Designation:E8/E8M−15a American Association Statesmallint
Highway and Transportation Officials Standard
AASHTO No.:T68
An American National Standard Standard Test Methods for
Tension Testing of Metallic Materials1
This standard is issued under thefixed designation E8/E8M;the number immediately following the designation indicates the year of
original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A
superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
This standard has been approved for u by agencies of the U.S.Department of Defen.
1.Scope*
1.1The test methods cover the tension testing of metallic materials in any form at room temperature,specifically,the methods of determination of yield strength,yield point elongation,tensile strength,elongation,and reduction of area.
1.2The gauge lengths for most round specimens are re-quired to be4D for E8and5D for E8M.The gauge length is the most significant difference between E8and E8M test specimens.Test specimens made from powder metallurgy (P/M)materials are exempt from this requirement by industry-wide agreement to keep the pressing of the material to a specific projected area and density.
1.3Exceptions to the provisions of the test methods may need to be made in individual specifications or test methods for a particular material.For examples,e Test Methods and Definition
s A370and Test Methods B557,and B557M.
1.4Room temperature shall be considered to be10to38°C [50to100°F]unless otherwi specified.
1.5The values stated in SI units are to be regarded as parate from inch/pound units.The values stated in each system are not exact equivalents;therefore each system must be ud independently of the other.Combining values from the two systems may result in non-conformance with the standard.
1.6This standard does not purport to address all of the safety concerns,if any,associated with its u.It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.
2.Referenced Documents
glass wool2.1ASTM Standards:2
A356/A356M Specification for Steel Castings,Carbon,Low Alloy,and Stainless Steel,Heavy-Walled for Steam Tur-bines
A370Test Methods and Definitions for Mechanical Testing of Steel Products
出生日期英语B557Test Methods for Tension Testing Wrought and Cast Aluminum-and Magnesium-Alloy Products
B557M Test Methods for Tension Testing Wrought and Cast Aluminum-and Magnesium-Alloy Products(Metric)
E4Practices for Force Verification of Testing Machines
E6Terminology Relating to Methods of Mechanical Testing E29Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E83Practice for Verification and Classification of Exten-someter Systems
E345Test Methods of Tension Testing of Metallic Foil
E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1012Practice for Verification of Testing Frame and Speci-men Alignment Under Tensile and Compressive Axial Force Application
D1566Terminology Relating to Rubber
E1856Guide for Evaluating Computerized Data Acquisition Systems Ud to Acquire Data from Universal Testing Machines
3.Terminology
3.1Definitions of Terms Common to Mechanical Testing—3.1.1The definitions of mechanical testing terms that ap-pear in the Terminology E6apply to this test method.
1The test methods are under the jurisdiction of ASTM Committee E28on Mechanical Testing and are the direct responsibility of Subcommittee E28.04on
Uniaxial Testing.
Current edition approved May1,2015.Published June2015.Originally approved in1924.Last previous edition approved2015as E8/E8M–15.DOI: 10.1520/E0008_E0008M-15A.
2For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes ction appears at the end of this standard Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959.United States
3.1.1.1The terms include bending strain,constraint, elongation,extensometer,force,gauge length,necking,re-duced ction,stress-strain diagram,testing machine,and modulus of elasticity.
3.1.2In addition,the following common terms from Termi-nology E6are defined:
3.1.3discontinuous yielding,n—in a uniaxial test,a hesita-tion orfluctuation of force obrved at the ont of plastic deformation,due to localized yielding.
3.1.3.1Discussion—The stress-strain curve need not appear to be discontinuous.
3.1.4elongation after fracture,n—the elongation measured byfitting the two halves of the broken specimen together. 3.1.5elongation at fracture,n—the elongation measured just prior to the sudden decrea in force associated with fracture.
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january3.1.6lower yield strength,LYS[FL-2]—in a uniaxial test, the minimum stress recorded during discontinuous yielding, ignoring transient effects.
3.1.7reduction of area,n—the difference between the original cross-ctional area of a tension test specimen and the area of its smallest cross ction.
3.1.7.1Discussion—The reduction of area is usually ex-presd as a percentage of the original cross-ctional area of the specimen.
3.1.7.2Discussion—The smallest cross ction may be mea-sured at or after fracture as specified for the material under test.
3.1.7.3Discussion—The term reduction of area when ap-plied to metals generally means measurement after fracture; when applied to plastics and elastomers,measurement at fracture.Such interpretation is usually applicable to values for reduction of area reported in the literature when no further qualification is given.(E28.04) 3.1.8tensile strength,S u[FL–2],n—the maximum tensile stress that a material is capable of sustaining.
3.1.8.1Discussion—Tensile strength is calculated from the maximum force during a tension test carried to rupture and the original cross-ctional area of the specimen.
3.1.9uniform elongation,El u,[%]—the elongation deter-mined at the maximum force sustained by the test piece just prior to necking or fracture,or both.
3.1.9.1Discussion—Uniform elongation includes both elas-tic and plastic elongation.
3.1.10upper yield strength,UYS[FL-2]—in a uniaxial test, thefirst stress maximum(stress atfirst zero slope)associated with discontinuous yielding at or near the ont of plastic deformation.
3.1.11yield point elongation,YPE,n—in a uniaxial test,the strain(expresd in percent)parating the stress-strain curve’s first point of zero slope from the point of transition from discontinuous yielding to uniform strain hardening.
3.1.11.1Discussion—If the transition occurs over a range of strain,the YPE end point is the interction between(a)a horizontal line drawn tangent to the curve at the last zero slope and(b)a line drawn tangent to the strain hardening portion of the stress-strain curve at the point of inflection.If there is no point at or near the ont of yielding at which the slope reaches zero,the material has0%YPE.
3.1.12yield strength,YS or S y[FL–2],n—the engineering stress at which,by convention,it is considered that plastic elongation of the material has commenced.
3.1.12.1Discussion—This stress may be specified in terms of(a)a specified deviation from a linear str
ess-strain relationship,(b)a specified total extension attained,or(c) maximum or minimum engineering stress measured during discontinuous yielding.
3.2Definitions of Terms Specific to This Standard:
3.2.1referee test,n—test made to ttle a disagreement as to the conformance to specified requirements,or conducted by a third party to arbitrate between conflicting results.D1566,
D11.08
4.Significance and U
4.1Tension tests provide information on the strength and ductility of materials under uniaxial tensile stress.This information may be uful in comparisons of materials,alloy development,quality control,and design under certain circum-stances.
4.2The results of tension tests of specimens machined to standardized dimensions from lected portions of a part or material may not totally reprent the strength and ductility properties of the entire end product or its in-rvice behavior in different environments.
4.3The test methods are considered satisfactory for ac-ceptance testing of commercial shipments.The test methods have been ud extensively in the trade for this purpo.
5.Apparatus
5.1Testing Machines—Machines ud for tension testing shall conform to the requirements of Practices E4.The forces ud in determining tensile strength and yield strength shall be within the verified force application range of the testing machine as defined in Practices E4.
5.2Gripping Devices:
三位外交官被驱逐5.2.1General—Various types of gripping devices may be ud to transmit the measured force applied by the testing machine to the test specimens.To ensure axial tensile stress within the gauge length,the axis of the test specimen should coincide with the center line of the heads of the testing machine.Any departure from this requirement may introduce bending stress that are not included in the usual stress computation(force divided by cross-ctional area).
N OTE1—The effect of this eccentric force application may be illus-trated by calculating the bending moment and stress thus added.For a standard12.5-mm[0.500-in.]diameter specimen,the stress incre
a is1.5 percentage points for each0.025mm[0.001in.]of eccentricity.This error increas to2.5percentage points/0.025mm[0.001in.]for a9mm [0.350-in.]diameter specimen and to3.2percentage points/0.025mm [0.001in.]for a6-mm[0.250-in.]diameter specimen.
N OTE2—Alignment methods are given in Practice E1012.
5.2.2Wedge Grips—Testing machines usually are equipped with wedge grips.The wedge grips generally furnish a satisfactory means of gripping long specimens of ductile
metal
andflat plate test specimens such as tho 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 may be introduced.When liners are ud behind the wedges,they must be of the same thickness and their faces must beflat and parallel.For best results,the wedges should be supported over their entire lengths by the heads of the testing machine.This requires that liners of veral thickness be availa
ble to cover the range of specimen thickness.For proper gripping,it is desirable that the entire length of the rrated face of each wedge be in contact with the specimen.Proper alignment of wedge grips and liners is illustrated in Fig.2.For short specimens and for specimens of many materials it is generally necessary to u machined test specimens and to u a special means of gripping to ensure that the specimens,when under load,shall be as nearly as possible in uniformly distributed pure axial tension(e5.2.3,5.2.4,and5.2.5). 5.2.3Grips for Threaded and Shouldered Specimens and Brittle Materials—A schematic diagram of a gripping device for threaded-end specimens is shown in Fig.3,while Fig.4 shows a device for gripping specimens with shouldered ends. Both of the gripping devices should be attached to the heads of the testing machine through properly lubricated spherical-ated bearings.The distance between spherical bearings should be as great as feasible.
5.2.4Grips for Sheet Materials—The lf-adjusting grips shown in Fig.5have proven satisfactory for testing sheet materials that cannot be tested satisfactorily in the usual type of wedge grips.
5.2.5Grips for Wire—Grips of either the wedge or snubbing types as shown in Fig.5and Fig.6orflat wedge grips may be ud.
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5.3Dimension-Measuring Devices—Micrometers and other devices ud for measuring linear dimensions shall be accurate and preci to at least one half the smallest unit to which the individual dimension is required to be measured.
5.4Extensometers—Extensometers ud in tension testing shall conform to the requirements of Practice E83for the classifications specified by the procedure ction of this test method.Extensometers shall be ud and verified to include the strains corresponding to the yield strength and elongation at fracture(if determined).
5.4.1Extensometers with gauge lengths equal to or shorter than the nominal gauge length of the specimen(dimension shown as“G-Gauge Length”in the accompanyingfigures)may be ud to determine the yield behavior.For specimens without a reduced ction(for example,full cross ctional area specimens of wire,rod,or bar),the extensometer gauge length for the determination of yield behavior shall not exceed80% of the distance between grips.For measuring elongation at fracture with an appropriate extensometer,the gauge length of the extensometer shall be equal to the nominal gauge length required for the specimen being tested.
6.Test Specimens
6.1General:
6.1.1Specimen Size—Test specimens shall be either sub-stantially full size or machined,as prescribed in the product specifications for the material being tested.
6.1.2Location—Unless otherwi specified,the axis of the test specimen shall be located within the parent material as follows:
6.1.2.1At the center for products40mm[1.500in.]or less in thickness,diameter,or distance betweenflats.
6.1.2.2Midway from the center to the surface for products over40mm[1.500in.]in thickness,diameter,or distance betweenflats.
6.1.3Specimen Machining—Improperly prepared test speci-mens often are the reason for unsatisfactory and incorrect test results.It is important,therefore,that care be exercid in the preparation of specimens,particularly in the machining,to maximize precision and minimize bias in test results.
6.1.3.1The reduced ctions of prepared specimens should be free of cold work,notches,chatter mar
ks,grooves,gouges, burrs,rough surfaces or edges,overheating,or any other condition which can deleteriously affect the properties to be measured.
N OTE3—Punching or blanking of the reduced ction may produce significant cold work or shear burrs,or both,along the edges which should be removed by machining.
6.1.3.2Within the reduced ction of rectangular specimens,edges or corners should not be ground or abraded in a manner which could cau the actual cross-ctional area of the specimen to be significantly different from the calculated area.
6.1.3.3For brittle materials,large radiusfillets at the ends of the gauge length should be ud.
6.1.3.4The cross-ctional area of the specimen should be smallest at the center of the reduced ction to ensure fracture within the gauge length.For this reason,a small taper is permitted in the reduced ction of each of the specimens described in the following ctions.
6.1.4Specimen Surface Finish—When materials are tested with surface conditions other than as manufactured,the surface finish of the test specimens should be as provided in the applicable product specifications.
N OTE4—Particular attention should be given to the uniformity and quality of surfacefinish of specimens for high strength and very low ductility materials since this has been shown to be a factor in the variability of test results.
6.2Plate-Type Specimens—The standard plate-type test specimen is shown in Fig.1.This specimen is ud for testing metallic materials in the form of plate,shapes,andflat material having a nominal thickness of5mm[0.188in.]or over.When product specifications so permit,other types of specimens may be ud,as provided in6.3,6.4,and6.5.
6.3Sheet-Type Specimens:
6.3.1The standard sheet-type test specimen is shown in Fig.
1.This specimen is ud for testing metallic materials in the form of sheet,plate,flat wire,strip,band,hoop,rectangles,and shapes ranging in nominal thickness from0.13to19mm [0.005to0.750in.].When product specifications so permit, other types of specimens may be ud,as provided in6.2,6.4, and6.5
.
Dimensions
Standard Specimens Subsize Specimen
Plate-Type,40mm [1.500in.]Wide Sheet-Type,12.5mm
[0.500in.]Wide
6mm
[0.250in.]Wide
mm[in.]mm[in.]mm[in.]
G—Gauge length(Note1and Note2)200.0±0.2
[8.00±0.01]
50.0±0.1
[2.000±0.005]
25.0±0.1
[1.000±0.003]
W—Width(Note3and Note4)40.0±2.0
[1.500±0.125,-0.250]
12.5±0.2
[0.500±0.010]
6.0±0.1
[0.250±0.005]
mojito是什么T—Thickness(Note5)thickness of material
R—Radius offillet,min(Note6)25[1]12.5[0.500]6[0.250] L—Overall length,min(Note2,Note7,and Note8)450[18]200[8]100[4] A—Length of reduced ction,min225[9]57[2.25]32[1.25] B—Length of grip ction,min(Note9)75[3]50[2]30[1.25] C—Width of grip ction,approximate(Note4and Note9)50[2]20[0.750]10[0.375] N OTE1—For the40mm[1.500in.]wide specimen,punch marks for measuring elongation after fracture shall be made on theflat or on the edge of the specimen and within the reduced ction.Either a t of nine or more punch marks25mm[1in.]apart,or one or more pairs of punch marks200 mm[8in.]apart may be ud.
N OTE2—When elongation measurements of40mm[1.500in.]wide specimens are not required,a minimum length of reduced ction(A)of75mm [2.25in.]may be ud with all other dimensions similar to tho of the plate-type specimen.
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N OTE3—For the three sizes of specimens,the ends of the reduced ction shall not differ in width by more than0.10,0.05or0.02mm[0.004,0.002 or0.001in.],respectively.Also,there may be a gradual decrea in width from the ends to the center,but the width at each end shall not be more than 1%larger than the width at the center.
N OTE4—For each of the three sizes of specimens,narrower widths(W and C)may be ud when necessary.In such cas the width of the reduced ction should be as large as the width of the material being tested permits;however,unless stated specifically,the requirements for elongation in a product specification shall not apply when the narrower specimens are ud.
N OTE5—The dimension T is the thickness of the test specimen as provided for in the applicable material specifications.Minimum thickness of40mm [1.500in.]wide specimens shall be5mm[0.188in.].Maximum thickness of12.5and6mm[0.500and0.250in.]wide specimens shall be19and6 mm[0.750and0.250in.],respectively.
N OTE6—For the40mm[1.500in.]wide specimen,a13mm[0.500in.]minimum radius at the ends of the reduced ction is permitted for steel specimens under690MPa[100000psi]in tensile strength when a profile cutter is ud to machine the reduced ction.
N OTE7—The dimension shown is suggested as a minimum.In determining the minimum length,the grips must not extend in to the transition ction between Dimensions A and B,e Note9.
N OTE8—To aid in obtaining axial force application during testing of6-mm[0.250-in.]wide specimens,the overall length should be as large as the material will permit,up to200mm[8.00in.].
N OTE9—It is desirable,if possible,to make the length of the grip ction large enough to allow the specimen to extend into the grips a distance equal to two thirds or more of the length of the grips.If the thickness of12.5mm[0.500-in.]wide specimens is over10mm[0.375in.],longer grips and correspondingly longer grip ctions of the specimen may be necessary to prevent failure in the grip ction.
N OTE10—For the three sizes of specimens,the ends of the specimen shall be symmetrical in width with the center line of the reduced ction within 2.5,1.25and0.13mm[0.10,0.05and0.005in.],respectively.However,for referee testing and when required by product specifications,the ends of the 12.5mm[0.500in.]wide specimen shall be symmetrical within0.2mm[0.01in.].
N OTE11—For each specimen type,the radii of allfillets shall be equal to each other within a toleranc
e of1.25mm[0.05in.],and the centers of curvature of the twofillets at a particular end shall be located across from each other(on a line perpendicular to the centerline)within a tolerance of2.5 mm[0.10in.].
N OTE12—Specimens with sides parallel throughout their length are permitted,except for referee testing,provided:(a)the above tolerances are ud;
(b)an adequate number of marks are provided for determination of elongation;and(c)when yield strength is determined,a suitable extensometer is ud. If the fracture occurs at a distance of less than2W from the edge of the gripping device,the tensile properties determined may not be reprentative of the material.In acceptance testing,if the properties meet the minimum requirements specified,no further testing is required,but if they are less than the minimum requirements,discard the test and retest.
FIG.1Rectangular Tension Test Specimens
N OTE 5—Test Methods E345may be ud for tension testing of materials in thickness up to 0.15mm [0.0059in.].
6.3.2Pin ends as shown in Fig.7may be ud.In order to avoid buckling in tests of thin and high-stren
gth materials,it may be necessary to u stiffening plates at the grip ends.6.4Round Specimens:
6.4.1The standard 12.5-mm [0.500-in.]diameter round test specimen shown in Fig.8is ud quite generally for testing metallic materials,both cast and wrought.
6.4.2Fig.8also shows small-size specimens proportional to the standard specimen.The may be ud when it is necessary to test material from which the standard specimen or specimens shown in Fig.1cannot be prepared.Other sizes of small round
specimens may be ud.In any such small-size specimen it is important that the gauge length for measurement of
elongation
FIG.2Wedge Grips with Liners for Flat
Specimens
FIG.3Gripping Device for Threaded-End
Specimens
FIG.4Gripping Device for Shouldered-End
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Specimens
FIG.5Gripping Devices for Sheet and Wire
Specimens
