ASTM E517-2018 0000 Standard Test Method for Plastic Strain Ratio r for Sheet Metal《金属板塑性应变比r的标准试验方法》.pdf

1、Designation: E517 18Standard Test Method forPlastic Strain Ratio r for Sheet Metal1This standard is issued under the fixed designation E517; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par

2、entheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers special tension testing for themeasurement of the plastic strain ratio, r, of sheet metalintended for deep-drawing applicati

3、ons.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any,

4、associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationall

5、y recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E6 Terminology

6、 Relating to Methods of Mechanical TestingE8/E8M Test Methods for Tension Testing of Metallic Ma-terialsE83 Practice for Verification and Classification of Exten-someter SystemsE92 Test Methods for Vickers Hardness and Knoop Hard-ness of Metallic MaterialsE177 Practice for Use of the Terms Precision

7、 and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Common to Mechanical Testing:3.1.1 The definitions relating to tension testing appearing inTerminology E6 shall apply to this test metho

8、d. Some of thoseimportant terms include discontinuous yielding, yield-pointelongation, and upper yield strength.3.2 Definitions of Terms Specific to This Standard:3.2.1 earing tendency delta, r or r, nmeasure of thetendency of sheet to draw in nonuniformly and to form ears inthe flange of deep-drawn

9、 cylindrical parts in the directions ofhigher values of r (see 10.4).3.2.1.1 DiscussionIn cold-reduced and annealed low-carbon steel sheet, r0and r90are usually greater than r45, whilein hot-rolled steels r45can be greater. Other earing tendenciesoccur; thus, for some materials the earing tendency c

10、an bebetter represented by rmax rmin.3.2.2 plastic strain ratio, r, nin sheet metal that has beenstrained by uniaxial tension sufficiently to induce plastic flow,the ratio of the true strain that has occurred in a width directionw perpendicular to the direction of applied stress and in theplane of t

11、he sheet, to the concomitant true strain in thethickness direction t.3.2.2.1 DiscussionThe plastic strain ratio, r, is numeri-cally equal tor 5 w/t(1)where:w= width strain, andt= thickness strain.3.2.2.2 DiscussionDue to difficulty in measuring thick-ness changes with sufficient precision, in practi

12、ce an equivalentrelationship is commonly used, based on length and widthstrain measurements (see 9.1.2).3.2.3 rmweighted average of values of r obtained in threedirections: 0 (parallel), 45 (diagonal), and 90 (transverse) tothe rolling direction (see 10.3).3.2.3.1 DiscussionSome materials may show s

13、ignificantlydifferent values of plastic strain ratio, r, for other testdirections, in which case an average value may include thesewhen special note is made and another subscript is used toavoid confusion with rmas defined in 3.2.3. Symbols that are1This test method is under the jurisdiction of ASTM

14、 Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.02 onDuctility and Formability.Current edition approved Jan. 1, 2018. Published March 2018. Originallyapproved in 1981. Last previous edition approved in 2010 as E517 00(2010)1.DOI: 10.1520/E0517-18.2For referen

15、ced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Co

16、nshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade

17、Organization Technical Barriers to Trade (TBT) Committee.1often used interchangeably with rmare r and r-Bar.4. Significance and Use4.1 The plastic strain ratio r is a parameter that indicates theability of a sheet metal to resist thinning or thickening whensubjected to either tensile or compressive

18、forces in the plane ofthe sheet. It is a measure of plastic anisotropy and is related tothe preferred crystallographic orientations within a polycrys-talline metal. This resistance to thinning or thickening contrib-utes to the forming of shapes, such as cylindrical flat-bottomcups, by the deep-drawi

19、ng process. The value of r, therefore, isconsidered a measure of sheet-metal drawability. It is particu-larly useful for evaluating materials intended for parts where asubstantial portion of the blank is drawn from beneath theblank holder into the die opening.4.2 For many materials the plastic strai

20、n ratio remainsessentially constant over a range of plastic strains up tomaximum applied force in a tension test. For materials thatgive different values of r at various strain levels, a superscriptis used to designate the percent strain at which the value of rwas measured. For example, if a 20 % el

21、ongation is used, thereport would show r20.4.3 Materials usually have different values of r when testedin different orientations relative to the rolling direction. Theangle of sampling of the individual test specimen is noted by asubscript. Thus, for a test specimen whose length is alignedparallel t

22、o the rolling direction, plastic strain ratio, r,isreported as r0. If, in addition, the measurement was made at20 % elongation and it was deemed necessary to note thepercent strain at which the value was measured, the valuewould be reported as r020.4.4 A material that has an upper yield strength (yi

23、eld point)point followed by discontinuous yielding stretches unevenlywhile this yielding is taking place. In steels, this is associatedwith the propagation of Lders bands on the surface. Theaccuracy and reproducibility of the determination of plasticstrain ratio, r, will be reduced unless the test i

24、s continuedbeyond this yield-point elongation. Similarly, the discontinu-ous yielding associated with large grain size in a materialdecreases the accuracy and reproducibility of determinations ofplastic strain ratio, r, made at low strains.5. Interferences5.1 Many factors affect the measurements tak

25、en for deter-mining the value of r. In particular, errors in the measurementof the change in width can cause the reported the value of r tobe invalid. The following phenomena are known to causesevere errors in the measurement of the change in width andaffect the value of r reported.5.1.1 CanoeingCan

26、oeing is a phenomenon that occurs insome materials when they are stretched. In these materials, thetest specimen bows about its longitudinal axis and takes on ashape resembling the bottom of a canoe. In this case, unless themeasurements of the change in width are compensated for,there will be signif

27、icant errors in the calculated value of r.5.1.2 Sharp Knife EdgesKnife edges, used to measure thechange in width automatically, while the specimen is stretched,can cause localized deformation of the specimen under theknife edges. This problem is intensified if the knife edges aresharp and attached t

28、o the specimen with high forces. Thiscombination produces a compressive stress 90 to the tensilestress being applied to stretch the specimen, which causeslocalized deformation.As a result, excessively high values of rare calculated.6. Apparatus6.1 Measuring Devices:6.1.1 Instruments for measuring le

29、ngth and width shall bechecked for accuracy and be graduated to permit measurementsto be made to 60.001 in. (6 0.02 mm) or better.6.1.2 If the longitudinal strain or the transverse strain, orboth, are to be obtained using an extensometer, the extensom-eter system shall conform to Practice E83 as Cla

30、ss C or better.The extensometer system shall be verified over a rangeappropriate for the strains used to determine the plastic strainratio, r.6.2 Testing MachineThe testing machine used to strain thespecimen shall be capable of uniaxially straining the specimenin accordance with the requirements in

31、9.2.5 or 9.3.4.7. Test Specimen7.1 SizeThe length and width of the specimen are notcritical, provided care is used to stretch the gauge section in auniform manner, avoiding grip effects and anomalous changesalong the gauge lengths.7.1.1 The specimen shall include the full sheet thicknessunless other

32、wise specified.7.1.2 The thickness of the gauge section of the specimenshall be uniform within 0.0005 in. (0.013 mm) in the gaugesection. If the as-received surface is nonuniform, the surfaceshall be prepared by machining or by grinding to this tolerance.7.1.3 The distance between a gauge mark and a

33、 grip shall beat least twice the width of the reduced section (or gauge widthfor parallel strips) of the specimen.7.1.4 Duplicate specimens should be tested and the averagevalue of r of these reported for each test direction. If necessary,a third determination may be made, rejecting the extreme.7.2

34、TypeAny of three types of specimen may be used.Other types including subsize specimens may be used providedthey give comparable values of equivalent accuracy.7.2.1 Specimen A, with reduced section, as shown in Fig.1While this is similar to Fig. 6 of Test Methods E8/E8M, thereduced section shall be p

35、arallel-sided rather than tapered.7.2.2 Specimen B, with a uniform width of 0.75 in. (20 mm),machined edges, and no reduced section, as shown in Fig. 2.7.2.3 Specimen C, precision-sheared a uniform width of1.125 in. (28.58 mm), or with machined edges and no reducedsection, as shown in Fig. 3.7.2.3.1

36、 Gauge lengths for Specimen C shall be marked onthe sheet surface perpendicular to and parallel to the specimenedges. The gauge marks shall be made with Vickers diamondindenters described in Test Method E92, or similar precisemarks.E517 1828. Specimen Preparation8.1 Specimen blanks shall be sheared

37、or sawed individuallyand with the exception of Specimen C, which may be used assheared, shall be machined individually or in packs to removecold-worked edges.8.2 The dimensions of each specimen shall be measured foruniformity of thickness and width in the gauge section to meetthe requirements of 7.1

38、.2 and 8.3.8.3 Within the gauge length, parallelism of the edges shallbe maintained so that no two width measurements differ bymore than 0.1 % of the measured width (Specimens A and Bonly).8.4 Reasonable care shall be taken to position the gaugemarks symmetrically to the midpoint and centerline of t

39、hespecimen or reduced section.8.4.1 Gauge marks shall be lightly scribed or punched in thesurface of the specimen or made with a Vickers diamondindenter.8.4.2 The gauge lengths shall comply with 7.1.3.8.4.3 For Specimen A, the gauge length shall be centered inthe reduced section.8.4.4 For Specimen C

40、, a double set of gauge marks shall beused in compliance with 7.2.3.1.DimensionsSpecimen AStandard Alternativein. mm in. mmG Gauge length 2.00 0.01 50 0.25 1.00 0.005 25 0.13W Width (Note 1 and Note 2) 0.500 0.01 12.5 0.25 0.500 0.01 12.5 0.25T Thickness thickness of material thickness of materialR

41、Radius of fillet, min12 1312 13L Overall length, min 8 200 714 180A Length of reduced section, min 3 75 214 60B Length of grip section, min 2 50 2 50C Width of grip section, approximate34 2034 20NOTE 1The edges of the reduced section shall be machined parallel over the gauge length within a toleranc

42、e of 0.0005 in. (0.012 mm).NOTE 2The ends of the reduced section shall not differ in width by more than 0.005 in. or 0.013 mm. However, the width within the gauge lengthshall conform to 8.3.FIG. 1 Rectangular Tension Test Specimens with Reduced Parallel SectionDimensionsSpecimen BStandard Alternativ

43、ein. mm in. mmGWgauge lengthgauge width2.00 0.010.75 0.005500.25200.131.00 0.0050.75 0.005250.13200.13T Thickness thickness of materialL Overall length, min 8 200 7 175C Width of specimen (Note) 0.75 0.005 20 0.13 0.75 0.005 20 0.13NOTE 1Edges of Specimen B shall be machined parallel over the full l

44、ength within a tolerance of 0.0008 in. (0.020 mm).FIG. 2 Machined Rectangular Tension Test Specimens, Parallel StripE517 1839. Procedure9.1 If the tensile properties of the material are unknown,establish strain limits for determining the plastic strain ratio.Either make an autographic force/extensio

45、n record or run aseparate tension test to determine the yielding characteristicsand the elongation in accordance with Test Methods E8/E8M,using the specimen shown in Fig. 6 of Test Methods E8/E8M.9.1.1 The plastic strain ratio, r, may be determined fromwidth and thickness changes resulting from plas

46、tic deformationprovided these changes can be measured with sufficient accu-racy in a tension test.9.1.2 For most thin sheet metals, however, the length andwidth changes should be measured and, assuming constantvolume, the value of r calculated by the Manual or AutomaticProcedure:9.2 Manual Procedure

47、:9.2.1 Determine the original width of the specimen, w0,within 60.0005 in. (60.013 mm). If a gauge length of 0.75 in.(20 mm) is used, as for Specimen C, one width measurementis sufficient. If a gauge length of 1.00 in. or (25 mm) or longeris used, make width measurements at a minimum of threeevenly

48、spaced places within the gauge length and use theaverage.9.2.2 Measure the original gauge length, l0, within 60.001in. (60.025 mm) in a 1.00-in. (25-mm), or a 0.75-in. (20-mm)gauge section, and within 60.002 in. (6 0.05 mm) in a 2.00-in.(50-mm) gauge section.9.2.3 When gauge marks are made with two

49、indentersmounted a known distance apart in a fixture, the original gaugelength measurements may be omitted.9.2.4 Pull the specimen axially until it is stretched beyondany yield-point elongation but not exceeding the strain atmaximum applied force.NOTE 1Measurement accuracy is improved as the strain is increasedwithin the above limits, as explained in X1.3.3.1. Strains of 1520% arecommonly used for determining the plastic strain ratio of formable lowcarbon steel products.9.2.5 The rate of straining shall be 0.