ASTM E517-00

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Designation:E517–00
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1.1 Discussion—Due to difficulty in measuring thick-
nesschangeswithsufficientprecision,inpracticeanequivalent
1.1 This test method covers special tension testing for the
relationship is commonly used, based on length and width
measurement of the plastic strain ratio, r, of sheet metal
strain measurements (see 9.1.2).
intended for deep-drawing applications.
3.1.2 r —weighted average of r values obtained in three
m
1.2 The values stated in inch-pound units are to be regarded
directions: 0° (parallel), 45° (diagonal), and 90° (transverse) to
as the standard. The SI equivalents may be approximate.
the rolling direction (see 10.3).
1.3 This standard does not purport to address all of the
3.1.2.1 Discussion—Somematerialsmayshowsignificantly
safety concerns, if any, associated with its use. It is the
different values of r for other test directions, in which case an
responsibility of the user of this standard to establish appro-
averagevaluemayincludethesewhenspecialnoteismadeand
priate safety and health practices and determine the applica-
another subscript is used to avoid confusion with r as defined
m
bility of regulatory limitations prior to use.
in3.1.2.Symbolswhichareoftenusedinterchangeablywithr
m
2. Referenced Documents
are r¯ and r-Bar.
3.1.3 delta r (D r)—measure of the tendency of sheet to
2.1 ASTM Standards:
draw in nonuniformly and to form ears in the flange of
E6 Terminology Relating to Methods of Mechanical Test-
deep-drawn cylindrical parts in the directions of higher r value
ing
(see 10.4).
E8 TestMethodsforTensionTestingofMetallicMaterials
3.1.3.1 Discussion—In cold-reduced and annealed low-
E83 Practice for Verification and Classification of Exten-
carbonsteelsheet, r and r areusuallygreaterthan r ,while
someters 0 90 45
in hot-rolled steels r may be greater. Other earing tendencies
E92 Test Method for Vickers Hardness of Metallic Mate-
occur; thus, for some materials the earing tendency may be
rials
better represented by r − r .
E177 Practice for Use of the Terms Precision and Bias in max min
3.1.4 yield point elongation (for a material that has a yield
ASTM Test Methods
point)isthetotalstrainassociatedwithdiscontinuousyielding.
E691 Practice for Conducting an Interlaboratory Study to
3.2 The definitions relating to tension testing appearing in
Determine the Precision of a Test Method
Terminology E6 shall apply to this test method.
3. Terminology
4. Significance and Use
3.1 Definitions of Terms Specific to This Standard:
4.1 Theplasticstrainratio risaparameterthatindicatesthe
3.1.1 plastic-strain ratio r (in sheet metal that has been
ability of a sheet metal to resist thinning or thickening when
strained by uniaxial tension sufficiently to induce plastic flow)
subjectedtoeithertensileorcompressiveforcesintheplaneof
is the ratio of the true strain that has occurred in a width
the sheet. It is a measure of plastic anisotropy and is related to
direction w perpendicular to the direction of applied stress and
the preferred crystallographic orientations within a polycrys-
in the plane of the sheet, to the concomitant true strain in the
talline metal. This resistance to thinning or thicken-ing con-
thickness direction t. Thus, r is numerically equal to
tributes to the forming of shapes, such as cylindrical flat-
r 5e /e (1)
w t
bottom cups, by the deep-drawing process. The r value,
therefore,isconsideredameasureofsheetmetaldrawability.It
where:
isparticularlyusefulforevaluatingmaterialsintendedforparts
e = width strain, and
w
e = thickness strain. where a substantial portion of the blank must be drawn from
t
beneath 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 applied
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 14.02. forceinatensiontest.Formaterialsthatgivedifferent rvalues
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E517–00
at various strain levels, a superscript is used to designate the 7. Test Specimen
percentstrainatwhichthe rvaluewasmeasured.Forexample,
7.1 Size—The length and width of the specimen are not
if a 20% elongation is used, the report would show r .
critical, provided care is used to stretch the gage section in a
4.3 Materials usually have different r values when tested in
uniform manner, avoiding grip effects and anomalous changes
differentorientationsrelativetotherollingdirection.Theangle
along the gage lengths.
of sampling of the individual test coupon is noted by a
7.1.1 The specimen shall include the full sheet thickness
subscript. Thus, for a test specimen whose length is aligned
unless otherwise specified.
parallel to the rolling direction, the r value would be reported
7.1.2 Thethicknessofthegagesectionofthespecimenshall
as r . If, in addition, the measurement was made at 20%
be uniform within 0.0005 in. or 0.013 mm in the gage section.
elongation and it was deemed necessary to note the percent
If the as-received surface is nonuniform, the surface shall be
strain at which the value was measured, the value would be
prepared by machining or by grinding to this tolerance.
reported as r .
7.1.3 The distance between a gage mark and a grip shall be
4.4 A material that has a yield point followed by discon-
at least twice the width of the reduced section (or gage 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
7.2 Type—Any of three types of specimen may be used.
discontinuous yielding associated with large grain size in a
Other types including subsize specimens are acceptable pro-
material decreases the accuracy and reproducibility of deter-
vided they give comparable values of equivalent accuracy.
minations of r made at low strains.
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. Interferences
reduced section shall be parallel-sided rather than tapered.
5.1 Many factors may affect the measurements taken for
7.2.2 Specimen B, with a uniform width of 0.75 in. or 20
determining rvalue.Inparticular,errorsinthemeasurementof
mm, machined edges, and no reduced section, as shown in Fig.
the change in width can cause the reported r value to be
2.
invalid. The following phenomena are known to cause severe
7.2.3 Specimen C, precision-sheared a uniform width of
errorsinthemeasurementofthechangeinwidththusaffecting
1.125in.or28.58mm,orwithmachinededgesandnoreduced
the r value reported.
section, as shown in Fig. 3.
5.1.1 Canoeing—Canoeing is a phenomenon which occurs
7.2.3.1 GagelengthsforSpecimenCshallbemarkedonthe
in some materials when they are stretched. In these materials,
sheet surface perpendicular to and parallel to the specimen
the test specimen bows about its longitudinal axis taking on a
edges. The gage 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
8.2 The dimensions of each specimen shall be measured for
stress being applied to stretch the specimen, which causes
localized deformation. As a result, excessively high r values uniformity of thickness and width in the gage section to meet
the requirements of 7.1.2 and 8.3.
may be calculated.
8.3 Withinthegagelength,parallelismoftheedgesshallbe
6. Apparatus maintained so that no two width measurements differ by more
than 0.1% of the measured width (Specimens A and B only).
6.1 Measuring Devices:
8.4 Reasonable care shall be taken to position the gage
6.1.1 Instruments for measuring length and width shall be
marks symmetrically to the midpoint and centerline of the
checkedforaccuracyandbegraduatedtopermitmeasurements
specimen or reduced section.
to be made to 60.001 in. (6 0.02 mm) or better.
8.4.1 Gage marks shall be lightly scribed or punched in the
6.1.2 If the longitudinal strain or the transverse strain, or
surface of the specimen or made with a Vickers diamond
both, are to be obtained using an extensometer, the extensom-
indenter.
eter shall conform to Practice E83 as Class C or better. The
8.4.2 The gage lengths shall be in compliance with 7.1.3.
extensometersshallbeverifiedoverarangeappropriateforthe
strains used to determine r value. 8.4.3 For Specimen A, the gage length shall be centered in
the reduced section.
6.2 Testing Machine—The testing machine used to strain
the specimen shall be capable of uniaxially straining the 8.4.4 For Specimen C, a double set of gage marks shall be
specimeninaccordancewiththerequirementsin9.2.5or9.3.4. used in compliance with 7.2.3.1.
E517–00
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 0.025
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.
FIG. 1 Rectangular Tension Test Specimens with Reduced Parallel Section, for r Determination
Dimensions
Specimen B
Standard Alternative
in. mm in. mm
G Gage length 2.00 6 0.01 50 6 0.25 1.00 6 0.005 25 6 0.13
W Gage 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. or 0.020 mm.
FIG. 2 Machined Rectangular Tension Test Specimens, Parallel Strip, for r Determination
9. Procedure 9.1.2 Formostthinsheetmetals,however,itispreferableto
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
9.2 Manual Procedure:
separate tension test to determine the yielding characteristics
9.2.1 Determine the original width of the specimen, w ,
and the elongation in accordance withTest Methods E8, using
within 60.0005 in. or 60.013 mm. If a gage length of 0.75 in.
the specimen shown in Fig. 6 of Test Methods E8. This will
or 20 mm is used, as for Specimen C, one width measurement
establish strain limits within which the r determination may be
is sufficient. If a gage length of 1.00 in. or 25 mm or longer is
made.
used, make width measurements at a minimum of three evenly
9.1.1 The plastic strain ratio r may be determined from
spaced places within the gage length and use the average.
widthandthicknesschangesresultingfromplasticdeformation
provided these changes can be measured with sufficient accu- 9.2.2 Measuretheoriginalgagelength,l ,within 60.001in.
racy in a tension test. or 60.025 mm in a 1.00-in. or 25-mm, or a 0.75-in. or 20-mm
E517–00
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
error in calculated r value decreases with increasing strain, higher
gagesection,andwithin 60.002in.or 60.05mmina2.00-in.
modulus, lower strength, and at lower r values.) Plastic strains can be
or 50-mm gage section.
determined by reducing the tensile force on the specimen to zero with the
9.2.3 When gage marks are made with two indenters
extensometersinplace,ortheycanbecalculatedbysubtractingtheelastic
mounted a known distance apart in a fixture, only final gage
strains from the total strains indicated by the extensometers. The longi-
length and width measurements are needed.
tudinal elastic strain at any point may be calculated by dividing the true
9.2.4 Pull the specimen axially until it is stretched beyond
stress at that point by the nominal value of the modulus of elasticity. The
any yield-point elongation but not exceeding the strain at transverse elastic strain may be calculated by multiplying the longitudinal
elastic strain by the nominal value of Poisson’s ratio. Examples: If an r
maximumappliedforce.Measurementaccuracyisimprovedas
value of 2.0 at 15% strain is determined for steel using longitudinal and
the strain is increased within the above limits, as explained in
transverse strain measurements measured at a true stress of 50 000 psi
X3.3.1.
(345 MPa), subtracting the elastic strain component from these measure-
ments would increase the r value calculated from 2.0 to approximately
NOTE 1—Strainsof15–20%arecommonlyutilizedfordeterminingthe
2.03. If an r value of 1.
...