens are used.NOTE 5The dimension T is the thickness of the test specimen as provided for in the applicable material specifications. Minimum thickness of 40 mm1.500 in. wide specimens shall be 5 mm 0.188 in. Maximum thickness of 12.5 and 6 mm 0.500 and 0.250 in. wide specimens shall be 19 and
45、 6mm 0.750 and 0.250 in., respectively.NOTE 6For the 40 mm 1.500 in. wide specimen, a 13 mm 0.500 in. minimum radius at the ends of the reduced section is permitted for steelspecimens under 690 MPa 100 000 psi in tensile strength when a profile cutter is used to machine the reduced section.NOTE 7The
46、 dimension shown is suggested as a minimum. In determining the minimum length, the grips must not extend in to the transition sectionbetween Dimensions A and B, see Note 9.NOTE 8To aid in obtaining axial force application during testing of 6-mm 0.250-in. wide specimens, the overall length should be
47、as large as thematerial will permit, up to 200 mm 8.00 in.NOTE 9It is desirable, if possible, to make the length of the grip section large enough to allow the specimen to extend into the grips a distance equalto two thirds or more of the length of the grips. If the thickness of 12.5 mm 0.500-in. wid
48、e specimens is over 10 mm 0.375 in., longer grips andcorrespondingly longer grip sections of the specimen may be necessary to prevent failure in the grip section.NOTE 10For the three sizes of specimens, the ends of the specimen shall be symmetrical in width with the center line of the reduced sectio
49、n within2.5, 0.25 and 0.13 mm 0.10, 0.01 and 0.005 in., respectively. However, for referee testing and when required by product specifications, the ends of the12.5 mm 0.500 in. wide specimen shall be symmetrical within 0.2 mm 0.01 in.NOTE 11For each specimen type, the radii of all fillets shall be equal to each other within a tolerance of 1.25 mm 0.05 in., and the centers ofcurvature of the two fillets at a particular end shal
