1、Designation: E8/E8M 15aE8/E8M 16 American 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 E8/E8M; the number immediately follow
2、ing the 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 () indicates an editorial change since the last revision or reapproval.This standard has been approve
3、d for use by agencies of the U.S. Department of Defense.1. Scope*1.1 These test methods cover the tension testing of metallic materials in any form at room temperature, specifically, the methodsof determination of yield strength, yield point elongation, tensile strength, elongation, and reduction of
4、 area.1.2 The gauge lengths for most round specimens are required to be 4D for E8 and 5D for E8M. The gauge length is the mostsignificant difference between E8 and E8M test specimens. Test specimens made from powder metallurgy (P/M) materials areexempt from this requirement by industry-wide agreemen
5、t to keep the pressing of the material to a specific projected area anddensity.1.3 Exceptions to the provisions of these test methods may need to be made in individual specifications or test methods for aparticular material. For examples, see Test Methods and Definitions A370 and Test Methods B557,
6、and B557M.1.4 Room temperature shall be considered to be 10 to 38C 50 to 100F unless otherwise specified.1.5 The values stated in SI units are to be regarded as separate from inch/pound units. The values stated in each system are notexact equivalents; therefore each system must be used independently
7、 of the other. Combining values from the two systems mayresult in non-conformance with the standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and heal
8、th practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A356/A356M Specification for Steel Castings, Carbon, Low Alloy, and Stainless Steel, Heavy-Walled for Steam TurbinesA370 Test Methods and Definitions for Mechanical Testing o
9、f Steel ProductsB557 Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy ProductsB557M Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products (Metric)E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Method
10、s of Mechanical TestingE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE83 Practice for Verification and Classification of Extensometer SystemsE345 Test Methods of Tension Testing of Metallic FoilE691 Practice for Conducting an Interlaboratory Study
11、 to Determine the Precision of a Test MethodE1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial ForceApplicationD1566 Terminology Relating to RubberE1856 Guide for Evaluating Computerized Data Acquisition Systems Used to Acquire Data from Unive
12、rsal Testing Machines1 These test methods are under the jurisdiction of ASTM Committee E28 on Mechanical Testing and are the direct responsibility of Subcommittee E28.04 on UniaxialTesting.Current edition approved May 1, 2015July 15, 2016. Published June 2015September 2016. Originally approved in 19
13、24. Last previous edition approved 2015 asE8/E8M 15.E8/E8M 15a. DOI: 10.1520/E0008_E0008M-15A.10.1520/E0008_E0008M-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to
14、 the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes
15、 accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr H
16、arbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions of Terms Common to Mechanical Testing3.1.1 The definitions of mechanical testing terms that appear in the Terminology E6 apply to this test method.3.1.1.1 These terms include bending strain, const
17、raint, elongation, extensometer, force, gauge length, necking, reduced section,stress-strain diagram, testing machine, and modulus of elasticity.3.1.2 In addition, the following common terms from Terminology E6 are defined:3.1.3 discontinuous yielding, nin a uniaxial test, a hesitation or fluctuatio
18、n of force observed at the onset of plasticdeformation, due to localized yielding.3.1.3.1 DiscussionThe stress-strain curve need not appear to be discontinuous.3.1.4 elongation after fracture, nthe elongation measured by fitting the two halves of the broken specimen together.3.1.5 elongation at frac
19、ture, nthe elongation measured just prior to the sudden decrease in force associated with fracture.3.1.6 lower yield strength, LYS FL-2in a uniaxial test, the minimum stress recorded during discontinuous yielding, ignoringtransient effects.3.1.7 reduction of area, nthe difference between the origina
20、l cross-sectional area of a tension test specimen and the area ofits smallest cross section.3.1.7.1 DiscussionThe reduction of area is usually expressed as a percentage of the original cross-sectional area of the specimen.3.1.7.2 DiscussionThe smallest cross section may be measured at or after fract
21、ure as specified for the material under test.3.1.7.3 DiscussionThe term reduction of area when applied to metals generally means measurement after fracture; when applied to plastics andelastomers, measurement at fracture. Such interpretation is usually applicable to values for reduction of area repo
22、rted in theliterature when no further qualification is given. (E28.04)3.1.8 tensile strength, Su FL2,nthe maximum tensile stress that a material is capable of sustaining.3.1.8.1 DiscussionTensile strength is calculated from the maximum force during a tension test carried to rupture and the original
23、cross-sectional areaof the specimen.3.1.9 uniform elongation, Elu, %the elongation determined at the maximum force sustained by the test piece just prior tonecking or fracture, or both.3.1.9.1 DiscussionUniform elongation includes both elastic and plastic elongation.3.1.10 upper yield strength, UYS
24、FL-2in a uniaxial test, the first stress maximum (stress at first zero slope) associated withdiscontinuous yielding at or near the onset of plastic deformation.3.1.11 yield point elongation, YPE, nin a uniaxial test, the strain (expressed in percent) separating the stress-strain curves firstpoint of
25、 zero slope from the point of transition from discontinuous yielding to uniform strain hardening.3.1.11.1 DiscussionIf the transition occurs over a range of strain, the YPE end point is the intersection between (a) a horizontal line drawn tangentto the curve at the last zero slope and (b) a line dra
26、wn tangent to the strain hardening portion of the stress-strain curve at the pointof inflection. If there is no point at or near the onset of yielding at which the slope reaches zero, the material has 0 % YPE.E8/E8M 1623.1.12 yield strength, YSorSy FL2,nthe engineering stress at which, by convention
27、, it is considered that plastic elongationof the material has commenced.3.1.12.1 DiscussionThis stress may be specified in terms of (a) a specified deviation from a linear stress-strain relationship, (b) a specified totalextension attained, or (c) maximum or minimum engineering stresses measured dur
28、ing discontinuous yielding.3.2 Definitions of Terms Specific to This Standard:3.2.1 referee test, ntest made to settle a disagreement as to the conformance to specified requirements, or conducted by a thirdparty to arbitrate between conflicting results. D1566, D11.084. Significance and Use4.1 Tensio
29、n tests provide information on the strength and ductility of materials under uniaxial tensile stresses. This informationmay be useful in comparisons of materials, alloy development, quality control, and design under certain circumstances.4.2 The results of tension tests of specimens machined to stan
30、dardized dimensions from selected portions of a part or materialmay not totally represent the strength and ductility properties of the entire end product or its in-service behavior in differentenvironments.4.3 These test methods are considered satisfactory for acceptance testing of commercial shipme
31、nts. The test methods have beenused extensively in the trade for this purpose.5. Apparatus5.1 Testing MachinesMachines used for tension testing shall conform to the requirements of Practices E4. The forces usedin determining tensile strength and yield strength shall be within the verified force appl
32、ication range of the testing machine asdefined in Practices E4.5.2 Gripping Devices:5.2.1 GeneralVarious types of gripping devices may be used to transmit the measured force applied by the testing machineto the test specimens. To ensure axial tensile stress within the gauge length, the axis of the t
33、est specimen should coincide with thecenter line of the heads of the testing machine. Any departure from this requirement may introduce bending stresses that are notincluded in the usual stress computation (force divided by cross-sectional area).NOTE 1The effect of this eccentric force application m
34、ay be illustrated by calculating the bending moment and stress thus added. For a standard12.5-mm 0.500-in. diameter specimen, the stress increase is 1.5 percentage points for each 0.025 mm 0.001 in. of eccentricity. This error increasesto 2.5 percentage points/ 0.025 mm 0.001 in. for a 9 mm 0.350-in
35、. diameter specimen and to 3.2 percentage points/ 0.025 mm 0.001 in. for a 6-mm0.250-in. diameter specimen.NOTE 2Alignment methods are given in Practice E1012.5.2.2 Wedge GripsTesting machines usually are equipped with wedge grips. These wedge grips generally furnish asatisfactory means of gripping
36、long specimens of ductile metal and flat plate test specimens such as those shown in Fig. 1. If,however, for any reason, one grip of a pair advances farther than the other as the grips tighten, an undesirable bending stress maybe introduced. When liners are used behind the wedges, they must be of th
37、e same thickness and their faces must be flat and parallel.For best results, the wedges should be supported over their entire lengths by the heads of the testing machine. This requires thatliners of several thicknesses be available to cover the range of specimen thickness. For proper gripping, it is
38、 desirable that the entirelength of the serrated face of each wedge be in contact with the specimen. Proper alignment of wedge grips and liners is illustratedin Fig. 2. For short specimens and for specimens of many materials it is generally necessary to use machined test specimens andto use a specia
39、l means of gripping to ensure that the specimens, when under 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 and Brittle MaterialsA schematic diagram of a gripping device forthreaded-end s
40、pecimens is shown in Fig. 3, while Fig. 4 shows a device for gripping specimens with shouldered ends. Both of thesegripping devices should be attached to the heads of the testing machine through properly lubricated spherical-seated bearings. Thedistance between spherical bearings should be as great
41、as feasible.5.2.4 Grips for Sheet MaterialsThe self-adjusting grips shown in Fig. 5 have proven satisfactory for testing sheet materialsthat cannot be tested satisfactorily in the usual type of wedge grips.5.2.5 Grips for WireGrips of either the wedge or snubbing types as shown in Fig. 5 and Fig. 6
42、or flat wedge grips may beused.5.3 Dimension-Measuring DevicesMicrometers and other devices used for measuring linear dimensions shall be accurate andprecise to at least one half the smallest unit to which the individual dimension is required to be measured.E8/E8M 163DimensionsStandard Specimens Sub
43、size SpecimenPlate-Type, 40 mm1.500 in. WideSheet-Type, 12.5 mm0.500 in. Wide6 mm0.250 in. Widemm in. mm in. mm in.GGauge length (Note 1 and Note 2) 200.0 0.28.00 0.0150.0 0.12.000 0.00525.0 0.11.000 0.003WWidth (Note 3 and Note 4) 40.0 2.01.500 0.125, -0.25012.5 0.20.500 0.0106.0 0.10.250 0.005TThi
44、ckness (Note 5) thickness of materialRRadius of fillet, min (Note 6) 25 1 12.5 0.500 6 0.250LOverall length, min (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, min (Note 9) 75 3 50 2 30 1.25CWidth of grip section, approxim
45、ate (Note 4 and Note 9) 50 2 20 0.750 10 0.375NOTE 1For the 40 mm 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
46、 more pairs of punch marks 200mm 8 in. apart may be used.NOTE 2When elongation measurements of 40 mm 1.500 in. wide specimens are not required, a minimum length of reduced section (A) of 75 mm2.25 in. may be used with all other dimensions similar to those of the plate-type specimen.NOTE 3For the thr
47、ee sizes of specimens, the ends of the reduced section shall not differ 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
48、width at the center.NOTE 4For each of the three sizes of specimens, 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 elon
49、gation in a productspecification shall not apply when these narrower 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 6mm 0.750 and 0.250 in., respectively.NOTE 6
