ASTM E517-00(2010)
(Test Method)Standard Test Method for Plastic Strain Ratio r for Sheet Metal
Standard Test Method for Plastic Strain Ratio r for Sheet Metal
SIGNIFICANCE AND USE
The plastic strain ratio r is a parameter that indicates the ability of a sheet metal to resist thinning or thickening when subjected to either tensile or compressive forces in the plane of the sheet. It is a measure of plastic anisotropy and is related to the preferred crystallographic orientations within a polycrystalline metal. This resistance to thinning or thicken-ing contributes to the forming of shapes, such as cylindrical flat-bottom cups, by the deep-drawing process. The r value, therefore, is considered a measure of sheet metal drawability. It is particularly useful for evaluating materials intended for parts where a substantial portion of the blank must be drawn from beneath the blank holder into the die opening.
For many materials this ratio remains essentially constant over a range of plastic strains up to maximum applied force in a tension test. For materials that give different r values at various strain levels, a superscript is used to designate the percent strain at which the r value was measured. For example, if a 20 % elongation is used, the report would show r20.
Materials usually have different r values when tested in different orientations relative to the rolling direction. The angle of sampling of the individual test coupon is noted by a subscript. Thus, for a test specimen whose length is aligned parallel to the rolling direction, the r value would be reported as r0. If, in addition, the measurement was made at 20 % elongation and it was deemed necessary to note the percent strain at which the value was measured, the value would be reported as r020.
A material that has a yield point followed by discontinuous yielding stretches unevenly while this yielding is taking place. In steels, this is associated with the propagation of Lüders' bands on the surface. The accuracy and reproducibility of the determination of r will be reduced unless the test is continued beyond this yield-point elongation. Similarly, the discontinuous yie...
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.
1.3 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 2010)
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.
1. Scope 3.1.1.1 Discussion—In cold-reduced and annealed low-
carbonsteelsheet, r and r areusuallygreaterthan r ,while
0 90 45
1.1 This test method covers special tension testing for the
in hot-rolled steels r may be greater. Other earing tendencies
measurement of the plastic strain ratio, r, of sheet metal
occur; thus, for some materials the earing tendency may be
intended for deep-drawing applications. 0.05.
better represented by r − r .
max min
1.2 The values stated in inch-pound units are to be regarded
3.1.2 plastic-strain ratio r (in sheet metal that has been
as standard. The values given in parentheses are mathematical
strained by uniaxial tension sufficiently to induce plastic flow)
conversions to SI units that are provided for information only
is the ratio of the true strain that has occurred in a width
and are not considered standard.
direction w perpendicular to the direction of applied stress and
1.3 This standard does not purport to address all of the in the plane of the sheet, to the concomitant true strain in the
safety concerns, if any, associated with its use. It is the
thickness direction t. Thus, r is numerically equal to
responsibility of the user of this standard to establish appro-
r 5 ε /ε (1)
w t
priate safety and health practices and determine the applica-
where:
bility of regulatory limitations prior to use.
ε = width strain, and
w
2. Referenced Documents
ε = thickness strain.
t
2.1 ASTM Standards:
3.1.2.1 Discussion—Due to difficulty in measuring thick-
E6Terminology Relating to Methods of Mechanical Testing
nesschangeswithsufficientprecision,inpracticeanequivalent
E8Test Methods for Tension Testing of Metallic Materials
relationship is commonly used, based on length and width
E83Practice for Verification and Classification of Exten-
strain measurements (see 9.1.2).
someter Systems
3.1.3 r —weighted average of r values obtained in three
m
E92TestMethodforVickersHardnessofMetallicMaterials
directions:0°(parallel),45°(diagonal),and90°(transverse)to
(Withdrawn 2010)
the rolling direction (see 10.3).
E177Practice for Use of the Terms Precision and Bias in
3.1.3.1 Discussion—Somematerialsmayshowsignificantly
ASTM Test Methods
different values of r for other test directions, in which case an
E691Practice for Conducting an Interlaboratory Study to
averagevaluemayincludethesewhenspecialnoteismadeand
Determine the Precision of a Test Method
another subscript is used to avoid confusion with r as defined
m
in3.1.3.Symbolswhichareoftenusedinterchangeablywith r
3. Terminology
m
are r¯ and r-Bar.
3.1 Definitions of Terms Specific to This Standard:
3.1.4 yield point elongation (for a material that has a yield
3.1.1 delta r (∆ r)—measure of the tendency of sheet to
point)isthetotalstrainassociatedwithdiscontinuousyielding.
draw in nonuniformly and to form ears in the flange of
3.2 The definitions relating to tension testing appearing in
deep-drawn cylindrical parts in the directions of higher r value
Terminology E6 shall apply to this test method.
(see 10.4).
4. Significance and Use
This test method is under the jurisdiction of ASTM Committee E28 on
4.1 Theplasticstrainratio risaparameterthatindicatesthe
Mechanical Testing and is the direct responsibility of Subcommittee E28.02 on
Ductility and Formability.
ability of a sheet metal to resist thinning or thickening when
Current edition approved Nov. 1, 2010. Published January 2011. Originally
subjectedtoeithertensileorcompressiveforcesintheplaneof
ε1
approved in 1981. Last previous edition approved in 2006 as E517–00(2006) .
the sheet. It is a measure of plastic anisotropy and is related to
DOI: 10.1520/E0517-00R10.
the preferred crystallographic orientations within a polycrys-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
talline metal. This resistance to thinning or thicken-ing con-
Standards volume information, refer to the standard’s Document Summary page on
tributes to the forming of shapes, such as cylindrical flat-
the ASTM website.
3 bottom cups, by the deep-drawing process. The r value,
The last approved version of this historical standard is referenced on
www.astm.org. therefore,isconsideredameasureofsheetmetaldrawability.It
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E517 − 00 (2010)
isparticularlyusefulforevaluatingmaterialsintendedforparts eter shall conform to Practice E83 as Class C or better. The
where a substantial portion of the blank must be drawn from extensometersshallbeverifiedoverarangeappropriateforthe
beneath the blank holder into the die opening. strains used to determine r value.
4.2 For many materials this ratio remains essentially con- 6.2 Testing Machine—Thetestingmachineusedtostrainthe
stant over a range of plastic strains up to maximum applied specimen shall be capable of uniaxially straining the specimen
forceinatensiontest.Formaterialsthatgivedifferent rvalues in accordance with the requirements in 9.2.5 or 9.3.4.
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 .
7.1 Size—The length and width of the specimen are not
4.3 Materials usually have different r values when tested in critical, provided care is used to stretch the gauge section in a
differentorientationsrelativetotherollingdirection.Theangle
uniform manner, avoiding grip effects and anomalous changes
of sampling of the individual test coupon is noted by a along the gauge lengths.
subscript. Thus, for a test specimen whose length is aligned
7.1.1 The specimen shall include the full sheet thickness
parallel to the rolling direction, the r value would be reported
unless otherwise specified.
as r . If, in addition, the measurement was made at 20%
7.1.2 The thickness of the gauge section of the specimen
elongation and it was deemed necessary to note the percent
shall be uniform within 0.0005 in. (0.013 mm) in the gauge
strain at which the value was measured, the value would be
section. If the as-received surface is nonuniform, the surface
reported as r .
shallbepreparedbymachiningorbygrindingtothistolerance.
7.1.3 Thedistancebetweenagaugemarkandagripshallbe
4.4 A material that has a yield point followed by discon-
at least twice the width of the reduced section (or gauge width
tinuous yielding stretches unevenly while this yielding is
for parallel strips) of the specimen.
takingplace.Insteels,thisisassociatedwiththepropagationof
7.1.4 Duplicate specimens should be tested and the average
Lüders’bandsonthesurface.Theaccuracyandreproducibility
r value of these reported for each test direction. If necessary, a
of the determination of r will be reduced unless the test is
third determination may be made, rejecting the extreme.
continued beyond this yield-point elongation. Similarly, the
discontinuous yielding associated with large grain size in a
7.2 Type—Any of three types of specimen may be used.
material decreases the accuracy and reproducibility of deter-
Other types including subsize specimens are acceptable pro-
minations of r made at low strains.
vided they give comparable values of equivalent accuracy.
7.2.1 Specimen A, with reduced section, as shown in Fig.
5. Interferences
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,
8.1 Specimen blanks shall be sheared or sawed individually
may cause localized deformation of the specimen under the
and with the exception of Specimen C, which may be used as
knife edges. This problem is intensified by the knife edges
sheared, shall be machined individually or in packs to remove
beingsharpandattachedtothespecimenwithhighforces.This
cold-worked edges.
combination produces a compressive stress 90° to the tensile
stress being applied to stretch the specimen, which causes
8.2 The dimensions of each specimen shall be measured for
localized deformation. As a result, excessively high r values
uniformity of thickness and width in the gauge section to meet
may be calculated.
the requirements of 7.1.2 and 8.3.
6. Apparatus 8.3 Within the gauge length, parallelism of the edges shall
be maintained so that no two width measurements differ by
6.1 Measuring Devices:
more than 0.1% of the measured width (Specimens A and B
6.1.1 Instruments for measuring length and width shall be
only).
checkedforaccuracyandbegraduatedtopermitmeasurements
to be made to 60.001 in. (6 0.02 mm) or better. 8.4 Reasonable care shall be taken to position the gauge
6.1.2 If the longitudinal strain or the transverse strain, or marks symmetrically to the midpoint and centerline of the
both, are to be obtained using an extensometer, the extensom- specimen or reduced section.
E517 − 00 (2010)
Dimensions
Specimen A
Standard Alternative
in. mm in. mm
G Gage length 2.00 ± 0.01 50± 0.25 1.00 ± 0.005 25 ± 0.13
†
W Width (Note 2 and Note 3) 0.500 ± 0.01 12.5 ± 0.25 0.500 ± 0.01 12.5 ± 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 ± 0.01 50±0.25 1.00 ± 0.005 25±0.13
W gauge width 0.75± 0.005 20± 0.13 0.75± 0.005 20± 0.13
T Thickness thickness of material
L Overall length, min 8 200 7 175
C Width of specimen (Note) 0.75 ± 0.005 20 ± 0.13 0.75± 0.005 20 ± 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
8.4.1 Gaugemarksshallbelightlyscribedorpunchedinthe and the elongation in accordance with Test Methods E8, using
surface of the specimen or made with a Vickers diamond the specimen shown in Fig. 6 of Test Methods E8. This will
indenter.
establish strain limits within which the r determination may be
8.4.2 The gauge lengths shall be in compliance with 7.1.3.
made.
8.4.3 For SpecimenA, the gauge length shall be centered in
9.1.1 The plastic strain ratio r may be determined from
the reduced section.
widthandthicknesschangesresultingfromplasticdeformation
8.4.4 For Specimen C, a double set of gauge marks shall be
provided these changes can be measured with sufficient accu-
used in compliance with 7.2.3.1.
racy in a tension test.
9.1.2 Formostthinsheetmetals,however,itispreferableto
9. Procedure
measure length and width changes and, assuming constant
9.1 If the tensile properties of the material are unknown,
volume, calculate r by one of the following procedures:
either make an autographic force/extension record or run a
separate tension test to determine the yielding characteristics 9.2 Manual Procedure:
E517 − 00 (2010)
Dimensions
Specimen C
in. mm
G Gage Length 0.75 ± 0.005 20 ± 0.13
W Gage Width 0.75 ± 0.005 20 ± 0.13
T Thickness thickness of material
L Overall Length, min 7 175
C Width of specimen 1.125 ± 0.125 28.58 ± 3.17
FIG. 3 Sheared Rectangular Tension Test Specimen, Parallel
Strip, for r Determination
9.2.1 Determine the original width of the specimen, w , 9.3.5 Determine the change in width corresponding to a
within 60.0005 in. (60.013 mm). If a gauge length of 0.75 in. change in length from the data created by the extensometers,
(20 mm) is used, as for Specimen C, one width measurement when the specimen is stretched beyond any yield-point
is sufficient. If a gauge length of 1.00 in. or (25 mm) or longer elongation, but has not exceeded the strain at maximum
is used, make width measurements at a minimum of three applied force. Measurement accuracy is improved as the strain
evenly spaced places within the gauge length and use the is increased within the above limits, as explained in X1.3.3.1.
average.
NOTE 2—For complete compatibility with the manual method, only the
9.2.2 Measure the original gauge length, l , within 60.001
plastic component of the strain values measured should be used in the
in. (60.025 mm) in a 1.00-in. (25-mm), or a 0.75-in. (20-mm)
determination of the r value by the automatic method, unless it can be
shown that the elastic component of the total strain is negligible. (The
gaugesection,andwithin 60.002in.(60.05mm)in
...
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