1、Designation:E8/E8M09 Designation: E8/E8M 11American 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 immediat
2、ely following 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 be
3、en approved for use by agencies of the 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 reducti
4、on of area.1.2 The gage lengths for most round specimens are required to be 4D for E8 and 5D for E8M. The gage 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 agreem
5、ent 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 independent
7、ly 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 he
8、alth 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
9、 of 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 Meth
10、ods 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 Stu
11、dy to Determine the Precision of a Test MethodE1012 Practice for Verification of Test Frame and SpecimenAlignment Under Tensile and CompressiveAxial ForceApplicationE1856 Guide for Evaluating Computerized Data Acquisition Systems Used to Acquire Data from Universal Testing Machines3. Terminology3.1
12、Definitions:3.1.1TheThe definitions of terms relating to tension testing appearing in Terminology E6 shall be considered as applying to theterms used in these test methods of tension testing. Additional terms being defined are as follows:3.1.23.1.1 discontinuous yieldingin a uniaxial test, a hesitat
13、ion or fluctuation of force observed at the onset of plastic1These 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 Dec. 1, 2009.2011. Published December 2009.Febru
14、ary 2012. Originally approved in 1924. Last previous edition approved 20082009 asE8/E8M 089. DOI: 10.1520/E0008_E0008M-0911.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information,
15、refer to the standards Document Summary page on the ASTM website.1This 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 al
16、l changes 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 standard.Copyright ASTM International,
17、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.deformation, due to localized yielding. (The stress-strain curve need not appear to be discontinuous.)3.1.33.1.2 elongation at fracturethe elongation measured just prior to the sudden decrease in force associated wit
18、h fracture.For many materials not exhibiting a sudden decrease in force, the elongation at fracture can be taken as the strain measured justprior to when the force falls below 10 % of the maximum force encountered during the test.3.1.43.1.3 lower yield strength, LYS FL-2in a uniaxial test, the minim
19、um stress recorded during discontinuous yielding, ignoringtransient effects.3.1.53.1.4 uniform elongation, Elu, %the elongation determined at the maximum force sustained by the test piece just prior tonecking or fracture, or both.3.1.5.13.1.4.1 DiscussionUniform elongation includes both elastic and
20、plastic elongation.3.1.63.1.5 upper yield strength, UYS 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.3.1.73.1.6 yield point elongation, YPEin a uniaxial test, the strain (expressed in p
21、ercent) separating the stress-strain curves firstpoint of zero slope from the point of transition from discontinuous yielding to uniform strain hardening. If the transition occursover a range of strain, the YPE end point is the intersection between (a) a horizontal line drawn tangent to the curve at
22、 the lastzero slope and (b) a line drawn tangent to the strain hardening portion of the stress-strain curve at the point of inflection. If thereis no point at or near the onset of yielding at which the slope reaches zero, the material has 0 % YPE.4. Significance and Use4.1 Tension tests provide info
23、rmation 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 standardized dimensions
24、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 shipments. The test method
25、s 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 application range of the
26、 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 gage length, the axis of the test specimen should c
27、oincide 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 may be illustrated by
28、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. fora9mm0.350-in. diameter specimen and t
29、o 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 long specimens of ductile
30、 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 the same thickness and thei
31、r 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 desirable that the entir
32、elength 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 special means of gripping to en
33、sure 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 specimens is shown in Fig.
34、 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 as feasible.E8/E8M 112Dim
35、ensionsStandard Specimens Subsize SpecimenPlate-Type, 40 mm1.500 in. WideSheet-Type, 12.5 mm0.500 in. Wide6mm0.250 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, -0.2
36、5012.5 6 0.20.500 6 0.0106.0 6 0.10.250 6 0.005TThickness (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
37、) 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 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 ni
38、ne 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 2When 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 th
39、ose of the plate-type specimen.NOTE 3For the three 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 eac
40、h end shall not be more than1 % larger than the 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, unles
41、s stated specifically, the requirements for elongation 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 spec
42、imens 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 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 u
43、nder 690 MPa 100 000 psi in tensile strength when a profile cutter is used to machine the reduced section.NOTE 7The 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
44、in obtaining axial force application during testing of 6-mm 0.250-in. wide specimens, the overall length should be 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 th
45、e grips a distance equalto two thirds or more of the length of the grips. If the thickness of 12.5 mm 0.500-in. wide 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 si
46、zes of specimens, the ends of the specimen shall be symmetrical in width with the center line of the reduced section within2.5, 0 1.25 and 0.13 mm 0.10, 0.015 and 0.005 in., respectively. However, for referee testing and when required by product specifications, the ends ofthe 12.5 mm 0.500 in. wide
47、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 shall be located across from each other (on a line perpe
48、ndicular to the centerline) within a tolerance of 0.2.5 mm 0.010 in.NOTE 12Specimens with sides parallel throughout their length are permitted, except for referee testing, provided: (a) the above tolerances are used;(b) an adequate number of marks are provided for determination of elongation; and (c
49、) when yield strength is determined, a suitable extensometer is used.If the fracture occurs at a distance of less than 2 W from the edge of the gripping device, the tensile properties determined may not be representative ofthe material. In acceptance testing, if the properties meet the minimum requirements specified, no further testing is required, but if they are less than theminimum requirements, discard the test and retest
