ASTM E2712-22

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Designation: E2712 − 15 E2712 − 22
Standard Test Methods for
Bulge-Forming Superplastic Metallic Sheet
This standard is issued under the fixed designation E2712; 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
1.1 These test methods describe procedures for determining the biaxial formability of a test specimen of superplastic metallic sheet
in a circular die.
1.2 The intent of these test methods are primarily to be used as tests of superplasticity as measured by the ability to form to a
prescribed depth in a die cavity without rupturing. These test methods can also be used to generate material for the measurement
of cavitation in the formed part. These can be used as go/no go criteria for qualification to a specification.
1.3 These test methods have been used successfully with aluminum alloys. The use of these test methods on other metals should
be verified.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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.
1.5 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E6 Terminology Relating to Methods of Mechanical Testing
E2448 Test Method for Determining the Superplastic Properties of Metallic Sheet Materials
3. Terminology
3.1 The terms specified temperature and indicated temperature are used as defined in Terminology E6.
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 May 1, 2015Nov. 1, 2022. Published July 2015December 2022. Originally approved in 2009. Last previous edition approved in 20092015 as
ε1
E2719–09–15. . DOI: 10.1520/E2712-15.10.1520/E2712-22.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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E2712 − 22
4. Summary of Test Method
4.1 Two methods of bulge forming are included in these test methods.
4.1.1 In the first test Dome Rupture Test method, the sheet test specimen is formed into a die of a fixed depth as prescribed in a
specification. If it touches the base of the die without rupturing, then it is considered to have met the specification.
4.1.2 In the second testCavitation Test method, the depth of the die is reduced so that the material fills the die. A portion excised
from the center of the formed part may be examined for internal cavitation within the sheet.test specimen.
5. Significance and Use
5.1 When a superplastic material is regularly being used in industrial production, it is often convenient to use the bulge test to
qualify a batch or heat lot to an acceptance criterion. Comparing these test methods with Test Method E2448, the bulge test does
not require a machined coupon, test specimen, it is more convenient to perform, and it most closely simulates the multiaxial
stresses and strains present in forming parts. These test methods do not measure the intrinsic superplastic properties of a material.
Test Method E2448 should be used in that instance.
6. Apparatus
6.1 The bulge test consists of forming a test specimen in the form of a sheet of material into a right circular cylindrical die using
pressurized gas. The apparatus is shown in Fig. 1. The die cavity has a 100-mm diameter and a specified depth in a vessel diameter
of the die cavity shall be 100 mm 6 0.5 mm, and the specified depth of the vessel shall be suitably designed for the pressure and
temperature envisaged for the test. The surface finish of the die cavity shall be R =0.4 μm.a=0.4 μm maximum.
A
6.2 The depth of the die (X in Fig. 1), may be varied by means of inserts or other methods to the depth set by the specification.
For convenience, a series of inserts of different heights may be installed in the die to provide different depths according to the bulge
test requirements.
NOTE 1—A depth of 55 mm has been successfully used on superplastic-forming (SPF) 5083 aluminum alloy.
6.2.1 The insert shall allow the free passage of gas around its periphery to the exhaust hole in the die.
6.3 The die entry radius shall be 5.0 mm 6 0.1 mm.
6.4 A lower plate with a control thermocouple may be moved to press against the die.
NOTE 2—A plate with a gas seal bead 0.7 mm high by 8 mm wide and a 136 mm inside diameter has been used successfully.
6.5 The die entry radius is 5 mm. A lower plate with a control thermocouple may be moved to press against the die. The plate
has a gas seal bead 0.7 mm high by 8 mm wide and a 136-mm inside diameter. A gas A gas pressurization system with a gauge
or other suitable means of measuring pressure and detecting sheet test specimen failure shall be provided at the lower plate to form
the material into the cavity. The pressure tolerance up to 1 MPa shall be 650 kPa, and above 1 MPa shall be 65 % of pressure.
An exhaust port in the die may be connected either to the atmosphere or to a second gas pressurization system that provides a back
pressure to the forming sheet.test specimen.
6.6 The apparatus shall be provided with a means of heating it to the specified temperature for the material being tested.
NOTE 3—Usually, it is enclosed in a furnace equipped with doors opening in the front
6.7 The apparatus is shall be provided with a means of heating it to the specified temperature for the material being tested. Usually,
it is enclosed in a furnace equipped with doors opening in the front. The allowed tolerance between indicated and nominal test
temperature is 63°C up to 700°C and 66°C above 700°C. The apparatus is provided with a means of moving the die or lower
plate to insert and remove sheets of material test specimens and also to provide a force on the plate to counteract the force exerted
by the pressurized gas. Usually, it is installed in a hydraulic press or clamping mechanism.
E2712 − 22
Dimensions
mm
X – Depth of the die, typical, approximate 55
R – Radius of the die entry 5.0±0.1
D – Diameter of the die cavity 100.0±0.5
Die cavity surface roughness average, Ra, max 0.4 μm
FIG. 1 Bulge-Forming Apparatus
NOTE 4—Usually, it is installed in a hydraulic press or clamping mechanism.
7. Procedure
7.1 Dome Rupture Test:
7.1.1 Test Specimen—Clean a sheet test specimen of superplastic material sized at least 160160 mm by 160 mm so that it is free
of surface contaminants. The die and plate shall be clean and free of any lubricant. No lubricant shall be used in the test unless
specifically required by the lot acceptance criteria. If desired, the rolling direction may be marked in one corner of the specimen.
NOTE 5—The presence of lubricant greatly affects the depth to which the material forms before rupturing. Although very important for production,
lubricant adds an unnecessary variable to the test method, which is why it shouldis not generally be used. It follows that the apparent superplasticity of
a ma
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