ASTM E517-2000(2006)e1 Standard Test Method for Plastic Strain Ratio r for Sheet Metal《金属薄板塑性应变率γ的标准试验方法》.pdf

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1、Designation: E 517 00 (Reapproved 2006)e1Standard Test Method forPlastic Strain Ratio r for Sheet Metal1This standard is issued under the fixed designation E 517; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev

2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEFigure 1 was editorially corrected in August 2007.1. Scope1.1 This test method covers special tension testing for themeasurement of

3、 the plastic strain ratio, r, of sheet metalintended for deep-drawing applications.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.

4、3 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 determine the applica-bility of regulatory limitations prior to use.2. Referenced Doc

5、uments2.1 ASTM Standards:2E6 Terminology Relating to Methods of Mechanical Test-ingE8 Test Methods for Tension Testing of Metallic MaterialsE83 Practice for Verification and Classification of Exten-someter SystemsE92 Test Method for Vickers Hardness of Metallic Mate-rialsE 177 Practice for Use of th

6、e Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 delta r (D r)measure of the tendency of sheet todraw in nonuniformly and to form ears

7、in the flange ofdeep-drawn cylindrical parts in the directions of higher r value(see 10.4).3.1.1.1 DiscussionIn cold-reduced and annealed low-carbon steel sheet, r0and r90are usually greater than r45, whilein hot-rolled steels r45may be greater. Other earing tendenciesoccur; thus, for some materials

8、 the earing tendency may bebetter represented by rmax rmin.3.1.2 plastic-strain ratio r (in sheet metal that has beenstrained by uniaxial tension sufficiently to induce plastic flow)is the ratio of the true strain that has occurred in a widthdirection w perpendicular to the direction of applied stre

9、ss andin the plane of the sheet, to the concomitant true strain in thethickness direction t. Thus, r is numerically equal tor 5ew/et(1)where:ew= width strain, andet= thickness strain.3.1.2.1 DiscussionDue to difficulty in measuring thick-ness changes with sufficient precision, in practice an equival

10、entrelationship is commonly used, based on length and widthstrain measurements (see 9.1.2).3.1.3 rmweighted average of r values obtained in threedirections: 0 (parallel), 45 (diagonal), and 90 (transverse) tothe rolling direction (see 10.3).3.1.3.1 DiscussionSome materials may show significantlydiff

11、erent values of r for other test directions, in which case anaverage value may include these when special note is made andanother subscript is used to avoid confusion with rmas definedin 3.1.3. Symbols which are often used interchangeably with rmare r and r-Bar.3.1.4 yield point elongation (for a ma

12、terial that has a yieldpoint) is the total strain associated with discontinuous yielding.3.2 The definitions relating to tension testing appearing inTerminology E6shall apply to this test method.4. Significance and Use4.1 The plastic strain ratio r is a parameter that indicates theability of a sheet

13、 metal to resist thinning or thickening whensubjected to either tensile or compressive 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 thicken-ing con-t

14、ributes to the forming of shapes, such as cylindrical flat-bottom cups, by the deep-drawing process. The r value,1This test method is under the jurisdiction of ASTM Committee E28 onMechanical Testing and is the direct responsibility of Subcommittee E28.02 onDuctility and Flexure Testing.Current edit

15、ion approved Sept. 1, 2006. Published September 2006. Originallyapproved in 1981. Last previous edition approved in 2000 as E 517 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume infor

16、mation, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.therefore, is considered a measure of sheet metal drawability. Itis particularly useful for evaluating materials

17、intended for partswhere a substantial portion of the blank must be drawn frombeneath the blank holder into the die opening.4.2 For many materials this ratio remains essentially con-stant over a range of plastic strains up to maximum appliedforce in a tension test. For materials that give different r

18、 valuesat various strain levels, a superscript is used to designate thepercent strain at which the r value was measured. For example,if a 20 % elongation is used, the report would show r20.4.3 Materials usually have different r values when tested indifferent orientations relative to the rolling dire

19、ction. The angleof sampling of the individual test coupon is noted by asubscript. Thus, for a test specimen whose length is alignedparallel to the rolling direction, the r value would be reportedas r0. If, in addition, the measurement was made at 20 %elongation and it was deemed necessary to note th

20、e percentstrain at which the value was measured, the value would bereported as r020.4.4 A material that has a yield point followed by discon-tinuous yielding stretches unevenly while this yielding istaking place. In steels, this is associated with the propagation ofLders bands on the surface. The ac

21、curacy and reproducibilityof the determination of r will be reduced unless the test iscontinued beyond this yield-point elongation. Similarly, thediscontinuous yielding associated with large grain size in amaterial decreases the accuracy and reproducibility of deter-minations of r made at low strain

22、s.5. Interferences5.1 Many factors may affect the measurements taken fordetermining r value. In particular, errors in the measurement ofthe change in width can cause the reported r value to beinvalid. The following phenomena are known to cause severeerrors in the measurement of the change in width t

23、hus affectingthe r value reported.5.1.1 CanoeingCanoeing is a phenomenon which occursin some materials when they are stretched. In these materials,the test specimen bows about its longitudinal axis taking on ashape resembling the bottom of a canoe. In this case, unless themeasurements of the change

24、in width are compensated for,there will be significant errors in the r value calculated.5.1.2 Sharp Knife EdgesKnife edges, used to measure thechange in width automatically, while the specimen is stretched,may cause localized deformation of the specimen under theknife edges. This problem is intensif

25、ied by the knife edgesbeing sharp and attached to 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 r valuesmay be calculated.6. Apparatus6.1 Mea

26、suring Devices:6.1.1 Instruments for measuring length 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

27、-eter shall conform to Practice E83as Class C or better. Theextensometers shall be verified over a range appropriate for thestrains used to determine r value.6.2 Testing MachineThe testing machine used to strainthe specimen shall be capable of uniaxially straining thespecimen in accordance with the

28、requirements in 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 thick

29、nessunless otherwise 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

30、gauge mark and a 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 averager value of these reported for each test direction. If necessary, athird determination may be made, rejecting the

31、 extreme.7.2 TypeAny of three types of specimen may be used.Other types including subsize specimens are acceptable pro-vided they 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, thereduced sect

32、ion shall be parallel-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

33、Fig. 3.7.2.3.1 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.8. Specimen Preparation8.1 Specimen blanks shall be sh

34、eared 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

35、of 7.1.2 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 centerlin

36、e of thespecimen 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.E 517 00 (2006)e128.4.2 The gauge lengths shall be in compliance with 7.1.3.8.4.3 For Specimen A, the gauge length shall be centered inthe re

37、duced section.8.4.4 For Specimen C, a double set of gauge marks shall beused in compliance with 7.2.3.1.9. Procedure9.1 If the tensile properties of the material are unknown,either make an autographic force/extension record or run aseparate tension test to determine the yielding characteristicsand t

38、he elongation in accordance with Test Methods E8, usingthe specimen shown in Fig. 6 of Test Methods E8. This willestablish strain limits within which the r determination may bemade.9.1.1 The plastic strain ratio r may be determined fromwidth and thickness changes resulting from plastic deformationpr

39、ovided these changes can be measured with sufficient accu-racy in a tension test.9.1.2 For most thin sheet metals, however, it is preferable tomeasure length and width changes and, assuming constantvolume, calculate r by one of the following procedures:9.2 Manual Procedure:DimensionsSpecimen AStanda

40、rd Alternativein. mm in. mmG Gage length 2.00 6 0.01 506 0.25 1.00 6 0.005 25 6 0.13W Width (Note 2 and Note 3) 0.500 6 0.01 12.5 6 0.25 0.500 6 0.01 12.5 6 0.25T Thickness thickness of material thickness of materialR Radius of fillet, min12 1312 13L Overall length, min 8 200 714 180A Length of redu

41、ced 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 gage length within a tolerance of 0.0005 in. (0.012 mm).NOTE 2The ends of the reduced section shall not differ i

42、n width by more than 0.005 in. or 0.013 mm. However, the width within the gage lengthmust conform to 8.3.Editorially corrected in June 2007.FIG. 1 Rectangular Tension Test Specimens with Reduced Parallel Section, for r DeterminationDimensionsSpecimen BStandard Alternativein. mm in. mmGWgauge lengthg

43、auge width2.00 6 0.010.756 0.00550 6 0.25206 0.131.00 6 0.0050.756 0.00525 6 0.13206 0.13T Thickness thickness of materialL Overall length, min 8 200 7 175C Width of specimen (Note) 0.75 6 0.005 20 6 0.13 0.756 0.005 20 6 0.13NOTE 1Edges of Specimen B shall be machined parallel over the full length

44、within a tolerance of 0.0008 in. (0.020 mm).FIG. 2 Machined Rectangular Tension Test Specimens, Parallel Strip, for r DeterminationE 517 00 (2006)e139.2.1 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,

45、 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 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)

46、, 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 indentersmounted a known distance apart in a fixture, only final gaugelength and width measurements are needed.9.2.4 Pull the specimen axially until it

47、is stretched beyondany yield-point elongation but not exceeding the strain atmaximum applied force. Measurement accuracy is improved asthe strain is increased within the above limits, as explained inX3.3.1.NOTE 1Strains of 1520% are commonly utilized for determining ther-value of formable low carbon

48、 steel products.9.2.5 The rate of straining shall be 0.5/min or less, unlessotherwise specified.9.2.6 Measure the final width, wf, and gauge length, lf,inthe same manner and tolerance as the initial values. Make thesemeasurements with no tensile force applied to the specimen.9.3 Automatic Procedure:

49、9.3.1 Attach extensometers conforming to 6.1.2 to thespecimen to measure the longitudinal and transverse strain.Transverse extensometers must not cause and must not mea-sure additional transverse deformation due to the knife edgesdeforming the specimen during the test.9.3.2 Record the gauge length of the extensometers. In thecase of the extensometer measuring transverse strain, the gaugelength may be the width of the specimen.9.3.3 Pull the specimen axially.9.3.4 The rate of straining shall be 0.5/min or less, unlessotherwise specified.9.3.5 Determi