ASTM E2492-07(2012)
(Test Method)Standard Test Method for Evaluating Springback of Sheet Metal Using the Demeri Split Ring Test (Withdrawn 2017)
Standard Test Method for Evaluating Springback of Sheet Metal Using the Demeri Split Ring Test (Withdrawn 2017)
SIGNIFICANCE AND USE
The formability of materials is affected by springback, the difference between the final shape of a part and the shape of the die that formed it. Materials having a large amount of springback create difficulties for the die designer and make die rework much more likely and complicated. This can add months and great costs to the achievement of successful dies. While dealing with springback in traditional metals is largely overcome by experience, new metals often have so much springback that they can only be used after much trial and error. The quantification and prediction of the tendency of metals to springback is addressed by this test method.
The magnitude of the springback is a convolution of the elastic modulus, the flow stress of the metal of interest, the sheet metal thickness and the amount and type of cold work introduced by the forming process. Since the cup forming process contains features of many forming operations, the amount of springback measured by the Demeri split ring test is indicative of the behavior of the metal in many stamping operations.
The amount of springback that occurs in this test is very large compared to other approaches. This improves measurement accuracy and reduces experimental error in all types of formable metals.
This test does not require measurement fixtures or any sophisticated profiling equipment for accurate measurement of springback. Conventional length measuring instruments are all that is needed to perform the required measurements.
This test can be used to rank materials according to their tendency to springback after a forming operation (see Refs 1-3). Since springback depends on the sheet thickness, metals should be compared at the same thickness. Experience has shown that the test can also be used in conjunction with an appropriate analysis to predict quantitatively the amount of springback occurring after a forming operation (see Refs 2-9).
This test provides a method to compare springback predictions by v...
SCOPE
1.1 This test method provides a means of evaluating the springback behavior of metals in a test that simulates a stretch-draw forming process. The test method can also be used to calibrate computer simulation codes by selecting appropriate control parameters to achieve satisfactory correlation between simulation and test results.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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.
WITHDRAWN RATIONALE
This test method provides a means of evaluating the springback behavior of metals in a test that simulates a stretch-draw forming process. The test method can also be used to calibrate computer simulation codes by selecting appropriate control parameters to achieve satisfactory correlation between simulation and test results.
Formerly under the jurisdiction of Committee E28 on Mechanical Testing, this test method was withdrawn in September 2017. This standard is being withdrawn without replacement due to its limited use by industry.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2492 − 07 (Reapproved 2012)
Standard Test Method for
Evaluating Springback of Sheet Metal Using the Demeri
Split Ring Test
This standard is issued under the fixed designation E2492; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope of the die that formed it. Materials having a large amount of
springback create difficulties for the die designer and make die
1.1 This test method provides a means of evaluating the
rework much more likely and complicated. This can add
springback behavior of metals in a test that simulates a
months and great costs to the achievement of successful dies.
stretch-drawformingprocess.Thetestmethodcanalsobeused
While dealing with springback in traditional metals is largely
tocalibratecomputersimulationcodesbyselectingappropriate
overcome by experience, new metals often have so much
control parameters to achieve satisfactory correlation between
springback that they can only be used after much trial and
simulation and test results.
error. The quantification and prediction of the tendency of
1.2 The values stated in SI units are to be regarded as
metals to springback is addressed by this test method.
standard. No other units of measurement are included in this
4.2 The magnitude of the springback is a convolution of the
standard.
elastic modulus, the flow stress of the metal of interest, the
1.3 This standard does not purport to address all of the
sheet metal thickness and the amount and type of cold work
safety concerns, if any, associated with its use. It is the
introduced by the forming process. Since the cup forming
responsibility of the user of this standard to establish appro-
process contains features of many forming operations, the
priate safety and health practices and determine the applica-
amount of springback measured by the Demeri split ring test is
bility of regulatory limitations prior to use.
indicative of the behavior of the metal in many stamping
operations.
2. Terminology
4.3 The amount of springback that occurs in this test is very
2.1 Definitions:
large compared to other approaches. This improves measure-
2.1.1 springback—the difference between the final shape of
ment accuracy and reduces experimental error in all types of
a part and the shape of the forming die.
formable metals.
2.1.2 Demeri Split Ring Test—a test that measures the
4.4 This test does not require measurement fixtures or any
springback behavior of sheet metal by comparing the diameter
of a ring extracted from the wall of a flat bottom cup and the sophisticated profiling equipment for accurate measurement of
springback. Conventional length measuring instruments are all
diameter of the same ring split to release residual stresses.
that is needed to perform the required measurements.
3. Summary of Test Method
4.5 Thistestcanbeusedtorankmaterialsaccordingtotheir
3.1 The test method consists of four steps: (1) deep draw a
tendency to springback after a forming operation (see Refs
cylindrical cup from a circular blank with a constant clamp or 2
1-3). Since springback depends on the sheet thickness, metals
blankholder force, (2) cut a circular ring from the mid-section
should be compared at the same thickness. Experience has
of the drawn cup, (3) split the ring along a certain direction to
shown that the test can also be used in conjunction with an
release residual stresses caused by the stretch-draw operation,
appropriate analysis to predict quantitatively the amount of
and (4) measure the opening of the ring (springback).
springback occurring after a forming operation (see Refs 2-9).
4. Significance and Use
4.6 This test provides a method to compare springback
predictions by various numerical simulation codes.Test results
4.1 The formability of materials is affected by springback,
canbeusedtocalibratecomputersimulationcodesbyselecting
the difference between the final shape of a part and the shape
proper control parameters and appropriate material models to
achieve satisfactory correlation between simulation and test
This test method is under the jurisdiction of ASTM Committee E28 on
Mechanical Testing and is the direct responsibility of Subcommittee E28.02 on
Ductility and Formability.
Current edition approved April 1, 2012. Published May 2012. Originally
approved in 2007. Last previous edition approved in 2007 as E2492–07. DOI: The boldface numbers in parentheses refer to the list of references at the end of
10.1520/E2492-07R12. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2492 − 07 (2012)
FIG. 1 Cross Section Through the Experimental Setup Used for Cup Drawing
results. Test data can be used to evaluate and improve current required accuracy and precision are acceptable for the first
forming and simulation capabilities. threemeasurements.Onlyanon-contactingmethod,suchasan
optical micrometer, traveling microscope, or comparator,
4.7 The experimental setup and test procedure are simple,
should be used for measuring the final diameter as this is very
and test results are highly repeatable.
sensitive to the presence of additional forces.
5. Apparatus
6. Hazards
5.1 Cup Forming Apparatus—A die set and punch are
6.1 Forming equipment can be dangerous. Care must be
needed to form the cup from circular sheet metal blanks for
taken to keep hands away when forming the cups.
subsequent testing. The die set consists of upper and lower
tools with centrally located circular holes. The sheet is held
6.2 Cutting and slicing equipment can also cause injury if
between these and formed into a cup by the action of a punch
care is not taken in their use.
that fits through the hole in the upper and lower dies. This
6.3 Sheet metal generally has sharp edges and burrs.
arrangement is shown in Fig. 1. The apparatus can be part of a
Precautions, such as gloves and safety glasses should be worn.
double acting press where the clamp force on the upper tool of
When the ring is split open, it is required to be restrained in
the die is generated hydraulically, followed by movement of
some way to avoid artifacts due to sudden springback. If it is
the punch to make the cup.Alternatively, the upper tool can be
not restrained, harm to the person splitting the ring may result.
held down by a combination of bolts and Belleville spring
washerstoachieveaconstantforce.Inthiscase,thecupcanbe
7. Sampling, Test Specimens, and Test Units
formed in a universal or compression testing machine.
7.1 Samples for testing shall be from the same lot or heat as
5.2 Ring SlicingApparatus—Thecuttingequipment,usedto
the material of interest except where the measurement of
slice the ring from the cup and split it, must not change the
springback is being made to rank different types of materials
worked state of the ring, as this will affect the result. Good
for future reference. In this latter case, it will suffice to use
results have been obtained with laser cutting equipment,
material typical of the specification.
electro discharge machining (EDM), and slow speed diamond
wheels. Shears have been shown to badly distort the ring and 7.2 Test units shall be in SI units.
leave burrs that affect the result. Other methods are acceptable
if they can be shown to agree with one of the successful 8. Procedure
methods.
8.1 The dimensions used in this section are defined here for
5.3 Dimensional Measurement Apparatus—Methods of convenience. The depth of the drawn cup is d (see Fig. 2). The
measuring the location of the ring to be extracted from the cup height of the ring extracted from the cup is h (see Fig. 2). The
(h ) (see Fig. 2), the initial ring diameter (D ), the ring height wall thickness of the cup is t . The diameter of the unsplit ring
o o w
(h), the ring wall thickness (t ) and the final diameter of the is D , measured to the midthickness (see Fig. 3). D is equal to
w o o
split open ring (D) are required. Most methods having the the average of the outside and inside diameters (OD/2 + ID/2)
f
E2492 − 07 (2012)
FIG. 2 Ring Location in a Drawn Cylindrical Cup
FIG. 3 Steps in Splitting a Test Ring
ortheoutsidediameterminusthewallthickness(OD–t ).The roughness of the tools should be typical of good practice
w
diameter of the split ring at midthickness is D (see Fig. 3) and (~0.8 µm). Punch speed shall be kept constant at (5 6 1)
f
may be determined in the same way as for the unsplit ring.The mm/second. Clamp (or blankholder) force shall be kept con-
chord length measured between the midthickness tips of the stant at a known value to produce wrinkle and split free cups.
split ring is C (see Fig. 3). The length of the section of the Aclampforceof88kNhasproducedsuccessfulcupsfromDS,
circumference removed by the splitting operation is X (see Fig. A6022-T4, BH210, HSLA50, DP600 and TRIP600 sheet
3). metals.The clamp (or blankholder) force is about one-third the
punch (drawing) force.
8.2 The initial step in obtaining samples for this test is to
form cylindrical cups from (200 6 2) mm diameter, drawing 8.3 Rings from the formed cups shall be cut (20 6 1) mm
oil-lubricated, circular blanks to a maximum depth, d,of55 from the bottom of the cup as shown in Fig. 2. The rings shall
mm. Cups of this depth have been routinely made from be (25 6 1) mm high (h) and have an external diameter OD of
formable aluminum and steel sheet. To minimize friction, a (110 6 1) mm. The wall thickness (t ) shall be measured in
w
sheet of solid lubricant is applied to the die side of the blank. three positions (top, middle, and bottom) in two locations
The tooling used for this test is shown in Fig. 1. Sheet metal (rolling and transverse) to an accur
...
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