ASTM E517-00(2006)e1
(Test Method)Standard Test Method for Plastic Strain Ratio r for Sheet Metal
Standard Test Method for Plastic Strain Ratio r for Sheet Metal
SCOPE
1.1 This test method covers special tension testing for the measurement of the plastic strain ratio, r, of sheet metal intended for deep-drawing applications.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:E517–00 (Reapproved 2006)
Standard Test Method for
Plastic Strain Ratio r for Sheet Metal
This standard is issued under the fixed designation E517; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Figure 1 was editorially corrected in August 2007.
1. Scope 3.1.1 delta r (D r)—measure of the tendency of sheet to
draw in nonuniformly and to form ears in the flange of
1.1 This test method covers special tension testing for the
deep-drawn cylindrical parts in the directions of higher r value
measurement of the plastic strain ratio, r, of sheet metal
(see 10.4).
intended for deep-drawing applications.
3.1.1.1 Discussion—In cold-reduced and annealed low-
1.2 The values stated in inch-pound units are to be regarded
carbonsteelsheet, r and r areusuallygreaterthan r ,while
as standard. The values given in parentheses are mathematical 0 90 45
in hot-rolled steels r may be greater. Other earing tendencies
conversions to SI units that are provided for information only
occur; thus, for some materials the earing tendency may be
and are not considered standard.
better represented by r − r .
max min
1.3 This standard does not purport to address all of the
3.1.2 plastic-strain ratio r (in sheet metal that has been
safety concerns, if any, associated with its use. It is the
strained by uniaxial tension sufficiently to induce plastic flow)
responsibility of the user of this standard to establish appro-
is the ratio of the true strain that has occurred in a width
priate safety and health practices and determine the applica-
direction w perpendicular to the direction of applied stress and
bility of regulatory limitations prior to use.
in the plane of the sheet, to the concomitant true strain in the
2. Referenced Documents
thickness direction t. Thus, r is numerically equal to
2.1 ASTM Standards: r 5´ /´ (1)
w t
E6 TerminologyRelatingtoMethodsofMechanicalTesting
where:
E8 Test Methods for Tension Testing of Metallic Materials
´ = width strain, and
w
E83 Practice for Verification and Classification of Exten-
´ = thickness strain.
t
someter Systems
3.1.2.1 Discussion—Due to difficulty in measuring thick-
E92 Test Method for Vickers Hardness of Metallic Materi-
nesschangeswithsufficientprecision,inpracticeanequivalent
als
relationship is commonly used, based on length and width
E177 Practice for Use of the Terms Precision and Bias in
strain measurements (see 9.1.2).
ASTM Test Methods
3.1.3 r —weighted average of r values obtained in three
m
E691 Practice for Conducting an Interlaboratory Study to
directions:0°(parallel),45°(diagonal),and90°(transverse)to
Determine the Precision of a Test Method
the rolling direction (see 10.3).
3.1.3.1 Discussion—Somematerialsmayshowsignificantly
3. Terminology
different values of r for other test directions, in which case an
3.1 Definitions of Terms Specific to This Standard:
averagevaluemayincludethesewhenspecialnoteismadeand
another subscript is used to avoid confusion with r as defined
m
This test method is under the jurisdiction of ASTM Committee E28 on
in3.1.3.Symbolswhichareoftenusedinterchangeablywithr
m
Mechanical Testing and is the direct responsibility of Subcommittee E28.02 on
are r¯ and r-Bar.
Ductility and Flexure Testing.
3.1.4 yield point elongation (for a material that has a yield
Current edition approved Sept. 1, 2006. Published September 2006. Originally
approved in 1981. Last previous edition approved in 2000 as E517–00. DOI: point)isthetotalstrainassociatedwithdiscontinuousyielding.
10.1520/E0517-00R06E01.
3.2 The definitions relating to tension testing appearing in
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Terminology E6 shall apply to this test method.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E517–00 (2006)
4. Significance and Use stress being applied to stretch the specimen, which causes
localized deformation. As a result, excessively high r values
4.1 Theplasticstrainratio risaparameterthatindicatesthe
may be calculated.
ability of a sheet metal to resist thinning or thickening when
subjectedtoeithertensileorcompressiveforcesintheplaneof
6. Apparatus
the sheet. It is a measure of plastic anisotropy and is related to
6.1 Measuring Devices:
the preferred crystallographic orientations within a polycrys-
6.1.1 Instruments for measuring length and width shall be
talline metal. This resistance to thinning or thicken-ing con-
tributes to the forming of shapes, such as cylindrical flat- checkedforaccuracyandbegraduatedtopermitmeasurements
to be made to 60.001 in. (6 0.02 mm) or better.
bottom cups, by the deep-drawing process. The r value,
therefore,isconsideredameasureofsheetmetaldrawability.It 6.1.2 If the longitudinal strain or the transverse strain, or
isparticularlyusefulforevaluatingmaterialsintendedforparts both, are to be obtained using an extensometer, the extensom-
where a substantial portion of the blank must be drawn from eter shall conform to Practice E83 as Class C or better. The
beneath the blank holder into the die opening. extensometersshallbeverifiedoverarangeappropriateforthe
strains used to determine r value.
4.2 For many materials this ratio remains essentially con-
6.2 Testing Machine—The testing machine used to strain
stant over a range of plastic strains up to maximum applied
the specimen shall be capable of uniaxially straining the
forceinatensiontest.Formaterialsthatgivedifferent rvalues
specimeninaccordancewiththerequirementsin9.2.5or9.3.4.
at various strain levels, a superscript is used to designate the
percentstrainatwhichthe rvaluewasmeasured.Forexample,
7. Test Specimen
if a 20% elongation is used, the report would show r .
4.3 Materials usually have different r values when tested in
7.1 Size—The length and width of the specimen are not
differentorientationsrelativetotherollingdirection.Theangle critical, provided care is used to stretch the gauge section in a
of sampling of the individual test coupon is noted by a
uniform manner, avoiding grip effects and anomalous changes
subscript. Thus, for a test specimen whose length is aligned along the gauge lengths.
parallel to the rolling direction, the r value would be reported
7.1.1 The specimen shall include the full sheet thickness
as r . If, in addition, the measurement was made at 20%
unless otherwise specified.
elongation and it was deemed necessary to note the percent
7.1.2 The thickness of the gauge section of the specimen
strain at which the value was measured, the value would be
shall be uniform within 0.0005 in. (0.013 mm) in the gauge
reported as r .
0 section. If the as-received surface is nonuniform, the surface
4.4 A material that has a yield point followed by discon- shallbepreparedbymachiningorbygrindingtothistolerance.
tinuous yielding stretches unevenly while this yielding is
7.1.3 Thedistancebetweenagaugemarkandagripshallbe
takingplace.Insteels,thisisassociatedwiththepropagationof
at least twice the width of the reduced section (or gauge width
Lüders’bandsonthesurface.Theaccuracyandreproducibility
for parallel strips) of the specimen.
of the determination of r will be reduced unless the test is
7.1.4 Duplicate specimens should be tested and the average
continued beyond this yield-point elongation. Similarly, the
r value of these reported for each test direction. If necessary, a
discontinuous yielding associated with large grain size in a
third determination may be made, rejecting the extreme.
material decreases the accuracy and reproducibility of deter-
7.2 Type—Any of three types of specimen may be used.
minations of r made at low strains.
Other types including subsize specimens are acceptable pro-
vided they give comparable values of equivalent accuracy.
5. Interferences
7.2.1 Specimen A, with reduced section, as shown in Fig.
1—While this is similar to Fig. 6 of Test Methods E8, the
5.1 Many factors may affect the measurements taken for
reduced section shall be parallel-sided rather than tapered.
determining rvalue.Inparticular,errorsinthemeasurementof
7.2.2 Specimen B, with a uniform width of 0.75 in. (20 mm),
the change in width can cause the reported r value to be
machined edges, and no reduced section, as shown in Fig. 2.
invalid. The following phenomena are known to cause severe
7.2.3 Specimen C, precision-sheared a uniform width of
errorsinthemeasurementofthechangeinwidththusaffecting
1.125 in. (28.58 mm), or with machined edges and no reduced
the r value reported.
section, as shown in Fig. 3.
5.1.1 Canoeing—Canoeing is a phenomenon which occurs
7.2.3.1 gauge lengths for Specimen C shall be marked on
in some materials when they are stretched. In these materials,
the sheet surface perpendicular to and parallel to the specimen
the test specimen bows about its longitudinal axis taking on a
edges. The gauge marks shall be made with Vickers diamond
shaperesemblingthebottomofacanoe.Inthiscase,unlessthe
indenters described in Test Method E92, or similar precise
measurements of the change in width are compensated for,
marks.
there will be significant errors in the r value calculated.
5.1.2 Sharp Knife Edges—Knife edges, used to measure the
8. Specimen Preparation
changeinwidthautomatically,whilethespecimenisstretched,
may cause localized deformation of the specimen under the 8.1 Specimen blanks shall be sheared or sawed individually
knife edges. This problem is intensified by the knife edges and with the exception of Specimen C, which may be used as
beingsharpandattachedtothespecimenwithhighforces.This sheared, shall be machined individually or in packs to remove
combination produces a compressive stress 90° to the tensile cold-worked edges.
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E517–00 (2006)
Dimensions
Specimen A
Standard Alternative
in. mm in. mm
G Gage length 2.00 6 0.01 506 0.25 1.00 6 0.005 25 6 0.13
†
W Width (Note 2 and Note 3) 0.500 6 0.01 12.5 6 0.25 0.500 6 0.01 12.5 6 0.25
T Thickness thickness of material thickness of material
1 1
R Radius of fillet, min ⁄2 13 ⁄2 13
L Overall length, min 8 200 7 ⁄4 180
A Length of reduced section, min 3 75 2 ⁄4 60
B Length of grip section, min 2 50 2 50
3 3
C Width of grip section, approximate ⁄4 20 ⁄4 20
NOTE 1—The edges of the reduced section shall be machined parallel over the gage length within a tolerance of 0.0005 in. (0.012 mm).
NOTE 2—The 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 gage length
must conform to 8.3.
†
Editorially corrected in June 2007.
FIG. 1 Rectangular Tension Test Specimens with Reduced Parallel Section, for r Determination
Dimensions
Specimen B
Standard Alternative
in. mm in. mm
G gauge length 2.00 6 0.01 50 6 0.25 1.00 6 0.005 25 6 0.13
W gauge width 0.756 0.005 206 0.13 0.756 0.005 206 0.13
T Thickness thickness of material
L Overall length, min 8 200 7 175
C Width of specimen (Note) 0.75 6 0.005 20 6 0.13 0.756 0.005 20 6 0.13
NOTE 1—Edges of Specimen B shall be machined parallel over the full length within a tolerance of 0.0008 in. (0.020 mm).
FIG. 2 Machined Rectangular Tension Test Specimens, Parallel Strip, for r Determination
8.2 The dimensions of each specimen shall be measured for 8.4 Reasonable care shall be taken to position the gauge
uniformity of thickness and width in the gauge section to meet marks symmetrically to the midpoint and centerline of the
the requirements of 7.1.2 and 8.3. specimen or reduced section.
8.3 Within the gauge length, parallelism of the edges shall 8.4.1 Gaugemarksshallbelightlyscribedorpunchedinthe
be maintained so that no two width measurements differ by surface of the specimen or made with a Vickers diamond
more than 0.1% of the measured width (Specimens A and B indenter.
only). 8.4.2 The gauge lengths shall be in compliance with 7.1.3.
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E517–00 (2006)
Dimensions
Specimen C
in. mm
G Gage Length 0.75 6 0.005 20 6 0.13
W Gage Width 0.75 6 0.005 20 6 0.13
T Thickness thickness of material
L Overall Length, min 7 175
C Width of specimen 1.125 6 0.125 28.58 6 3.17
FIG. 3 Sheared Rectangular Tension Test Specimen, Parallel
Strip, for r Determination
NOTE 1—Strainsof15–20%arecommonlyutilizedfordeterminingthe
8.4.3 For SpecimenA, the gauge length shall be centered in
r-value of formable low carbon steel products.
the reduced section.
8.4.4 For Specimen C, a double set of gauge marks shall be
9.2.5 The rate of straining shall be 0.5/min or less, unless
used in compliance with 7.2.3.1.
otherwise specified.
9.2.6 Measure the final width, w , and gauge length, l,in
f f
9. Procedure
thesamemannerandtoleranceastheinitialvalues.Makethese
9.1 If the tensile properties of the material are unknown,
measurements with no tensile force applied to the specimen.
either make an autographic force/extension record or run a
9.3 Automatic Procedure:
separate tension test to determine the yielding characteristics
9.3.1 Attach extensometers conforming to 6.1.2 to the
and the elongation in accordance with Test Methods E8, using
specimen to measure the longitudinal and transverse strain.
the specimen shown in Fig. 6 of Test Methods E8. This will
Transverse extensometers must not cause and must not mea-
establish strain limits within which the r determination may be
sure additional transverse deformation due to the knife edges
made.
deforming the specimen during the test.
9.1.1 The plastic strain ratio r may be determined from
9.3.2 Record the gauge length of the extensometers. In the
widthandthicknesschangesresultingfromplasticdeformation
caseoftheextensometermeasuringtransversestrain,thegauge
provided these changes can be measured with sufficient accu-
length may be the width of the specimen.
racy in a tension test.
9.1.2 Formostthinsheetmetals,however,itispreferableto 9.3.3 Pull the specimen axially.
measure length and width changes and, assuming constant
9.3.4 The rate of straining shall be 0.5/min or less, unless
volume, calculate r by one of the following procedures:
otherwise specified.
9.2 Manual Procedure:
9.3.5 Determine the change in width corresponding to a
9.2.1 Determine the original width of the specimen, w ,
0 change in length from the data created by the extensometers,
within 60.0005 in. (60.013 mm). If a gauge length of 0.75 in.
when the specimen is stretched beyo
...
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