1、Designation: E8/E8M 16a 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 following the d
2、esignation 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 approved for use
3、 by agencies of the U.S. 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 pointelongation, tensile strength, elongation, and reduction of area.1.2 T
4、he gauge lengths for most round specimens are re-quired to be 4D for E8 and 5D for E8M. The gauge length isthe most significant difference between E8 and E8M testspecimens. Test specimens made from powder metallurgy(P/M) materials are exempt from this requirement by industry-wide agreement to keep t
5、he pressing of the material to aspecific projected area and 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 A370 and Test Methods B557, and B557M.1.4
6、 Room 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. C
7、ombining 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
8、 determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A356/A356M Specification for Steel Castings, Carbon, LowAlloy, and Stainless Steel, Heavy-Walled for Steam Tur-binesA370 Test Methods and Definitions for Mechanical Testingof Steel Product
9、sB557 Test Methods for Tension Testing Wrought and CastAluminum- and Magnesium-Alloy ProductsB557M Test Methods for Tension Testing Wrought and CastAluminum- and Magnesium-Alloy Products (Metric)E4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical T
10、estingE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE83 Practice for Verification and Classification of Exten-someter SystemsE345 Test Methods of Tension Testing of Metallic FoilE691 Practice for Conducting an Interlaboratory Study toDetermine the
11、Precision of a Test MethodE1012 Practice for Verification of Testing Frame and Speci-men Alignment Under Tensile and Compressive AxialForce ApplicationD1566 Terminology Relating to RubberE1856 Guide for Evaluating Computerized DataAcquisitionSystems Used to Acquire Data from Universal TestingMachine
12、sE2658 Practices for Verification of Speed for Material Test-ing Machines3. Terminology3.1 Definitions of Terms Common to Mechanical Testing1These test methods are under the jurisdiction of ASTM Committee E28 onMechanical Testing and are the direct responsibility of Subcommittee E28.04 onUniaxial Te
13、sting.Current edition approved Aug. 1, 2016. Published September 2016. Originallyapproved in 1924. Last previous edition approved 2016 as E8/E8M 16. DOI:10.1520/E0008_E0008M-16A.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
14、For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.
15、1 The definitions of mechanical testing terms that ap-pear in the Terminology E6 apply to this test method.3.1.1.1 These terms include bending strain, constraint,elongation, extensometer, force, gauge length, necking, re-duced section, stress-strain diagram, testing machine, andmodulus of elasticity
16、.3.1.2 In addition, the following common terms from Termi-nology E6 are defined:3.1.3 discontinuous yielding, nin a uniaxial test, a hesita-tion or fluctuation of force observed at the onset of plasticdeformation, due to localized yielding.3.1.3.1 DiscussionThe stress-strain curve need not appearto
17、be discontinuous.3.1.4 elongation after fracture, nthe elongation measuredby fitting the two halves of the broken specimen together.3.1.5 elongation at fracture, nthe elongation measuredjust prior to the sudden decrease in force associated withfracture.3.1.6 lower yield strength, LYS FL-2in a uniaxi
18、al test,the minimum stress recorded during discontinuous yielding,ignoring transient effects.3.1.7 reduced parallel section, A, nthe central portion ofthe specimen that has a nominally uniform cross section, withan optional small taper toward the center, that is smaller thanthat of the ends that are
19、 gripped, not including the fillets.3.1.7.1 DiscussionThis term is often called the parallellength in other standards.3.1.7.2 DiscussionPrevious versions of E8/E8M definedthis term as “reduced section.”3.1.8 reduction of area, nthe difference between theoriginal cross-sectional area of a tension tes
20、t specimen and thearea of its smallest cross section.3.1.8.1 DiscussionThe reduction of area is usually ex-pressed as a percentage of the original cross-sectional area ofthe specimen.3.1.8.2 DiscussionThe smallest cross section may be mea-sured at or after fracture as specified for the material unde
21、r test.3.1.8.3 DiscussionThe term reduction of area when ap-plied to metals generally means measurement after fracture;when applied to plastics and elastomers, measurement atfracture. Such interpretation is usually applicable to values forreduction of area reported in the literature when no furtherq
22、ualification is given. (E28.04)3.1.9 tensile strength, SuFL2,nthe maximum tensilestress that a material is capable of sustaining.3.1.9.1 DiscussionTensile strength is calculated from themaximum force during a tension test carried to rupture and theoriginal cross-sectional area of the specimen.3.1.10
23、 uniform elongation, Elu, %the elongation deter-mined at the maximum force sustained by the test piece justprior to necking or fracture, or both.3.1.10.1 DiscussionUniform elongation includes bothelastic and plastic elongation.3.1.11 upper yield strength, UYS FL-2in a uniaxial test,the first stress
24、maximum (stress at first zero slope) associatedwith discontinuous yielding at or near the onset of plasticdeformation.3.1.12 yield point elongation, YPE, nin a uniaxial test, thestrain (expressed in percent) separating the stress-strain curvesfirst point of zero slope from the point of transition fr
25、omdiscontinuous yielding to uniform strain hardening.3.1.12.1 Discussion If the transition occurs over a rangeof strain, the YPE end point is the intersection between (a) ahorizontal line drawn tangent to the curve at the last zero slopeand (b) a line drawn tangent to the strain hardening portion of
26、the stress-strain curve at the point of inflection. If there is nopoint at or near the onset of yielding at which the slope reacheszero, the material has 0 % YPE.3.1.13 yield strength, YS or SyFL2,nthe engineeringstress at which, by convention, it is considered that plasticelongation of the material
27、 has commenced.3.1.13.1 DiscussionThis stress may be specified in termsof (a) a specified deviation from a linear stress-strainrelationship, (b) a specified total extension attained, or (c)maximum or minimum engineering stresses measured duringdiscontinuous yielding.3.2 Definitions of Terms Specific
28、 to This Standard:3.2.1 referee test, ntest made to settle a disagreement as tothe conformance to specified requirements, or conducted by athird party to arbitrate between conflicting results. D1566,D11.084. Significance and Use4.1 Tension tests provide information on the strength andductility of ma
29、terials 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 tostandardized dimensions from selected portions of a part ormaterial
30、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 shipments. The test methodshave been used extensively in the trade for
31、 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 application range of the testingmachine as defined in Practices E4. Wh
32、ere verification of thetesting machine speed is required, Practices E2658 shall beused unless otherwise specified.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
33、 stresswithin the gauge length, the axis of the test 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).E8/E8M
34、16a2NOTE 1The effect of this eccentric force application may be 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
35、 percentage points/ 0.025 mm 0.001 in. fora9mm0.350-in. diameter 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 E1012.5.2.2 Wedge GripsTesting machines usually are equippedwith wedge grips. These wedge gri
36、ps generally furnish asatisfactory means of gripping long specimens 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 li
37、ners are used behind thewedges, they must be of the same thickness 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 o
38、f specimen thickness. For propergripping, it is desirable that 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 u
39、se machined test specimens and to usea special means of gripping 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 dia
40、gram of a gripping devicefor threaded-end specimens is shown in 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 betw
41、een spherical bearingsshould be as great as feasible.5.2.4 Grips 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 snubbi
42、ngtypes as shown in Fig. 5 and Fig. 6 or flat wedge grips may beused.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 Ex
43、tensometersExtensometers used in tension testingshall conform to the 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
44、 (if determined).5.4.1 Extensometers with gauge lengths equal to or shorterthan the nominal gauge length of the specimen (dimensionshown as “G-Gauge Length” in the accompanying figures) maybe used to determine the yield behavior. For specimens withouta reduced section (for example, full cross sectio
45、nal areaspecimens of wire, rod, or bar), the extensometer gauge lengthfor the determination of yield behavior shall not exceed 80 %of the distance between grips. For measuring elongation atfracture with an appropriate extensometer, the gauge length ofthe extensometer shall be equal to the nominal ga
46、uge lengthrequired for the specimen being tested.6. Test Specimens6.1 General:6.1.1 Specimen SizeTest specimens shall be either sub-stantially full size or machined, as prescribed in the productspecifications for the material being tested.6.1.2 LocationUnless otherwise specified, the axis of thetest
47、 specimen shall be located within the parent material asfollows:6.1.2.1 At the center for products 40 mm 1.500 in. or lessin thickness, diameter, or distance between flats.6.1.2.2 Midway from the center to the surface for productsover 40 mm 1.500 in. in thickness, diameter, or distancebetween flats.
48、6.1.3 Specimen MachiningImproperly prepared test speci-mens often are the reason for unsatisfactory and incorrect testresults. It is important, therefore, that care be exercised in thepreparation of specimens, particularly in the machining, tomaximize precision and minimize bias in test results.6.1.
49、3.1 The reduced section including the fillets of preparedspecimens should be free of cold work, notches, chatter marks,grooves, gouges, burrs, rough surfaces or edges, overheating,or any other condition which can deleteriously affect theproperties to be measured.NOTE 3Punching or blanking of the reduced section may producesignificant cold work or shear burrs, or both, along the edges which shouldbe removed by machining.6.1.3.2 Within the reduced parallel section of rectangularspecimens, edges or corners should not
